Journal of Zoology最新文献

Movement is a key component of an animal's life history. While there are numerous factors that influence movement, there is an inherent link between a species' social ecology and its movement ecology. Despite this inherent relationship, the socio-spatial ecology of many species remains unknown, hampering ecological theory and conservation alike. Here, we use fine-scale GPS location data and continuous-time stochastic processes to study the socio-spatial ecology of 23 giant anteaters (Myrmecophaga tridactyla) in the Brazilian Cerrado. We found that individuals occupied stable home ranges with a mean area of 5.45 km² with males having significantly larger home ranges than females. The average amount of home-range overlap was low (0.20, n = 121 dyads), with no evidence that giant anteater home ranges were structured based on territorial, mate-guarding, or other social behaviour. We also identified a total of 2774 encounter events. Interestingly, both female–male and male–male dyads had significantly more encounters than female–female dyads, with two pronounced seasonal peaks in female–male encounters. Though encounters occurred frequently, associations between dyads were generally weak and there was little evidence of any correlated movement (mean amount of total correlation = 0.01). Collectively, these findings suggest giant anteaters are a solitary and largely asocial species that readily share space with conspecifics. Despite their present capacity to share space, the combined pressures of being condensed into smaller areas and decreased food availability due to increased pesticide use may cause behavioural changes radiating throughout the population. Our study provides insight into heretofore unknown aspects of the socio-spatial ecology of this iconic, but understudied species, as well as crucial information for proactive area-based management. Ultimately, these findings contribute towards sustainable development while potentially maintaining the ecological integrity of giant anteaters and their habitats.

Migration plays a central role in many ecological and evolutionary processes. Global patterns of climatic variation are having a profound influence upon animal migration patterns. Even though regular counts of bird migrations at bottleneck sites can certainly offer insights into how natural populations of different species at different scales are responding to changes in weather conditions, they have not yet been widely used. By analysing a time series of regular counts, collected during autumn, of 126 species migrating during the daytime through one of the most important migratory bottlenecks in Western Europe, we found that an increase in temperature at the regional scale, as well as a decrease in precipitation level during the breeding period, may result not only in a decrease in the migration rate during autumn but also in a delay in the timing of fall migration. Furthermore, adverse weather conditions at the local scale interrupted bird migration through the bottleneck until favourable weather conditions returned. Importantly, temporal variation in the number of migratory birds followed a nonlinear pattern, something which might be partially due to the idiosyncratic responses of migratory species with different life-history characteristics to changes in weather conditions. Our results highlight that migration is a nonlinear, multiscale and multi-faceted process, suggesting that it will be difficult to predict the responses of idiosyncratic migratory species to the unpredictable effects of climate change.

Although most carabids are carnivorous generalists, some species show dietary specializations such as malacophagy, which is characterized by two main strategies of snail predation: entering the shell or breaking it. The shell-breaking strategy has been well studied in the malacophagous specialists of the tribe Licinini. However, little is known about the ability of other carabids to feed on snails and, in particular, to use the shell-breaking strategy. Therefore, the main objective of this study was to investigate the ability of various generalist carabid species to feed on snails under laboratory conditions. We recorded 723 instances of predation in 89 of 180 carabid individuals (representing 23 of 33 species); all of them were exclusively shell-breaking attacks. While carabids mostly favoured individuals <8 mm as prey, they showed no preference for shell shape. Using a subset of 14 carabid species with a high frequency of snail predation, we found significant differences between the predation rates of carabid species depending on their body size using GLMMs. This study revealed that many generalist carabids can indeed feed on snails by breaking the shell, but predation rates were highly inconsistent among individual species. Shell-breaking patterns of generalists differed markedly from those of malacophagous specialists reported in the literature, as damage parallel to the shell coiling axis occurred more frequently than spiral damage. Our results show that the shell-breaking predation patterns of carabids are closely related to their degree of dietary specialization on snails and that many generalist carabids frequently accept snails as their prey.

Behaviours designated as basking span a broad array of ectothermic and endothermic animals. Understanding the role that basking plays in thermal biology is important because maintaining body temperatures within certain limits is essential to survival, growth and reproduction, and may affect responses to climate change. In the case of turtles and tortoises, behaviours designated as basking may occur out of water, at the surface of a water body or deep in a water body, during the day or at night, and with or without exposure to solar radiation or another heat source. On the available evidence, the primary function of most nominal chelonian basking is thermoregulatory warming, which provides numerous benefits including expediting gonadal recrudescence, enhancing foraging, feeding, digestion and growth, and amelioration of infectious disease and endoparasitism. Substantial evidence supports conditioning of the skin and shell as a common additional function of chelonian basking. Other functions of nominal chelonian basking with some supporting evidence for particular species and environments are thermoregulatory cooling, leech removal, vitamin D synthesis and osmotic control. Nominal chelonian basking may sometimes be undertaken for resting or avoiding aggression, but supporting evidence is scant. The only uniting feature of all chelonian behaviours designated as basking is quiescence, but not all quiescent chelonian behaviours are labelled as basking. Consequently, the general meaning of chelonian basking is indeterminate. Avoiding ambiguity requires the provision of explicit criteria by which basking can be distinguished from other quiescent behaviours, and the attachment of qualifiers that specify the applicable time of day, medium and environmental exposure.

Chiroptera is the only mammalian order that has adapted to active flight, offering a unique platform to study ecomorphological adaptations. While bats exhibit a diverse diet, the focus of this study is on insectivorous bats, specifically four species: Myotis daubentonii, Nyctalus noctula, Plecotus austriacus and Rhinolophus ferrumequinum. It is important to note that despite sharing an insectivorous diet, these species occupy different ecological niches, perform distinct feeding strategies and explore varied habitats to capture prey. Using 2-D geometric morphometrics, we analysed a sample of mandibles to identify differences in size and shape among these species. We also investigated ecogeographical variation within their overlapping distribution across continental Europe. Significant differences in both mandibular size and shape were found among the four species. Sexual dimorphism influenced only the mandibular shape of R. ferrumequinum. A latitudinal gradient in mandibular size was found solely in N. noctula, while longitude significantly explained shape variation in M. daubentonii. These findings suggest that even within the ecological guild of insectivorous bats, there exists a diverse range of morphological adaptations that allow these species to occupy distinct ecological niches.

The timing and size of metamorphosis are crucial for the future fitness of organisms with complex life cycles, such as amphibians. In some amphibian species, a portion of tadpoles will metamorphose in their natal year whereas others from the same cohort overwinter as tadpoles. Low temperature and food availability were previously assumed to be the underlying reasons; however, the factors influencing the decision to overwinter as tadpoles or metamorphose in the natal year have not been extensively studied. This study investigated these factors by conducting laboratory-rearing experiments on Babina subaspera tadpoles. The tadpoles were individually reared under controlled temperature and light conditions that simulated five different growing seasons (i.e., the start month) observed in the field. Four different food quantity levels were set to induce different growth rates, which were measured individually. The results revealed that 33 tadpoles metamorphosed within their natal year, whereas 52 tadpoles were overwintered as tadpoles and metamorphosed the following spring. The size at metamorphosis was larger in tadpoles that metamorphosed after winter than in those that metamorphosed before winter. Whether tadpoles metamorphosed before or after winter was influenced by the individual growth rate and growing season. Tadpoles with slower growth rates were more likely to metamorphose after winter, possibly because slower growth prevented them from reaching the critical size threshold required for metamorphosis before winter. The threshold for the occurrence of larval overwintering varied with the growing season; tadpoles that spawned later in the year were more likely to overwinter, even with a high growth rate. The results suggested that slow-growing B. subaspera tadpoles with insufficient time until the onset of winter would gain a higher fitness by metamorphosing after winter. This would be advantageous due to the tadpoles' potentially high survival rate during dormancy as well as their larger size at metamorphosis in the following year.

Hibernation is a key adaptation for coping with unfavorable climatic conditions and low food availability in areas with severe winter conditions. While understanding the physiology and phenology of this adaptation has received considerable attention, comparatively little information is available on how hibernation will be affected by changing climate conditions. We used GPS telemetry data from 20 free-ranging brown bears monitored over 31 winters between 2007 and 2022, to identify behavioral strategies of bears during winter. We applied behavioral change point analysis to quantify brown bears’ hibernation phenology in a population close to the bear's southern latitudinal range limit in Europe where supplementary food is available to bears year-round. We observed winter behavior patterns that varied across age and reproductive classes but also within individuals between winters. Among 31 winter events, we registered six cases in which bears exhibited a single hibernation/stationary period and 19 events where hibernation was split into up to five stationary periods. Moreover, six winter events did not show behaviors consistent with hibernation and individuals remained partly or completely active throughout winter. The movement of these active bears decreased with increasing snow depth. In addition, these winter-active bears showed higher fidelity to supplementary feeding sites during the winter period compared to the rest of the year. Our data suggest that an abundance of human-provided food resources during winter may facilitate the emergence of different wintering strategies in brown bears. Furthermore, supplemental feeding sites in combination with predicted mild winters and prolonged natural food availability suggest that the use of hibernation as an energy-saving strategy to overcome severe environmental conditions may decrease in the future.

Knowledge of vertebrate territoriality and spatial use is a topic of great interest in the study of animal behaviour and conservation biology. Investigating the plasticity of territory boundaries, the shape of territories and how territories can be modified depending on their owners is important to deepen our knowledge of the behaviour of territorial species. We analysed the variation and tested the similarity of the distribution area of individuals from the same territory between 2015 and 2021, using data from 51 Bonelli's eagles (Aquila fasciata) from 22 different territories, tagged with GPS/GSM transmitters in eastern Spain. We calculated the percentage of overlap between the territories of the same individual in different years using the 95% kernel density estimator. We also analysed the changes in territory size and shape following the replacement of territory owners either by a single individual or by the whole pair. Our results show that territories retain the same shape and extent regardless of the occupying members, and that their boundaries change little over time. Identifying and maintaining large eagle territories, regardless of their owners, is therefore key to ensuring the long-term recovery of these threatened species.

Morphological diversity within organisms can arise from factors other than genetic diversity alone. Local adaptations and combinations of various factors are also involved in shaping morphology. We investigated the relationship between morphological diversity and ecological niche divergence within two related tropical stream-dwelling newt species from Indochina: Paramesotriton deloustali and P. guangxiensis. We identified sexual dimorphism within both species and a significantly larger body size in P. deloustali than in P. guangxiensis. Our findings highlighted that climatic variables strongly influence Asian warty newt distribution, indicating the potential effects of climate change on tropical newt populations. Furthermore, we identified significant intra- and interspecific morphological and niche differentiation across five populations of the two newt species, suggesting that newt morphology is responsive to environmental factors. A significant negative relationship was observed only between ecological niche similarity and geographic distance among various combinations of factors, indicating that the distinct morphology of the study species mirrors ecological adaptation.

The hindlimbs of Accipitriformes are vital for capturing prey. Research on hindlimb musculature has primarily focused on species preferring avian and mammalian prey, whereas piscivorous species have received limited attention. This study aims to investigate the quantitative characteristics of hindlimb muscles in two piscivorous Accipitriformes, Pandion haliaetus and Haliaeetus albicilla, to discern potential muscular features associated with their specific food preference. The mass and proportion of all hindlimb muscles in both species were assessed based on their primary function (flexion or extension). A Kruskal-Wallis test was employed to analyze possible differences in muscle mass between species. The allometric relationships between the muscles and body mass were explored with the reduced major axis method. Additionally, a study on the architectural parameters of the primary gripping muscles in P. haliaetus was conducted, using published information from other raptorial birds for comparison. The isometric scaling relationship predominated in the majority of individual muscles helping maintain a proportional relationship relative to body mass. Both species exhibited a similar pattern in terms of quantitative muscle features, implying a preservation of muscle characteristics linked to their predatory capabilities. The largest proportion of hindlimb muscle mass was dedicated to digit flexion in accordance with the grasping abilities of birds of prey. The muscles tibialis cranialis, flexor digitorum longus and flexor hallucis longus exhibited the greatest mass, high physiological cross-sectional area values, and long fibre, categorizing them as high-power specialists. These muscles are crucial in the flexion movements that produce the gripping action that characterizes birds of prey. Although no statistically significant differences were detected, each species displayed slightly distinct muscular characteristics, particularly in the architectural properties of the flexor muscles controlling digits II, III, and IV. These variations seem to be associated with differences in their prey preferences.