Composition of schools of sperm whales physeter catodon linn. East of New Zealand

Abstract

The composition and social structure of schools of sperm whales Physeter catodon Linn, in temperate latitudes east of New Zealand to longitude 150° W are examined and discussed. The study is based on sightings of about 1,572 animals supplemented by catch data from among this number.Six major social categories were recognised: solitary males, male pairs, schools of bachelor males, mixed‐sex schools consisting almost entirely of immature animals, harems, and nursery schools. Male pairs probably represent the final stage in the break‐up of bachelor male schools into solitary animals, but the possibility that they could be temporary homosexual associations is considered. The schools of immature animals of both sexes are probably very temporary.An inverse relationship in male schools between school size and mean body length is demonstrated. Mean testis weights of solitary males and bachelor school males are shown to be significantly different at P < 0.001. No relationship between seminiferous tubule diameter and body length was found for pubertal and mature males, as had been demonstrated by a previous worker.Some data are presented which support the contention by Best (1969) that sexual maturity in the male sperm whale is attained at body length of about 45 ft (12.6 m), rather than at 36.6–41.0 ft (10.3–11.3 m) as suggested by earlier authors. © 1970 Taylor & Francis Ltd.