Journal of Zoology最新文献

With the increasing frequency and intensity of heatwaves due to climate change, the survival and reproductive success of mammals could be under significant threat. However, the specific effects of these environmental stressors on mammalian reproductive fitness remain insufficiently explored. This study investigates the impact of a simulated heatwave on male fertility indices in two African rodent species: the mesic four-striped field mouse (Rhabdomys dilectus) and the Namaqua rock mouse (Micaelamys namaquensis) during the breeding season. We measured key indicators of male fertility, including testes mass, testes volume, seminiferous tubule diameter, the presence of sperm, and plasma testosterone levels. Our findings reveal that both species experienced significant effects on male fertility indices, with the smaller R. dilectus showing a decline in all fertility indices following a simulated heatwave. These results suggest that the projected increase in heatwave events may compromise the reproductive success of small mammals, potentially leading to population declines. Finally, this study highlights the need for focused studies on the effect of heatwaves on long-term reproductive success in both males and females.

Small mammal populations fluctuate significantly in abundance over time, affecting the entire food web. However, changes in their occupancy across a landscape receive less attention. While habitat features are relevant for some predators, diet specialization and prey distribution and abundance might play an important role in shaping predator populations. Using a multi-season occupancy analysis, we examined the spatio-temporal patterns of Mediterranean mesocarnivores—common genet, stone marten and red fox—focusing on the factors that influence their occupancy dynamics, particularly small mammal occupancy as a prey resource. Data was collected from December 2020 to May 2021 in the Sant Llorenç del Munt i l'Obac Natural Park using a camera-trap grid. We analysed small mammal occupancy dynamics and used these as covariates in predator occupancy models to explore predator–prey relationships. Additionally, we included the occurrence of each carnivore as a predictor for interspecific analysis, and kernel density functions were used to assess daily activity overlaps. Results showed that interspecific competition significantly affected mesocarnivore occupancy, as genet occupancy was negatively correlated with the red fox occupancy. Although prey occurrence did not influence mesocarnivore occupancy, it did affect detectability, with genet and stone marten detectability being positively related to small mammal presence and high daily activity overlap between predators and prey. This suggests that mesopredators respond rapidly to prey abundance, highlighting the intricate temporal dependence between predator activity and prey occupancy. Dynamic occupancy and activity models provide a deeper understanding of predator–prey relationships at the local scale.

Human impacts on the environment and wildlife populations are increasing globally, threatening thousands of species with extinction. While wildlife-based tourism is beneficial for educating tourists, generating income for conservation efforts, and providing local employment, more information is needed to understand how this industry may impact wildlife. In this study, we used motion-activated cameras at 12 waterholes on a private game reserve in northern Namibia to determine if the presence of humans and permanent infrastructure affected mammal visits by examining their (1) number of visits, (2) time spent, and (3) diel activity patterns. Our results revealed no differences in the number of visits based on human presence for any of the 17 mammal species studied. However, giraffes (Giraffe camelopardalis) spent more time at waterholes before observer presence compared to during. Additionally, several species changed diel activity patterns when human observers were present. Notably, several carnivore and ungulate species increased overlap in their activity patterns during periods while humans were present relative to when humans were absent. These modifications of mammal temporal activity patterns due to human presence could eventually lead to changes in community structure and trophic dynamics because of altered predator–prey interactions. As humans continue to expand into wildlife habitats, and wildlife-based tourism increases globally, it is imperative that we fully understand the effects of anthropogenic pressures on mammal behavior. Monitoring of wildlife behavioral changes in response to human activity is crucial to further develop wildlife tourism opportunities in a way that optimizes the impact of conservation goals.

The evolution and ecomorphology of rodent craniomandibular apparatus have been extensively studied at a broad spatial scale. However, the question of how phenotypes and developmental instability interact with ecological pressures in human-modified landscapes has been less explored. In this study, we test the influence of evolutionary history, diet, and habitat use on skull and mandible shape variation within a rodent community composed of eight cricetid species from an agroecosystem in central Argentina. We used geometric morphometrics, phylogenetic relationships, and ecological specializations in diet and habitat use to test the interplay between these factors. Our results indicated a strong phylogenetic signal for the symmetric components of the skull shape, but not for the mandible or asymmetric shapes. The strict insectivorous Oxymycterus rufus was the most phenotypically diverged within the rodent community. In general, more generalist species, both in terms of diet and habitat use, presented more phenotypic disparity (diversity) than specialists (e.g., strict insectivorous and natural and semi-natural specialists) in craniomandibular shape variation. Dietary generalists and non-strict granivores presented a tendency to show more skull asymmetric variation than non-strict insectivores. These results suggest that generalist species exhibit higher levels of variation compared to specialist species, likely due to their wider range of responses to environmental stress. In cricetid species with similar ecological preferences, coexistence may thus be facilitated by morphological partitioning and developmental instability canalization based on dietary differences.

Color polymorphisms in lizards are maintained by complex interactions between environmental factors, genetics, and physiological traits (e.g., immunity) that can differ among morphs. Here, we investigated the relationship between mite load, throat coloration (orange, yellow, and white), and cell-mediated immune responsiveness (CMI) in the Atlas day gecko, Quedenfeldtia trachyblepharus (Boettger, 1874) during its post-mating period. We also evaluated the relationship between the patterns of infestation by ectoparasites and sex, throat color, and host size. The prevalence and intensity of infestation by mites did not differ by sex, host body length, or throat color. Furthermore, there was no significant relationship with host body condition. The CMI was related to sex and lizard body size (SVL). Additionally, there was a positive correlation between the intensity of infestation and the CMI response of the gecko hosts. Likewise, there was a significant positive correlation between CMI and the scaled mass index (SMi) of the lizards. In addition, geckos with broken tails had a significantly higher CMI than those with regenerated or intact tails. Moreover, CMI differed significantly among morphs; orange morphs had a higher immune response than yellow one, while the white individuals presented the lowest response. Thus, CMI is morph-specific in this gecko, suggesting that this immunological trait could play a determinant role in maintaining throat color polymorphism in this species.

Certain parasites can manipulate their hosts to enhance their own fitness and transmission success. Rhizocephalan barnacles are a notable example, inducing significant changes in their crustacean host's morphology, physiology, and behaviour. Until recently, it was believed that the spider crab Scyra aff. ferox is parasitized by a single species Sacculina pilosella in the Sea of Japan. However, previous molecular studies have revealed a complex of unrelated species, Sacculina pugettiae (fam. Sacculinidae) and Parasacculina pilosella (fam. Polyascidae). These rhizocephalans can even parasitize one host specimen simultaneously. Here, we investigated the interaction of S. pugettiae and P. pilosella with the nervous system of their common host. Species were identified based on receptacle morphology, with further validation through 18S gene phylogenetic analysis. The parasites interacted differently with the host nervous system: S. pugettiae had goblet-shaped organs in the ganglion periphery, while P. pilosella lacked these structures, instead possessing numerous neuropil rootlets. In case of simultaneous infection, both goblet-shaped organs and neuropil rootlets were present. Histochemistry revealed the presence of muscular rosettes in the rootlets of both species, suggesting a similar organization of the muscular system despite phylogenetic differences. Scanning electron microscopy confirmed the presence of host cell projections enveloping the rootlets. This study provides insights into the morphological features of rhizocephalan-decapod interaction and highlights differences in their interaction with host nervous tissue between families. Our results also confirmed the loss of the goblet-shaped organs in Polyascidae.

Human-wildlife conflicts have increased and are particularly acute when predators are involved. A frequent source of conflict is some people's misbeliefs related to the alleged impact of predators on game species and livestock. In this context, quantifying the impact of expanding predators on their prey can be useful in designing conflict mitigation strategies. We estimated the predation impact of the Egyptian mongoose (Herpestes ichneumon), an expanding mesocarnivore in southwestern Europe, on European rabbit (Oryctolagus cuniculus) and red-legged partridge (Alectoris rufa) populations, two declining prey species highly valued by hunters. We estimated mongoose densities in three areas of central Spain through live capture, GPS/VHF tagging, camera-trapping and spatial mark-resight models. Rabbit and partridge densities were estimated through transect counts and distance sampling. We quantified the mongoose diet by scat analysis. Finally, we compared the number of individuals consumed by the predator population with the estimated total prey populations. European rabbits were the most important mongoose food in two of the study areas, whereas red-legged partridges were rarely consumed in all the areas. Rabbit density varied widely among study areas (14.0–881.4 rabbits/km²), while partridge density was low in all the areas (2.3–6.9 partridges/km2). The predation impact on rabbits was low in the area with the highest rabbit density (1.9–3.8% of estimated population) and higher (5.6–29%) in the other areas. In contrast, the predation impact on partridge populations was low (<9%) in all the study areas. This is the first study that estimates the Egyptian mongoose impact on small-game species, a necessary step to deal with the conflicts over the management of this expanding species. The study of predation impact may contribute to the effective management of human-wildlife conflicts involving predators, by improving the understanding of where additional management may take place to protect prey species or deter predator populations.

Autotomy in animals, the voluntary loss of a body part at a specific location, is a widespread behaviour observed across various groups. This mechanism provides several advantages, such as predator evasion, escape from entrapments, and even reduced injury costs from agonistic interactions. Lizards display tail autotomy in response to predation and intraspecific aggression. Moreover, it is common for these reptiles to have sexually dimorphic traits, such as colouration and body size, which may influence predation risk and consequently their antipredatory strategies. This study focuses on the Achala copper lizard (Pristidactylus achalensis) which inhabits an isolated highland ecosystem in central Argentina. This species is an ideal study model due to its territorial and aggressive behaviour, high intraspecific competition and sexual dichromatism. The aims of this study were to determine the influence of sex and body size on the occurrence of tail autotomy in P. achalensis. Additionally, we assessed the cost of autotomy by analysing the distance between the vent and the tail cut. Furthermore, we investigated the possibility of repeated tail autotomy by a single individual. Our results showed that in P. achalensis, sex and body size interacted significantly resulting in different patterns of tail autotomy. In females, the frequency of autotomy increased gradually with body size, whereas in males it increased more abruptly and reached its maximum frequency at smaller body sizes than in females. Males presented higher autotomy frequencies than females, likely because they are more likely to be perceived by avian predators than cryptic females. The findings of this study contribute to broadening the knowledge of lizard behaviour, shedding light on the complex interplay between predation, intraspecific competition and reproductive dynamics in this unique species.

Hair offers a non-invasive way to assess mercury exposure in diverse species, but variable and poorly understood molt patterns in wildlife may hamper the interpretation of tracer levels in hair. The reliability of using hair to precisely assess internal mercury burden, thus, varies across species, but few studies have assessed the reliability of using claw. Claws grow continuously, and growth rate may be easier to monitor than molt patterns. We quantified total mercury concentration (THg) in internal and keratinous tissues of 55 red foxes (Vulpes vulpes) legally harvested near Arctic tree line in Canada in winter (i.e., when mobility and opportunistic foraging are maximal) to compare the performance of hair and claw in predicting internal mercury burden, and examine the overall capacity of THg in keratinous tissues to predict internal THg at low exposure. Red foxes are widespread, occur at high densities and occupy a high trophic position, and thus could be a good sentinel species for monitoring mercury in the less-studied terrestrial food webs. We found generally low levels of THg in all fox tissues (range: 0.06 mg kg⁻¹ in brain to 1.13 mg kg⁻¹ in hair) indicating overall low contamination of this low-Arctic terrestrial food web. Relationships between THg of diverse internal organs were strong, but THg in both claws and hair were poor predictors of THg in internal organs. We thus advise caution when interpreting mercury levels in keratinous tissues of highly mobile species, as they may over- or underestimate the overall levels of exposure of a population because of non-continuous or seasonal growth. Adding a time component using segmental analysis of continuously growing keratinous tissues, or associating multiple tissues reflecting diverse timeframes and physiological processes, may offer a more accurate and complete understanding of toxicological risks.

The great snipe Gallinago media, as a long-distant migrant wintering in Africa, faces the challenge of accumulating sufficient energy reserves before departing from European breeding grounds. Despite possible trade-offs in resource allocation, this species additionally initiates moult of flight feathers before southward migration. Here, we discuss the strategy of flight feather moult and fuelling for female and male great snipes from the Eastern European lowland population, exploring their scheduling constrained by the timing of breeding and departure. We found significant intersexual differences in both moult initiation date and the speed of moult. Males start flight feather replacement more than 2 weeks earlier and moult at a faster rate compared to females. However, neither sex completed this process on breeding grounds before the migration, as late in the season all males and half of the females had suspended their primary moult, with the remaining females not moulted at all. Moult of secondaries rarely occurred in the studied population. We observed non-linear energetic stores gain in the studied period, where both sexes maintained stable and low energy stores until the end of July, coinciding with the primary moulting period. Subsequently, there was an increase in energy stores of approximately 1% of the lean body mass per day, indicating a shift towards fuelling for migratory flight. The overlap between stages of stable and low energy stores and moulting suggests a resource allocation towards feather growth before initiating fuelling. Besides limiting a trade-off in resource allocation, this strategy may also contribute to minimizing predation risk, as both increased body mass and missing flight feathers may impair flight. Our study describes moult strategy in great snipe conducted on their breeding grounds, highlighting intersexual differences likely resulting from different parental duties of males and females of this lekking species.