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Results from regression analyses of number of nests oviposited vs. daily rainfall (mm) during three consecutive years. Variables were Log n -transformed.
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Timing of nesting affects fitness of oviparous animals living in seasonal environments, and females may cue on environmental factors for their nesting behavior, but these relationships are understudied in tropical turtles. Here, the timing and synchrony of egg-laying relative to environmental factors were examined in the South American freshwater t...
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... did not find a significant relationship between daily rainfall and the number of nests laid per night (Table 1). Rainfall was much higher in 1999 ( Figure 3a) and 2000 ( Figure 3b) when nesting beaches flooded and interrupted oviposition, and only for these two years there was a negative linear relationship between river levels and the number of nests laid per night (Table 2). ...Citations
... Examples of masking factors are nocturnal luminosity (that is influenced not only by moon phases but also by weather conditions), predation risk, anthropogenic disturbance (including noise and light pollution), and food availability [8][9][10][11][12]. Masking factors can also have a direct inhibitory or excitatory effect on several physiological and behavioral variables [3,13,14]. ...
The activity patterns of mammals depend on environmental changes (e.g., moon luminosity, food availability, weather) and endogenous rhythms. Behavioral observations are traditionally used to estimate the activity patterns of animals, but low visibility and the cryptic nature of some species entail that, in certain conditions, the animal is visible only for around 60% of the time. Recent advances in technology allow automatic data collection on the activity levels of animals. We used five years of data collected via accelerometers to understand how moon luminosity, seasonality, sex, and weather conditions influence the activity levels of the nocturnal and cryptic Javan slow loris. We collected 9589 h on six females and 7354 h on six males. Via Generalized Additive Mixed Models, we found that lorises are lunarphobic; they reduce activity levels during cold nights, they have higher activity levels when the relative humidity is close to 100%, and they have high peaks of activity between December and February and between June and August. The activity levels are thus influenced by avoidance of predators, food availability, consumption of insects and nectar, physiological, and behavioral adaptations to cold temperatures and energy requirements during reproductive stages. We highlight the importance of using bio-loggers for cryptic animals as with behavioral observations only, and the observer might underestimate active behaviors and overestimate inactivity.
... Web of Sciece 17 [23,24,35,[38][39][40][41][42][43][44][45][46][47][48][49][50][51] "Turismo", "Conservación", "Charapa" y "Ecuador" ...
Biodiversity at the species and ecosystem level is an important basis for tourism, especially for tourism economies in landscapes optimal for the conservation and sustainable use of biodiversity , which are addressed under the Convention on Biological Diversity. In the last two decades , the Podocnemis unifilis turtle has presented problems represented in a decrease of individuals in their populations in the Ecuadorian Amazon. The objective of the study was to describe the characteristics and current situation of the charapa turtle (Podocnemis unifilis), to analyze the perception of the community of the Indillama River towards this species and finally to establish a proposal for its conservation with a socioeconomic contribution from the community tourism segment. The methodology used consisted of a bibliographic review, semi-structured interviews and expert judgment. The main results indicate that the charapa turtle has had population problems in the last 30 years due to various anthropogenic pressures. The inhabitants of the Río Indillama community perceive this species mainly as a source of economic income (sale of individuals and their eggs) and food by consuming their eggs and adult individuals. Finally, we present a proposal for conservation through tourism that provides experiential activities for the collection of P. unifilis eggs, nesting and release (sponsorship) of individuals, providing economic benefits to local communities. This will contribute to its conservation and local socioeconomic development.
... Pig-nosed turtles (Carettochelys insculpta) ceased nesting for up to several days during cool periods in the tropical (winter) dry season (Doody et al., 2003). Rather than rainfall, additional studies have noted associations of nesting activity with bright moon phases, possibly a function of social facilitation and/or as a mechanism to reduce individual or nest predation (Escalona et al., 2019;Buckardt et al., 2020). These complexities show that single-factor analyses of rainfall frequencies alone (e.g., Aresco, 2004;Geller, 2012a) are not likely to be as informative for a given species and context as studies incorporating rainfall amounts and a broader array of meteorological parameters in their analyses, such as the concurrent effects of air and water temperatures, and time since last rainfall (noted by Jackson and Walker, 1997;Muell et al., 2021). ...
... Fisher's Exact Tests found no association of nesting and rain within previous 24 h; 53.9% (n = 102) of nests were constructed more than 24 h after previous rain; effect of rainfall amount not assessedEscalona et al., 2019 Podocnemis unifilis Linear regression found no association of nesting with daily rainfall amount; nesting activity was associated with intermediate air temperatures and full moon phasesLazure et al., 2019 ...
Rainfall following turtle nest construction has long been believed to increase nest survival by its effects on reducing the location cues used by nest predators. However, it is unclear if this is generally the case and if nesting turtles actively use this mechanism to increase their reproductive fitness by deliberately timing nesting to occur before or during rainfall. To address this question, we reviewed studies that examined freshwater turtle nesting behavior and nest predation rates in relation to rainfall. We supplemented our review with data on rainfall and nesting patterns from a 12-year study of two nesting populations of Ouachita Map Turtles (Graptemys ouachitensis). Our review revealed a diversity of responses in rainfall effects on predation and in the propensity for turtles to nest in association with rain. Our mixed findings could reflect a diversity of species- or population-specific responses, local adaptations, species composition of predator community, confounding abiotic factors (e.g., temperature decreases after rainfall) or methodology (e.g., most studies did not quantify rainfall amounts). Our case study on map turtles found very high yearly predation rates (75–100%), precluding our ability to rigorously analyze the association between nest predation and rainfall. However, close examination of the exact timing of both rainfall and predation revealed significantly lower predation rates when rain fell within 24 h after nesting, indicating that rainfall during or after nesting may reduce nest predation. Despite this effect, the best fitted model explaining the propensity to nest found that map turtles were more likely to nest after dry days than after days with rainfall, suggesting that rainfall was not a major factor driving turtles to nest in our populations. In both our review and in our map turtle populations there was little evidence that turtles can anticipate rainfall and nest prior to it occurring (e.g., in response to falling barometric pressure).
... However, not all beaches in intertropical regions receive the same number of marine turtle nests; some beaches host high densities of nests, whereas others, sometimes located in the same region, may have very few nests [1]. The origin of this difference in nesting at nearby beaches may relate to several factors: (i) accessibility to the beach from the sea [2], (ii) social facilitation for finding a nesting beach [3,4], and (iii) female philopatry with past heterogeneous nesting activity [5]. Philopatry is the tendency of an organism to stay in or habitually return to a particular area [6]. ...
In marine turtles, sex is determined during a precise period during incubation: males are produced at lower temperatures and females at higher temperatures, a phenomenon called temperature-dependent sex determination. Nest temperature depends on many factors, including solar radiation. Albedo is the measure of the proportion of reflected solar radiation, and in terms of sand color, black sand absorbs the most energy, while white sand reflects more solar radiation. Based on this observation, darker sand beaches with higher temperatures should produce more females. As marine turtles show a high degree of philopatry, including natal homing, dark beaches should also produce more female hatchlings that return to nest when mature. When sand color is heterogeneous in a region, we hypothesize that darker beaches would have the most nests. Nevertheless, the high incubation temperature on beaches with a low albedo may result in low hatching success. Using Google Earth images and the SWOT database of nesting olive ridleys (Lepidochelys olivacea) in the Pacific coast of Mexico and Central America, we modeled sand color and nesting activity to test the hypothesis that darker beaches host larger concentrations of females because of feminization on darker beaches and female philopatry. We found the opposite result: the lower hatching success at beaches with a lower albedo could be the main driver of nesting activity heterogeneity for olive ridleys in Central America.
... This hypothesis proposes that daughters are produced at nesting sites that confer higher survival, to which they return to nest as adults, thus attaining higher fitness than sons whose reproductive output is unaffected by their natal site if they survive to maturity. P. expansa is a gregarious nester, and females reutilize nesting beaches with high fidelity when available [Ojasti, 1971;Alho et al., 1979], perhaps following a social facilitation behavior akin to that reported for its congener P. unifilis [Escalona et al., 2009[Escalona et al., , 2019. However, although initial studies detected genetic structure among nesting beaches in P. expansa using microsatellite DNA consistent with natal homing [Valenzuela, 2001b], later metapopulation analyses using mitochondrial DNA demonstrated a lack of natal homing in both sexes [Pearse et al., 2006a]. ...
The adaptive significance of temperature-dependent sex determination (TSD) remains elusive for many long-lived reptiles. Various hypotheses proposed potential ecological drivers of TSD. The Charnov-Bull'77 model remains the most robust, and explains the maintenance of TSD in short-lived vertebrates, where sex ratios correlate with seasonal temperatures within years that confer sex-specific fitness (colder springs produce females who grow larger and gain in fecundity, whereas warmer summers produce males who mature at smaller size). Yet, evidence of fitness differentials correlated with incubation temperature is scarce for long-lived taxa. Here I propose that the Charnov-Bull'77 model applies similarly to short-lived taxa, but at a longer temporal scale, by revisiting ecological and genetic data from the long-lived turtle Podocnemis expansa. After ruling out multiple alternatives, I hypothesize that warmer-drier years overproduce females and correlate with optimal resource availability in the flood plains, benefitting daughters more than sons, whereas resources are scarcer during colder-rainier years (due to reduced flowering/fruiting) that overproduce males, whose fitness is less impacted by slower growth rates. New technical advances and collaborative interdisciplinary efforts are delineated that should facilitate testing this hypothesis directly, illuminating our understanding of TSD evolution in P. expansa and other long-lived TSD reptiles.
... Two papers in this SI focused on nesting behavior, one of the most well-studied aspects of turtle behavior. Escalona et al. [18] evaluated the effects of environmental factors on the timing and synchrony of yellow-spotted Amazon river turtle (Podocnemis unifilis) nesting. Not surprisingly, nesting started at the onset of the dry season when river levels were dropping. ...
The approximately 356 species of testudines (turtles) are remarkable for their blend of phylogenetic conservatism and diversity [...]
Painted terrapin is among Malaysia’s most critically endangered species on the IUCN Red List 2018. In Peninsular Malaysia, they can be found in several states, such as Negeri Sembilan, Melaka, Kelantan, Pahang, Perak, and the largest population can be found in Terengganu. We present here the status of nesting beaches and reproductive output (number of nests) of painted terrapins in Terengganu from the year 2010 to 2017, based on data available from the Turtle Information Centre Rantau Abang (Department of Fisheries, Malaysia). Thirteen nesting beaches from four Terengganu districts (Kemaman, Dungun, Setiu, and Besut) contributed to this study, with southern districts (Kemaman and Dungun) having a higher number of nests than northern districts (Setiu and Besut) due to a greater number of nesting beaches available. We also presented beach morphology and sediment characteristics results of five nesting beaches and associated them with the reproductive output of painted terrapins. Results showed no correlation between them except a station close to the Dungun River mouth with an active zone and poorly sorted sediment may be responsible for the low number of nests recorded. The number of nests recorded were also higher at the steep narrow beaches compared to the ones that have medium-large intertidal zones.
Oviparous animals, such as turtles, lay eggs whose success or demise depends on environmental conditions that influence offspring phenotype (morphology, physiology, and in many reptiles, also sex determination), growth, and survival, while in the nest and post-hatching. Consequently, because turtles display little parental care, maternal provisioning of the eggs and female nesting behavior are under strong selection. But the consequences of when and where nests are laid are affected by anthropogenic habitat disturbances that alter suitable nesting areas, expose eggs to contaminants in the wild, and modify the thermal and hydric environment experienced by developing embryos, thus impacting hatchling survival and the sexual fate of taxa with temperature-dependent sex determination (TSD) and genotypic sex determination (GSD). Indeed, global and local environmental change influences air, water, and soil temperature and moisture, which impact basking behavior, egg development, and conditions within the nest, potentially rendering current nesting strategies maladaptive as offspring mortality increases and TSD sex ratios become drastically skewed. Endocrine disruptors can sex reverse TSD and GSD embryos alike. Adapting to these challenges depends on genetic variation, and little to no heritability has been detected for nest-site behavior. However, modest heritability in threshold temperature (above and below which females or males develop in TSD taxa, respectively) exists in the wild, as well as interpopulation differences in the reaction norm of sex ratio to temperature, and potentially also in the expression of gene regulators of sexual development. If this variation reflects additive genetic components, some adaptation might be expected, provided that the pace of environmental change does not exceed the rate of evolution. Research remains urgently needed to fill current gaps in our understanding of the ecology and evolution of nest-site choice and its adaptive potential, integrating across multiple levels of organization.
