Seasonal comparisons of daily activity budgets of gray squirrels (Sciurus carolinensis) in urban areas

Long-term, medium-term and acute stress response of urban populations of Eurasian red squirrels affected by different levels of human disturbance

Animals in urban areas often encounter novel and potentially stressful conditions. It is important to understand how wildlife cope with anthropogenic disturbance. To investigate this specific adaptation we live-trapped squirrels in two study sites in Warsaw: a forest reserve and an urban park and we estimated stress responses at three levels: long-term and medium-term stress (the level of stress hormones, i.e. cortisol and cortisone concentrations, in hair and feces) and acute reaction to human-induced stress (measured during handling with the aid of the three indices: breath rate, struggle rate, and vocalization). According to GLMM models no difference in the stress hormones level was found between the two populations. The only differences in cortisol concentrations clearly depended on the season, i.e. being higher in autumn and winter comparying to other seasons. There was no influence of sex, or reproductive status on stress hormones. Forest squirrels had significantly higher breath rates, suggesting they were more stressed by handling. There was no difference in the struggle rate between study areas, this index was mostly affected by season (i.e. being highest in winter). First-trapped squirrels vocalized less than during the subsequent trappings. Assumingly, during the first, and more stressful trapping, squirrels used 'freezing' and/or little vocalization, while during next captures they used alarm calls to warn conspecifics. Overall, we showed that the two squirrel populations differed only in terms of their breath rate. This suggests that they did not differ in medium-term and long-term stress in general, but they can differ in acute response to handling. This also suggests that both populations were similarly affected by environmental factors. The lack of clear effects may also be due to population heterogeneity. Thus, in order to assess the effects of anthropogenic stressors a broader range of indicators and diverse analytical methods, including behavioral analyses, should be employed.

Gray squirrels consume anthropogenic food waste most often during winter

Urban habitats provide wildlife with predictable, easily accessible and abundant food sources in the form of human food waste. Urban eastern gray squirrels (Sciurus carolinensis) are commonly observed feeding in trash bins, but we lack data regarding the type, quantity and seasonal changes in food waste usage. We observed five trash bins on an urban university campus during four different observation periods. We recorded the time squirrels spent on and inside trash bins and type of retrieved food items. We also recorded ambient temperature, human presence and trash bin filling. Moreover, we determined changes in squirrel population density in a natural and three anthropogenic habitats during the same periods. Trash bins were fuller when human presence was higher. The higher human presence, the more squirrels went on and inside the bin, but there was no effect on number of retrieved food items. Trash bin usage by squirrels decreased when ambient temperature and bin filling increased. Most food items were retrieved during the coldest observation period, a period of high human presence, and the majority of retrieved food items were starchy foods (e.g., bread, French fries). The relationship between the number of squirrels observed along transects and a measure of urbanization, the normalized difference built-up index, was negative in periods with high ambient temperatures and positive in periods with low ambient temperatures, indicating winter may be less challenging in urban areas, likely facilitated by the availability of anthropogenic food sources, allowing a higher level of activity throughout winter.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42991-022-00326-3.

Bone dispersal by vertebrate taxa in an urban park environment in New England, USA

The questions of the frequency, distance, and maximum size of the bones that carnivores, rodents, and other common taxa can disperse have been little addressed, especially in the later phases of skeletonization when individual bones are more subject to transport and loss. The present research utilized a sample of dry white-tailed deer (Odocoileus virginianus) bones in two locations in a forested urban environment dense with eastern gray squirrels (Sciurus carolinensis), chipmunks (Tamias striatus), coyotes (Canis latrans), raccoons (Procyon lotor), and other potential scavenging taxa. Game cameras were used to document their dispersal behavior. A total of 1731 visits were recorded, by a minimum of 12 mammalian and 9 avian taxa. Small amounts of dispersal impacted the bone samples continuously throughout the observation period, with 52.2% of all movement in the range of 1-5 cm. The bones were dispersed a maximum distance of 1252 cm, and the largest bone moved had an initial mass of 194.6 g. Rodent dry-bone gnawing behavior affected 72.7% of the sample. The project also assessed a smaller sample of Tile Mate® tracking chips for their utility in dispersal research, and these were found to have a useful potential though were not pivotal in acquiring the data presented here. Forensic surface search methods and interpretations of skeletal recovery patterns should take into consideration the ability of these common species to disperse even dry bones away from their initial locations, and this behavior may continue years after the time of initial deposition.

Wavelet methods reveal big cat activity patterns and synchrony of activity with preys

Appropriate temporal and spatial scales are important prerequisites for obtaining reliable results in studies of wildlife activity patterns and interspecific interactions. The spread of camera-trap technology has increased interest in and feasibility of studying the activity patterns and interspecific interactions of wildlife. However, such studies are often conducted at arbitrary spatial and temporal scales, and the methods used impose scale on the study rather than determining how activity and species interactions change with spatial scale. In this study, we used a wavelet-based approach to determine the temporal and spatial scales for activity patterns and interspecific interactions on Amur leopard and their ungulate prey species that were recorded using camera traps in the main Amur leopard occurrence region in northeast China. Wavelets identified that Amur leopards were more active in spring and fall than summer, and fluctuated with periodicities of 9 and 17 days, respectively. Synchronous relationships between leopards and their prey commonly occurred in spring and fall, with a periodicity of about 20 days, indicating the appropriate seasons and temporal scales for interspecific interaction research. The influence of human activities on the activity patterns of Amur leopard or prey species often occurred over longer time periods (60-64 days). Two-dimensional wavelet analyses showed that interactions between leopard and prey were more significant at spatial scales of 1 km² . Overall, our study provides a feasible approach to studying the temporal and spatial scales for wildlife activity patterns and interspecific interaction research using camera trap data.