Mammal Research最新文献

The assessment of animal body condition has important practical and management implications for endangered wildlife populations. The nutritional condition of a population can be evaluated in a non-invasive way using photogrammetry techniques, avoiding direct manipulation. This study evaluates the utility of using body condition scoring (BCS) based on the visual assessment of subcutaneous fat and muscle from the body contour as a non-invasive method to quantify body condition in free ranging bears from camera trap photographs. Photographs of Apennine brown bears (Ursus arctos marsicanus), taken between 2007 and 2009 in the Abruzzo, Lazio and Molise National Park (PNALM, Italy), were used to evaluate the potential of this technique. BCS assessment was performed on 754 photographs representing 71 independent observations. Forty-eight of these photographs were selected to also score quantitative body ratios using a standardised measure of torso height. BCS varied seasonally, as expected by food availability and brown bear nutritional physiology, and it was also positively correlated to all three body ratios. Our findings indicate that BCS assessment is a good proxy for body condition, and that camera trap data can be effectively used to assess and monitor the nutritional condition of bear populations, such as the critically endangered one in central Italy.

An understanding of individual variation in animal habitat selection is important for effective conservation and management as well as predicting species responses to a rapidly changing world. Functional responses to habitat availability can explain some of this variation, but not accounting for behavioral grouping may oversimplify inference and mask the diversity of habitat use strategies present in a population. We investigated within-home range habitat selection variation at the group level in a reintroduced population of elk (Cervus canadensis) in Kentucky, USA, during 2020–2022, analyzing satellite tracking data from 103 individuals to quantify variance in responses to seven landscape variables. We used group-level selection coefficients estimated with mixed-effects resource selection functions to model population-level functional responses and classify groups into within-season behavioral clusters. We then used cross validation to assess if these methods of generalizing group-level variation improved predictions of space use. We found that elk had highly variable responses to several covariates, and that some of this variation could be attributed to functional responses to either cover type availability or configuration. When we generalized behavioral tactics via clustering, we found significant increases in group-level predictive ability over the global model and, in some cases, the functional models. This suggests that clustered behaviors are also driving individual heterogeneity in this population. Our results highlight the importance of considering individual differences when studying wildlife-habitat relationships and underscore the need for a more complete understanding of the mechanisms behind this variation to inform habitat management and conservation efforts.

Endangered species recovery requires knowledge of species abundance, distribution, habitat preferences, and threats. Endangered beach mouse populations (Peromyscus polionotus subspp.) occur on barrier islands in Florida and Alabama. Camera traps may supplement current methods and strengthen inferences of animal activity. Between November 2020-February 2022, we conducted 140 camera surveys across 86 track tubes on Tyndall Air Force Base, Florida. We used generalized linear models to explore the relationships between beach mouse detections and environmental factors. We detected beach mice on 6,397 occasions across all tubes. Detections ranged from 0 to 147 observations/survey. Our top model suggested that beach mouse detection was related to cover type with positive associations with grassland and dune compared to scrub. Detections further varied depending on islands, were negatively associated with predator detections, and increased in winter months. Our results suggest that cameras can supplement inference about vegetation associations at broader scales to complement monthly track tube surveys since detection counts are more informative than presence/absence data alone. Given that all tubes exhibited at least one observation, the camera trap network may provide a less frequent and more robust survey method relative to monthly track tube surveys. Adopting such a multifaceted approach may reduce effort and strengthen inference to inform recovery objectives and adaptive management range-wide for all listed beach mouse subspecies.

Small carnivores play an important role in ecosystems, but their often hidden lifestyle makes them generally hard to observe. Camera-trapping methodology shows great promise as a standardized monitoring tool for small carnivores. The European polecat (Mustela putorius) is a species of conservation concern, listed on the Annex V of the EU Council’s Directive on the conservation of natural habitats and of wild fauna and flora. Because of this, EU member states have to report the status of their polecat populations regularly. However, standardized methods to estimate the population size of polecat populations are currently lacking. We present a tube-based camera-trapping system, the Polecam, designed to obtain photographs of the facial masks of individual polecats. We tested the system in four study areas in southern Sweden during Spring and Autumn 2021. We obtained 52 observations of polecats, out of which we were able to identify 38 (73%) to individual. From these observations, we estimated area and season specific estimates of density for five season-area combinations using a multi-session spatial capture-recapture model. Density estimates ranged from 0.84 to 2.7 individuals/1000 ha, similar to the estimates from similar landscapes in other countries in Europe. We also obtained observations of six other species of small carnivores, suggesting that the Polecam could be used for multi-species monitoring, as well as density estimation of European polecats.

Camera traps are a powerful tool to monitor the activity pattern of species over long time periods. Camera data can be used to analyze activity patterns of or temporal niche partitioning among species. Temporal niche partitioning plays an important role for species coexistence and is under constant evolutionary pressure from predator-prey relationships. Our study aimed to investigate temporal shifts in activity patterns of red squirrels and two mammalian predators, red fox and marten (Martes spec.). Previous studies yielded different activity patterns for these species depending on location, season, predator-prey interactions, and food- availability. We used camera traps to monitor the activity of squirrels, red fox and martens throughout a whole year in a mountainous forest in southwestern Germany. We also investigated a possible difference in activity among different color morphs as coloration in mammals is often associated with concealment, for squirrels, however, such an effect could not be demonstrated so far. We found a diurnal activity for squirrels in all seasons with a bimodal activity pattern during spring, trimodal in summer and unimodal in fall and winter. Activity patterns did not differ between black and red color morphs. The activity of the squirrels showed only low to moderate overlaps with fox and marten, but there was still slight variation among seasons. Activity overlaps were higher in spring and summer, which coincides with breeding season. Our results suggest that predators might adjust their activity during squirrel breeding season to increase the chance of preying on their offspring. Squirrels in turn could benefit by minimizing the activity overlap during wintertime when they are highly visible to predators as trees are leaf-free or even snow might enhance the contrast between them and their background. Lastly, our results indicate that temporal niche portioning among red squirrel, red fox and martens might be rather fine scaled.

Trophic ecology has major implications for understanding species’ natural history and functional role in ecosystems. This type of information is key to define resource requirements and constraints for conservation planning, especially for threatened specialist species. Here we describe the items that compose the diet of giant armadillos (Priodontes maximus) in the Brazilian wetlands, characterizing their functional role and evaluating if they are true myrmecophages. We sorted 113 fecal samples collected throughout 10 years of monitoring of 29 individuals to identify prey items to the finest possible taxonomic level. Then we estimated the Relative Frequency of Occurrence of each item. The sampling effort was shown to closely represent the expected local prey diversity. Giant armadillos preyed on a diverse array of invertebrates and plants: 23 morphotypes of Isoptera, 50 morphotypes of Hymenoptera, 14 types of seeds, one vertebrate (bone), unidentifiable fragments of Arthropoda, Scarabaeidae fragments, invertebrate eggs, and Acari. All individuals consumed termites (Cornitermes sp. and Nasutermitinae) and plant fragments. There was a high variation on the occurrence of ant morphotypes among samples, most being consumed by few individuals. The most consumed ants were Carebara coeca and Atta vollenweideri, considered crop pests, highlighting armadillo’s importance to society through pest control. Fruits were consumed opportunistically by multiple individuals, likely not incidentally as previously hypothesized, and the role of this large mammal as a seed disperser should be further explored. Although giant armadillo’s diet is more diverse than expected, the high prevalence of termites and ants confirms its myrmecophagous specialization, making them the largest Neotropical specialist insectivore.

Although the presence of the golden jackal (Canis aureus moreoticus) in Italy has been documented since 1984, it has long been considered an accidental species confined to a limited portion of the northeastern sector of the country. Recently, dispersing individuals of golden jackal have been reported in different areas of northern Italy, suggesting an enhanced spreading attitude compared to the past. However, despite a wider covered area, no evidence of reproductive groups south of the Po River has ever been documented, suggesting possible geographical limitations due to the habitat or ecological conditions. This study witnesses the overcoming of this large freshwater course by the species, and describes the first reproductive group of golden jackals south of Po River in a context of a highly industrialized area. The results are obtained using different methods (citizen science, howling, camera trapping, search of signs) able to demonstrate an expansion of this mesocarnivore outside its traditional northeastern Italian distribution range. Interesting questions are also raised about the species ecology with special regard to its southern migration pattern through anthropic zones.