Journal of Zoology最新文献

During the reproductive period, mating strategies are a significant driver of adaptations in animal behaviour. For instance, for polygamous species, greater movement rates during the mating season may be advantageous due to the increased probability of encountering several potential mates. The brown bear Ursus arctos is a solitary carnivore that lives at low densities, with a polygamous mating system and an extended mating season of nearly 3 months. Here, we hypothesized that male brown bears may show changes in movement patterns and space-use behaviour during their mating season. Using long-term (2002–2013) telemetry data from the Finnish Karelia male population (n = 24 individuals; n = 10 688 GPS locations), we first analysed daily movement metrics, that is, speed, net and total distance with respect to the period (mating vs. post-mating) and several environmental predictors. Then, we conducted a step-selection analysis for each of these periods. Throughout the year, male bears selected forested/shrub habitats and increased movement rates near main roads. During the mating season, reproductive needs seem to trigger roaming behaviour in adult males to maximize encounter rates with potential receptive females. However, all movement metrics increased within areas of high human activity, suggesting a bear response to a higher risk perception while using those areas. During the post-mating period, overlapping with the bear hyperphagia and the hunting season, males selected anthropogenic areas farther from main roads and trails, suggesting a trade-off between foraging opportunities and risk avoidance.

Habitats resulting from agricultural intensification harbour a wide array of stressors for resident organisms. Environmental stress during development can leave imprints on the phenotype that are useful as indicators of its impairment. Among them, fluctuating asymmetry (FA), considered the morphological manifestation of developmental instability (DI), may reflect the increment of developmental noise and the inefficiency of buffering mechanisms. Here, we evaluated for the first time the impact of intensive agriculture on the development of a viviparous reptile, the asp viper, Vipera aspis (Linnaeus 1758), by means of FA. To this end, we first quantified unsigned asymmetry indexes (uAI) of dorsal head shape captured by geometric morphometrics (GM) and of seven pholidotic traits in 127 and 482 individuals, respectively. Using linear models, we then tested for variation in uAI according to habitat type. Furthermore, we tested the effect of climatic variables with a potential influence on development, and thus, on FA. We performed analyses at the V. aspis zinnikeri subspecies range and at the population level, including three well-sampled natural localities (NAT) and three sites of intensive agriculture (AGR). We found significantly higher FA levels in dorsal head shape in individuals from agricultural habitats than in those from natural habitats, which suggests that asp viper development is impaired by stressors resulting from agricultural intensification. Our results also point to a lower sensitivity of traditional morphological tools to capture the signal that intensive agriculture leaves on development and a lack of capacity of climatic factors in isolation to predict variation in the degree of asymmetry. In addition to encouraging the use of high-precision methods, we hypothesize on the overall effect of different stressors linked to intensive agriculture as the real constraint.

Predators with diverse diets can use generalized feeding behavior to consume different prey types or can alter behavior based upon the functional demands of each prey type. Prey choice and feeding behavior are especially important for limbless, gape-limited predators, such as snakes, because the head must capture, subdue, and ingest prey. Although previous studies have described how snakes feed on dangerous prey, these studies have not compared how behaviors might vary with different prey types. We analyzed the feeding behavior of ground snakes (Sonora episcopa) that were fed scorpions, spiders, and centipedes. Ground snakes successfully consumed each prey type using different behaviors for each prey. To capture prey, snakes used the unusual behavior of pinning prey with the ventral surface of the head with a closed mouth strike before biting. Snakes grasped and envenomated scorpions in all trials, and this behavior lasted significantly longer for scorpions than for spiders. During envenomation, snakes used their body to pin the telson of the scorpion to reduce the likelihood of being stung. Rather than using body restraint to subdue spiders, the snakes often dragged spiders across the substrate with the mandible. Scorpions repeatedly pinched and stung snakes during feeding and snakes used body restraint to subdue this prey significantly more often than spiders. Our study revealed that ground snakes alter feeding behavior based upon prey defenses and use novel prey capture and handling behaviors to subdue prey, suggesting there is yet unappreciated diversity of feeding behavior in snakes allowing them to exploit dangerous arthropod prey.

Understanding species coexistence requires information about how species interact and partition their ecological niche. Niches of closely related species tend to be quite similar and thereby, when syntopic, overlap can result in competition when shared resources are limiting. Brocket deer of tropical forests are ecologically similar species due to convergence or relatedness. As a group, what little is known about their ecology suggests spatial and temporal niche separation while dietary differences among species remain largely unknown. The possibility of competition has been suggested, as it is rare for more than two species to co-occur. If competition is important, then it may limit syntopy of more species and its importance should increase with relatedness between species. Based on analyses of faecal samples, camera traps, and stable isotopes and multidimensional analysis of niche space, we test spatial, temporal and dietary niche differences and compare niche breadth in two syntopic species pairs: Mazama rufa with M. nana (both of subtribe Odocoileina) and M. jucunda (Odocoileina) with Subulo gouazoubira (Blastocerina). In 2007–2008 and 2017–2019, 240 faecal samples and 375 records were collected in the Brazilian Atlantic Forest. Spatial partitioning among both species pairs was found, with S. gouazoubira and M. nana having greater niche breadth, which may permit or facilitate coexistence. Odocoileina tend to be nocturnal, while Blastocerina tend to be diurnal, which suggests that phylogeny may influence species coexistence. Furthermore, the species tended to overlap with respect to diet. These results suggest interference competition avoidance by niche partitioning at the level of habitat and time, allowing coexistence. Thereby, despite the morphological similarities, brocket deer species of evolutionarily convergent subtribes preserve differences in ecological niche dimensions that facilitate the coexistence of their populations.

Although usually considered part of the plankton, cubozoans are strong swimmers. The aim of this study was to determine the influence of the active swimming ability of the box jellyfish Carybdea marsupialis on the spatial distribution of a well-studied population in the NW Mediterranean where adults and juveniles do not overlap geographically. To accomplish this, we analyzed the swimming speed, effective velocity, effective displacement index (EDI), and proficiency of 27 individuals with diagonal bell widths (DBWs) ranging from 1.1 to 36 mm. The laboratory analysis utilized conventional video recordings and the video analysis tool Tracker. Mean swimming speed for small juveniles, medium juveniles and adults was 9.7 ± 0.8, 21.9 ± 2.3 and 43.1 ± 1.8 mm s⁻¹ (mean ± se), respectively. Effective velocity was also proportional to size, ranging from 5.0 ± 0.7 to 38.8 ± 3.1 mm s⁻¹ (mean ± se). The calculated EDI for each group was 0.51 ± 0.05, 0.84 ± 0.06 and 0.90 ± 0.05 (mean ± se), respectively. Proficiency showed an inverse trend, from 6.4 ± 0.6 s⁻¹ for the small juveniles to 1.36 ± 0.05 for adults (mean ± se). Comparing the swimming speed results with the local currents obtained from drifting buoys analyzed in the area, adults would be able to swim strongly enough to overcome almost 70% of the currents, whereas the small juveniles would not reach 17%. This would allow larger individuals to select their habitat, while smaller individuals are left dependent on advection. Although experiments adding currents in aquaria would be necessary to confirm these theoretical results, the data obtained would be useful in improving the performance of bio-mathematical models used to predict jellyfish blooms since, even though the sting of C. marsupialis is non-fatal, it may produce systemic effects in sensitive swimmers.

Groups of wild animals can vary considerably in their composition, including in the proportion of group members who are male or female, that is the within-group sex ratio. Variation in within-group sex ratios can arise from active adjustment of litter sex ratios by mothers, from sex differences in mortality, dispersal and immigration, or from stochastic variation in recruitment. Variation in the within-group sex ratio can have consequences for within-group competition and can affect individual life histories throughout development. In this paper, we explore which processes may generate variation in within-group sex ratios in wild Damaraland mole-rats (Fukomys damarensis), a singular cooperative breeder. We investigate whether within-group sex ratios predict the growth, body condition and philopatry of individuals. We show that although the population-level sex ratio is balanced, skewed within-group sex ratios are common, particularly among small groups. Our data suggests that stochastic variation in the sex of recruits explains natural variation in the sex ratio of wild groups. Non-breeding individuals in groups with a sex ratio biased towards their own sex grow more slowly than individuals in groups biased towards the opposite sex, suggesting that intra-sexual competition may decrease growth rates. We suggest that the costs of competition may contribute to the large variation in growth observed in social mole-rat groups.

The study of colour, including physical properties and patterns, is an essential step in comprehensively understanding the role, evolution and diversification of this trait involved in functions like survival, performance, reproductive success and communication. While quantitative studies on colour have primarily focused on colour attributes, such as hue or brightness, the quantitative assessment of how colours are distributed across an organism's body (i.e. pattern) has received less attention despite its high functionality irrespective and together with colour. This gap is particularly noticeable in amphibians, especially in highly polymorphic, continuously variable species. In this study, we use the urodele Salamandra salamandra as a study model to apply an analytical approach for extracting and quantifying colour proportions and patterns variation using the recently developed R packages patternize and recolorize to precisely describe and compare colour distribution at both taxonomic and habitat levels. We first assessed the potential application of this workflow in taxonomic studies by examining its accuracy and sensitivity in differentiating morphs, using S. s. bernardezi and S. s. gallaica subspecies. Subsequently, we applied the same analytical approach to compare colour and colour pattern shifts among population of S. s. bernardezi within an urban–forest system. Our results demonstrated that this methodological workflow effectively detects differences in colour patterns at the taxonomic and habitat levels, confirming its utility in different fields, from systematics to eco-evolutionary studies. Furthermore, our results revealed an increased prevalence of melanistic colouration and a less homogeneous colour pattern within urban settings, contributing to the limited number of studies about amphibian colouration in anthropic habitats. We outline and discuss alternative hypotheses to explain these patterns, although further investigation is necessary to address several new questions that arise from our results.

Morphological variation along the spatial distribution of species has been extensively investigated in ecological studies, and several ecogeographical rules explore the relationships between morphological traits and the environment. Many morphological traits are correlated, providing an opportunity to evaluate the validity of multiple ecogeographical rules simultaneously. Bergmann's rule predicts that endothermic animals in colder locations are larger than those in warmer locations. Jordan's rule predicts that fish from colder locations have more vertebrae than those from warmer locations. We tested the validity of Bergmann's and Jordan's rules for the neotropical lancehead snake Bothrops jararaca. We evaluated three morphological characters of 342 specimens: number of ventral scales (proxy for vertebrae number), snout–vent length (a linear measure of body size) and stoutness (volumetric body size). We implemented spatial regressions to evaluate the variation of morphological dimensions using climatic predictors: the minimum temperature and evapotranspiration. SVL was poorly related to minimum temperature and evapotranspiration. However, stouter individuals were found in colder places with greater evapotranspiration, following Bergmann's rule and the water conservation hypothesis. Individuals in warmer locations also had a greater number of ventral scales, reversing Jordan's rule. We showed that different selective pressures act on different morphological dimensions. Although stoutness follows Bergmann's rule, its variation would arise from an energy storage demand rather than heat conservation. Also, stoutness variation along evapotranspiration gradients could represent a mechanism to avoid hydric stress in environments with considerable climatic variations. The variation in vertebrae number along temperature gradients could be related to ecological factors and foraging. We highlight that physioecological mechanisms to deal with climatic variation and ecological aspects could be identified in snakes through intraspecific analyses, contrasting with interspecific studies that can hardly detect general trends. Due to different environmental effects on body size, we shed new light on the importance of exploring multiple morphological dimensions in macroecological studies.

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.

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.