Notes on giant otter (Pteronura brasiliensis) behavior in the lake of the Balbina hydroelectric power station, Amazonas, Brazil

Abstract

Since September 2001 the authors have been studying the reproductive period, vocalization, feeding habits and usage of the 3246km 2 lake of the Balbina hydroelectric power station by Pteronura brasiliensis (de Mattos et al., 2002 3 ; Zuanon et al., 2002 4 ; Rosas and de Mattos, 2003). In this note we describe some aspects of the behavior of giant otters in Balbina lake and compare them with the literature. We also report some new information on their reproductive behavior, which to our knowledge has not been published elsewhere. On 21 August 2003 we observed that the den labeled JAU-7, located on one of the 3299 islands (01°35'11.9"S, 59°40'17.4"W) of Balbina lake, wain use'. We decided to return there early the next morning in order to record the number of animals and their group composition. We arrived at JAU-7 at 05:51am on 22 August and remained in our aluminum boat, about 40m from the den. A strong smell of feces and urine, characteristic of the communal latrines of P. brasiliensis, was noticed. At 06:18am a giant otter appeared in the den's entrance and left it, followed by another animal, and both started their morning routine of marking the land in front of the den. They were identified as an adult male (Male A) and a nursing female (Female N1) (Figure 1). The marking behavior was carried out by both animals, with the male spending a considerably longer time than the female in that process (the male spent 100% of the time marking the land, whereas the female spent 70%). The female had very enlarged nipples, suggesting that she was nursing and probably with newborn cubs inside the den. Marking continued for 4min 55s, during which time the animals entered the water and returned to the land in the area in front of the den, spreading urine with their paws. About 3min after the couple had emerged from the den, two other individuals appeared, approaching from the water. These two animals noticed our presence