The few available information on the reproductive behavior of Hydromedusa tectifera (Chelidae) are based on captive individuals. The H. tectifera reproductive biology was verified from 1996 to 2002 by non-systematic surveys in the Estação Ecológica do Taim, southern Brazil. Forty-six intact and damaged nests of the species were found. Mean clutch size was 11.6 eggs which exhibited a mean size of 36.5 x 23.9 mm and an average weight of 11.5 g. Individual mean eggs volume resulted an average of 10148.31 mm³. Nests had an average depth of 11.1 and 5.8 cm from the surface to the first egg. The eggs volume variation in the same nest was smaller (CV = 4.71%) than among different nests (CV = 12.32%). The eggs width was positively dependent of their length. In the same hatch the number of eggs did not depended of their size or volume. Nesting behavior was observed in November and December. The species showed higher frequency for nesting between 6 and 8 p.m., in areas with certain inclination of the substratum, between 20° and 30° of declivity. Higher nest abundance was verified up to 5 m from the lagoon. The results show that the data obtained for H. tectifera are similar to those previously reported for Australian snake-necked turtles and for species of Chelidae from southern Brazil.
South American snake-necked turtle; nesting site; eggs; nests
