Home ranges and activity patterns of island arctic foxesстатья Электронная публикация

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Дата последнего поиска статьи во внешних источниках: 9 марта 2017 г.

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[1] Home ranges and activity patterns of island arctic foxes / A. A. Pletenev, E. P. Kruchenkova, Y. I. Mikhnevich et al. // Принципы экологии (Principy èkologii). — 2016. — Vol. 5, no. 3. — P. 127–127. The analysis of space use helps elucidate environmental and social factors, which guide animal behavior. Food distribution and predation pressure are usually considered the main factors. We examined range use and activity of Arctic fox (Vulpes lagopus beringensis), an apex predator on the oceanic island with rich, clumped food patches. We conducted the study in July-August 2014 in the northern part of Bering Island (the Commander Islands, North Pacific). Study area partially included the northern fur seals rookery. Thereby in summertime these foxes had an extraordinary abundant source of food resources (seal placentas and carcasses). Four adult foxes (2 males and 2 females) from 3 adjacent reproductive family groups were equipped with GPS-collars. Collars were set to record GPS positions at regular 5-minute intervals. We evaluated home ranges using the Brownian bridge movement model, BBMM (Bullard, 1991; Horne, 2007). BBMM estimates the probability density of a path between every two successive relocations. Then these densities are summed over the area to yield utilization distribution (UD). We considered 99,9% isopleth line of that UD as home range boundaries. Mean seasonal home range size was 40 hectares for male and lactating female from the same mated pair, and 90 and 100 hectares for male and lactating female from two other family groups. These were 5–10 times less than summer home ranges of mainland arctic foxes (Anthony, 1997; Eide, 2004.). For foxes from adjacent family groups, the overlap in home ranges was 2–18% by area and 0-17% by time. The overlap of male and female from the mated pair was 82–84% by area and 99% by time. Our results suggest that abundance of food resources has led to the shrinkage of home range, but has not significantly affected fox territoriality. If GPS position did not change for three and more successive relocations, we considered the animal as “non-active”, otherwise “active”. The activity pattern was estimated daily, then median (M), the first and third quartiles (1Q and 3Q) were obtained for each fox. Activity characteristics were similar for all four foxes and stable throughout the observation period: “active” status (M: 33–40%, 1Q: 31–37%, 3Q: 38–45%); average daily speed (M: 1,1–1,4, 1Q: 1,0–1,3, 3Q: 1,5–1,7 km/h); daily movement distances (M: 8–13, 1Q: 7–11, 3Q: 14–18 km). Thus, due to richness and high predictability of food resources, the activity level of Bering foxes was lower compared with mainland foxes (Eberhardt, 1982) and day-to-day variability of the activity level was also low. We built regression model with activity as a response variable and time of day as a predictor. The daily activity pattern had two distinct peaks. The evening peak of each fox occurred at twilight (20:00-21:00 local time). The morning peaks differed significantly and occurred from 4 to 9 AM. Male and female from the mated pair had very similar morning and evening activity maximums (3:30 and 4:30, 20:00 and 20:30). To study stability of daily activity pattern we estimated models with identical specification separately for each day and determined location of peak points for the first and second halves of the day. Females’ morning activity peak varied greatly from day to day (1Q–3Q: 5:30–9:30 and 3:30–9:00); it was not the case for males (4:30–5:30 and 4:30–5:00). Evening activity peaks evening showed similar variance for all foxes (1Q: 17:00–18:30, 3Q: 20:30–21:30). The tidal schedule significantly affected the pattern of all four foxes daily activity, however, did not shift the time of morning and evening peaks. Although day–night cycle had no effect on distribution and availability of main food resources (seal placentas and carcasses) and there was no predation risk either, daily activity of artic foxes showed bimodal pattern similar to many other carnivores (Merrill, 2003; Heurich, 2015). The study was supported by RFBR grants 13-04-00302 and 15-29-02459.

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