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Food insecurity increases energetic efficiency, not food consumption: An exploratory study in European starlings

Lookup NU author(s): Professor Melissa Bateson, Dr Clare Andrews, Dr Jonathon Dunn, Charlotte Egger, Francesca Gray, Molly McHugh, Professor Daniel Nettle

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Copyright 2021 Bateson et al.Food insecurity—defined as limited or unpredictable access to nutritionally adequate food—is associated with higher body mass in humans and birds. It is widely assumed that food insecurity-induced fattening is caused by increased food consumption, but there is little evidence supporting this in any species. We developed a novel technology for measuring foraging, food intake and body mass in small groups of aviary-housed European starlings (Sturnus vulgaris). Across four exploratory experiments, we demonstrate that birds responded to 1–2 weeks of food insecurity by increasing their body mass despite eating less. Food-insecure birds therefore increased their energetic efficiency, calculated as the body mass maintained per unit of food consumed. Mass gain was greater in birds that were lighter at baseline and in birds that faced greater competition for access to food. Whilst there was variation between experiments in mass gain and food consumption under food insecurity, energetic efficiency always increased. Bomb calorimetry of guano showed reduced energy density under food insecurity, suggesting that the energy assimilated from food increased. Behavioural observations of roosting showed inconsistent evidence for reduced physical activity under food insecurity. Increased energetic efficiency continued for 1–2 weeks after food security was reinstated, indicating an asymmetry in the speed of the response to food insecurity and the recovery from it. Future work to understand the mechanisms underlying food insecurity-induced mass gain should focus on the biological changes mediating increased energetic efficiency rather than increased energy consumption.


Publication metadata

Author(s): Bateson M, Andrews C, Dunn J, Egger CBCM, Gray F, McHugh M, Nettle D

Publication type: Article

Publication status: Published

Journal: PeerJ

Year: 2021

Volume: 9

Online publication date: 28/05/2021

Acceptance date: 10/05/2021

Date deposited: 18/06/2021

ISSN (electronic): 2167-8359

Publisher: PeerJ Inc.

URL: https://doi.org/10.7717/peerj.11541

DOI: 10.7717/peerj.11541


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