Cub biometry, litter size and reproductive period of giant oters (Pteronura brasiliensis) at the Balbina Hydroelectric Reservoir, Amazonas, Brazil

Abstract

According to the literature, giant otters produce one to six cubs at each gestation, with birth peaks occurring from the end of the flood season to the beginning of the low-water period. With the aim of describing some reproductive parameters of the giant otters living in a hydroelectric lake, 56 field excursions to Balbina Hydroelectric Reservoir, hereafter Balbina Lake, were carried out between September 2001 and September 2010 in order to gather information about cub weight and length, litter size and reproductive period of the species in that area. About 80% of the birth records occurred between September and December, characterized by the receding water season and the beginning of the dry season. The number of cubs per gestation varied from one to three animals (mean = 2; n = 36) and average weight and length of neonates were 316.25 ± 64.21g (n = 4) and 31.75 ± 4.86cm (n = 4), respectively. The reproductive period and the litter size produced by giant otters in Balbina Lake were within the range reported in literature for non-dammed areas, indicating that these reproductive parameters were not changed by the reservoir. The weight of cubs analyzed in the reservoir was in average 35% greater than the weight of captive newborn cubs reported in the literature. However, as the animals here analyzed were healthy, it is reasonable to assumethat they represent the weight of free-ranging newborn cubs. Artificial lakes had been reported in the literature as favorable environments for giant otters in Guyana, and the results obtained here seem to corroborate this hypothesis and show the plasticity of the species in its use of different habitats as long as the habitats are inside some category of protection, in this way minimizing additional impacts caused by an intense human occupation of the area.