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The individual counts: within sex differences in foraging strategies are as important as sex-specific differences in masked boobies Sula dactylatra


Sommerfeld, Julia and Kato, A and Ropert-Coudert, Y and Garthe, S and Hindell, MA, The individual counts: within sex differences in foraging strategies are as important as sex-specific differences in masked boobies Sula dactylatra, Journal of Avian Biology, 44, (6) pp. 531-540. ISSN 0908-8857 (2013) [Refereed Article]

Copyright Statement

Copyright 2013 The Authors. Journal of Avian Biology Copyright 2013 Nordic Society Oikos

DOI: doi:10.1111/j.1600-048X.2013.00135.x


Understanding how animals allocate their foraging time is a central question in behavioural ecology. Intrinsic factors, such as body mass and size differences between sexes or species, influence animals' foraging behaviour, but studies investigating the effects of individual differences in body mass and size within the same sex are scarce. We investigated this in chick-rearing masked boobies Sula dactylatra, a species with reversed sexual dimorphism, through the simultaneous deployment of GPS and depth-acceleration loggers to obtain information on foraging movements and activity patterns. Heavier females performed shorter trips closer to the colony than lighter females. During these shorter trips, heavier females spent higher proportions of their flight time flapping and less time resting on the water than lighter females did during longer trips. In contrast, body mass did not affect trip duration of males, however heavier males spent less time flapping and more time resting on the water than lighter males. This may occur as a result of higher flight costs associated with body mass and allow conservation of energy during locomotion. Body size (i.e. wing length) had no effect on any of the foraging parameters. Dive depths and dive rates (dives h-1) were not affected by body mass, but females dived significantly deeper than males, suggesting that other factors are important. Other studies demonstrated that females are the parent in charge of provisioning the chick, and maintain a flexible investment under regulation of their own body mass. Variation in trip length therefore seems to be triggered by body condition in females, but not in males. Consequently, shorter trips are presumably used to provision the chick, while longer trips are for self-maintenance. Our findings underline the importance of accounting for the effects of body mass differences within the same sex, if sex-specific foraging parameters in dimorphic species are being investigated. Β© 2013 The Authors.

Item Details

Item Type:Refereed Article
Keywords:seabird, foraging behaviour
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Environmental Management
Objective Group:Coastal and estuarine systems and management
Objective Field:Assessment and management of coastal and estuarine ecosystems
UTAS Author:Sommerfeld, Julia (Ms Julia Sommerfeld)
UTAS Author:Hindell, MA (Professor Mark Hindell)
ID Code:89059
Year Published:2013
Web of Science® Times Cited:27
Deposited By:IMAS Research and Education Centre
Deposited On:2014-02-24
Last Modified:2017-10-31

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