Journal of Zoology最新文献

Nest construction is a feature of a range of taxa, yet the functional properties of nests are poorly understood. Avian nests offer thermal insulation, structural support and protection from rain, but to date there are few studies that have explored these functions for mammal nests. Here nests constructed by harvest mice (Micromys minutus) were studied ex situ to determine the thermal insulation provided by the nest wall and the degree to which simulated rainfall was absorbed. Nests were collected from across Great Britain and analysis explored whether nest size and geographical location affected insulation or rainproofing. Nests were constructed from grass leaves woven into an outer wall that surrounded smaller pieces of grass that filled the interior of the nest. Nest mass was positively related to thermal insulation but unrelated to geographical location. By contrast, nest mass was positively related to the amount of water nest absorbed after simulated rain but volume and longitude were inversely related to the time it took the nest to dry out. In many ways, harvest mice nests had similar functional properties to those of small songbirds, i.e., to provide thermal insulation and rainproofing. This study was the first to explore the environmental protection potentially offered to harvest mice by their nests. The study has highlighted our poor understanding of the factors that determine the function of mammal nests. There is scope for more research into the functional properties, e.g., thermal insulation or rainproofing, of a wide variety of mammal nests.

After centuries of extinction due to human persecution, Eurasian beavers Castor fiber L. have been released to Southern Europe in the last decades. Being ecosystem engineers, beavers have attracted great attention regarding restoration of aquatic and terrestrial ecosystems. Nonetheless, the effects of the species on aquatic invertebrates known to date are not univocal and mostly refer to central European riverine systems. Here, we evaluated the effects of beaver presence on aquatic macroinvertebrates for the first time in a Mediterranean riverine ecosystem, by applying a sound control-impact sampling design and controlling for seasonal variation in macroinvertebrate assemblage composition. A significant variation in response to season was evident for macroinvertebrate communities, revealing distinct assemblages during spring and summer. Furthermore, the presence of beavers was also identified as a significant driver of species composition, as samples near the beaver dam showed significant variation from control sites. Macroinvertebrate community traits changed according to the relative position to the beaver dam, as control sites featured on average higher abundances of taxa with higher values of bioindication score, larger size, lower adaptation to drag, and were less frequently of introduced origins. Yet, these differences were strongly taxon- and season-specific in their intensity and direction. Differences across sites were mainly driven by the relative abundances of few taxa—including both alien species and high environmental quality indicators—such as those from genera Potamopyrgus, Baetis, Habrophlebia, Ephemerella, Leuctra, and Radix, which explained about 70% of the observed divergence among conditions. Our results indicate that beavers and their engineering activity may induce highly variable species-specific responses in macroinvertebrates, thus possibly representing a driver of environmental heterogeneity along Mediterranean rivers, and that both bioindicators and alien species may exploit such heterogeneity.

Males of many species develop disproportionately large weapons, and frequently the weapon size increases more quickly with body size in small than in large males—a trend often considered to result from the depletion of developmental resources limiting male weapon exaggeration. Based on the cost-minimization hypothesis, a shallower weapon-body size allometric slope in large than in small males could be selected for if the energetic maintenance costs of having oversized weapons increase faster in large than in small males. Whether males of different size groups that differ in the weapon-body size allometric relationship also differ in the energetic costs of maintaining their weapons has not yet been investigated. Consequently, we studied this using the stag beetle (Cyclommatus mniszechi), in which males are larger in size and have larger mandibles than do females and are divided into two morphs: majors are larger and have longer mandibles than minors. In both male morphs, mandible size increases disproportionately with their body size, but it increases more quickly in minors than in majors. We measured the standard metabolic rate (SMR) of the three types of these beetles (the two male morphs and females) to investigate whether the energetic maintenance cost of carrying weapons differs among them. Body weight explained 80% of the variation in the SMR in the three types of beetles, and SMR increased more quickly with body weight in major males than in minor males or females. Weapon and body size also jointly explained approximately 80% of the variation in the SMR. Whereas SMR increased with body size in all three types of beetles (with a higher rate of increase in major males than in minor males or females), only the major males' SMR increased with weapon size. Overall, being heavier and larger and carrying oversized weapons are energetically costly in major males, something which could constrain the exaggeration of their weapons.

Loggerhead turtles (Caretta caretta), being ectothermic organisms, could be especially susceptible to climate change effects, and may exhibit climate-related variation in their reproductive behaviours such as phenology, annual nest numbers, clutch size, hatching success, incubation period and sex ratio. This study investigated the reproductive phenology and outputs of loggerhead turtles and their relationships with climatic variables over a 5-year period (2019–2023) at Patara Beach, Türkiye. We found significant fluctuations in atmospheric temperature, sea surface temperature and relative humidity, and that female turtle emergences on Patara Beach could temporarily adjust their phenology in response to these minor environmental changes. We highlight the importance of understanding the impacts of phenological shifts on the ability to satisfy the conditions over the nesting season that determine reproductive output. Our statistical analyses also showed that increasing sea water temperatures and atmospheric temperatures, as well as decreasing precipitation and relative humidity, had direct and/or indirect effects on the nesting phenology and reproductive output of loggerhead turtles. The findings from this study indicate that atmospheric temperature significantly affected incubation period, hatching success rate, the number of dead embryos and the number of empty eggshells. Additionally, relative humidity had a significant impact on the incubation period and the number of empty eggshells. In this context, rising temperatures led to drier nest conditions, decreased incubation periods and increased nest temperatures, resulting in higher proportions of female offspring. In conclusion, there are still gaps in our understanding of the effects of climate change on the reproductive biology of loggerhead turtles, and more studies are needed at both the Mediterranean and global scales to better understand these effects.

Studying positional behaviors is important for understanding how animals interact with their immediate environment. This is particularly important in arboreal species since arboreal milieus are primarily characterized by three-dimensional problems that arboreal species must overcome to efficiently access resources. Similarly, a fundamental aspect of an animal's ecology is its daily activity pattern. This information is important for understanding the basic ecology of animal species and their eco-evolutionary dynamics. This study sought to understand the habitat use and nocturnal lifestyle of the highly arboreal kinkajou (Potos flavus) by documenting variation in positional behaviors and activity patterns using 2223 photographs obtained from 27 camera traps in French Guiana. Data were analyzed using descriptive statistics, Kernel density estimation (KDE), and Gantt charts. Our results indicate that kinkajous show a strictly nocturnal activity pattern beginning from 19:00 h to 05:57 h, with peak active periods between 01:00 h and 02:00 h. The most frequent activities were scanning (48.33%) and traveling (47.13%). Quadrupedal walking (95.43%) was the main locomotor behavior during traveling. However, when crossing gaps between two substrates, kinkajous would either bridge (42.22%), leap (33.33%), or drop (26.67%) across gaps. Inactive periods were characterized by grooming (77.32%) and resting (27.84%) while mostly assuming a sitting (90.67%) or a catlike body curl posture (92.59%), interchangeably. This study highlights the broad array of positional behaviors displayed by kinkajous, further providing information to understand its basic ecology and eco-evolutionary dynamics.

Although previously close to extirpation in the southeastern United States, American black bear (Ursus americanus) abundance and distribution have increased with habitat management and harvest regulation. The north Georgia black bear population, the most abundant and widely distributed in the state, is currently being exposed to pressures from increasing anthropogenic disturbances, such as recreation and vehicle traffic. We evaluated the effects of environmental factors and anthropogenic activity on habitat use of black bears within a wildlife management area open to public recreation. We used detection/non-detection data from camera surveys conducted at 448 locations from April to December 2023 to fit hierarchical single-species occupancy models. Black bear detection was best explained by Julian date, its quadratic effect, and weekly human activity index. Detection increased through the spring, peaked in June, and declined throughout late summer and fall. In contrast to detection, occupancy was not affected by seasonal differences in black bear activity. Occupancy increased with increasing elevation, distance to water, and distance to high-use recreation areas. The spatial distribution of food resources likely contributed to the observed black bear occupancy pattern related to elevation and distance to water, while human disturbance in the study area also influenced black bear occupancy. Thus, our results suggest that in a landscape open to public recreation, black bear occupancy was driven by a combination of environmental and anthropogenic factors. Identifying patterns of occupancy at a scale typical of management provides important information for managing black bear populations throughout the large, connected network of national forests in the Appalachian region.

Delphinidae is the most diverse family within the toothed whale clade, displaying two biosonar modes, different feeding strategies, and diving and habitat adaptations. This work examines the delphinid mandible to determine the association between shape, size and ecological variables in extant species. Geometric morphometric analysis on 95 mandibles belonging to 30 (out of 38) extant species, representatives of all 17 extant genera, was performed in occlusal (or dorsal) and lateral (or labial) view. The results reveal that feeding mode and climate primarily drive mandibular shape in extant species. Biosonar mode is an evolutionary driver in mandibular shape in occlusal view, while diet and maximum prey size play a significant role in size only in both views. By contrast, Diving Ecology, Superficial Temperature and Rostral index do not play a significant role in driving delphinid mandibular shape and size.

This study investigates the effects of individuality and harem-holding status on the acoustic parameters of rutting calls (bugles) of 14 stags of Siberian wapiti Cervus canadensis sibiricus. The stags competed for mating with hinds in a large herd, free ranging inside a fenced area with complex landscape. We considered as harem-holders the stags, which kept a harem of 5 or more hinds for at least 2 days. Of the 15 days of observations enveloping the most active rutting period, during 3 days there was only one harem in the enclosure, during 9 days two harems, during 2 days three harems and during 1 day four harems. Stag bugles displayed both individual and status-related variation. Harem-holders compared with peripheral stags had shorter bugles with higher minimum fundamental frequency. After winning a harem and changing status from harem-candidate to harem-holder, stags shortened the duration of their bugles, lowered the beginning and maximum fundamental frequency and increased the minimum fundamental frequency. Significantly higher than the levels expected by chance, discriminant analysis classified 78.9% of bugles by the correct stag status and 53.2% of bugles by the correct individual callers. Different acoustic parameters encoded the status and individuality of the bugles. Status was encoded by the duration of the start and end parts and by the beginning and end fundamental frequencies. Individuality was encoded by the maximum fundamental frequency. We discuss that rutting calls of Siberian wapiti, although individualized, do not represent vocal signatures. However, these calls reliably mark stag harem-holding status.

Environmental factors and interspecific interactions, such as competition and facilitation, can shape species' geographic ranges. Here, we tested the relationship between geographic range overlap of squamate sister species, and their divergence in body size, diel activity, and microhabitat use. Competition theory predicts that sister species with similar traits will overlap less geographically than sister pairs with dissimilar traits. However, similar distributions may present similar selective pressures and favour similar adaptations, such that habitat filtering may result in species with more similar traits in sympatry. Across 1434 sister species contrasts, we found little relationship between range overlap and niche divergence. In some models, the divergence in body size and microhabitat use marginally increased with sympatry, while in other models, sympatric sisters had similar activity times. However, the low R-squared values of almost all these models lend only weak support to predictions from competition or habitat filtering theories. Sympatric sister species within the same biome showed more similar activity times than expected, lending some support to habitat filtering. Niche divergence in allopatry or sympatry, as calculated using a multi-trait dissimilarity index, did not show a phylogenetic signal, and niches of sister species from different squamate clades did not deviate significantly from the null expectation. Overall, niche divergence or convergence, across the axes we explored, is not a prerequisite for regional species co-occurrence. We suggest here that the lack of consistent support for either limiting similarity or habitat filtering may reflect that both these forces act as transient phenomena. More fine-grained analyses, in space and time, would be needed to detect their fingerprints. Thus, coexistence in the face of competition can arise due to various evolutionary and biogeographic mechanisms, acting concurrently or asynchronously.

Hair hormone analysis has received increasing attention in the fields of wildlife management and conservation over the last decade. However, few studies focused on sex steroid hormones, even though hair sex steroid hormone analysis has the potential to provide information on an individual's reproductive health, leading to a better understanding of animal reproductive biology and the assessment of individual and population health. Here, we tested the assay validation and examined whether hair progesterone concentration (HPC) differs between different sexes and age classes in the Asian black bear, Ursus thibetanus. We also investigated the effects of reproductive condition, age, and body condition index (BCI) on HPC to determine the utility of hair progesterone analysis in bears. The assay validation was reported in our study. We found a significantly higher HPC in adult females than in juvenile females and juvenile and adult males. In addition, we found no effects of age and BCI on HPC but a significant positive effect of reproductive condition, as the HPC in breeding adult females was significantly higher than in nonbreeding adult females. These results suggest that hair progesterone analysis has the potential to evaluate the reproductive condition of Asian black bears.