UNDERWATER VOCALIZATIONS OF ICE BREEDING GRAY SEALS

Grey seals (Halichoerus grypus) breed both on land and on the ice. In January 1991, 36 h of underwater recordings were made from Amet Island , located in ice-covered waters in the southern Gulf of St. Lawrence. All vocalizations were examined for spectral and temporal structure an d then classified into 1 of 7 call types. The majority of calls consis ted of guttural ''rups'' and ''rupes'' (frequency = 100 - 3000 Hz), an d low-frequency growls (100-500 Hz). Other less common vocalizations w ere low-frequency clicks (3000 Hz), as well as loud knocks, similar to knocking vocalizations recorded in walrus, and which had not been des cribed previously for grey seals. The total number of vocalizations an d the number of specific call types showed seasonal variations. The ra te of vocalizations increased with the intensity of social activity an d with the number of agonistic behaviors during the progression of the breeding season. Comparisons between night and day showed some change s in the vocal repertoire. Low-frequency clicks were recorded more oft en during darkness (17.1% of calls) than in daylight (1.9%), and when ice cover was more extensive.