Behavior and social development of juvenile southern right whales (Eubalaena australis) and interspecific interactions at Peninsula Valdes, Argentina

The behavior and interspecific interactions of juvenile southern right whales (Eubalaena australis) (ages 1--4) were studied off Peninsula Valdes, Argentina. Mother-calf separation occurred when infants were at least 11 months old. After separation, yearlings became significantly more social. Separation was relatively sudden, and maternal aggression was not observed. Social opportunities at Valdes may reduce weaning conflict.; Juveniles spent approximately half of the time alone and the remaining time socializing, primarily with other juveniles. Juveniles engaged in solitary, social and object play. Females played with calves and interacted with mother-calf pairs more often than males. Males engaged in homosexual behavior. Juvenile females displayed behavior patterns typical of adult females in mating groups. Young right whales may establish social relationships and practice behavior that is relevant during adult life at Valdes. Behavioral sex differences begin to be established early in the whales' lives.; A technique was developed to estimate the age of right whales based on measurements taken on lateral photographs. Multiple regression models explained three quarters of the variability in the square root of age as response variable. Rostral curvature was the best age predictor. Age prediction was most accurate for younger whales. The technique does not require disturbance of whales, and can help to improve estimates of demographic parameters based on the age of individuals.; Orcas and right whales were observed together on 117 occasions between 1971 and 2000. Behavioral responses varied from apparent indifference to high levels of activity in both species. Orca group size was highest and duration of encounters was longest during attacks. Right whale behavior patterns appeared adaptive to reduce orca predation. The relatively higher risk of predation at certain sites may influence right whale habitat choice at Valdes.; The frequency of kelp gull attacks on right whales was updated through to 2002. Attacks tripled since 1995. Mother-calf pairs were attacked five times more often than juveniles, who were attacked more frequently during interactions with mother-calf pairs. The interrelationship between whales, gulls, fishery waste and landfills is discussed, and management recommendations to decrease attack frequency are proposed.