Data associated to: A bioenergetics approach to understanding sex differences in the foraging behaviour of a sexually monomorphic species

Many animals show sexually divergent foraging behaviours reflecting
different physiological constraints or energetic needs. We used a
bioenergetics approach to examine sex differences in foraging behaviour of
the sexually monomorphic northern gannet. We used the relationship between
dynamic body acceleration and energy expenditure to investigate energetic
cost of prey capture attempts (plunge dives). Fourteen gannets were
tracked using GPS, TDR, and accelerometers. All plunge dives in a foraging
trip represented <4% of total energy expenditure, with no
significant sex differences in expenditure. Despite females undertaking
significantly more dives than males, the low energetic cost resulted in no
sex differences in overall energy expenditure across a foraging trip.
Bayesian stable isotope mixing models based on blood samples highlighted
sex differences in diet, however, calorific intake from successful prey
capture was estimated to be similar between sexes. Females experienced
9.6% higher energy demands, due to unequal chick provisioning. Estimates
show a minimum of 21% of dives have to be successful for females to meet
their daily energy requirements, and 29% for males. Our analyses suggest
northern gannets show sex differences in foraging behaviour primarily
related to dive rate and success rather than the energetic cost of
foraging or energetic content of prey.