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

Abstract

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 derived a relationship between dynamic body acceleration and energy expenditure to quantify the energetic cost of prey capture attempts (plunge dives). Fourteen gannets were tracked using GPS, time depth recorders (TDR) and accelerometers. All plunge dives in a foraging trip represented less than 4% of total energy expenditure, with no significant sex differences in expenditure. Despite females undertaking significantly more dives than males, this 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 10.28% higher energy demands, primarily due to unequal chick provisioning. Estimates show a minimum of 19% of dives have to be successful for females to meet their daily energy requirements, and 26% 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.

Large‐scale movement patterns in a social vulture are influenced by seasonality, sex, and breeding region

“…Differences in foraging performance between sexes are common in mammals and birds and are often due to differences in body size and parental duties (Lewis et al, 2002 ), In monomorphic species such as the Griffon Vulture, these differences might be associated with energetic and nutritional requirements for reproduction (Bennison et al, 2022 ; Pinet et al, 2012 ). Our results showed that females have larger home‐ranges and travel farther than males.…”

Using accelerometers to infer behaviour of cryptic species in the wild

“…Using an approach based on accelerometer sensors, ecologists will be increasingly able to remotely and continuously estimate specific behaviours of wild animals and how they may vary among individuals (Bidder et al . 2020; Bennison et al . 2022) and over time (e.g.…”

“…vigilance (Benhaiem et al 2008;Favreau et al 2014)), usually during the day and in habitats that provide high observability. Using an approach based on accelerometer sensors, ecologists will be increasingly able to remotely and continuously estimate specific behaviours of wild animals and how they may vary among individuals (Bidder et al 2020;Bennison et al 2022) and over time (e.g. according time of day and season (Hammond et al 2016;Rast et al 2020), according to environmental conditions).…”

Handedness and individual roll-angle specialism when plunge diving in the northern gannet

“…Dives were identified from accelerometry using threshold analysis [37,38]. Dives occurred when average acceleration (running average of 2 s) in the x-axis was less than 0 g and standard deviation in the mean x-axis was greater than 1.4 g following Bennison et al [39]. Roll was calculated as the rotation of the individual in the x-axis and is calculated using the following formula:Roll=(true0yx2+ z2) × (true0180π)where x is the acceleration in the forward-facing surge channel, y is the acceleration in the lateral sway channel, and z represents the acceleration in the vertical heave channel.…”

“…Dives were identified from accelerometry using threshold analysis [37,38]. Dives occurred when average acceleration (running average of 2 s) in the x-axis was less than 0 g and standard deviation in the mean x-axis was greater than 1.4 g following Bennison et al [39]. Roll was calculated as the rotation of the individual in the x-axis and is calculated using the following formula:…”