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Landscape patterns of ocelot–vehicle collision sites

Authors:
Annmarie Blackburn at Texas A&M University - Kingsville
Annmarie Blackburn
Jane Anderson at Smithsonian Institution
Jane Anderson
Amanda M. Veals Dutt at Sul Ross State University
Amanda M. Veals Dutt
Michael Tewes at ROSEN Group
Michael Tewes
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Context Road networks can negatively impact wildlife populations through habitat fragmentation, decreased landscape connectivity, and wildlife-vehicle collisions, thereby influencing the spatial ecology and population dynamics of imperiled species. The ocelot (Leopardus pardalis) is a federally endangered wild felid in South Texas, with a high mortality rate linked to vehicle collisions. Objectives Using a multi-scale approach, we quantified and examined landscape spatial structure at ocelot roadkill locations, and between roadkill locations of male and female ocelots. Methods We quantified the spatial distribution of land cover types at 26 ocelot–vehicle collision sites in South Texas that occurred from 1984–2017. We compared landscape metrics of woody, herbaceous, and bare ground cover types across multiple spatial scales at roadkill locations to those from random road locations, and between male and female ocelots. Results Roadkill sites consisted of 13–20% more woody cover than random locations. Woody patches at roadkill sites were 7.1–11% larger (2.4 ha) closer to roads and spaced 10–16 m closer together farther away from roads compared to random locations. Percent woody cover was the best indicator of ocelot–vehicle collision sites; there were no differences in woody cover between male and female road mortality locations. Conclusion These findings suggest that ocelots are likely struck by vehicles while crossing between habitat patches. Roads that bisect areas of woody cover have negative impacts on ocelots by increasing habitat fragmentation and vulnerability to vehicle collisions. Crossing structures should be placed in areas with ≥ 30% woody cover and 3.5 ha woody patches.
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RESEARCH ARTICLE
Landscape patterns of ocelot–vehicle collision sites
AnnMarie Blackburn .C. Jane Anderson .Amanda M. Veals .
Michael E. Tewes .David B. Wester .John H. Young Jr. .Randy W. DeYoung .
Humberto L. Perotto-Baldivieso
Received: 15 May 2020 / Accepted: 6 November 2020 / Published online: 17 November 2020
ÓSpringer Nature B.V. 2020
Abstract
Context Road networks can negatively impact wild-
life populations through habitat fragmentation,
decreased landscape connectivity, and wildlife-vehi-
cle collisions, thereby influencing the spatial ecology
and population dynamics of imperiled species. The
ocelot (Leopardus pardalis) is a federally endangered
wild felid in South Texas, with a high mortality rate
linked to vehicle collisions.
Objectives Using a multi-scale approach, we quan-
tified and examined landscape spatial structure at
ocelot roadkill locations, and between roadkill loca-
tions of male and female ocelots.
Methods We quantified the spatial distribution of
land cover types at 26 ocelot–vehicle collision sites in
South Texas that occurred from 1984–2017. We
compared landscape metrics of woody, herbaceous,
and bare ground cover types across multiple spatial
scales at roadkill locations to those from random road
locations, and between male and female ocelots.
Results Roadkill sites consisted of 13–20% more
woody cover than random locations. Woody patches at
roadkill sites were 7.1–11% larger (2.4 ha) closer to
roads and spaced 10–16 m closer together farther
away from roads compared to random locations.
Percent woody cover was the best indicator of
ocelot–vehicle collision sites; there were no differ-
ences in woody cover between male and female road
mortality locations.
Conclusion These findings suggest that ocelots are
likely struck by vehicles while crossing between
habitat patches. Roads that bisect areas of woody
cover have negative impacts on ocelots by increasing
habitat fragmentation and vulnerability to vehicle
collisions. Crossing structures should be placed in
areas with C30% woody cover and 3.5 ha woody
patches.
Keywords Landscape ecology Multi-scale spatial
analyses Ocelot Wildlife-vehicle collisions
Wildlife crossing structures
Introduction
Roads can negatively impact survival and movements
of wildlife, including reptiles and amphibians (Marsh
et al. 2005; Shephard et al. 2008), birds (Laurance
et al. 2005), and mammals (Oxley et al. 1974; Groot
Bruinderink and Hazebroek 1996). Negative impacts
A. Blackburn (&)C. J. Anderson
A. M. Veals M. E. Tewes D. B. Wester
R. W. DeYoung H. L. Perotto-Baldivieso
Caesar Kleberg Wildlife Research Institute, Texas A&M
University-Kingsville, 700 University Boulevard, MSC
218, Kingsville, TX 78363, USA
e-mail: annmarieblackburn8@gmail.com
J. H. Young Jr.
Environmental Affairs Division, Texas Department of
Transportation, 125 E. Street, Austin,
TX 78701, USA
123
Landscape Ecol (2021) 36:497–511
https://doi.org/10.1007/s10980-020-01153-y(0123456789().,-volV)(0123456789().,-volV)
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... By identifying differences in habitat selection between ocelots and bobcats, we can better understand how coexistence is facilitated and, ultimately, improve conservation of a threatened, native carnivore. In addition, understanding the factors that influence nocturnal movement can potentially improve recovery and conservation efforts to minimize the impact of vehicle collisions, the largest source of mortality for Texas ocelots [32,33]. ...
... Identifying the abiotic factors that influence movement and habitat selection are essential to understanding the ecology of a species and can provide insight into interspecific coexistence, foraging ecology, and recovery efforts for endangered species such as the ocelot. Our results may also have applications for wildlife-road ecology studies, wherein lunar periods of higher movement may influence the timing and where species successfully cross roadways [33] or succumb to vehicle-collisions [32,[56][57][58]. In the case of ocelots, understanding the factors that influence movement can play a vital role in management by better identifying periods of higher movement which may influence ocelot-vehicle collisions, an important source of mortality for Texas ocelots [32]. ...
... Our results may also have applications for wildlife-road ecology studies, wherein lunar periods of higher movement may influence the timing and where species successfully cross roadways [33] or succumb to vehicle-collisions [32,[56][57][58]. In the case of ocelots, understanding the factors that influence movement can play a vital role in management by better identifying periods of higher movement which may influence ocelot-vehicle collisions, an important source of mortality for Texas ocelots [32]. As such, darker nights may be particularly high-risk for vehicle collisions due to decreased visibility and higher movement rates of ocelots. ...
Ocelots in the moonlight: Influence of lunar phase on habitat selection and movement of two sympatric felids
Article
Full-text available
Various landscape and environmental factors influence animal movement and habitat selection. Lunar illumination affects nocturnal visual perception of many species and, consequently, may influence animal activity and habitat selection. However, the effects of varying moon stage may differ across taxa. Prey species often reduce activity during highly visible periods of night while predators may increase activity or alter their habitat use. Ocelots ( Leopardus pardalis ) and bobcats ( Lynx rufus ), two nocturnal predatory felids that coexist in southern Texas, may also alter their behavior in response to the phase of the moon. To evaluate the effects of lunar phase on habitat selection of ocelots and bobcats, we executed a step selection analysis using high-frequency GPS-telemetry data collected on each species (ocelot, N = 8; bobcat, N = 13) in southern Texas during 2017–2021 and compared step length during new versus full moons. We predicted that ocelots would increase use of dense thornshrub to reduce their visibility during a full moon. However, as bobcats are habitat generalists and are more active during crepuscular periods, we predicted less influence of moon phase on activity. Ocelots did not alter habitat selection in response to lunar phase but moved shorter distances during full moon phases. Conversely, bobcats selected for greater vegetation cover during full moons, possibly to facilitate hunting during brighter periods, but exhibited no difference in movement across lunar phase. We provide, to our knowledge, the first example of habitat selection by predators in relation to lunar phase and show differences across new versus full moons by ocelots and bobcats such that ocelots alter step length but not habitat selection while bobcats altered habitat selection but not step length in response to shifting lunar phase. Further, we suggest the high potential for ocelot-vehicle collisions on darker nights due to increased movement by ocelots and poor visibility for drivers.
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... In carnivores, the European wildcat (Felis sylvestris) showed decreased habitat use and avoidance in areas within 200 m of roadways (Klar et al. 2008). Blackburn et al. (2021a) assessed the scale of effect of ocelot (Leopardus pardalis) road mortality locations and random sites and found that land cover beyond 1050 m only had significant effects with patches that were closer together. Knowledge of the extent of the REZ and the spatial arrangement of land cover types within the REZ has powerful implications for understanding where species successfully traverse roads and where they succumb to road mortalities. ...
... Road mortalities enhance the negative effects of decreased gene flow, limited connectivity, recruitment, and dispersal of wildlife species (van der Ree et al. 2015). Wildlife-vehicle mortalities have often been linked to areas near vegetative cover , spatial aggregations of habitat patches (Main and Allen 2002), and landscape structure of vegetative cover (Blackburn et al. 2021a). Understanding differences in spatial arrangements of locations where wildlife species successfully traverse roads compared to wildlife-vehicle observations is important to mitigate future mortality (Neumann et al. 2012) and help inform placement of wildlife crossing structures. ...
... Over the last 20 years, evidence has grown of the importance of incorporating landscape structure and landscape metrics in understanding of effects of rapid urbanization on woody cover (Lombardi et al. 2020), ocelot habitat use (Jackson et al. 2005;Lombardi et al. 2021), and road ecology in southern Texas (Blackburn et al 2021a(Blackburn et al , 2022Schmidt et al. 2020;Veals et al. 2022a, b). Ocelots in large private ranchlands devoid of highways use large, low-density patches of live oak (Quercus virginiana) forest and thornshrub with lower shape indices and high aggregations (Lombardi et al. 2021). ...
Examining the Spatial Structure of Woody Cover Within a Highway Road Effect Zone for Ocelots in Texas
Article
Full-text available
  • May 2023
  • Urban Ecosyst
Assessment of locations where wildlife species cross highways is a key question in mitigating future wildlife-vehicle mortality. Examination of the spatial structure, complexities, and patterns of vegetation or other land-use types (i.e., cropland, urban areas) near roadways allows scientists to identify any thresholds that influence where animals are likely to die or successfully cross the roadway. We used a historic 1982 to 2017 dataset of ocelot (Leopardus pardalis pardalis) mortality locations and approximate road crossing locations of telemetered ocelots in the Lower Rio Grande Valley in Texas to examine the spatial structure of woody vegetation within a hypothesized road effect zone. We determined if there were differences in the spatial structure of woody cover within a 1050 m buffer of each successful crossing and roadkill location using PERMANOVA and principal component analyses. We used a similarity percentages analysis to determine the relative contribution of each aspect of spatial structure on differences in successful crossing and roadkill locations. We found statistically significant differences in spatial attributes of patches at the locations of successful crossing versus roadkill locations of ocelots at the 150 m spatial extent (pseudo-F 1,41 = 4.85, P(perm) = 0.008, permutations = 9949). Largest patch index contributed most to the differences between successful crossing and roadkill locations (15.94%), followed by mean patch area (15.44%), percent woody cover (15.18%), aggregation indices (14.53%), Euclidean nearest neighbor (13.47%), edge (13.08%) and patch densities (12.36%). Roadkill locations were clustered in locations with lower-quality woody cover within 300 m of the highway. This suggests areas immediately surrounding roads need to contain woody patches that are larger and closer together to reduce the barrier-effects of roads. Such information is important for informing highway planners about where to encourage crossings or to build wildlife crossing structures to promote movement across the highway.
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... This area hosts the only known breeding populations in the US (Tewes and Everett 1986;Janečka et al. 2011), with a majority of high-quality habitat occurring on private lands . Ocelots are considered forest cover specialists across their geographic range (Cruz et al. 2019;Wang et al. 2020;Lombardi et al. 2021); ocelots in South Texas demonstrate consistent use and selection of woody cover and show strong negative responses to roads (Blackburn et al. 2020;Veals et al. 2022). Ocelots have demonstrated consistent habitat-relationships over the last several decades despite habitat loss and fragmentation (Lombardi et al. 2020a;Veals et al. 2022), making this species an ideal model for examining trends in landscape connectivity. ...
... We examined the distribution of estimated connectivity values from our six models in the areas surrounding ocelot road mortalities and completed wildlife crossing structures targeted for ocelots in the study area. We used an independent data set of ocelot road mortality locations (n = 26) from 1984 to 2017 (Blackburn et al. 2020) and wildlife crossing structures (n = 15) built for ocelots completed as of 2020 . We used focal statistics to determine the average connectivity value in the neighboring raster cells surrounding road mortalities and crossing structures (radius = 270 m) for each connectivity model. ...
... We used focal statistics to determine the average connectivity value in the neighboring raster cells surrounding road mortalities and crossing structures (radius = 270 m) for each connectivity model. Many of the completed wildlife crossing structures built for ocelots have been placed based on previous road mortalities, typically in areas of nonwoody cover that lack the vegetation structure ocelots in South Texas use (Blackburn et al. 2020;Lombardi et al. 2021;Blackburn et al. 2022;Veals et al. 2022). Given the diverging approaches for crossing structures to be placed based on mortality hotspots vs. movement corridors (e.g., Kang et al. 2016;Laliberté & St-Laurent 2020;Cerqueira et al. 2021), we wanted to evaluate if mortality locations as well as current crossing structures were in areas predicted to have high landscape connectivity for ocelots. ...
Landscape connectivity for an endangered carnivore: habitat conservation and road mitigation for ocelots in the US
Article
Full-text available
  • Dec 2022
  • LANDSCAPE ECOL
Context Maintaining landscape connectivity for wildlife has become a conservation priority in response to increasing land development and road networks. Roads affect many wildlife populations worldwide, with the distribution and density of roads having negative impacts on gene flow and landscape connectivity. Objectives We aimed to identify areas along roadways that promote movement in a fragmented landscape. Our objective was to gain a deeper understanding of drivers of connectivity in a patchwork landscape of human uses. Methods We applied a spatial absorbing Markov chain (SAMC) framework to test hypotheses about landscape connectivity for a federally endangered carnivore, the ocelot (Leopardus pardalis). We modeled landscape connectivity for ocelots based on spatio-temporal trends in habitat use, which we derived using telemetry dataset collected 1982–2017. We compared three increasingly restrictive resistance surfaces to predict trends in landscape connectivity. Results Ocelot avoidance of high-traffic roads (> 5000 cars/day) largely influenced patterns of predicted connectivity. We simulated connectivity between habitat patches and identified highly connected areas of conservation concern due to proximity to high-traffic roads. Connectivity was greatly influenced by ocelot habitat use rather than resistance scenarios. Further, we found no evidence of connectivity between populations of ocelots, indicating isolation within a fragmented landscape. Conclusion Our spatially-explicit results describing landscape connectivity with respect to roads provides critical information needed for strategic placement of wildlife crossing structures. Wildlife crossing structures for resident ocelots should be placed in areas of relatively high conductance near roads with well-connected habitat on both sides of the road. We describe an approach that leverages long-term habitat use data for examining connectivity and improving landscape permeability.
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... Regarding home range placement, we expected ocelots to strongly and consistently select for areas with higher woody cover, and that woody cover would largely drive the predicted distribution of ocelots through time (Harveson et al., 2004;Horne et al., 2009;. Vehicle-induced mortality of ocelots continues to occur (Blackburn et al., 2020(Blackburn et al., , 2021Haines et al., 2005). Therefore, we expected the impact of roads to increase through time as indicated by ocelots avoiding areas closer to high-traffic roads in more recent years. ...
... This pattern has important implications for ocelot conservation where individuals with greater availability of roads within their home ranges may be more susceptible to vehicle collisions. Since ocelots did not avoid roads as much as expected at third order, crossings structures and exclusion fencing should funnel movement into safer areas (i.e., higher proportions of woody cover and lower road densities; Blackburn et al., 2020). Strategically placing crossing structures within suitable habitat that connect to the broader landscape are a key factor in crossing success (Clevenger & Huijser, 2011;Forman et al., 2003). ...
Multiscale habitat relationships of a habitat specialist over time: The case of ocelots in Texas from 1982 to 2017
Article
Full-text available
  • Aug 2022
Abstract Evaluating temporal trends in habitat and behavioral responses is critical for conservation, yet long‐term monitoring studies are rare. We used a 35‐year dataset (1982–2017) to assess multiscale habitat use and selection by an endangered carnivore, the ocelot (Leopardus pardalis), in South Texas, USA. We used a time series of remotely sensed imagery to map changes in availability of woody cover, habitat critical to ocelots that has diminished due to anthropogenic development and increased road infrastructure. Our objectives were to characterize habitat relationships, predict high‐quality habitat, and assess behavior with changing environmental conditions. We fit functional response (third order) and individual‐specific resource selection (second order) functions to assess multiscale habitat use of vegetation cover and roads. Within home ranges, ocelots used woody cover greater than availability. Ocelots used areas near roads in proportion to availability, with minor exceptions. We observed changes in habitat use by ocelots across time with higher proportions of woody and non‐woody cover used in later time periods. Average availability of woody cover decreased in the study area between the 1980s and 2010s (0.44 in 1985 to 0.39 in 2015, p
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... By 1986, it was estimated that <1% of this habitat type occurred in southern Texas (Tewes & Everett, 1986), but current estimates are unknown. This rapid decline in habitat, along with road mortality and historic hunting and trapping, has been responsible for declines in ocelot populations (Blackburn et al., 2021;Haines et al., 2005). Despite the decreasing availability of woody cover, research indicates an increasing selection of woody vegetation in recent decades, suggesting an increasing dependency on this specific habitat type (Veals et al., 2022). ...
Selection in the third dimension: Using LiDAR derived canopy metrics to assess individual and population-level habitat partitioning of ocelots, bobcats, and coyotes
Article
Full-text available
  • Nov 2023
Wildlife depends on specific landscape features to persist. Thus, characterizing the vegetation available in an area can be essential for management. The ocelot (Leopardus pardalis) is a federally endangered, medium-sized felid adapted to woody vegetation. Quantifying the characteristics of vegetation most suitable for ocelots is essential for their conservation. Furthermore, understanding differences in the selection of sympatric bobcats (Lynx rufus) and coyotes (Canis latrans) can provide insight into the mechanisms of coexistence between species. Because of differences in hunting strategy (cursorial vs. ambush) and differences in use of land cover types between species, these three carnivores may be partitioning their landscape as a function of vegetation structure. Light detection and ranging (LiDAR) is a remote sensing platform capable of quantifying the sub-canopy structure of vegetation. Using LiDAR data, we quantified the horizontal and vertical structure of vegetation cover to assess habitat selection by ocelots, bobcats, and coyotes. We captured and collared 8 ocelots, 13 bobcats, and 5 coyotes in southern Texas from 2017 to 2021. We used step selection functions to determine the selection of vegetation cover at the population and individual level for each species. Ocelots selected for vertical canopy cover and dense vegetation 0-2 m in height. Bobcats selected cover to a lesser extent and had a broader selection, while coyotes avoided under-story vegetation and selected areas with dense high canopies and relatively open under-stories. We observed a high degree of variation among individuals that may aid in facilitating intraspecific and interspecific coexistence. Management for ocelots should prioritize vegetation below 2 m and vertical canopy cover. We provide evidence that fine-scale habitat partitioning may facilitate coexistence between sympatric carnivores. Differences among individuals may enhance coexistence among species, as increased behavioral plasticity of individuals can reduce competition for resources. By combining accurate, fine-scale measurements derived from LiDAR data with high-frequency global positioning system locations, we provide a more thorough understanding of the habitat use of ocelots and two sympatric carnivores.
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... com), is located 25 km south of Laguna Atascosa National Wildlife Refuge and surrounded by extensive agriculture and urban development (Veals et al., 2022). Inbreeding depression and loss of genetic diversity (Janecka et al., 2016), land conversion (Lombardi et al., 2020a;Veals et al., 2022), and road mortality (Blackburn et al., 2021) have continued to negatively affect ocelot populations in Texas. Currently, there has yet to be an updated formal analysis using SECR models to estimate local population density and population size in any part of the ocelot's geographic range in Texas. ...
Spatial capture-recapture and LiDAR-derived vegetation metrics reveal high densities of ocelots on Texas ranchlands
Article
Full-text available
  • Dec 2022
Reliable estimates of population density and size are crucial to wildlife conservation, particularly in the context of the Endangered Species Act. In the United States, ocelots (Leopardus pardalis pardalis) were listed as endangered in 1982, and to date, only one population density estimate has been reported in Texas. In this study, we integrated vegetation metrics derived from LiDAR and spatial capture-recapture models to discern factors of ocelot encounter rates and estimated localized population estimates on private ranchlands in coastal southern Texas. From September 2020 to May 2021, we conducted a camera trap study across 42 camera stations on the East Foundation’s El Sauz Ranch, which was positioned within a larger region of highly suitable woody and herbaceous cover for ocelots. We observed a high density of ocelots (17.6 ocelots/100 km2) and a population size of 36.3 ocelots (95% CI: 26.1–58.6) with the 206.25 km2 state space area of habitat. The encounter probability of ocelots increased with greater canopy cover at 1-2 m height and decreasing proximity to woody cover. These results suggest that the incorporation of LiDAR-derived vegetative canopy metrics allowed us to understand where ocelots are likely to be detected, which may aid in current and future population monitoring efforts. These population estimates reflect the first spatially explicit and most recent estimates in a portion of the northernmost population of ocelots in southern Texas. This study further demonstrates the importance of private working lands for the recovery of ocelots in Texas.
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... For example, the amount of natural cover leading to an undercrossing entrance is important for mesocarnivores (Ng et al. 2004;Grilo et al. 2008). At the landscape scale, habitat selection may influence undercrossing use, particularly for carnivores, depending on the habitat where the undercrossing is situated (Rodriguez et al. 1996;Grilo et al. 2008;Blackburn et al. 2021). In particular, riparian drainages can facilitate movement through undercrossings along natural travel routes (Beier 1995;Clevenger and Waltho 2000;Hilty and Merenlender 2004). ...
Mammal use of undercrossings is influenced by openness and proximity to riparian corridors
Article
Full-text available
  • Jul 2022
Context A central problem in road ecology is the need to minimise roadkill without exacerbating fragmentation. The best current solution to this problem is wildlife-exclusion fencing combined with crossing structures. However, because species vary in their propensity to use crossing structures, optimising their design for a suite of species remains a challenge. Aims We investigated medium- and large-mammal use of undercrossings along Highway 101 in the Central Coast of California. Specifically, we quantified how undercrossing size, surrounding habitat, and the presence of a wildlife-exclusion fence, influenced overall species richness, as well as use by black bear, mule deer, puma, and bobcat. Methods Using wildlife cameras, we documented mammal use at 11 undercrossings in our study area. We calculated the openness index of each undercrossing and remotely measured habitat features, such as percentage tree cover, and distance to nearest stream. We determined the relative importance of these factors on overall species richness, and the activity of focal species, using generalised linear mixed models in an information-theoretic framework. Key results Mesocarnivores used a wider variety of undercrossings, and used them more frequently, than did larger mammals. Species richness and bear activity were greater closer to streams, and there was more bear activity at undercrossings within the wildlife-exclusion fence zone than outside it. Deer activity was strongly and positively related to undercrossing openness. Our puma and bobcat analyses were uninformative, likely because we detected puma too infrequently, and because bobcats showed little variation in use across sites. Conclusions Our results support previous research highlighting natural travel corridors (e.g. riparian areas) as important places for wildlife crossings, both for a diversity of medium–large mammals and a low-density large carnivore. Ungulates may be the most selective taxa in respect to undercrossing use. Implications Large, open undercrossings along natural travel routes accommodate the greatest diversity of medium–large mammal species.
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Mesocarnivores of Western Rangelands
Chapter
Full-text available
  • Sep 2023
There are 22 species of mesocarnivores (carnivores weighing < 15 kg) belonging to five families that live in rangelands of the western United States. Mesocarnivores are understudied relative to large carnivores but can have significant impacts on ecosystems and human dimensions. In this chapter, we review the current state of knowledge about the biology, ecology, and human interactions of the mesocarnivores that occupy the rangelands of the central and western United States. In these two regions, mesocarnivores may serve as the apex predator in areas where large carnivores no longer occur, and can have profound impacts on endemic prey, disease ecology, and livestock production. Some mesocarnivore species are valued because they are harvested for food and fur, while others are considered nuisance species because they can have negative impacts on ranching. Many mesocarnivores have flexible life history strategies that make them well-suited for future population growth or range expansion as western landscapes change due to rapid human population growth, landscape development, and alterations to ecosystems from climate change; however other mesocarnivores continue to decline. More research on this important guild is needed to understand their role in western working landscapes.
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Spatial and temporal trends in western polecat road mortality in Wales
Article
Full-text available
  • Dec 2022
Roads have considerable ecological effects that threaten the survival of some species, including many terrestrial carnivores. The western polecat is a small-medium sized mustelid native to Asia and Europe, including Britain where its historical stronghold is in Wales. Polecats are frequently killed on roads and road casualties represent the most common source of data on the species in the UK. However, little is known about the factors that increase the risk of collision. We used Generalized Additive Models to explore seasonal patterns in collisions as well as using Principal Component Analysis and regression modelling to identify landscape characteristics associated with polecat road casualties in Wales. Polecat road casualties had a bimodal distribution, occurring most frequently in March and October. Casualties were more frequently associated with road density, traffic volume, presence of rabbits, habitat patchiness and the abundance of proximal improved grassland habitat. Casualties were negatively associated with elevation and the abundance of semi-natural grassland habitat. The results of this study provide a framework for understanding and mitigating the impacts of roads on polecats in their historic stronghold, hence has considerable value to polecat conservation as well as broader applicability to ecologically similar species.
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Ocelot occupancy in fragmented areas of the Brazilian Cerrado and Atlantic Forest
Article
  • Jul 2022
Species occurrence in the landscape is influenced by habitat characteristics such as vegetation structure and resource availability. Habitat fragmentation causes a reduction or elimination of required resources, leading to the decline or disappearance of populations and species. Among carnivores, variables such as vegetation characteristics, prey availability, and human infrastructure were strongly associated with species occupancy. However, the relationship between these variables and ocelot (Leopardus pardalis) occupancy in fragmented landscapes remains poorly understood. The aim of this study was to investigate the influence of habitat characteristics, prey availability, and human infrastructure on ocelot occupancy in the protected areas of São Paulo. We sampled 55 sites using unbaited camera traps from October 2012 to August 2017 with a sampling effort of 10.175 trap-nights. We fitted models to determine how vegetation characteristics, prey availability, and human infrastructure affect ocelot occupancy. Ocelots were detected in 40% of sites, with a higher occupancy probability in sites with a greater relative abundance of prey and a farther distance from urban areas; however, there was no significant relationship with native vegetation. Thus, preservation of the ocelot requires the reduction of human impacts on these landscapes.
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Habitat use by ocelots in south Texas: implications for restoration
Article
Full-text available
  • Sep 2004
  • Wildl Soc Bull
The ocelot (Leopardus pardalis) is an endangered cat native to south Texas. Urbanization and agricultural development have resulted in limited and fragmented habitat, making ocelot habitat restoration an important factor in the cat's recovery. We evaluated the use of United States Department of Agriculture‐Natural Resource Conservation Service (USDA‐NRCS) soil surveys to identify potential restoration sites by examining ocelot habitat use in south Texas from 1982–1990. We analyzed an 8‐year data set of ocelot radiotelemetry locations using Geographic Information Systems (GIS) and Bailey's confidence intervals. Ocelots selected habitat with dense (>95%) canopy cover more than open (<75%) canopy cover. Ocelots also selected Camargo, Lardeo, Olmito, and Point Isabel soil series in greater proportion than available. The selected soils also represented 82% of the selected dense canopy cover areas. Our results suggest that USDA‐NRCS soil survey maps can be used as a tool for identifying potential areas for ocelot habitat restoration.
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Evaluating methods for identifying large mammal road crossing locations: black bears as a case study
Article
Full-text available
  • Aug 2020
  • LANDSCAPE ECOL
ContextRoads have several negative effects on large mammals including restricting movements, isolating populations, and mortality due to vehicle collisions. Where large mammals regularly cross roads, driver safety is also a concern. Wildlife road crossing structures are often proposed to mitigate the negative effects on wildlife and human safety. However, few studies have compared the efficacy of different methods in identifying wildlife road crossing and mitigation locations.Objectives We examined five commonly used methods to identify road crossing locations for wildlife to determine which method best captured empirical crossing locations.Methods We used GPS collar data on black bears in Massachusetts, USA, to estimate road crossing locations with a road crossing resource selection function, factorial least-cost paths, resistant kernels, Circuitscape, and an individual based movement model. We evaluated model performance on each road class and all road classes combined with a hold out road crossing data set.ResultsAll methods performed well, but Circuitscape consistently outperformed the other methods, both for each road class and all road classes combined.Conclusions Road mitigation efforts for wildlife are often costly and have a long-term footprint on the landscape, therefore, it is important to select locations for these efforts that provide functional connectivity for wildlife. We are the first to compare different road crossing models for large mammals across a large study area and on different road types. Our results provide information to assist researchers and managers in selecting an analytical method for identifying potential road mitigation locations for large mammals.
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Identifying landscape predictors of ocelot road mortality
Article
Full-text available
  • Jul 2020
  • LANDSCAPE ECOL
ContextFor depleted wildlife populations, understanding and effectively mitigating the direct and indirect impacts of roads can be a key component of recovery efforts. The ocelot is a federally endangered wild felid at risk of local extinction in south Texas, where vehicle collisions are their largest known source of mortality.Objectives To support road mortality mitigation, we evaluated mortality risk across the south Texas road network. We also assessed whether a sympatric carnivore, the bobcat, could serve as a surrogate to inform mortality risk.Methods We used several presence-only species distribution models to evaluate a suite of candidate landscape and road attributes and identify those associated with elevated road mortality risk using a 35-year wild felid road mortality dataset. Consensus predictions among models identified high-risk road segments for ocelots and bobcats. We compared predictions between species to determine overlap of high-risk areas.ResultsAreas where core ocelot habitat intersected roadways represented the greatest mortality risk, reflecting ocelot reliance on intact habitat and avoidance of degraded and fragmented landscapes. Bobcat road mortality risk had similar relationships to landscape features, with nearly all areas classified as high-risk for ocelots also identified as high-risk for bobcats.Conclusions Ocelots are vulnerable to road mortality in areas where roads intersect their intact scrub habitat. Bobcats, with appropriate data filters in place, are an acceptable surrogate for informing ocelot road mortality, particularly when ocelot mortality data are limited and for time-sensitive conservation decision-making. For ocelots and other fragmentation-intolerant carnivore species, wildlife underpasses and fencing in focused areas where roads and intact habitat intersect may be feasible options to reduce road mortality.
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Spatial structure of woody cover affects habitat use patterns of ocelots in Texas
Article
Full-text available
  • May 2020
About 80% of the known breeding population of ocelots (Leopardus pardalis) in the USA occurs exclusively on private ranches in northern Willacy and Kenedy counties in South Texas. These private ranches support several large contiguous undisturbed patches of thornscrub, which is preferred by ocelots. Past studies have indicated ocelots in South Texas select for woody patches that contain extremely dense thornscrub (i.e., 95% canopy cover and 85% vertical cover) and require large patches of woody cover to survive. Landscape metrics have been used to explain ocelot habitat use in fragmented areas, but their application in less-fragmented rangelands is lacking. From 2011 to 2018, we used camera traps on the East Foundation’s El Sauz Ranch to assess seasonal habitat use of ocelots relative to landscape structure, configuration, and complexity and other site-level factors in South Texas. Seasonal habitat use and detection were positively influenced by larger mean patch area and lower landscape shape index values. We also observed ocelots were less likely to be detected during periods of drought and exhibited a seasonal trend in detection. Ocelots used woody patches that were larger and more regularly shaped, indicating a preference for areas with a lower degree of fragmentation across the study area. As patches become larger, they will coalesce over time and form larger woody aggregates, which will promote ocelot habitat use. Brush management needs to be strategic as patch area and shape index are a limiting factor to promote ocelot habitat use on working rangelands in South Texas. These results demonstrate the ability to use landscape metrics to discern the effects of spatial structure of vegetation communities relative to ocelot occupancy parameters.
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Land Cover Trends in South Texas (1987–2050): Potential Implications for Wild Felids
Article
Full-text available
  • Feb 2020
The Rio Grande Delta and surrounding rangelands in Texas has become one of the fastest urbanizing regions in the United States over the last 35 years. We assessed how land cover trends contributed to the large-scale processes that have driven land cover change since 1987. We classified LANDSAT imagery from 1987 to 2016 to quantify different rates of land cover change and used housing density scenarios to project changes in the amount and spatial distribution of woody cover until 2050 and its potential impact on wild felid habitat. Since 1987, woody cover increased from 3.9% along with patch and edge density, whereas mean patch area and Euclidean nearest neighbor decreased. Closer inspection revealed that woody encroachment of small patches (<1 ha) was the leading cause of woody cover increase by a magnitude of 4, with an observed significant skewness and kurtosis in the frequency distribution of patch size across years. By 2050, urbanization will be the dominant landscape type and at least 200 km2 of woody cover may be lost, thereby affecting felid populations in South Texas. These results provide important information for predicting future woody cover fragmentation and its potential impact on the connectivity of wild felid populations.
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The scale of effect of landscape context varies with the species’ response variable measured
Article
Full-text available
  • Apr 2019
  • LANDSCAPE ECOL
Context To detect an effect of landscape context on a species’ response, the landscape variables need to be measured within the appropriate distance from the species’ response, i.e. at the scale of effect. However, it is not clear what factors determine the scale of effect. Objective Our objective was to test the prediction that the scale of effect should be smallest when the species’ response is fecundity, larger for abundance, and larger still for occurrence. Methods We compared the scale of effect of two landscape variables (road density, forest proportion) on the three responses (fecundity, abundance, occurrence) for the wood frog (Lithobates sylvaticus) in eastern Ontario, Canada. We used egg mass surveys of 34 ponds to estimate fecundity (mean eggs/mass), abundance (number of masses), and occurrence (presence/absence of egg masses). We then empirically estimated the scale of effect of each landscape variable on each response. Results The scale of effect differed among responses, from 0.2 to 3.0 km radii; however, it did not vary in the predicted order. Furthermore, the order was not consistent between the two landscape variables. Conclusions Our results show that the scale of effect of a landscape variable on a given species can differ for different response variables. However, they also suggest that these differences in the scale of effect are not predictable. Thus, the most reliable way to ensure a landscape context study is conducted at the correct spatial extent is to estimate the scale of effect empirically, rather than ‘guesstimating’ the extent a priori.
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Multi-level, multi-scale habitat selection by a wide-ranging, federally threatened snake
Article
Full-text available
  • May 2018
  • LANDSCAPE ECOL
ContextAlthough multi-scale approaches are commonly used to assess wildlife-habitat relationships, few studies have examined selection at multiple spatial scales within different hierarchical levels/orders of selection [sensu Johnson’s (1980) orders of selection]. Failure to account for multi-scale relationships within a single level of selection may lead to misleading inferences and predictions. Objectives We examined habitat selection of the federally threatened eastern indigo snake (Drymarchon couperi) in peninsular Florida at the level of the home range (Level II selection) and individual telemetry location (Level III selection) to identify influential habitat covariates and predict relative probability of selection. Methods Within each level, we identified the characteristic scale for each habitat covariate to create multi-scale resource selection functions. We used home range selection functions to model Level II selection and paired logistic regression to model Level III selection. ResultsAt both levels, EIS selected undeveloped upland land covers and habitat edges while avoiding urban land covers. Selection was generally strongest at the finest scales with the exception of Level II urban edge which was avoided at a broad scale indicating avoidance of urbanized land covers rather than urban edge per se. Conclusions Our study illustrates how characteristic scales may vary within a single level of selection and demonstrates the utility of multi-level, scale-optimized habitat selection analyses. We emphasize the importance of maintaining large mosaics of natural habitats for eastern indigo snake conservation.
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