Journal of Zoology最新文献

Isolation and extreme environmental conditions have significantly impacted terrestrial invertebrate biodiversity in Antarctica, with glacial cycles further limiting animal diversity to a small number of species. Among these, springtails are relatively abundant, though their taxonomic diversity remains low. Antarctic glaciers may serve as major dispersal barriers, leading to high levels of genetic divergence among isolated populations. In Victoria Land (continental Antarctica), the Tucker Glacier has been proposed as an example of such a barrier; however, different species or taxa may respond differently to the same geographical features. In this study, we tested whether geographic distance, major glacier tongues, and seawater channels influence the distribution of Kaylathalia klovstadi (Collembola; Isotomidae) in Northern Victoria Land. We conducted mitochondrial DNA haplotype analysis on fragments of cytochrome c oxidase subunit 1 (cox1) and ATP synthase 6 (atp6) in 62 individuals from six K. klovstadi populations. Our analysis provides new insights into the genetic diversity and distribution patterns of K. klovstadi by incorporating additional sampling sites, specimens, and molecular markers. We challenge previous views regarding the role of the Tucker Glacier as a significant physical barrier to springtail dispersal in Northern Victoria Land. Our findings suggest that the impact of physical barriers on the genetic diversity of Antarctic Collembola, including the species studied here, requires a more careful evaluation.

Cooperation and group living have been suggested to facilitate survival in varying environments and under challenging conditions. However, group living may also be associated with costs, particularly in species where individuals within groups may compete for limited resources. The costs and benefits of cooperative group living on cooperatively breeding mammals in varying environments remain unclear. Here, we use data collected from wild, cooperatively breeding Natal mole-rats (Cryptomys hottentotus natalensis) inhabiting a seasonally varying environment to assess whether body condition changes between seasons and whether these changes are contingent upon group size. We demonstrate that the body condition of reproductive females improved with increasing helper number during both the benign summer and the harsher winter seasons. However, the body condition of other group members showed little dependency on group size or season. Only when including one extremely large group did the body condition of non-breeders weakly, albeit significantly, change depending on group size and seasonality. These results suggest that larger group sizes may yield some benefits for non-breeding group members during winter and may invoke some costs during summer. Group living in Natal mole-rats is likely promoted by a combination of collective foraging, thermoregulatory benefits, and potentially some indirect fitness benefits through improved body condition of the breeding female.

Characterizing the dietary niche partitioning of sympatric mesocarnivores is fundamental for understanding their mechanisms of coexistence and ecosystem function. By utilizing scat DNA and DNA metabarcoding, our study revealed a detailed picture of the trophic interaction between two mesocarnivores in a cool temperate forest ecosystem in Northeast China. Both red foxes (Vulpes vulpes) and leopard cats (Prionailurus bengalensis) consumed a diverse range of prey (52 prey taxa from 11 orders) dominated by Rodentia (56.5–64.9%). Bipartite trophic network analysis suggested that both predators are generalists and have a high degree of niche overlap (Pianka's index = 0.77). However, diet patterns differed between the predators. Both predators consumed more diverse prey during the snow-free period than during the snow-covered period, which resulted in lower niche overlap between the predators (Pianka's index = 0.43). Another important source of diet niche partitioning was the proportion of large prey consumed, with red foxes consuming more ungulates than leopard cats do throughout the year in regions with two apex carnivores, tigers (Panthera tigris) and leopards (P. pardus). The presence of apex carnivores provides more stable carrion resources, which facilitates dietary niche partitioning and the coexistence of mesocarnivores. Our study provides important clues about the strategies of dietary niche partitioning between sympatric mesocarnivores, which is critical for understanding coexistence within carnivore communities.

The phenotypic plasticity of the digestive system is important to cope with the variations in food quality for wild small mammals, in particular for the lactating females because they must increase food intake to meet the highest energy requirements of offspring. This study aimed to investigate the energy budget and reproductive performance of striped hamsters (Cricetulus barabensis) fed on a high-fiber or high-fat diet across lactation. Body mass, food intake, resting metabolic rate (RMR), milk energy output (MEO), and litter size and mass were measured at peak lactation. The body composition, digestive enzymes activity, as well as the hypothalamus-driven gene expression relating to orexigenic or anorexigenic neuropeptides was determined at weaning. The food intake at peak lactation was not significantly changed in the females fed on a high-fiber diet, while it was decreased in those fed on a high-fat diet compared with the females fed a control diet. The females fed a high-fiber diet did not change RMR, but decreased MEO, and had smaller litters with lower masses. The females fed a high-fiber diet had a larger stomach, small and large intestine, and caecum, in parallel with increases in maltase and aminopeptidase activity, but these females did not show significant changes in amylase, lipase, lactase, or chymotrypsin compared with the females fed a control diet. The mRNA expression of AgRP was increased, and POMC was decreased in the hamsters fed a high-fiber diet compared with control ones. The high-fat group did not vary from the control group in almost all of the parameters. These findings suggest that the adaptive modulations in the digestive enzyme activity may be maximized at peak lactation, creating a hard limitation for SusEI in response to a high-fiber diet, which may be independent of either orexigenic or anorexigenic neuropeptides.

Morphological traits of animals have evolved to solve ecological requirements, the optimization of locomotion in each environment being one of the most frequent selective forces shaping morphology. Amphisbaenians are strictly fossorial reptiles that have evolved various snout shapes for burrowing head-first underground, yet the evolutionary and ecological origins of these different morphologies are little known. Here, we used a geometric morphometric approach to investigate head shape intrapopulational variation in the round-snouted checkerboard worm lizard (Trogonophis wiegmanni). We took 2D photographs of live animals in a North African island population. At each capture site, we also measured microhabitat characteristics and soil compaction, and took soil samples to analyze soil physical structure. While we detected no signal of sexual dimorphism in head shape and overall head disparity was low, we found significant relationships between the head shape of T. wiegmanni and some characteristics of vegetation and soil. Relatively more tapered snouts and narrower heads occurred in sites with taller bushes and soils containing higher amounts of clay (i.e. harder substrates that are more difficult to excavate). We hypothesise that differences in head shape due to microhabitat and soil variation might be considered a scenario under which different amphisbaenian head morphologies initially evolved.

Mate guarding is a common behavioral adaptation in males to ensure mating or to hinder current partners from remating with rival males. In the decorated cricket, Gryllodes sigillatus, males transfer a spermatophore to females at mating, comprising a sperm-containing ampulla enveloped in a large gelatinous mass, the spermatophylax, that serves as a nuptial food gift for the female. Males guard the female while she feeds on the nuptial gift and while sperm are evacuated from the ampulla into her reproductive tract. Mate guarding behavior functions to prevent competitors from mating with the female but may also represent a behavioral counter-adaptation to the propensity of females to cease nuptial feeding and to terminate sperm transfer prematurely. Using an experimental evolution approach, we tested the prediction that males would guard females more vigorously in response to an experimentally intensified sexual conflict. We recorded the intensity of male mate guarding from replicate lines reared for 25 generations at either an elevated or a reduced intensity of sexual conflict by imposing male- and female-biased adult sex ratios each generation, respectively. We observed the evolution of higher intensity mate guarding behavior in one of the four male-biased selection lines, but in none of the female-biased lines; previous work has revealed that the males in this specific line also produce less manipulative food gifts, suggesting the existence of alternative mating strategies. Additionally, we found a positive correlation between the behavioral investment in mate guarding and the duration of the sperm transfer from the ampulla. As such, this provides a possible mechanism through which more intense mate guarding could increase male fitness.

Understanding feeding behaviour of large carnivores is crucial for unveiling how adaptations to human-modified landscapes can alter their behaviour and ecological role. In this study, we investigated wolf feeding activity during winter through interpretative field surveys of 454 clusters of GPS locations obtained from 8 wolves in the Abruzzo, Lazio, and Molise national Park (central Italy, 2008–2011). Using generalized linear mixed models, we explored spatio-temporal use of feeding sites (i.e. kill and scavenging sites) accounting for the effect of ecological and anthropogenic factors. We detected feeding activity in 18.1% of the investigated GPS clusters, with 51.5% of the inspected feeding sites indicating scavenging on domestic prey. Wolves used feeding sites for an average of 2.4 days and revisited them about 3 (±2.7) times before being abandoned. Prey type (wild vs. domestic) and wolf category (i.e. solitary floaters, newly established breeding pairs, pack members) affected both prey handling time and recurrency of feeding site use. Pack members (≥3 wolves) spent relatively more time at feeding sites, especially those featuring large prey, and visited them more frequently compared to solitary floaters and wolf pairs. Although wolves used feeding sites mostly during the night, nocturnality significantly decreased with increasing distance to roads but not to settlements. We also revealed that time of cluster formation, number of visits, and mean slope best predict the presence of a feeding site at a GPS cluster. Despite the inclusion of scavenging sites and domestic prey, and limited to prey ≥15 kg, our predictive model would have revealed 62% of the feeding sites in the GPS clusters we investigated, while reducing of about 59% the field time required for ground truthing GPS clusters.

Previous work has focused on how prey availability and fear of people affect apex predators' habitat selection, but few have studied the effects of intraguild interactions. Patterns of co-occupancy between sympatric carnivores have started to be well described, but understanding the underlying habitat selection processes is lacking. We evaluated whether the risk of encountering African lions (Panthera leo) influences habitat selection by spotted hyaenas (Crocuta crocuta, hyaena hereafter) using GPS-collar data and two approaches: (1) resource selection functions considering the static long-term risk of encountering lions, and (2) step selection functions considering the dynamic, immediate risk of encountering lions. We explored the interplay between the risk of encountering lions, vegetation type and moonlight illumination, and examined individual variation in habitat selection. As expected, hyaenas did not avoid areas intensively used by lions, and there was even a positive effect of the long-term risk of encountering lions on habitat selection by hyaenas. As in other study sites, this likely arises because hyaenas select the same areas as lions. At the finer scale, unexpectedly, hyaenas did not generally move away from lions. We believe this occurs because hyaenas can sometimes be attracted to lions because of scavenging opportunities or because they outnumber lions and are likely to win an aggressive encounter. These two circumstances can lead to highly contrasting outcomes and highlight the high dynamics of intraguild interactions. This also illustrates the limits of GPS-based studies that lack crucial information about the context of interactions. While at the population level, we detected a selection for open vegetation areas, which are rich in prey in the study ecosystem and potentially good hunting grounds for cursorial predators, such as hyaenas; our results show a very high inter-individual heterogeneity underlying this population level result. Our work therefore illustrates the importance of investigating individual habitat selection.

The ability of animals to find shelter is vital for survival, providing protection from predators and harsh conditions. In lab studies, animals often favor walls and corners, suggesting a natural inclination toward enclosed spaces for safety reasons. Here, we investigated how shelter characteristics, specifically its size and corner angles, affect usage by the red flour beetle, Tribolium castaneum, a cosmopolitan pest of stored products, as well as the beetle's movement. The beetles remained longer in narrow shelters than in medium-sized shelters, with no significant difference from wide shelters. They spent less time in obtuse-angled corners than in right-angled ones, and more time in acute-angled corners than in right-angled ones, indicating their ability to differentiate among corners and choose suitable ones. Next, we examined whether movement through a corridor is delayed more strongly by the presence of obstacles forming acute angles with walls than by obstacles forming obtuse angles. Although there was no difference in the proportion of arrivals at the destination cell or the time required to cross the corridor, acute-angled obstacles caused a higher frequency of reentries into the origin cell, possibly due to the beetles' tendency to follow walls. This research may have applied importance, such as enhancing our understanding of beetle movement, strategies to delay their arrival in new areas, and the optimal placement of traps.

Armadillos are considered important ecosystem engineers as their burrows can benefit many species. Monitoring burrows with camera traps allows us to obtain relevant biological data on the species that utilize this resource. Our goal in this study was to examine the lesser anteater's (Tamandua tetradactyla) use of giant armadillo (Priodontes maximus) burrows as a first attempt to assess how user species benefit from them. We took camera trap data from a long-term monitoring study (2011–2020) in the Brazilian Pantanal wetland. We then evaluated and classified the frequency and way in which the burrows were used by the individual lesser anteaters. We also assessed the time of entrance and exit from the burrows related to sleep, the period of activity and activity pattern. This species used most monitored burrows, and these were used more than once by the same individuals or by more than one individual at different times. We described four types of uses: inspection of the burrow entrance, inspection of the interior of the burrow, exploratory/resting and sleeping. The lesser anteater was active on average 7 h 42 m per day with a primarily nocturnal activity pattern, which started in the early evening and ended at dawn. This is the first study to evaluate a focal species' use of giant armadillo burrows. Our data suggest that burrows are a valuable resource for the lesser anteater as shelter. Burrow monitoring proved to be effective in obtaining records and key information on the ecology and behaviour of the lesser anteater. New studies may explore this approach to acquire data on other species who frequently use these burrows, including agoutis, tayras, ocelots and coatis.