NESTING ECOLOGY OF A POPULATION OF TRACHEMYS DORBIGNYI (EMYDIDAE) IN SOUTHERN BRAZIL

Transformation of habitats for agriculture is one of the main causes of reduction in diversity worldwide. We observed reproductively-active female turtles of Trachemys dorbignyi and their nests from 1995 to 2001 in an intensively farmed area in southern Brazil. The area was selected because of the existence of a previous study done 20 yr earlier in the same locality, which allowed us to evaluate the possible effects of human activities on the reproductive ecology of T. dorbignyi. Nesting occurred between October and January, with most activity in November and December (the warmest months). An average of 31% of the females nested in each year, laying up to three clutches at intervals of about 15 days. The females usually constructed nests between 0,700 and 1100 h and deposited 6 to 19 eggs (mean = 12.1) per nest. Clutch size was strongly correlated with carapace length. The eggs were, on average, 39.3 ± 1.73 mm long and 25.8 ± 0.91 mm wide, with a mean mass of 14.9 ± 1.29 g. Multivariate Analysis of Variance showed that egg size differed from year to year. In spite of the intense human activity, the parameters analyzed were nearly unchanged after two decades. However, aspects such as reproductive success, reduction of nesting sites, and the effects of agrotoxins, which could affect the long-term conservation of the species, were not assessed.