Daily movements of Brown bears (Ursus arctos) in Kamchatka and Sakhalin

Abstract

Knowledge of ecological parameters of the population, which are associated with the use of the animal territory, is important for developing a plan for the conservation and sustainable use of the brown bear (Ursus arctos Linnaeus, 1758). Daily movement is a parameter used in calculating the number of animals. Formerly in Russia, the movement of animals by radio telemetry was studied only in the Sikhote-Alin, whereas for Kamchatka and Sakhalin this issue is considered for the first time. The aim of this work was to assess and characterize daily movements of brown bears in Kamchatka and Sakhalin. The study included determination of the average distance over which the bears shifted for one day during the year, the seasons and each of the months of the nonhibernating period; assessment of the possibility of using a linear model to determine the approximated daily movement of animals; revelation of types of daily movements of bears and factors on which they depend. The studies were carried out in two regions of Kamchatka Krai (54°25ꞌ50ꞌꞌN, 160°08ꞌ22ꞌꞌE; 56°49ꞌ35ꞌꞌN, 159°59ꞌ08ꞌꞌE) and in Sakhalin Oblast (50°36ꞌ18ꞌꞌN, 143°41ꞌ48ꞌꞌE) in 2005-2012 (See Fig. 1). The collars (LOTEK GPS 4400) were put on seven brown bears (See Table 1). Collars were programmed to determine their location by GPS-receiver once every 1-3 hours. To characterize the movements, the daily linear distance was determined, which was the distance between the pairs of GPS positions of each bear, the time interval between which was about a day. Bear daily linear distances were determined 1031 times. For two females from Sakhalin, two values were calculated for 70 days: the sum of 24 segments of the movement (approximated daily movement) and the distance between the first and last positions (daily linear distance). The ratio of these two parameters reflects, at least, how many times the distance actually covered by animals exceeds its daily displacement in space. Using the parameters of the approximated daily movement and daily linear distances allowed us to build a linear model in the R program to predict the first parameter for those days when only the second parameter was known. This made it possible to predict the approximated daily movement, which took into account the tortuosity of the movement for those days when only the daily linear distance was known. The study was conducted in compliance with ethical requirements when working with animals. Data on daily movements over the whole year were obtained for two females from Kamchatka and two females from Sakhalin. In Kamchatka, the average daily linear distances of females during the year were significantly higher than in Sakhalin and averaged 1812 and 967 m, respectively. In spring, the daily linear distances of females in both regions were less than in the summer and autumn periods (See Table 2). The smallest movement activity of female bears was observed in April-May and October-November (See Tables 3 and 4). There were relatively more daily movements from June to September. The maximum activity of the females was in August (See Fig. 2). In summer and autumn, the movement activity depended primarily on the distribution of salmon. The presence of female cubs of the first year of life limited the range of its movements. The length of the daily linear distances of bears was positively correlated with the size of their home ranges. The linear model showed a statistically-valid relation between the approximated daily movement and the daily linear distances of the animal and a significant level for the parameters under consideration (See Table 5). The degree of tortuosity of the bears’ movement decreases with an increase in their daily linear distances. The linear model is promising for determining the daily movement of animals, when it cannot be done by other methods. The results of the linear model are applicable for calculating the population density of animals. Analysis of hourly movements per day allowed us to identify three types of the bear’s movements. The first type is the purposeful transition from one part of the home range to another part. The ratio of the approximated daily movement to the daily linear distance with this type of movement was small (<2 in the most typical cases), while the daily linear distance was relatively big (See Fig. 3a). In the second type of movement, the animal moves relatively long distances during the day, but returns to his preferred place, the location of which may be associated with feeding or rest. With such movements, the approximated daily movement is more than 10 times the daily linear distance (See Fig. 3b). In the third type of movement, the bear does not make significant transitions, adhering to the local preferred site. In such cases, the approximated daily movement and daily linear distance were small (usually up to 3 km), and their ratio was more often average. The paper contains 3 Figures, 5 Tables and 35 References. The Author declares no conflict of interest. No animals were harmed in this research.