Abstract

(…) The vaquita or Gulf of California harbor porpoise, Phocoena sinus Norris and McFarland 1958, has been observed rarely (Wells et al. 1981, Brownell 1983, Brownell 1986). Although a number of sightings of P. sinus have been reported in recent years (Villa-R. 1976, Wells et al. 1981, Vidal et al. 1987, Silber 1988), a paucity of observations of this species can be attributed to a severely depleted population, characteristically small group sizes, and a low surfacing profile. Little is known about the natural history or behavior of the vaquita (Brownell 1983). Descriptions of diving behavior and ventilation cycles have been reported for free-ranging Phocoena phocoena (Scheffer and Slipp 1948, Shapunov 1972, Gaskin et al. 1974, Watson and Gaskin 1983, Read and Gaskin 1985) and for Phocoena spinipinnis (Würsig et al. 1977), but there are no accounts of behavior of P. sinus. We present the only information to date on the behavior and ventilation cycles of P. sinus, which may prove valuable in future studies of this animal. (…)