Journal of Zoology最新文献

Chemical communication is the most ancient and widespread form of communication. In many species, specialised structures called scent glands have evolved to facilitate this communication. These glands vary considerably among species in structure, size, body location and the composition of their secretions. Histological analysis is therefore required to confirm the presence of scent glands, identify secretion types and assess potential roles of the immune system and microbiota in modifying secretions. Here, we investigated the distribution and structure of scent glands in the banded mongoose (Mungos mungo), a cooperatively breeding, group-living mammal. We found that individuals possess two large (1.5 cm diameter) anal glands, each consisting of a central sac surrounded by glandular tissue. This in turn is surrounded by a layer of striated muscle, which likely facilitates the deposition of relatively large quantities of odorous chemicals when engaging in deliberate scent marking behaviour. The glands are lined by two different types of epithelia (keratinised and non-keratinised) which may impact how immune genes such as the major histocompatibility complex (MHC) affect the microbiome of the glands, and therefore, the chemicals that are secreted during scent marking. Additionally, we reveal a previously unidentified small (0.75 mm in length) scent gland in the cheek, which may be used for scent marking. We provide evidence that banded mongooses may use their chin and abdomen for scent rubbing, as these regions are often rubbed in odorous substances, but we found no evidence of specialised scent glands in these areas. Our findings highlight the importance of integrating anatomical, behavioural and biochemical approaches to understand the mechanisms and purposes of scent communication. This study serves as a foundation for future research on the interplay between scent marking and rubbing behaviours, and the role of immune genes and microbiota in shaping chemical communication in banded mongooses and other mammalian species.

Cooperative breeding, a rare trait in <1% of mammals, is explored within African wild dog packs (Lycaon pictus), where alpha females typically produce the first litters, but subordinate females may also breed, resulting in second litters within the same pack. We investigated the reproductive dynamics of wild dog packs in Zimbabwe's Savé Valley Conservancy (SVC) using 14 years of data from 49 packs and 131 den sites, obtained through spoor tracking, radio telemetry, sighting reports and camera traps during denning periods. Among packs capable of multiple litters, 41.15% of breeding events produced multiple litters annually, with 24.86% of all litters from subordinate females, primarily litter sisters of the alpha. Generalized linear mixed models revealed that younger packs and those with more subordinate females were significantly more likely to produce multiple litters, indicating weaker dominance hierarchies. Within multiple litter packs, pup survival to 1 year was significantly higher for second-born than first-born litters. However, 2-year survival significantly increased with higher pre-emergence rainfall, older alpha females and higher maximum temperatures. Across both litter types, 1-year and 2-year pup survival significantly improved with larger packs, while 2-year survival also significantly increased with pre-emergence rainfall. Pups from single litters had significantly lower survival to 2 years compared to multiple litters. Despite the potential for reproductive conflict, we found low infanticide (2%) and moderate pup stealing or adoption (14%), suggesting that kin selection promotes reproductive tolerance. These findings highlight the social and ecological complexity of cooperative breeding and its conservation relevance.

Amphibians are the most endangered group of vertebrates, facing numerous threats, and detailed data are required to identify stressors and prioritize conservation efforts. While these data exist for many species, gaps remain, especially in understudied regions. Citizen science is an approach that can vastly increase the available data for informed decision-making. This study aims to use such an approach to investigate the population dynamics of two amphibian species in urban environments. We used the program MARK to perform a capture-mark-recapture analysis on two datasets: a large dataset collected in a multiyear citizen-science program, focused on two urban near eastern fire salamander (Salamandra infraimmaculata) populations, both found within a large city; and a second dataset, collected in a 1-year survey, focused on two green toad (Bufotes sitibundus) populations in an urban park and in a nearby nature reserve. Individuals of both species have unique patterns of dorsal spots, allowing for noninvasive recapture identification. Using repeated measurements of recaptured salamanders, we derived a species-specific growth curve that converts body length into an age estimate. Combined with a survival analysis of the capture–recapture dataset, this age estimate revealed a prolonged period of increased vulnerability during the salamanders' terrestrial phase, from metamorphosis until they reach full size. Additionally, the two case studies suggest that exotic fish introduction can have highly detrimental impacts on these amphibian species and should be the focus of future studies.

Animal locomotion occurs at different speeds in nature, but much of the current literature focuses on investigating maximal speeds. Voluntary speeds are likely a better approximation of optimal speeds that are more economical and more widely used in nature, which should be more widely considered. Autotomy, voluntary self-amputation, is a common strategy beneficial for escaping life-threatening situations. Spiders frequently autotomize legs in response to predatory encounters. It has been shown that despite this benefit, autotomy causes a reduction in maximal speeds, which makes it more difficult for spiders to evade predators, locate food, and search for mates. However, maximal speeds are rarely used in nature because of their energetic cost and negative impacts on maneuverability and accuracy of leg placement. Studies are lacking on how leg autotomy influences voluntary (optimal) speeds which spiders use to mitigate the costs of maximal speeds. This study examined the effects of leg autotomy, incline (horizontal and vertical), and body mass on optimal running speeds of cellar spiders, Pholcus phalangioides Fuesslin, 1775. Voluntary speeds were assessed twice for all spiders on both inclines. The first run consisted of non-autotomized spiders. Then, half of the spiders were induced to autotomize one front leg, while the other half were run again intact. Overall, while autotomy did not result in significantly different speeds, vertical speeds were slower than horizontal speeds and males were faster than females. Running speeds decreased with increasing size for both autotomized and control spiders. We found the speeds of control spiders slightly increased between the first and second set of trials, whereas autotomized spiders showed a slight decrease. These results suggest that, regardless of incline, cellar spiders are able to compensate for leg autotomy with only a small hindrance on optimal performance. Future work should seek to directly compare forced and voluntary movements to further examine how spiders compensate for leg autotomy.

The skin serves as the outermost barrier between an organism and its environment and fulfills numerous physiological and ecological functions. In lizards, scale morphology is an important adaptive trait that mediates responses to environmental influences such as extreme temperatures, ultraviolet radiation, drought and anthropogenic disturbances. Our study provides an analysis of the environmental drivers influencing intraspecific variation in the scale ecomorphology of the island lizard Gallotia galloti across 3700 m of elevation, taking into account different macro- and microclimatic conditions and varying degrees of anthropogenic influences and across three body regions: dorsal, ventral and tail. We found several correlations suggesting multiple dependencies of scale morphology on environmental variation. The positive correlation between July temperature and wind speed at 3 cm above the ground and dorsal scale density showed that more densely packed scales are associated with hotter and drier environments. This could possibly be related to the thermoregulatory and hydroregulatory function of the skin, since the dorsal side of the body is most exposed. Higher sun exposure was associated with larger dorsal and tail scales, indicating a possible photoprotective function. Ventral scales are not exposed to the pressure of solar radiation and wind. Accordingly, ventral scales showed no correlation with these factors, but we found that a higher ratio of day-to-night temperature variation relative to seasonal changes (isothermality) was associated with a higher density of ventral scales. The human footprint index positively correlated with larger and denser ventral (and not dorsal or tail) scales. Overall, our results illustrate the complexity of responses of scale morphology to different environmental variations. Evidently, G. galloti exhibits morphological diversity in response to climatic conditions and urbanization, highlighting the potential ecological significance of scale size variation. Future research should investigate the genetic basis and possible effects of climate change on scale morphology.

An understanding of mechanisms by which non-territorial solitary mammalian species receive, produce, and respond to communication signals has remained limited, particularly for marsupials. The bare-nosed wombat (Vombatus ursinus) represents a potentially tractable marsupial system to understand communication in a solitary non-territorial herbivorous mammal, particularly as a function of their distinct cube-shaped faeces that facilitate deposition in aggregations. We undertook a multifaceted approach to assess evidence of scat-associated olfactory communication and create a foundation for further research in bare-nosed wombats, linking themes of capacity for signal reception, signal location in the environment and emission and signal response. First, cranial sections identified gross morphological features consistent with a vomeronasal organ, indicative of developed olfactory signal reception. Second, field surveys demonstrated that bare-nosed wombat latrines are associated with features in their landscape (particularly rocks, logs, and burrow entrances), which we hypothesize serve as a visual cue for locations where olfactory communication is concentrated. Third, gas-chromatography/mass-spectrometry on scats showed individually distinctive chemical signatures. Finally, using field experiments, we showed that introducing scats from unfamiliar bare-nosed wombats increased investigatory behaviors at manipulated latrines, and that these effects may depend on local recruitment and latrine density. Collectively, our research provided evidence that olfaction is functionally significant in bare-nosed wombats, provides a foundation from which more detailed investigations can build upon, and suggested this marsupial species is a tractable system for research on communication in a non-territorial solitary mammal.

The expansion of human activities into natural environments constantly exposes wild animals to novel and potentially dangerous conditions, forcing them to modify their behaviour to cope with these challenges. Here we analysed the behavioural responses of a threatened South American seabird to novel stimuli in controlled experimental situations. In particular, we assessed responses to novel objects, considering intrinsic characteristics of the individuals (i.e., sex and age), and their relationship with the propensity to try novel food. We tested 40 Olrog's gull (Larus atlanticus) for neophobia in the presence of different novel objects placed near their familiar food while isolated in outdoor aviaries. We also conducted a novel food test to analyse individuals' propensity to approach and eat novel food. We found that individuals took longer to consume food in the presence of novel objects compared to the familiar situation. The neophobic responses varied with the object type, but not with either sex or age. The propensity to try novel food did not vary with sex and age, and was not related to their neophobic response towards novel objects. In threatened species like the Olrog's gull, the differences in neophobic responses of individuals within a population may provide insight about the behavioural flexibility required to cope with environmental challenges, especially when individuals are exposed to unfamiliar stimuli, such as objects or food. This flexibility may be critical to quickly adapt to environmental changes, which are becoming more frequent with the increasing urbanization of natural environments.

Shifts in phenological events (reproduction, migration, etc.) appear to be a common response to a changing climate by many taxa. Phenological shifts may elicit stronger responses in organisms with complex life histories as effects could compound across life stages. To better understand growth and survival consequences in the early-breeding wood frog (Rana sylvatica), we examined larval response to hatching phenology (early and late [+14 days]) and increased pond temperatures (ambient and warm [+4.3°C above ambient]) on tadpole growth and development. We expected that tadpoles would respond to delayed hatching via accelerated growth and development. However, we hypothesized that increased temperatures would be antagonistic to a compensatory acceleration of tadpole growth and development and result in slower tadpole growth, later metamorphosis, and smaller size at metamorphosis. Contrary to our expectations, tadpole responses to delayed hatching were not temperature-dependent. While temperature and hatch timing had significant effects on all focal response variables, their effects were independent and additive. Larvae were able to compensate for the 2-week delay in hatch timing through accelerated growth and developmental rates. In fact, delayed tadpoles appeared to overcompensate, metamorphosing several days earlier than their early-hatching counterparts. Finally, although accelerated growth rates in delayed treatments could help compensate for a later start, they were ultimately insufficient to equalize size at metamorphosis. Our results portray the complexity in growth and developmental rate responses due to variation in reproductive timing and temperature. They also highlight a clear need to understand the putative fitness costs of compensatory responses across life stages.

In this study, we examine the dimensions of the nasal horns of woolly rhinoceroses and describe the longest rhino horn known to date, which was recently discovered in the permafrost of Yakutia. The extinct woolly rhinoceros is an iconic representative of the Late Pleistocene mammoth fauna of Eurasia, characterized by two huge keratinous horns. The nasal horn is considerably longer than the frontal one; it is laterally flattened and has a saber-like shape, which is unparalleled among modern-day rhinoceroses. The nasal horns of adult woolly rhinoceroses range in length along the anterior curvature from 68.5 to 134 cm (101.7 cm on average). Their mass varies between 2.5 and 11.4 kg (6 kg on average). Both of these values exceed those of all extant rhinoceroses. The record-breaking nasal horn discovered in Yakutia last year reaches 164.7 cm along the anterior curvature and weighs ~9 kg. The relatively small size of the skull in this specimen indicates that it probably belonged to a rhinoceros female. This suggests that Coelodonta antiquitatis may have had the longest horns in females, similar to modern-day African rhinoceroses. The number of periodic transverse bands (each of which consists of two, darker and lighter, keratin zones) along the length of the horn suggests that the discovered horn belonged to the oldest known woolly rhinoceros with an individual age of ≥40 years. Thus, this discovery not only provides insights into the morphological features of woolly rhinoceroses but also offers valuable information about their palaeoecology and sexual dimorphism.