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As clear as day: nocturnal activity differs from diurnal activity in a temporally constrained capital breeder

Fraser, Z.L.; Culloch, R.M.; Twiss, S.D.

As clear as day: nocturnal activity differs from diurnal activity in a temporally constrained capital breeder Thumbnail


Z.L. Fraser

R.M. Culloch


Time-activity budgets are fundamental to behavioural studies, allowing examination of how individuals allocate their time, and potentially energy, and how these patterns vary spatially and temporally and in relation to habitat, individual identity, sex, social status and levels of anthropogenic disturbance. Direct observations of animal behaviour, especially in the wild, are often limited to daylight hours; therefore, many activity budgets relate to diurnal activity only, or assumptions are made about nocturnal activity. Activity budgets have been a key component of many behavioural and energetics studies of breeding grey seals (Halichoerus grypus, Fabricius, 1791), and yet very little is known about nocturnal activity of grey seals, and a general, implicit assumption of no significant change from day to night seems to pervade the literature. Here we use a combination of high resolution digital video and thermal imaging video camera to follow known individual grey seal mothers from day into night to examine activity patterns during lactation. We show distinct differences in nocturnal activity budgets relative to diurnal activity budgets. Mothers spent significantly more time resting with a reduction of time spent in the alert and comfort move behavioural categories during nocturnal periods. It is clear that diurnal time-activity patterns of breeding female grey seals cannot be extrapolated to represent activity across a 24-hour cycle. These considerations are particularly critical in studies that aim to use time-activity budgets as proxies for energy budgets.

Journal Article Type Article
Acceptance Date Mar 2, 2019
Online Publication Date Mar 26, 2019
Publication Date 2019
Deposit Date Mar 14, 2019
Publicly Available Date Mar 26, 2020
Journal Behaviour
Print ISSN 0005-7959
Electronic ISSN 1568-539X
Publisher Brill Academic Publishers
Peer Reviewed Peer Reviewed
Volume 156
Issue 10
Pages 997-1016
Public URL


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