Proportional underwater call type usage by Weddell seals (Leptonychotes weddellii) in breeding and nonbreeding situations

Twenty-four hour recordings were collected in 2002 at two sites. One hundred consecutive calls from each of 248 recordings were classified into one of ten common call types. Time to 100 calls provided the calling rate.

The study period was divided into four periods representing initial sea-ice formation, pre-pupping, pupping, and mating. Calling rate and light-dark differences were also examined. No presence-absence differences were observed for any of the call types with season.

The largest difference between nonbreeding and breeding situations was an increase from 32.2% to 38.1% for descending whistles (F[3,244] = 4.483, p = 0.004). Trills gradually increased from 1.8% to 7.3% toward the mating period (F[3,244] = 30.932, p less than 0.001). The proportion of trills, chugs, descending whistles, and other call types also varied with calling rate and light-dark conditions.

Some pre-reproductive behaviours may occur in winter, but no call types of Weddell seals function solely in the breeding season.