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Effects of ear-tagging on survival of moose calves
Abstract
A critical assumption of radiotelemetry studies is that the radiotransmitters themselves do not influence mortality. Here we report the effects of marking techniques on survival of moose (Alces alces) calves from birth to the beginning of the autumn hunting season. We marked and followed 181 moose calves with ear tags and 71 with ear transmitters, and we also followed 175 unmarked control calves, all with marked mothers, in 5 study areas in Sweden; 2 areas had resident brown bears (Ursus arctos), and 3 did not. Survival was lower for calves with ear transmitters than for those with ear tags (P < 0.001) and for control calves (P < 0.001). There was no difference in survival between control calves and calves with ear tags (P = 0.09). Survival was lower in areas with bears, but bears apparently did not prey differentially on calves marked with ear transmitters. Marking newborn moose calves with plastic ear tags did not have measurable effects, but we do not recommend marking calves with ear transmitters, because of the high mortality rates calves experienced.
... Carrying a radiocollar in itself, however, had no effect on kid production, female dominance status, survival, foraging efficiency, or time spent alert, although there was a suggestion that it might influence kid survival (Côté, et al. 1998). In moose (Alces alces) calves, however, some types of marks do not seem to affect calf mortality (expandable neck collars, Larsen and Gauthier 1989;plastic ear tags, Swenson et al. 1999), whereas others do (ear-tag mounted radiotransmitters, Swenson et al. 1999). In Scandinavia, few effects of capture, handling, and immobilization have been documented for adult moose, although rectal palpation seems to reduce fetal and neonatal survival (Solberg et al. 2003). ...
... Solberg et al. (2003) analyzed data from 227 immobilizations of moose on Vega Island, Norway, and concluded that the immobilization of moose from helicopter with etorphine in winter can be considered a safe procedure, because no individuals died during capture or handling nor were found dead within 6 weeks of the procedure. Swenson et al. (1999) studied the effects of marking moose calves <3 days old with a radiotransmitter, with a mortality function, mounted on an ear tag (Televilt model TXP-2M; the entire assembly weighed 29 g, Fig. P) and a colored, plastic ear tag weighing 3.5 g. The entire procedure took about 5 min. ...
... Mortality was higher in areas with bears, but this did not have an additive effect on the mortality of those with radiotransmitters. The reason for the higher mortality among calves with ear-tag mounted radiotransmitters was not known, although Swenson et al. (1999) speculated that the clicking sound made by the iron switch may have negatively affected the mother-calf bond (silent mercury switches are not allowed in Sweden). They did not recommend using this type of radiotransmitters on moose calves. ...
... As the handling of animals through direct sampling techniques (e.g. radiocollaring) has demonstrated adverse effects for other studied ungulate species (Côté et al. 1998, Swenson et al. 1999, Morellet et al. 2009), it is best that any negative effects to already small, declining populations be avoided (Murray and Fuller 2000). Where no direct evidence exists to relate the adverse effects of direct capture techniques on woodland caribou, common sense and the precautionary principle should prevail. ...
... Côté et al. (1998) demonstrated that chemical immobilization of mountain goats led to decreased fertility rates and an increase in the rate of abandonment by mothers of calves. Swenson et al. (1999) demonstrated that ear placed radiotransmitters significantly increased the rate of mortality for sampled moose calves. Krausman et al. (2005) recorded instances of caribou mortalities due to bacterial infections of lesions caused by radio-collar placement. ...
... Regardless of the weight of radio transmitters, it is essential to consider their potential undesired effects, which may lead to biased vital rate estimates and erroneous management decisions. Although some studies have identified effects of radio transmitters on animal behavior (Brooks et al. 2008), mass loss (Legagneux et al. 2013), reproductive success (Demers et al. 2003), or survival (Swenson et al. 1999), much is still unknown and several results appear contradictory (e.g., Godfrey and Bryant 2003). ...
... For example, heavier devices are more likely to have a negative impact than light ones (Brooks et al. 2008, Venturato et al. 2009). In addition, younger individuals may be more affected than adults (Cypher 1997, Swenson et al. 1999. Migratory species such as greater snow goose (Anser caerulescens atlanticus) or caribou (Rangifer tarandus) that travel hundreds or thousands of kilometers each year may be particularly susceptible to the effects of collars (Demers et al. 2003, Haskell andBallard 2007), because the energetic costs of long migrations exacerbate the burden of wearing a transmitter. ...
Radio transmitters are widely used in wildlife management; therefore, it is essential to assess any effects that they may have on animal survival. We compared the survival of 269 randomly selected adult migratory caribou (Rangifer tarandus) fitted with either light very high frequency or heavy Argos satellite collars during the same period. Heavy collars reduced annual survival of caribou in a declining population with generally poor body condition by about 18%. Accurate estimates of survival are crucial for management decisions and possible effects of collars should be considered when calculating estimates. © 2014 The Wildlife Society.
... Often, tags are assumed to have negligible effects on large animals ). However, significant deleterious effects have been reported for several large animals, including moose (Alces alces) calves (Swenson et al. 1999) and mountain goat (Oreamnos americanus) kids (Côté et al. 1998). Brooks et al. (2008) showed that even small changes in the weight and fit of tags can cause behavioral responses in large mammals. ...
... Similarly, vaginal radio tags did not affect reproductive output in whitetailed deer (Bowman and Jacobsen 1998) or elk (Cervus elaphus nelson; Johnson et al. 2006). In contrast, Swenson et al. (1999) observed decreased survival of moose calves with affixed ear transmitters and Côté et al. (1998) reported a decline in mountain goat kid survival due to increased abandonment by mothers immobilized and fit with radio collars. Brooks et al. (2008) found that, while foraging, plains zebras (Equus burchelli antiquorum) wearing GPS collars weighing 0.6% body mass had a >50% lower travel rate compared to zebras fitted with collars weighing 0.4% of body mass, suggesting even small changes in collar weight might have behavioral effects. ...
... Bears killed about 26% of the calves and 92% of the predation took place when the calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears (Swenson et al. 1999c, in press b). Females that lost their calves in spring produced more calves the following year (1.54 calves/cow) than females that kept their calves (1.11 calves/cow), which reduced the net loss of calves due to predation to about 22% (Swenson et al. in press b). ...
... We do not know whether this economic equation favors the bear or the moose, but it would be important to the large-carnivore debate to find out. Although we now understand the effects of bear predation on moose quite well (Swenson et al. 1999c, in press b), relatively little is known about the effects of bear predation on reindeer, especially reindeer calves. A documentation of this effect is important for the Swedish compensation system for damage caused by large carnivores. ...
... Effects of marking can also extend from the individual animal to populations and interactions between species. Studies on a range of bird and mammalian species have shown that markings can cause pain and distress, interfere with natural behaviour, and reduce survival and reproduction (Pavone and Boonstra 1985; Pietz et al. 1993; SchwartzkopfGenswein et al. 1997c; Swenson et al. 1999). For example, zebra finches (Poephila guttata) fitted with coloured plastic leg bands showed mating preferences for particular colours (red, pink and black bands) while avoiding mating with other birds fitted with light-blue or light-green bands (Burley et al. 1982). ...
... The commonly used marking method of toe-clipping decreased the overall life span of meadow voles (Microtus pennsylvanicus; Pavone and Boonstra 1985). Animals carrying transmitters may also have higher mortality rates, as shown for moose calves (Alces alces; Swenson et al. 1999) and meadow voles ...
Wildlife research often requires marking and tagging animals to collect data on survival, reproduction, movement, behaviour and physiology. Identification of individual marine mammals can be carried out using tags, brands, paint, dye, photogrammetry, telemetry and other techniques. An analysis of peer-reviewed articles published from January 1980 to April 2011 addressing the effects of marking revealed a preponderance of studies focussed on short-term effects such as injuries and behavioural changes. Some marking techniques were reported to cause pain and to change swimming and haul-out behaviour, maternal attendance, and duration of foraging trips. However, marking has typically not been found to affect survival. No published research has addressed other possible long-term effects of marking related to injuries or pain responses. Studies of the more immediate effects of marking (mostly related to externally attached devices such as radio-transmitters) have shown a variety of different types and magnitudes of responses. It is important to note that studies failing to find treament differences are less likely to be published, meaning that the present and any other reviews based on published literature may be a biased sample of all research conducted on the topic. Publishing results that found no or low impacts (i.e. best practices) as well as those that found significant impacts on animals should both be encouraged. Future research under more controlled conditions is required to document acute effects of marking, including injury and pain, and to better understand longer-term effects on health, reproduction and survival. We recommend that studies using marked animals standardise their reports, with added detail on methodology, monitoring and sampling design, and address practices used to minimise the impact of marking on marine mammals.
... Animal-borne tags are assumed to have negligible effects on large animals (Withey et al. 2001). However, deleterious effects have been reported for several large animals, including moose (Alces alces) calves (Swenson et al. 1999) and mountain goat (Oreamnos americanus) kids (Côté et al. 1998). Brooks et al. (2008) showed that even small changes in the weight and fit of tags might cause behavioral responses in large mammals. ...
... Similarly, vaginal radiotags did not affect reproductive output in white-tailed deer (Bowman and Jacobsen 1998) or elk (Cervus elaphus; Johnson et al. 2006). In contrast, Swenson et al. (1999) observed decreased survival of moose calves with affixed ear transmitters and Côté et al. (1998) reported a decline in mountain goat kid survival due to increased abandonment by mothers immobilized and fitted with radiocollars. Brooks et al. (2008) observed that, while foraging, plains zebras (Equus burchelli) wearing GPS collars weighing 0.6% body mass had a .50% ...
Animal-borne video and environmental data collection systems (AVEDs) are an advanced form of biotelemetry that combines video with other sensors. As a proxy for physiological stress, we assessed fecal glucocorticoid metabolite (FGM) excretion in 7 white-tailed deer (Odocoileus virginianus) fitted with AVED dummy collars; 9 additional deer served as controls. We collected fecal samples over 3 2-week periods: pretreatment, treatment, and posttreatment periods. There were no differences in FGMs across time periods (F2,218 = 1.94, P = 0.147) and no difference between FGMs of control and treatment individuals (F1,14 = 0.72, P = 0.411). Fecal glucocorticoid metabolite excretion in AVED-collared deer was indistinguishable from uncollared animals and within the normal, baseline range for this species. Absence of an adrenal response to collaring suggested that AVED collaring does not induce physiological stress in deer.
... Normally, accelerometers are mounted to the animal's body with a device that is designed for such use (e.g., a collar or vest), but this does not affect its behaviour. The effect of mounting the accelerometer varies considerably according to the taxon and the technique used [9], and it has been studied in several groups [10][11][12]. ...
Accelerometers are a technology that is increasingly used in the evaluation of animal behaviour. A tri-axial accelerometer attached to a vest was used on Tamandua tetradactyla individuals (n = 10) at Biodiversity Park. First, the influence of using a vest on the animals’ behaviour was evaluated (ABA-type: A1 and A2, without a vest; B, with a vest; each stage lasted 24 h), and no changes were detected. Second, their behaviour was monitored using videos and the accelerometer simultaneously (experimental room, 20 min). The observed behaviours were correlated with the accelerometer data, and summary measures (X, Y and Z axes) were obtained. Additionally, the overall dynamic body acceleration was calculated, determining a threshold to discriminate activity/inactivity events (variance = 0.0055). Then, based on a 24 h complementary test (video sampling every 5 min), the sensitivity (85.91%) and precision (100%) of the accelerometer were assessed. Animals were exposed to an ABA-type experimental design: A1 and A2: complex enclosure; B: decreased complexity (each stage lasted 24 h). An increase in total activity (%) was revealed using the accelerometer (26.15 ± 1.50, 29.29 ± 2.25, and 35.36 ± 3.15, respectively). Similar activity levels were detected using video analysis. The results demonstrate that the use of the accelerometer is reliable to determine the activity. Considering that the zoo-housed lesser anteaters exhibit a cathemeral activity pattern, this study contributes to easily monitoring their activities and responses to different management procedures supporting welfare programs, as well as ex situ conservation.
... Data collection via collars, however, is limited for fine-scale local conditions (Schauber et al. 2007, Dore et al. 2020. Previous studies have monitored early life survival by attaching radio collars to neonates (Valkenburg et al. 2004); however, capture and collaring of newborn ungulates can have negative impacts on their survival (Swenson et al. 1999, Venturato et al. 2009, Rasiulis et al. 2014). In addition, local communities and the general public often disapprove of neonate captures (Kendrick et al. 2005). ...
Monitoring survival of juveniles in wild populations of vertebrates is challenging because capture and marking of neonates may influence survival and induce biases. Camera collars have proven effective in resource and habitat selection studies, but their effectiveness to assess offspring survival is unknown. Our objective was to monitor the survival of neonates using camera collars installed on 24 preparturient female migratory caribou ( Rangifer tarandus ) of the Rivière‐aux‐Feuilles herd, from 2016 to 2018, in Nunavik, Canada. Females were captured with a net gun fired from a helicopter and pregnancy was confirmed by ultrasound. Cameras recorded a 10‐second video every 20 min from 1 June until 1 September 2017, when the collar detached automatically. We used Cormack‐Jolly‐Seber models to assess survival and resighting probabilities of calves based on their observation in the videos. Three collars failed, recording less than 30% of the expected videos, including one on a female that did not give birth. Among the 21 females wearing a functional collar, one gave birth to a stillborn calf. We analyzed 25,820 videos recorded from 20 collars. Calf sightings in videos were less frequent as the monitoring period advanced, but we estimated the probability of observing a live calf at 0.77 (SE = 0.42) over the sampling period. Videos indicated a survival rate of 0.67 (SE = 0.11) from birth to 1 September. Our results suggest that camera collars installed on adult females can be used to reliably assess offspring survival, and thus improve our understanding of caribou population dynamics. The application of camera collars should be useful for other large vertebrate species for which the assessment of neonate survival is lacking or difficult to obtain. © 2021 The Wildlife Society.
... Although our study concentrated on short-term effects of tags, we would be remiss if we did not note the potential long-term impacts. Such effects are generally thought to be more of a concern for smaller animals, although biotelemetry devices have been recorded to negatively impact behavior (Brooks et al. 2008) and survival (Swenson et al. 1999, Rasiulis et al. 2014) among large terrestrial mammals, although the trend is by no means universal. In addition, there is evidence that migratory species may be particularly susceptible to these potential effects as any effect of tags on the cost of transport would be magnified by the considerable distances they travel (Rasiulis et al. 2014). ...
Animal-borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers (<1% of animals’ mass and front profile) on the swimming speeds and energy expenditure of four female northern fur seals (Callorhinus ursinus) while swimming at depth. Swim speeds and rates of oxygen consumption were measured as the trained fur seals repeatedly swam an underwater circuit, with or without the tags. We found the placement of either tested tag significantly affected both the behavior and energetics of the fur seals in our study. Diving metabolic rate increased an average of 8.1%–12.3% (depending on tag type) and swim speed decreased an average of 3.0%–6.0% when wearing the tags. The combined changes in velocities and metabolic rates resulted in a 12.0%–19.0% increase in the total energy required by the fur seals to swim a set distance. The demonstrated effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer-term impacts on the studied animals.
... moose (Swenson et al. 1999, Odden et al. 2006), but the main predation pressure came from bear, wolf and wolverine (Haglund 1974, Valdmann et al. 2005. Even though many studies revealed that roe deer were the dominating prey species for lynx in the winter (Okarma et al. 1997, Odden et al. 2006, we failed to detected such relationship, maybe because of the limited lynx occurrences (only 35 times) and different habitat requirements between lynx and roe deer in this area. ...
Patterns of habitat use profoundly influence interactions among wildlife species and ecological communities, the sustainability of species and the stability of populations. The Eurasian lynx Lynx lynx, sable Martes zibellina, moose Alces alces, roe deer Capreolus pygargus and mountain hare Lepus timidus are sympatric carnivore and herbivore species in Hanma Nature Reserve in the Greater Khingan Mountains, northeastern China. We conducted snow track sample plot surveys of these mammals during the winter of 2012–2013 and analyzed habitat selection characteristics and interspecific interactions. We screened the preferred habitat variables of each species and predicted their potential occurrence probability by generalized linear mixed model (GLMM) and further, selected the best model of each species that incorporated other species' potential occurrence probability in GLMM. Our results showed that when we only considered habitat factors in the model: 1) river valley was the most favored habitat factor in winter that lynx, moose and mountain hare showed strong selection on; 2) lynx preferred areas with steep slope and coniferous forest; 3) sable only avoided the forest edge; 4) roe deer avoided sparse shrub forest but preferred coniferous forest. When we incorporated other species' presence probability in GLMM: 1) the presence probability of moose and roe deer had no significant relationship with other species; 2) lynx preferred areas with higher mountain hare potential occurrence probability; 3) sable preferred areas with higher mountain hare but less lynx occurrence probability; 4) mountain hare preferred to inhabit areas with sympatric roe deer and lynx. These results will provide guidance for species specific habitat conservation and restoration, and wildlife population management based on interspecific interactions.
... In theory, telemetry technology permits collection of data via remote radio towers or portable telemetry units that minimize observer effects on individual organisms. However, in some instances the weight and resistance associated with telemetry tags have been shown to influence both organism behavior and survivability (Marcströ m et al., 1989;Swenson et al., 1999;Barron et al., 2010). A common limitation of telemetry studies is the ability to capture and instrument enough animals for sound ecological inference on habitat selection. ...
... Capture-induced abandonment of ungulate neonates is a little-understood phenomenon in which mothers permanently reject offspring ostensibly in response to the disturbance of capture, marking of the neonate, or some combination of factors (Livezey 1990, Swenson et al. 1999). It is defined as "the permanent separation of mother and young causing death of the young," occurring ≤1 day after marking (Livezy 1990:193). ...
Neonatal moose (Alces alces) may be prone to maternal abandonment induced by capture activities. We observed unexpectedly high levels of abandonment during the first year of our study of calf survival and cause-specific mortality in northeastern Minnesota. In response, we crafted a capture-induced abandonment contingency plan to reduce calf deaths caused by such abandonment. Locations and movements of dams relative to calves were used to gauge whether abandonment was occurring and to trigger retrieval of live calves. The Minnesota Zoo and a private facility accepted abandoned calves in viable condition. As undesirable as it is to remove calves from the population and landscape, we found it preferable to leaving them to succumb to starvation, hypothermia, or predation. We believe variations of this plan may be used in other study areas to mitigate neonate mortality due to capture-induced abandonment.
... transmitter should weigh 3% of the instrumented animal, Kenward 2001), certain species may be affected in some cases. For instance, moose Alces alces calves equipped with ear-tag transmitters had higher mortality than moose equipped with ear-tags only (Swenson et al. 1999). Migratory caribou Rangifer tarandus equipped with heavier satellite collars exhibited lower survival than caribou equipped with lighter very high frequency (VHF) radiocollars (Rasiulis et al. 2014). ...
One key assumption often inferred with using radio-equipped individuals is that the transmitter has no effect on the metric of interest. To evaluate this assumption, we used a known fate model to assess the effect of transmitter type (i.e. tail-mounted or peritoneal implant) on short-term (one year) survival and a joint live--dead recovery model and results from a mark--recapture study to compare long-term (eight years) survival and body condition of ear-tagged only American beavers Castor canadensis to those equipped with radio transmitters in Voyageurs National Park, Minnesota, USA. Short-term (1-year) survival was not influenced by transmitter type (wi = 0.64). Over the 8-year study period, annual survival was similar between transmitter-equipped beavers (tail-mounted and implant transmitters combined; 0.76; 95% CI = 0.45-0.91) versus ear-tagged only (0.78; 95% CI = 0.45-0.93). Additionally, we found no difference in weight gain (t9 = 0.25, p = 0.80) or tail area (t11 = 1.25, p = 0.24) from spring to summer between the two groups. In contrast, winter weight loss (t22 = - 2.03, p = 0.05) and tail area decrease (t30 = - 3.04, p = 0.01) was greater for transmitterequipped (weight = - 3.09 kg, SE = 0.55; tail area = - 33.71 cm2, SE = 4.80) than ear-tagged only (weight = - 1.80 kg, SE = 0.33; tail area = - 12.38 cm2, SE = 5.13) beavers. Our results generally support the continued use of transmitters on beavers for estimating demographic parameters, although we recommend additional assessments of transmitter effects under different environmental conditions.
... In theory, telemetry technology permits collection of data via remote radio towers or portable telemetry units that minimize observer effects on individual organisms. However, in some instances the weight and resistance associated with telemetry tags have been shown to influence both organism behavior and survivability (Marcströ m et al., 1989;Swenson et al., 1999;Barron et al., 2010). A common limitation of telemetry studies is the ability to capture and instrument enough animals for sound ecological inference on habitat selection. ...
Habitat selection research examines how organisms make use of their environment. This research area has moved beyond mere documentation of habitat that organisms use, by striving to understand why an organism selects a particular habitat and to determine the mechanisms that drive a population of organisms to inhabit certain areas. There are limitations on inference that result from issues such as definitions of habitat selection and availability, scale, spatial and temporal autocorrelation, and locational imprecision. Nevertheless, habitat selection is an incredibly powerful area of research that has the potential to inform ecology through analysis of organism–habitat associations.
... For example, one study found using flipper bands to mark king penguins Aptenodytes patagonicus to track survival and reproduction of individuals significantly reduced survival rates and breeding success (Wilson 2011). Another example of reduced survival of marked individuals was reported by Swenson et al. (1999) where moose Alces alces calves marked with ear transmitters experienced a significantly higher mortality rate than control calves or those marked only with ear tags. Immobilized animals may experience direct and indirect adverse effects as a result of capture and immobilization procedures and vary depending on the species, age of the animal, drug and dosages used, capture procedures utilized, and timing of capture during the pregnancy cycle for females (Ballard and Tobey 1981;Larsen and Gauthier 1989;and Roffe et al. 2001). ...
Since 1998, 83 female moose Alces alces have been captured and instrumented with radiocollars as part of a population dynamics study in southwestern Alaska. Moose were pursued and immobilized with carfentanil citrate and xylazine HCl administered from a dart gun fired from a helicopter. We investigated the potential for capture and radiotelemetry instrumentation to alter calf production or recruitment of 78 radiocollared adult female moose. Calf production or recruitment by radioed females was not significantly different between capture and noncapture years (P < 0.290; P < 0.789, respectively). We recommend the continued use of these capture and immobilization methods for deploying radiocollars to study moose population dynamics in this region.
... The underlying assumption in all animal activity budget studies is that tagging an animal will not bias natural behavior. Previous research on other mammals has both supported (white-tailed deer (Odocoileus virginianus ): Moll et al., 2009) and refuted this assumption (mountain goats (Oreamnos americanus): Côté et al., 1998; moose (Alces alces): Swenson et al., 1999). Brooks et al. (2008) tested various weights and fittings of GPS collars on plains zebras (Equus burchelli antiquorum) and found that rate and distance traveled were significantly affected. ...
The use of tracking devices (e.g., VHF radio collars, GPS collars, ear transmitters) enables researchers to assess activity budgets, species-specific movement patterns, effects of environmental enrichment, and exercise levels in zoo animals. The fundamental assumption in these studies of tagged animals is that attachable tracking devices have negligible effects on the animals’ behavior. The present study examined solitary and social behavior rates, as well as overall activity budgets, in eight African elephants living at the San Diego Zoo Safari Park, Escondido, CA, USA. Each elephant was trained over several months to wear leather collars affixed with GPS units encased in watertight plastic containers. Behavioral data collected while the GPS collars were worn (16 daylight hours, 16 night hours) were compared to behavioral data when the GPS collars were not worn (16 daylight hours, 16 night hours) throughout June and July 2010. No significant differences (P < 0.05) in behavior rates or average per
... The extent to which such change may apply to other taxa awaits further investigation. Swenson et al. (1999), Testa (1998), Bowyer et al. (1998, Ballard et al. (1991), Larsen et al. (1989), and Gasaway et al. (1992) Click on thumbnail for full-sized image. ...
Because most large, terrestrial mammalian predators have already been lost from more than 95-99% of the contiguous United States and Mexico, many ecological communities are either missing dominant selective forces or have new ones dependent upon humans. Such large-scale manipulations of a key element of most ecosystems offer unique opportunities to investigate how the loss of large carnivores affects communities, including the extent, if any, of interactions at different trophic levels. Here, we demonstrate a cascade of ecological events that were triggered by the local extinction of grizzly bears ( Ursus arctos) and wolves (Canis lupus) from the southern Greater Yellowstone Ecosystem. These include (1) the demographic eruption of a large, semi-obligate, riparian-dependent herbi- vore, the moose (Alces alces), during the past 150 yr; (2) the subsequent alteration of riparian vegetation structure and density by ungulate herbivory; and (3) the coincident reduction of avian neotropical migrants in the impacted willow communities. We contrasted three sites matched hydrologically and ecologically in Grand Teton National Park, Wyo- ming, USA, where grizzly bears and wolves had been eliminated 60-75 yr ago and moose densities were about five times higher, with those on national forest lands outside the park, where predation by the two large carnivores has been replaced by human hunting and moose densities were lower. Avian species richness and nesting density varied inversely with moose abundance, and two riparian specialists, Gray Catbirds (Dumetella carolinensis) and MacGillivray's Warblers ( Oporornis tolmiei), were absent from Park riparian systems where moose densities were high. Our findings not only offer empirical support for the top-down effect of large carnivores in terrestrial communities, but also provide a scientific rationale for restoration options to conserve biological diversity. To predict future impacts, whether overt or subtle, of past management, and to restore biodiversity, more must be known about ecological interactions, including the role of large carnivores. Restoration options with respect to the system that we studied in the southern Greater Yellowstone Ecosystem are simple: (1) do nothing and accept the erosion of biological diversity, (2) replace natural carnivores with human predation, or (3) allow continued dispersal of grizzly bears and wolves into previously occupied, but now vacant, habitat. Although additional science is required to further our understanding of this and other terrestrial systems, a larger con- servation challenge remains: to develop public support for ecologically rational conser- vation options.
... In other words, we are certain that the research does not have negative effects on the animals that will in turn influence our research results (Powell and Proulx 2003). However, the number of reports suggesting otherwise has grown in recent years, with some of these bringing to question the validity of research results based on widely used techniques (e.g., see Cattet et al. 2008 for methods of capture; and Saraux et al. 2011;Swenson et al. 1999 for methods of marking). their efforts to better understand the animal welfare implications of their studies. ...
Although biologists and veterinarians have shown considerable success in working together to address wildlife-related issues, including disease, chemical immobilization, reproductive biology, and conservation biology, examples of shared efforts to evaluate and ensure the welfare of study animals are mostly absent. I present the case that this deficiency arises primarily from a lack of mutual understanding between fields with respect to the other's training and experience in addressing animal welfare issues. In effect, each assumes that the final word on animal welfare rests with the other. The reality is, however, that neither field contains the knowledge and skills required to address animal welfare concerns alone. Nevertheless, wildlife researchers are increasingly encountering difficulties conducting research on wild animals because of opposition from stakeholders on the basis of animal welfare concerns. Further, a growing number of articles in the peer-reviewed scientific literature are reporting on potential biases in research results developing from the welfare impacts of widely used techniques, including methods of capturing and marking wildlife. By viewing animal welfare as a shared responsibility and combining their knowledge and skills, wildlife biologists and veterinarians have an opportunity to reform "invasive" wildlife research in a manner that is less harmful to the animals being studied, less likely to bias research results, and less objectionable to the stakeholders who ultimately influence or make decisions on how wildlife research is conducted.
... We captured moose calves, marked them with ear tags, and weighed and sexed them. To control for marking and handling effects we randomly assigned litters as non-handled controls between 1990 and 1995 (Swenson et al. 1999). For offspring (i.e., whose mothers had a functioning transmitter, n ϭ 351 calves, Table 1), we had data on mortality and age of the mother (see above). ...
A general prediction for aging placental mammals is that they should show a decline in reproductive value, and reproductive effort is therefore predicted to increase with age. To test this, we monitored known-age radio-collared females of a large ungulate, the moose (Alces alces), in a Swedish population. Female moose showed senescence in reproduction (i.e., litter size) from about 12 yr of age. Further evidence of senescence was a decrease in parental care during summer (expressed as increased offspring mortality) with the mother's age. Moreover, aging females facing a declining reproductive value increased their reproductive effort by giving birth to heavier offspring regardless of litter size. A logistic regression model showed that older moose have to give birth to heavier offspring to achieve the same offspring summer survival as that for offspring of younger mothers. This suggests that females increase their reproductive effort (by increasing offspring mass) as they get older. Furthermore, the rather intense harvest in our population may select for an increased reproductive effort in terms of litter size, which furthermore may select for an earlier onset of senescence in reproductive characters and mortality.
... If a female had given birth, but was found alone before the harvest period, she was always rechecked to confirm the absence of calves. An evaluation and a thorough description of the method used can be found in Swenson et al. (1999). ...
In life history theory one recognises that there is a cost related with all resource allocation. For female moose (Alces alces), the cost of reproduction in terms of survival may be reduced for females if calves, or cows without calves, are selectively hunted during the fall. Cows with calves might experience higher hunting survival and therefore face a reduced trade-off between survival and reproduction. This hypothesis was tested during a seven-year study in northern Sweden. Female age and whether she had given birth or not best explained female moose survival during the hunting period, not the number of calves born or alive at the hunt. Still, the analysis suggests that the cost of reproduction was reduced for middle-aged females. Females not giving birth experienced a 3.2 fold greater risk of being harvested compared to those giving birth. This suggests that the application of life-history theory is crucial to fully understand the evolutionary consequences of management decisions on heavily harvested populations of ungulates.
Key words: hunting, life history, moose, predation, reproduction, selection, survival.
... Thus, these methods may produce unreliable estimates, lack error estimates, and not incorporate individual differences. In addition, Swenson et al. (1999b) recommended not marking moose (Alces alces) calves with ear transmitters, because of increased mortality rates. ...
The recent development in Global Positioning System (GPS) techniques has started a new era in predation studies. Estimates of kill rates based on animal movements and GPS relocation clusters have proven to be valid in several obligatory carnivores. The main focus has been to obtain accurate mean predation estimates for the management of wildlife populations. We present a model to estimate individual kill rates of moose calves by adult female brown bears in Sweden, based on spatiotemporal clustering of 30,889 bear GPS relocations and 71 moose calves verified killed during 714 field investigations in 2004—2006. In this virtually single-predator single large prey system, the omnivorous brown bear is an efficient predator on moose calves up to 4 weeks of age. The top model set only included models with cluster radii of 30 m or 50 m, indicating very high kill-site fidelity. The best model included a cluster radius of 30 m and number of periods of bear activity at the kill site as a single covariate. The mean estimated individual kill rate of 7.6 ± 0.71 (n = 18, x̄ ± SE) moose calves per calving season is comparable to the estimate of 6.8 from a previous study of radio-tracked moose in our study area, though at a lower moose/bear ratio. The mean annual kill rates varied from 6.1 to 9.4 calves per bear. The estimated individual kill rates ranged from 2 to 15 calves per season, indicating a large individual variation in hunting skills and possibly effort. Predation and livestock depredation represent a core conflict between humans and carnivores in rural Scandinavia. Accurate predation estimates represent an important step in quantifying costs of carnivores and reducing human—carnivore conflicts. Our technique may be applied in the exploration of predation mechanisms and predator—prey interactions, and contribute to the old and global debate of problem individuals in livestock depredation.
... Radio tracking technology has been extensively applied to studies of vertebrates, particularly mammals and birds (e.g., Mech, 1980;Koenig et al., 1996;Nakamura and Miyazawa, 1997;Swenson et al., 1999). Recent reductions in transmitter size have allowed these techniques to be applied to invertebrates without attendant loading or behavioural hindrances (Wolcott, 1995). ...
Radio tracking technology has, for many years, been applied successfully to studies of vertebrates, particularly mammals and birds. Recent reductions in transmitter size have enabled these techniques to include invertebrates. However, perhaps because the radio tracking of invertebrates is especially problematic, relatively few studies have been carried out. In particular, there are relatively few radio tracking studies of decapod crustaceans, especially terrestrial species. Here we report the practical use of radio transmitters to track a tropical, amphibious fresh-water land crab, Eudaniela garmani, in the rainforests of the Caribbean island of Tobago. We include a method for gluing tags to the crabs' carapaces which allows individuals to be tracked for periods of up to 12 months.
... Mortality among the radiomarked moose calves (61%) was higher than among unmarked calves (36%; v 2 1 ¼ 5.47, P ¼ 0.02). However, a comparison of mortality among marked and unmarked calves in 5 areas in Sweden, including our area, showed that there was no interaction between marking with ear-tag–mounted transmitters and the presence of bears in the pattern of calf mortality (Swenson et al. 1999b). Thus, we could estimate the real predation rate on moose calves by bears to be the total mortality rate among unmarked calves times the ...
In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km2 and 920/1,000 km2, respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%.
... We captured moose calves, marked them with ear tags, and weighed and sexed them. To control for marking and handling effects we randomly assigned litters as non-handled controls between 1990 and 1995 (Swenson et al. 1999). For offspring (i.e., whose mothers had a functioning transmitter, n 351 calves,Table 1), we had data on mortality and age of the mother (see above). ...
We tested whether the ungulate moose (Alces alces) showed senescence in survival. Senescence, i.e., a progressive deterioration with age, may be obscured by multiple mortality causes in a wild population. Thus, we followed radio-marked individuals of known age to separate different mortality causes in adult moose. The risk of dying of causes not linked to humans increased with age. For females, the increase in natural mortality was first observable after age 10. Tooth wear was significantly related to age for both sexes, but was stronger for males. It suggests that males would experience senescence in survival earlier than females in a non-hunted population. The senescence in mortality observed for female moose may be a result of delayed cost of reproduction acting in concert with tooth wear due to a reduced ability to process food. We also found an increase in hunting mortality with age for both sexes, with males facing a higher risk of dying than females. The age-related hunting mortality may be a result of selectivity by the human predator, or a change in moose behaviour with age.
... We considered this assumption to be reasonable for our case, as several independent studies from the same ecological system found no evidence of relevant compensation between predation, human harvest and other causes of natural mortality in the two prey species (Nilsen & Solberg 2006; Andersen et al. 2007; Nilsen et al. 2009a). In Norway, roe deer survival was 35% lower in environments with human harvest and large predators (Nilsen et al. 2009a), compared to areas where both these factors were absent (Cobben et al. 2009), and Swenson et al. (1999) found that moose calves in areas with and without brown bears in Sweden had the same probability of dying because of other reasons than predation. Following Nilsen et al. (2009b), who included the effect of lynx social status on per capita kill rates, lynx functional response was calculated separately for solitary individuals and family groups, thus accounting for the higher kill rates by females with kittens. ...
1. Understanding the role of predation in shaping the dynamics of animal communities is a fundamental issue in ecological research. Nevertheless, the complex nature of predator–prey interactions often prevents researchers from modelling them explicitly.
2. By using periodic Leslie–Usher matrices and a simulation approach together with parameters obtained from long-term field projects, we reconstructed the underlying mechanisms of predator–prey demographic interactions and compared the dynamics of the roe deer–red fox–Eurasian lynx–human harvest system with those of the moose–brown bear–gray wolf–human harvest system in the boreal forest ecosystem of the southern Scandinavian Peninsula.
3. The functional relationship of both roe deer and moose λ to changes in predation rates from the four predators was remarkably different. Lynx had the strongest impact among the four predators, whereas predation rates by wolves, red foxes, or brown bears generated minor variations in prey population λ. Elasticity values of lynx, wolf, fox and bear predation rates were −0·157, −0·056, −0·031 and −0·006, respectively, but varied with both predator and prey densities.
4. Differences in predation impact were only partially related to differences in kill or predation rates, but were rather a result of different distribution of predation events among prey age classes. Therefore, the age composition of killed individuals emerged as the main underlying factor determining the overall per capita impact of predation.
5. Our results confirm the complex nature of predator–prey interactions in large terrestrial mammals, by showing that different carnivores preying on the same prey species can exert a dramatically different demographic impact, even in the same ecological context, as a direct consequence of their predation patterns. Similar applications of this analytical framework in other geographical and ecological contexts are needed, but a more general evaluation of the subject is also required, aimed to assess, on a broader systematic and ecological range, what specific traits of a carnivore are most related to its potential impact on prey species.
... Studies on avian taxa have shown that radiotagging may alter behavior (Pietz et al. 1993), body condition (Greenwood and Sargeant 1973), reproduction (Rotella et al. 1993, Paquette et al. 1997, or survivorship (Gammonley and Kelley 1994). Radiotagged mammals might have reduced activity levels (Mikesic and Drickamer 1992) and survivorship (Swenson et al. 1999). While the effects of radiotransmitter attachment have been documented on avifauna and mammals (see Withey et al. 2001 for review), few studies have examined effects on turtles (but see Boarman et al. 1998 for review). ...
The increased use of radio-telemetry for studying movement, resource selection, and population demographics in reptiles necessitates closer examination of the assumption that radiotransmitter attachment does not bias study results. We determined the effects of radiotransmitter attachment on fecal glucocorticoid metabolite levels of wild three-toed box turtles (Terrapene carolina triunguis) in captivity. During May 2002 we captured 11 adult three-toed box turtles in central Missouri. We housed turtles in individual pens in a semi-natural outdoor setting. We radio-tagged 6 turtles, and the remaining 5 turtles served as controls. We captured and handled all turtles similarly during treatments. We collected feces daily prior to attachment (14 June–05 July 2002), while transmitters were attached (06 July–02 August 2002), and after transmitters were removed (03 August–24 August 2002). We conducted a standard assay validation and found that the assay accurately and precisely quantified fecal glucocorticoid metabolites of box turtles. We did not find a significant effect of radiotransmitter attachment on fecal glucocorticoid metabolite levels of three-toed box turtles (F1, 9 =0.404, P=0.541). Fecal glucocorticoid metabolite levels of control and treatment turtles increased significantly during the study (F2,166=7.874, P= 0.001), but there was no treatment:period interaction (F2,166 = 0.856, P = 0.427). Additionally, we did not find a significant relationship between glucocorticoid metabolite levels and time in captivity (r2=0.01, F1,179=2.89, P=0.091) or maximum daily temperature (r2
Vaginal implant transmitters (VITs) are a popular tool in ungulate parturition studies and have been used in moose ( Alces alces ), but their potential impact on animal performance has not been thoroughly assessed. We looked at potential short‐term impacts of VIT use on maternal condition through assessments of neonate calf mass, early calf survival, and parturition date. We also assessed long‐term impacts of VIT use on future reproduction and the inflammatory response after prolonged VIT retention through qualifying discharge at VIT removal and measures of acute phase proteins haptoglobin and ceruloplasmin. We captured 54 neonates and assessed over 900 potential parturition events of 278 adult moose over multiple years and we did not detect any evidence of a negative impact of VIT use on neonate calf mass, parturition date, or future reproduction. We did find elevated haptoglobin and ceruloplasmin levels in non‐pregnant individuals that had unintentional VIT retention past parturition, but this was not universal across all cases. We found a potential negative impact of VIT use on early calf survival which was likely driven by biased sampling. A bias can exist (i.e., left truncation) if sampling is mixed between cows that had a VIT (and, therefore, a known parturition time) and those without a VIT that were sampled opportunistically. Future evaluations need to overcome this bias when assessing early calf survival. With that caveat, we did not detect clear negative impacts of VIT use on moose and recommend late winter to early spring VIT insertion in pregnant females to minimize retention time.
Hirveä voidaan pitää monella tavalla maamme merkittävimpänä riistaeläimenä. Riistasaaliin laskennallisella arvolla mitattuna hirvisaaliin arvo kattaa noin kaksi kolmasosaa koko riistasaaliin arvosta Suomessa ja hir-venmetsästyksellä on merkittävä virkistysarvo ja sosiaalinen merkitys. Haittoja hirvi aiheuttaa liikenteessä hirvionnettomuuksina, joissa koetaan myös henkilövahinkoja. Hirvi aiheuttaa ravinnonkäyttönsä vuoksi vahinkoja myös maa- ja metsätaloudelle. Hirvellä on lisäksi merkittävä vaikutus suomalaisessa ekosystee-missä oman valikoivan ravinnon käyttönsä kautta sekä suurpetojen ravintona.
Hirvikannan koko oli 1900-luvun alussa vain muutaman tuhannen yksilön luokkaa ja metsästys vähäistä tai kokonaan kiellettyä. Hirvikannan elpyminen ja saalismäärien kasvu käynnistyivät 1950-luvulla, säilyen kui-tenkin vaatimattomalla tasolla. 1970-luvulla omaksuttu uudenlainen verotusmalli ja runsaat ravintovarat johtivat kannan tuottavuuden nousuun ja hirvimäärän nopeaan kasvuun kokonaan uudelle tasolle. Hirvikantaa pienennettiin, kunnes 1990-luvun lopulla kanta kääntyi jälleen voimakkaaseen kasvuun ja saavutti ennennäkemättömän korkean tason 2000-luvun alussa. Korkea kanta johti runsaisiin vahinkoihin ja kantaa pienennettiin voimakkaalla metsästyksellä. Nykyistä hirvikannan säätelyjärjestelmää kohtaan on esitetty kritiikkiä mm. sen vuoksi, että hirvikannan koko on vaihdellut voimakkaasti ja johtanut vuoroin voimakkaas-ti kasvaneen kannan myötä kärjistyneeseen vahinkotilanteeseen ja vuoroin tavoiteltua pienempään kan-taan ja paikallisiin hirvityhjiöihin. Hirvikannan hoitoon liittyviä keskeisimpiä kysymyksiä on pitkään ollut hirvikannan sopiva koko sekä se miten ja millä perusteilla kannan hoidon tavoitteet tulisi asettaa.
Hirvikannan hoitosuunnitelma luo pohjan tulevalle hirvikannan hoidolle ja hoitosuunnitelman avulla pyri-tään osaltaan toteuttamaan julkisen riistakonsernin strategiassa määritellyt tavoitteet. Hoitosuunnitelmat ovat olennainen osa julkisen riistakonsernin strategiaa ja keskeisiä välineitä riistapolitiikan toimeenpanossa. Maa- ja metsätalousministeriö johtaa hoitosuunnitelmatyötä ja Suomen riistakeskus vastaa hoitosuunni-telmien valmistelusta, seurannasta ja päivittämisestä. Valtakunnallinen ja alueelliset riistaneuvostot osallistuvat hoitosuunnitelmien laadintaan ja riistaneuvostojen tehtävänä on muun muassa järjestää sidosryhmi-en osallistava kuuleminen.
Hirvikannan hoitosuunnitelman valmistelu aloitettiin vuonna 2011 ja valmisteluun tarjottiin eri tahoille laajat osallistumismahdollisuudet. Syksyllä 2011 ja keväällä 2012 alueelliset riistaneuvostot kutsuivat kaikil-la alueilla hirveen liittyvät eri tahot sidosryhmätilaisuuksiin esittämään näkemyksiään hirvikannan hoidosta ja työstämään alustavia esityksiä. Tilaisuuksiin osallistui yhteensä noin 340 eri tahojen edustajaa mm. maa- ja metsätaloutta ja maanomistajia edustavista järjestöistä, metsästyksen vapaaehtoisjärjestöistä ja riistan-hoitoyhdistyksistä, liikenteen, luonnonsuojelun, maaseudun kehittämisen järjestöistä, ja viranomaisista
sekä tutkimuslaitoksista. Syksyllä 2011 järjestettiin lisäksi kaikille kansalaisille tarkoitettu hirvikysely, johon saatiin noin 4500 vastausta. Osallistamistoimissa kertynyt aineisto muodosti keskeisen taustan hoitosuunnitelman linjauksille ja toimenpide-ehdotuksille.
Hirvikannan hoitosuunnitelma on kaksiosainen. Ensimmäisessä osassa kuvataan hirveä koskevaa säädös- ja sopimustaustaa, hirven biologiaa ja hirvikannan tilaa, hirvikannan säätelyä sekä hirvikannan vaikutuksia ajantasaisten tutkimustulosten, kirjallisuuden ja tilastojen valossa. Toinen osa on varsinainen toimenpide-osa, jossa esitellään hirvikannan hoitoon liittyviä linjauksia ja toimenpide-ehdotuksia taustoituksineen. Hoitosuunnitelmassa esitettyjen toimenpiteiden toteuttamisen tärkeysjärjestystä, aikataulua ja toteutusvastui-ta tarkastellaan julkisen riistakonsernin strategiaprosessissa.
Hirvikannan hoitosuunnitelmassa esitettyjen linjausten ja toimenpiteiden avulla on tavoitteena saavuttaa vakaa ja rakenteellisesti tasapainoinen hirvikanta. Hirvikannan hoidon tavoiteasettelussa esitetään siirtymistä alueellisen tavoiteasettelun malliin, millä pyritään alueellisten erityispiirteiden parempaan huomioon ottamiseen sekä eri tahojen vaikuttamismahdollisuuksien parantamiseen hirvikannan hoidossa. Tavoitteena on joustavien toimintamallien edistäminen, mikä lisää osaltaan pyyntiluvansaajien paikallista harkintavaltaa ja –vastuuta hirvikannan hoidossa. Kattavalla ja luotettavalla hirvitiedolla on tärkeä merkitys kannan säätelyssä ja sen onnistumisen seurannassa. Hirvitiedon ajantasaisuutta ja hyödynnettävyyttä on tavoitteena parantaa mm. sähköisten tietojärjestelmien kehittämisen avulla. Hoitosuunnitelmassa esitetyillä toi-menpiteillä on lisäksi tavoitteena edistää hirven ja suurpetojen välisen vuorovaikutuksen huomi-oon ottamista, samoin kuin edistää hirvestä saatavaa hyvinvointia ja metsästyksen jatkuvuutta. Hoitosuunnitelmassa esitetyillä toimenpiteillä on tavoitteena ennaltaehkäistä hirven liikenteelle sekä metsä-, maa- ja porotaloudelle aiheuttamia vahinkoja ja parantaa hirvivahinko- ja onnettomuustiedon tarkkuutta ja hyödynnettävyyttä.
Wildlife diseases have become increasingly important recently due to their effect upon human health, veterinary medicine, wildlife, and conservation biology. Gary Wobeser's successful book from 1994 has been completely updated and enlarged in a new second edition. An in-depth overview of the available techniques for the investigation and management of disease in free-ranging animals is provided. The subjects are illustrated with examples drawn from around the world, with emphasis on the special requirements involved in working with wild animals. Techniques are assessed critically with regard to their efficacy and effectiveness. The book draws on the author's training as a wildlife biologist and veterinarian and his experience over four decades with wildlife disease. From the reviews of the first edition ". has done an admirable job of outlining the problems associated with diagnosing and controlling disease in wildlife populations. The author has commendably presented a difficult topic and has shown that the usually successful approach to treating disease in domestic animals is extremely difficult and rarely successful in wildlife populations. I recommend this book to all who are looking for an introduction to the investigation and managment of disease in wildlife." (Canadian Veterinary Journal)". the author has made a major contribution to the field by providing a conceptual framework for wildlife disease investigations and by highlighting the inadequacies that often exist. His willingness to challenge dogma and constructively present perspectives based on a combination of extensive literature review, personal experiences, and beliefs is one of the values of this well organized and easy to read publication. this publication should be read by biologists, administrators, and disease specialists having responsibility for combatting disease in populations of free-living wildlife." (Journal of Wildlife Diseases)
We used radio-collared individuals to examine the seasonal, annual, and regional variation in age-specific survival of moose (Alces alces) in three populations (Vega, Beiarn, and Troms) in northern Norway. In the two populations subject to a regular hunt, the annual mortality from hunting was higher, on average, than that from natural mortality for adult cows. In these study areas, the hunting mortality rate was higher for calves than for cows. For both age groups there was significant annual variation in hunting mortality, which was associated with differences in quota size among years. The survival rate of adult cows was high outside the hunting season (96%). There was seasonal variation in survival among calves, the highest significant mortality being found among neonates during summer in Vega and Troms and significantly higher mortality being found during winter in Beiarn. The natural mortality of calves differed significantly among regions during both summer and winter. The combined effects of density dependence, changes in age structure, and environmental stochasticity may explain this variation in calf-survival rate. In contrast, no significant seasonal or regional variation occurred in the survival rate of adult females.
The capture and handling of live European wild rabbits (Oryctolagus cuniculus) are unavoidable initial steps for immunization by vaccination against viral hemorrhagic disease (VHD) and myxomatosis as a management tool aimed at enhancing wild rabbit populations. We investigated the short-term effects of vaccination campaigns against VHD and myxomatosis on the survival of 206 European wild rabbits in a Spanish population. While no effect was observed on the survival of adult rabbits, young and subadult rabbits (P < 0.001) had higher mortality rates during the first week after handling than in the subsequent 3 weeks. The hazard rate of death from disease was inversely correlated with body condition (P < 0.001) during the first week. Vaccination increased the hazard rate of death due to disease during the first 7 days post-handling, although this detrimental effect was higher in young rabbits (P = 0.012) and modulated by body condition (P = 0.004). The hazard rate of dying from predation during the first week was higher for males than females (P = 0.023) and in subadults compared to young rabbits (P = 0.004). Body condition was inversely related to the predation hazard rate (P = 0.002). Our results suggest that vaccination campaigns had a short-term negative impact caused by the stress of handling in addition to the detrimental effects of vaccination against VHD and myxomatosis. Future studies should consider this negative impact to assess the true efficacy of vaccination campaigns in wild populations.
Survival estimation is an important aspect of population ecology and conservation biology, and radiotelemetry is a major tool for assessing factors influencing survival time in free-ranging birds and mammals. Despite the advantage of telemetry in providing extensive and continuous survival information, telemetry-based survival estimates can be biased or imprecise when methods are misused. Simple cumulative survival estimators like the Heisey and Fuller and Kaplan-Meier methods have underlying assumptions and sampling requirements that commonly remain unverified by researchers. Telemetry studies often limit survival analysis to simple univariate tests that do not consider the range of factors potentially influencing mortality risk in free-ranging animals. Continuous-time modeling approaches like Cox Proportional Hazards or Anderson-Gill methods, or their discrete-time analogues, are superior because they are robust to a range of study design limitations and can handle multiple categorical or continuous covariates including those that vary with time or subject age. Parametric models may be difficult to fit in telemetry studies because the appropriate hazard function in wildlife populations usually is not known. The main assumptions in survival study design are that 1) subjects represent the population of interest, 2) mortality risk is independent between subjects, and 3) subjects are lost to follow-up (i.e., censored) randomly. These assumptions are prone to violation in telemetry research, and their assessment and possible remediation should be prioritized. Telemetry studies often are characterized by small sample size or short duration; both attributes lead to low numbers of mortalities and thus lack of precision in the survival estimate. I conclude that telemetry-based survival estimation will benefit from increased emphasis on modeling approaches designed to elucidate survival determinants in complex systems, combined with more rigorous attention to basic assumptions and study design limitations.
Reproductive technology, especially the diagnosis of pregnancy by radioimmunoassay of fecal steroid metabolites, is an important component of captive propagation, but its role in our understanding of ecological interactions and in situ biological restoration has been more limited. Where large herbivores have been “released” from predation by the extirpation of carnivores, controversy often exists about possible detrimental effects at the ecosystem level. A related concern is that the reestablishment of large carnivores may decrease the availability of prey populations for human subsistence. We suggest that pregnancy assays can be a valuable tool to help distinguish between the roles of predation versus food-imposed limitations on population size and their effects on juvenile recruitment in wild species. We explored this issue through analyses of fecal progestagen concentration ( FPC) levels to document pregnancy in moose (Alces alces) in the southern Greater Yellowstone Ecosystem, a site where wolves (Canis lupus) and grizzly bears ( Ursus arctos) are recolonizing former habitats after an absence of more than 60 years. Pregnancy was clearly discernible (mean FPC for pregnant and nonpregnant females, respectively: 10.60 vs. 2.57 μg/g; p < 0.0001). Among the potential confounding variables that need to be considered if FPC is applied to ecological and demographic questions are whether baseline values are affected by handling, whether neonate survival has been assessed, and whether sampling efforts are directed at both pregnant and nonpregnant animals. With these issues accounted for, the local moose population experienced juvenile survival rates among the highest in North America. Pregnancy rates, however, dropped from 90% in 1966 to about 75% today, rendering them in the lowest fifteenth percentile among moose populations in North America. Our findings suggest that a relatively low frequency of juvenile moose is not the likely result of predation, and they illustrate how endocrinology can be applied to issues involving reproductive events within an ecological context. They also affirm that noninvasive and generally inexpensive endocrinological procedures will be applicable to understanding interactions between recolonizing predators and prey, an issue that will continue to arise because of global restoration efforts, and to the study of rare ungulates in remote systems where data on reproductive events are difficult to obtain.
Resumen: La tecnología reproductiva, especialmente el diagnóstico de embarazo por radioinmunoensayo de metabolitos fecales es un componente importante de la progación en cautiverio, pero su papel en el entendimiento de interacciones ecológicas y en restauraciones biológicas in situ ha estado mas limitado. En sitios donde se he “liberado” a herbívoros grandes mediante la extirpación de carnívoros, se presentan frecuentemente controversias sobre los posibles efectos negativos a nivel de econsistema. Una preocupación relacionada es que el re-establecimineto de carnívoros grandes podría disminuir la viabilidad de poblaciones de presas para subsistencia humana. Nosotros sugerimos que los análisis de preñez pueden ser una herramienta valiosa para ayudar a distinguir entre los papeles de depredación contra limitaciones de alimento impuestas en el tamaño poblacional y sus efectos en el reclutamiento de juveniles en poblaciones silvestres. Exploramos este tema mediante el análisis de niveles de concentración de progestágenos fecales ( FPC) para documentar embarazos en alces (Alces alces) en el ecosistema sureño del gran Yellowstone, un sitio donde los lobos (Canis lupus) y osos grizzly ( Ursus arctos) estan recolonizando hábitats anteriormente usados, después de una ausencia de mas de 60 años. El embarazo fué claramente discernible (FCP promedio pra hembras preñadas y no preñadas respectivamente: 10.6 vs 2.57 mg /g; p < 0.001). Entre las variables potencialmente confundentes que necesitan ser consideradas si el FCP es aplicado en situaciones ecológicas y demográficas estan el saber si los valores base son afectados por el manejo, evaluar la supervivencia de neonatos y dirijir los esfuerzos de muestreo tanto a animales preñados como no preñados. Con estos aspectos tomados en consideración, la población local de alces ha experimentado tasas de supervivencia de juveniles entre las mas altas de Norteamérica. Sin embargo, las tasas de embarazo disminuyeron de un 90% en 1966 a cerca de 75% actualmente, colocándolas en el quinceavo percentil mas bajo entre las poblaciones de alces de Norteamérica. Nuestros resultados sugieren que la relativamente baja frecuencia de alces juveniles no es una posible causa de la depredación, e ilustran como la endocrinología puede ser aplicada en asuntos relacionados con eventos reproductivos dentro de un contexto ecológico. Esto también afirma que los procedimientos endocrinológicos no invasivos y generalmente baratos pueden ser aplicados para: Entender las interacciones entre depredadores recolonizando y sus presas, un asunto que continuará sugiendo debido a los esfuerzos globales de restauración, y el estudio de ungulados raros en sistemas remotos donde los datos de eventos reproductivos son dificiles de obtener.
The current extinction of many of Earth's large terrestrial carnivores has left some extant prey species lacking knowledge
about contemporary predators, a situation roughly parallel to that 10,000 to 50,000 years ago, when naı̈ve animals first encountered
colonizing human hunters. Along present-day carnivore recolonization fronts, brown (also called grizzly) bears killed predator-naı̈ve
adult moose at disproportionately high rates in Scandinavia, and moose mothers who lost juveniles to recolonizing wolves in
North America's Yellowstone region developed hypersensitivity to wolf howls. Although prey that had been unfamiliar with dangerous
predators for as few as 50 to 130 years were highly vulnerable to initial encounters, behavioral adjustments to reduce predation
transpired within a single generation. The fact that at least one prey species quickly learns to be wary of restored carnivores
should negate fears about localized prey extinction.
Reviews information concerning marking-induced abandonment of wild, newborn North American ungulates to: 1) alert biologists of these occurrences, 2) present methods to minimize these losses, 3) encourage use of these methods, 4) emphasize the importance of including these mortalities in data analysis, and 5) motivate consideration and testing of the suspended causes of marking-induced abandonment. Abandonment is the permanent separation of mother and young causing the death of the young. Newborn ungulates abandoned by their dams ≤1 day after marking (ear-tagging or radio-tagging) are considered here to be abandoned due to marking. -from Author
Because of scientific, management, and ethical considerations, it is important to know if capture and handling of neonatal ungulates increases their mortality risk. At the National Bison Range in northwestern Montana, where coyotes annually kill many young, I captured and marked young pronghoms (Antilocapra americana) in most years from 1981 to 1996 and recorded the number that were bom and the number that survived to weaning each year. Mortality of young was ≥56% in all years, and the number of coyotes removed from the range of pronghorns in May and June was significantly correlated with the percentage of young that survived. Capture effort varied from none to intense among years, and not all young were captured in any year. I found no evidence that mortality risk was increased due to handling. With proper precautions, one may handle young pronghoms without exposing them to additional risk.
We recorded recovery rates for 300 adult female ring-necked pheasants (Phasianus colchicus) and 150 juveniles (82 M, 68 F) marked with 2 different dummy radio tags or leg bands. Birds with backpack tags in all age and sex categories disappeared more quickly and were recovered by shooting or trapping less often than birds with necklace tags or with leg bands (P < 0.05 for juv and ad F). Survival was not affected by weight of necklaces (15 or 25 g) or by the color of the backpacks (white or brown). Necklace radio tags, at 2-3% of body weight, are more suitable than backpacks for studies of pheasant survival.
We assessed effects of radio collars on survival of Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) in western Idaho during 1983-86. Thirty-eight grouse were colorbanded and equipped with radio collars, and 9 were colorbanded only. Four nonradioed grouse were the only marked birds resighted 1 year following capture. Radio collars did not restrict flight but altered the appearance, sound in flight, and perhaps the behavior of grouse. Avian predators caused most of the mortality and probably preyed on radio-collared birds selectively. Timing of mortality coincided with spring and autumn dancing periods, presence of northern goshawks (Accipiter gentilis) in the study area, and seasonal lows in vegetative cover. Despite poor survival of radio-collared grouse, we detected no decline in the population.
The estimation of survival distributions for animals which are radio-tagged is an important current problem for animal ecologists. Allowance must be made for censoring due to radio failure, radio loss, emigration from the study area and animals surviving p88l. :~the end of the study period. First we show that the Kaplan-Meier .procedure wid~ly used in medical and engineering studies can be applied to this problem. An example using some quail data is given for illustration. As radios maItunction -or are lost, new radio-tagged animals have to be added to the study. We show how this modification can easily be incorpor~.ted inf.<? the basic Kaplan-Meier procedure. Another example using quail data is used to illustrate the extension. We also show how the log rank test commonly used to compare two survival distributions can be generalized to allow for additions. Simple computer programs which can be run on a PC are available from the authors.