Behavioral Capabilities of Seals and Sea Lions: A Review of Their Hearing, Visual, Learning and Diving Skills

Abstract

Behavioral capabilities of seals and sea lions (the pinnipeds) are described and summarized in tabular form. Major features of sound detection, pitch perception, sound localization, visual spectral sensitivity, visual acuity, learning potential and constraints on learning and memory, and maximum diving depths are presented for these large-brained amphibious marine mammals. Among those species tested, phocids hear higher frequencies under water than do otariids and the opposite is true for airborne sounds. All pinnipeds are more sensitive to underwater sounds than they are to airborne sounds. There is little evidence to support the notion that most pinnipeds have evolved an echolocation capability. Scotopic sensitivity of several species is correlated with radiant energy in the marine environment. Visual acuity is equally sharp in air and under water, but deteriorates more rapidly in air than in water when the ambient light is decreased. Sea lions generally behave optimally when confronted with ambiguous cues signaling food reward. Although visual form discrimination and generalization is highly developed, thus far abstraction abilities have not been demonstrated easily in pinnipeds. Although many pinnipeds dive to 200–250 m, only the Weddell seal has been observed to dive to 600 m.