Abstract

The Dall porpoise Phocoenoides dalli is common in south central California waters from October through June. During the summer months it is not commonly found farther south than about 35°.

Four Dall porpoises were captured by a crew from the Marine Biology Facility, Point Mugu, California. One male survived less than twenty-four hours in captivity. Two pregnant females survived 26 days and a second male is adapting well after 10 months in captivity.

Phocoenoides dalli is a very fast swimmer and appears to be a deep diver. A 120 Kg male Dall porpoise requires 15 Kg of mackerel (Pneumatophorus diego) daily in order to maintain body weight.

Sounds produced by the captive Phocoenoides dalli consist entirely of repeated bursts of low-frequency clicks. No whistles have been recorded.

Dissections revealed the Dall porpoises to have a very large heart, very thin blubber and a small brain as compared to Lagenorhynchus obliquidens and Tursiops truncatus. Other remarkable anatomical features include: a peculiar book-like folding of the vestibular nasal sacs, an extremely massive skeletal musculature, an unusual fatty pad along the margin of each lung, very thick tracheal cartilage amid comparatively large adrenals.