Aggression in the Female Northern Elephant Seal, Mirounga Angustirostris
Maternal aggressive behavior of northern elephant seals enhances reproductive success by increasing the likelihood of pup survival. Detailed observations of marked mother-pup pairs revealed that female aggressiveness increased dramatically after giving birth. Maternal aggressiveness also correlated negatively with the number of times the pup was bitten by alien females. Mothers of these pups were less aggressive than the 17 whose pups survived. Pup behavior was not directly related to mortality. Frequencies of interfemale aggressive encounters were compared for different beach areas. Aggression was most frequent on the smallest area, where interfemale distance was the shortest, and tidal action extreme. Aggression was least frequent on the sparcely populated beach, affected little by tide or male activity. Interfemale distance was greatest here. Reproductive advantages and disadvantages of pupping on each area are noted.