The Giant river otter Pteronura brasiliensis is endemic to South America and is Endangered. Breeding in captivity is one of the strategies for conservation of the species, despite the fact that historically this has not been successful. Between 1999 and 2004 a study into the behaviour and reproductive biology of a pair of Giant river otters was carried out at Cali Zoo. The ♀ gave birth to nine litters, with 14.6.1 pups born, 6.4 (48%) of which survived to > 1 year old. Two litters were reared with older siblings in the family group. Evidence of delayed implantation and pseudopregnancy were observed. The roles of the ♀, ♂ and juveniles in pup rearing are described. Significant features of infant development were recorded and a growth curve was established for P. brasiliensis up to 2 months old.