Observations on the composition and behaviour of groups of female sperm whales near the Galapagos Islands

Abstract

During visual and acoustic tracking of sperm whales, Physeter macrocephalus, off the Galapagos Islands, observations were made on the composition and behaviour of the 13 photographically identified groups being followed. Observations of calves and the high incidence of animals with dorsal fin calluses suggested that the groups could be categorized as mixed groups, which contain females and their offspring. Animals recorded to be escorting calves were probably females. Individual calves were escorted by different individuals at different times, and known individuals were observed to escort more than one calf on different occasions. There was a significant difference in the proportion of open and closed fluke notches between groups, suggesting some relatedness of individuals within a group. Twenty-one percent of the identified individuals had tooth mark scars on their flukes, but there was no significant variation in this proportion between groups.