ИСТИНА

We studied motor preferences in Eurasian beaver (Castor fiber) in the wild and captivity. 260 hours of observations with photo/video registration were carried out for 42 captive beavers of the Voronezh Beaver breeding ground from July, 2019 to August, 2021. For the data on wild individuals, Voronezh Reserve trail cameras' recordings (2014-2021) of wild beavers behavior were analyzed. Evaluation of preferences in the use of forelimbs at the group level was carried out according to the handedness index (IHI). Also, for each individual, the Malashichev Unimanual Coefficient (MUC) was calculated, showing the expression of single limb action in the manual behavior of an individual.The animals were also presented with specially designed T-shaped feeders of different diameters. Separately we evaluated the asymmetric transfer of plant material (branches) on one side of the body by mouth.The analysis of video recordings revealed a correlation between the limb preference and the material (food and building) transfer bias in wild beavers: when moving branches, beavers place most of them on the side opposite to the leading limb (r(s) = -0.76, P = 0.012). Significant differences in MUC were found between beavers differing in the environmental enrichment of living conditions (H=27.9, P<0.001, Kruskal-Wallis test: In beavers living in natural conditions and engaged in building activities, the degree of unimanuality is higher than in captive beavers (P<0.05, post-hoc test), significant differences were also found in the degree of preference (F(2;47) =3.55 , P=0.037, ANOVA; in beavers in pens, the median [HI] was 0.140, for wild beavers it was 0.415). No significant correlation was found between lateralization and levels of cognitive activity and boldness (P<0.05, multinomial regression). The degree of expression of motor preferences in beavers increased significantly in complex manipulation tasks (W = 0, P < 0.001). Beaver temperament, however, did not affect motor asymmetry