Journal of Zoology最新文献

Alkaloids and methoxypyrazines play a crucial role in the defence strategies of ladybirds against both arthropod and vertebrate predators. We investigated the response of the black garden ant (Lasius niger) to extracts from various ladybird species mixed with honey solution at decreasing concentrations. The tested ladybird species included Adalia bipunctata, Hippodamia undecimnotata, Coccinella septempunctata, Harmonia axyridis, Halyzia sedecimguttata, and Tytthaspis sedecimpunctata, with the lesser mealworm (Alphitobius diaperinus) serving as a control. The acceptance rate of the mixtures by ants decreased almost linearly with increasing concentrations of ladybird extract, while the acceptance of the control mealworm extract remained constant. Furthermore, no correlation was observed between the degree of deterrence and the body size, conspicuousness of aposematic coloration, or feeding specialization of the tested ladybirds. The degree of deterrence exhibited significant statistical differences among the ladybird species, with the concentration required to deter 50% of ants ranging from 3 to 7% of crude extract in a 4% honey solution. However, these differences were small and variable, suggesting limited biological significance. The degree of deterrence of individual species of ladybirds to ants that we found should be compared with their deterrence to other predators.

Mammalian carnivores are vulnerable to anthropogenic pressures, including habitat modifications, disturbance, and the introduction of non-native species. Forests throughout Madagascar are under persistent pressure from extraction of timber and non-timber products, and conversion of forest habitat to agriculture. Yet research into the impact of anthropogenic pressures on endemic carnivores is only recent, and relatively little is known about their populations in the extreme south of the island. We sought to explore how disturbance affects the occurrence of small carnivores in lowland humid forests and their varying degrees of adaptability to human-modified landscapes. To answer this, we conducted exploratory camera trap surveys of endemic Euplerid carnivores at two sites in Tsitongambarika Nouvelle Aire Protégée, between July 2019 and February 2020. We confirmed the presence of four Euplerid species at both survey sites, that is, fosa (Cryptoprocta ferox), spotted fanaloka (Fossa fossana), ring-tailed vontsira (Galidia elegans), and broad-striped vontsira (Galidictis fasciata), and three non-native carnivore species, that is, small Indian civet (Viverricula indica), domestic dog (Canis familiaris), and exotic/feral cat (Felis sp.). We used single-species, single-season occupancy modeling to predict the occurrence of the four Euplerids, using covariates relating to habitat degradation and human disturbance to test the anthropogenic factors that best predicted their use of landscape. We recorded high occupancy levels of all four native species, suggesting that the intact interior of Tsitongambarika continues to support viable populations. However, similar to research in other Malagasy forests, our modeling suggests that the occurrence of spotted fanaloka and fosa is negatively affected by forest degradation, though ring-tailed vontsira show some evidence of flexibility to degraded habitat. We highlight the need to prioritize small carnivore conservation in Tsitongambarika and recommend that urgent measures be taken to reduce habitat degradation and the incursion of invasive species. Without targeted action, human activities will precipitate the local extinction of Euplerids.

Wolves are known to be habitat generalists, but they may have critical requirements during key life-cycle stages, such as reproduction and pup rearing. Especially in human-dominated landscapes, wolves may become particularly choosy concerning the location of their homesites to reduce human-related risk and disturbance, thus enhancing pup survival. From 2005 to 2010, we investigated habitat selection by wolves when establishing the territory at the landscape scale (i.e., 2nd order selection) and when locating rendezvous sites within the territory (i.e., 3rd order selection), the latter based on 31 acoustically and field-verified rendezvous sites (RVs) in 8 packs in the Abruzzo Lazio and Molise National Park, a historical stronghold of the species in central Italy where wolves always coexisted with humans. Using a hierarchical, multi-scale habitat selection approach through multi-grain resource selection functions (MRSFs), we investigated environmental, topographic, and anthropogenic factors affecting territory and RVs selection by wolves. At the landscape scale, wolves avoided human settlements and primary roads and selected forested areas, shrubland, and rough terrain, likely to improve concealment and decrease human-associated risks; however, they also positively selected pastures and trails to possibly improve efficiency in hunting and traveling. When locating RVs within the territory, wolves still selected forested areas, shrubland, and pastures but differently than the 2nd order, they avoided anthropogenic linear features (secondary roads and trails) and rough terrain. Our findings confirm that habitat selection by wolves is better understood through a multi-scalar approach, which may reveal trade-offs in selection decisions across different spatial scales.

Environmental drivers can influence animal behaviour, affecting movement patterns and spatial dynamics with a cascading effect. Furthermore, most species adapt their behaviour to ecological factors, such as predation risk. In human-dominated landscapes, most medium-to-large terrestrial mammals are crepuscular or nocturnal, limiting their opportunities for other temporal changes. However, the role of nocturnal illumination and the lunar cycle in these spatiotemporal patterns remains understudied. We used camera trapping data, kernel density estimation, and generalized additive models to analyse the effects of the lunar cycle and moonlight on activity patterns of wolves Canis lupus and their ungulate prey in a Mediterranean area, accounting for cloudiness and habitat. Our results give no support to spatial avoidance by prey, and wolves were spatially synchronized with them. Additionally, we found no evidence of changes in animal activity modulated by moon brightness. Instead, we identified more refined mechanisms driving the relationships between wolves and their prey. Specifically, wolves seemed to exploit darker nights in areas more frequently used by their main prey (i.e. wild boar Sus scrofa and fallow deer Dama dama). Wild boar were more active during the brightest nights in the sites most used by the predator, whereas fallow deer were more active in the sites used in an intermediate way by the wolf and during nights with a middle nocturnal light intensity. Roe deer Capreolus capreolus were slightly more active during darker nights and in more concealed sites. These outcomes suggest that animal activity patterns reflect a trade-off between species-specific physiological features (e.g. poor nocturnal visual acuity in wild boars), the need for foraging, prey availability, vigilance, predation risk, human disturbances, and ambient light levels. Our results contribute to shed light on the underexplored effects of lunar illumination on predator and prey activities and relationships, particularly in ecosystems experiencing the return of apex predators.

Body size is an important organismal trait on which many physiological and behavioral factors depend, and can be used to study how animals adapt to insular environments. In this regard, reptiles on islands exhibit remarkable size extremes, ranging from giants to some of the smallest vertebrate species in the world. In addition, the dependence of ectotherms on external temperature makes them particularly sensitive to climatic conditions. We tested the hypotheses that adult body size in Lesser Antillean iguanas (Iguana delicatissima) would increase with island area and isolation, as well as with increasing annual rainfall and ambient temperature. We used a database of 6878 individuals collected on seven islands in the French West Indies from 2009 to 2021. We measured individual size by the snout-vent length. GLMM analyses showed that iguana body size increased with island size, and that iguanas on the islands located closer to the mainland were larger compared to those on islands located the furthest from the mainland. Regarding climatic conditions, we found that annual rainfall and ambient temperature had no significant effect on iguana body size. These findings indicate that geographical conditions have a greater influence on iguana size compared to climatic conditions. The lack of influence of climatic conditions may be related to the fact that iguanas are critically endangered, meaning that their populations consist of limited numbers of individuals far from the carrying capacity of their habitat. If ecological resources are not currently a limiting factor for Lesser Antillean iguanas, then conservation efforts could successfully promote the growth of their populations.

Largely due to the work of arachnologist Robert Jackson, spiders are now considered as excellent animals in which to investigate sensory detection, perceptual processes and cognition—topics which are reviewed here. Spider sensory systems include, among others, mechanoreception of touch, substrate and airborne vibrations, as well as chemoreception (taste and smell) and, in some groups, exceptional vision. Some of these sensory systems are believed to be the most acute of any animal. This is mirrored in spider behaviour, which includes complex communication and signalling behaviour and eavesdropping to improve outcomes of future behaviour. Spiders also exhibit learning and reversal learning, significant problem-solving ability, basic numerical ability, and possibly the ability to ‘plan’ ahead. I discuss the implications of having a small brain on the trade-offs made by spiders regarding behavioural decisions, as well as evolutionary trade-offs with respect to their ecology and even their morphology. Spiders make for particularly interesting study organisms due to the diversity of habitats in which they live and their foraging ecology. Some spiders are active cursorial hunters while others are sit-and-wait predators, and this has significant ramifications on the problems that they must overcome and on the sensory systems that they employ. Spiders also display extreme size differences between species and have the largest sexual size dimorphism (with females typically being larger) of any terrestrial animal. Furthermore, upon emerging from the eggsac, the fully formed spiderlings must hunt and behave as adults do, but may be orders of magnitude smaller. These attributes make spiders an appropriate group for studies of comparative cognition and to ascertain trade-offs in cognition or behavioural flexibility due to miniaturization. This century will surely see an increase in spider cognition studies and a concomitant increase in the awareness of the sensory and cognitive abilities of these fascinating animals.

Parasitoid wasp adult females need to select optimally sized hosts to ensure sufficient nourishment for their larvae. Ichneumonid polysphinctine spider-ectoparasitoids have commonly been observed attacking medium-sized host spiders. This behavior may result from a trade-off between ensuring enough mass for larvae and avoiding larger, more dangerous spiders. However, exceptions to this tendency have been documented. Acrothapus chedelae, for example, seems to mainly target medium-small individuals of Argiope argentata. We hypothesized that medium-small spiders can be optimal hosts if they provide enough mass for the wasp larvae. Instead, a higher incidence of parasitoids was noted in small spiders. Despite this, the hypothesis was supported since spiders in this category had body masses significantly greater than those of adult wasps. This mass surplus is likely crucial for larval development, given the energy expenditure required until pupation and the possibility that some host spiders may not acquire enough prey during the brief period of parasitoidism. This study advances our theoretical understanding of size biases in host selection by parasitoid wasps. Most previous studies have focused solely on parasitoid-host size relationships, often overlooking the mass available in the hosts and the energy requirements for larval development. Finally, we also described the variation in cocoon webs and their construction induced by A. chedelae larva on female A. argentata spiders.

It has been hypothesized that biofluorescence is a trait linked to intraspecific signaling in many taxa, especially those with enhanced modes of conspecific signaling in complex habitats. Chameleons possess bone-based fluorescent tubercles (FTs) on their head ornaments that purportedly facilitate intraspecific signaling. We investigated the hypothesis that dwarf chameleons (Bradypodion) use biofluorescence for signaling by testing if the number of FTs associated with their ornaments can be explained by sexual dimorphism or ecological variation in five species from various habitats (i.e. fynbos, Afrotemperate forest, and shrublands). If the trait is used for signaling, we would expect males to have more FTs than females due to sexual selection, and/or forest species/populations to have more FTs than open-habitat species/populations via natural selection because forests are expected to be the most conducive terrestrial environment for fluorescent signals. Our results revealed that the number of FTs was greater for the larger sex (regardless of the direction of size dimorphism) but was not significantly different between sexes when adjusted for body size or head area. Forest species had more FTs than smaller-bodied fynbos species but fewer than the large-bodied shrublands species in absolute number, but there were no differences in FTs across species from different habitats when corrected for size and phylogeny. Moreover, there were no differences in FTs between natural and urban populations when correcting for body or head size. These findings suggest that larger-bodied species have more FTs than smaller-bodied species regardless of the conduciveness of their habitats toward facilitating biofluorescence. Therefore, FT trait magnitude is likely explained best by chameleon size rather than natural or sexual selection for increased signaling capability between sexes, species, or populations. We interpret these findings to suggest that it is unlikely that Bradypodion use biofluorescence as a signaling mechanism.

The invasive yellow-legged hornet (Vespa velutina nigrithorax Buysson, 1905) is a social hymenopteran native to Asia and an invasive species in Europe. This species poses a significant threat to local ecosystems and economies across Europe due to its predation on a wide range of insects, mainly honeybees. Despite its presence on the European continent for nearly 20 years, there is limited information about its trophic spectrum. This study aims to unravel the qualitative prey spectrum of V. velutina within the local entomofauna using DNA metabarcoding tools. Meconium samples were collected from yellow-legged hornet nests removed in Mallorca (Balearic Islands, Spain) and DNA barcodes were amplified and sequenced using an arthropod-specific mitochondrial cytochrome c oxidase subunit I (COI) primer set. Results showed that a fraction of the detected diet is unique to each nest and revealed a preference for Apidae, Calliphoridae, Vespidae, Muscidae, and Sarcophagidae insect prey. The study also identified the potential impacts of V. velutina on local insect populations with diverse functional roles, highlighting the ecological implications of this invasive species. The implementation of advanced molecular techniques allowed us to assess the dietary diversity of V. velutina and its potential role in shaping local entomofaunal communities. This research enhances our understanding of predator–prey interactions in invaded ecosystems and underscores the importance of DNA metabarcoding tools for studying the foraging behavior of invasive species.

In numerous studies, it has been seen that the reproductive attributes of an insect may vary according to their body size, food fluctuation in the environment and their mating status. However, studies on the interactive effects of such biotic factors on mating behaviour and reproductive attributes are lacking. Therefore, the present study was designed to investigate the interactive effects of body size variation, different food conditions and the mating status on specific reproductive attributes such as sexual maturity, time to commencement of mating (TCM), latent period (LP), mating duration (MD), fecundity and per cent egg viability of spotted tortoise beetle, Aspidomorpha miliaris (Coleoptera: Chrysomelidae). For this, small- and large-sized females were raised in different feeding conditions (limited and unlimited food) from emergence to sexual maturity and then allowed to mate once, twice, or multiple times with males of intermediate size. Results revealed a significant influence of body size on sexual maturity, as well as mating status on the time to commence mating and showed a significant interactive effect of food conditions and mating status on latent period and mating duration, as well as body size, food conditions, and mating status on fecundity and per cent egg viability of adult females. In the present study, small females attained sexual maturity earlier than large females. Fecundity and per cent egg viability were recorded at maximum in multiply mated large females in the unlimited food treatment. Food conditions substantially influenced fecundity, which was zero in females with limited food conditions. Therefore, this study suggests that multiply mated larger females with unlimited food have better reproductive outputs. It was also concluded that the interactive effect of biotic factors had a significant impact on reproductive outputs together with different sexual behaviours.