Variação temporal da estrutura e tamanho de bandos de capivaras na Estação Ecológica do Taim, Rio Grande do Sul, Brasil

BAGER, A.; ROSA, C.A.; LOUREIRO, L.; CORRÊA, R.; CARMO, J.; GARCIAS, F. 2010. Variação temporal da estrutura e tamanho de bandos de capivaras na Estação Ecológica do Taim, Rio Grande do Sul, Brasil. Revista Brasileira de Zoociências 12(3):273-280.

Abstract. Temporal variation of structure and size of capybara groups in Taim Ecological Station, Rio Grande do Sul, Brasil. A capybara (Hydrochoerus hydrochaeris) population was monitored in a borderline region between ESEC Taim (Taim Ecological Station) and southernmost areas of rice cultivation, located in the state of Rio Grande do Sul (RS, Brazil). The aim was compared the structure and size of groups, in different seasons, with variations of temperature and precipitation during two years. A total of 25 censuses,  obtained through the direct count technique, were performed from August 2003 to August 2005. These samplings were performed in a transect of 4000-meter on the margins of Mangueira Lagoon. The capybaras were separated by age and sex. The average number of groups (NB) was of 24±0.65. The highest NB value was observed in spring of 2004 (29.7) and 2005 (26.2), as well as in the winter of 2005 (27.5), differing these seasons from the others (P<0.01). The average number of adults in the groups (NAB) was of 15.1±0.65 individuals. The NAB presented a strong negative relation with number of groups. This was observed in autumn, 2005 (P<0.001). The average number of individuals per groups (NTB) was of 26.3±1.10, and presented a temporal pattern similar to the adults. The correlation analysis between biotic factors (NB, NAB and NTB), and abiotic factors (temperature and precipitation) have not presented any significant values (P>0.05). The variations of structure observed in the groups are probably due to changes in the size of dry area  near the lake through the year, therefore resulting in different levels of approaching and grouping behaviors. The negative relation  between number of individuals per group and number of groups existing in the area reinforces the hypothesis of structural changes  of groups according to the period of the year.