The vocal behaviour of the grey seal (Halichoerus grypus)
Abstract
This thesis is an observational and experimental study of the vocal behaviour in the grey
seal (Halichoerus grypus). It provides the first comprehensive description of in-air and
underwater vocalisations for the eastern Atlantic population of grey seals and compares
it to the western Atlantic population. Two out of 6 in-air call types were very similar to
underwater vocalisations and of the 10 eastern Atlantic underwater vocalisations 5 were
comparable to the western Atlantic repertoire described earlier. Most calls were found to
occur on their own, while some were preferentially associated in time with other call
types. In addition, the number of particular types of underwater vocalisation did not
display any diurnal variation, but did vary' across the breeding season. Experimental
studies were also carried out on the role of pup vocalisations in mother-pup vocal
recognition at two reproductively isolated colonies: the Isle of May, Scotland and Sable
Island, Nova Scotia, Canada. Pup vocalisations were found to be both stereotyped and
individually distinctive, features normally associated with a system of individual
recognition. Allo-suckling was observed to be widespread on the Isle of May but was
absent on Sable Island. Playback experiments revealed that mothers on the Isle of May
did not respond more to vocalisations of their own pup than to those of non-filial pups.
In contrast, on Sable Island, mothers were able to discriminate between their own and
other pup calls. This suggests that different selective pressures may be affecting the two
colonies, and possible reasons are discussed.
Type
Thesis, PhD Doctor of Philosophy
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