Activity and haul out behaviour of captive harp seals (Pagophilus groenlandicus)

Moulton, Valerie D. (1997) Activity and haul out behaviour of captive harp seals (Pagophilus groenlandicus). Masters thesis, Memorial University of Newfoundland.

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Abstract

The annual cycle of all pinnipeds includes seasonal changes in behaviour linked to key events such as reproduction, moult, and in some species, migration. These changes in behaviour have generally been quantified in terms of haul out or diving, but rarely for more than one season. Weather conditions have been shown to influence the haul out pattern of some pinniped species but these studies have also had limited seasonal scope. This study measured activity levels (seal body movements per minute) and haul out behaviour of nine captive harp seals (Pagophilus groenlandicus) using modified time-depth recorders for a fourteen-month period. Solar radiation, temperature, wind velocity, and relative humidity were concurrently monitored throughout the study. The harp seal was selected for study because relatively little quantitative information exists for this species' behaviour and because circannual patterns in their food intake and energy demands have been detected. -- Activity levels and amount of time spent hauled out varied seasonally for most harp seals, but individual variation often precluded generalization. However, certain trends occurred during key annual cycle events. Seals spent significantly more time hauled out, and time of day of haul out shifted closer to midday during moult. Increasing wind velocity had a negative influence on haul out during this time, whereas solar radiation had a positive effect. These behavioural responses to weather conditions are energetically beneficial to seals, because exposure to warm temperatures accelerates the growth of skin and hair. Activity significantly increased in only two seals during the breeding period. Seasonal patterns of daily activity and haul out were overlaid by circadian rhythms. Activity consistently peaked around midday and was lowest at night when seals were found to haul out The midday feeding schedule probably acted as an "entraining" mechanism for these rhythms. This suggests that factors like habits of prey (i.e., availability or ease of access) may play a role in determining the daily activity patterns of harp seals in the wild. Although no conclusive evidence exists to support this idea, daily dive patterns of several other seal species and the behaviour of their prey suggest that it is true.

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