FIRST RECORD OF A TRUEI-TYPE DALL'S PORPOISE FROM THE EASTERN NORTH PACIFIC

On 28 August 1989, we were informed by California State Park Ranger Robert Breen that a small porpoise had washed ashore at the James Fitzgerald Marine Reserve, San Mateo County, California (37 degree 31'N, 122 degree 31'W). Upon recovering the animal, we discovered that it was a 97-cm-long newborn (as evidenced by fetal folds on the flanks and flukes, and remnants of the umbilical cord) female Dall's porpoise (Phocoenoides dalli ) of the truei -type color pattern. Animals of this color type have the light flank patch extending forward to the level of the flipper, rather than only to the level of the anterior insertion of the dorsal fin, as is the case in the normally occurring dalli -type. Truei -type animals were originally described as a separate species (Phocoenoides truei ) by Andrews. However, it is now thought that Dall's porpoise is polymorphic, and dalli and truei forms merely represent color types of P. dalli . The presence of a truei -type newborn among a dalli -type population supports the view of color types, rather than separate species or subspecies.