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Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus) / SIENA MCQUADE

Swansea University Author: SIENA MCQUADE

Abstract

Movement (body translocation) is a fundamental aspect of life for many animals and tends to have a clear purpose that enhances lifetime reproductive success. Obligate ram-ventilated sharks must move continuously to respire, making their patterns of movement less defined by clear behaviours. Among ot...

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Published: Swansea, Wales, UK 2023
Institution: Swansea University
Degree level: Master of Research
Degree name: MRes
Supervisor: Wilson, Rory P.
URI: https://cronfa.swan.ac.uk/Record/cronfa63273
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spelling v2 63273 2023-04-28 Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus) cdd016b654ebf37b3d776620d71afc2f SIENA MCQUADE SIENA MCQUADE true false 2023-04-28 Movement (body translocation) is a fundamental aspect of life for many animals and tends to have a clear purpose that enhances lifetime reproductive success. Obligate ram-ventilated sharks must move continuously to respire, making their patterns of movement less defined by clear behaviours. Among other functions, sharks must feed and behaviourally regulate their body temperature, and their position in the water column can play a key role in both. Sharks display bimodality in their use of depth, either ‘surface swimming’ or ‘diving’ (term used to encompass all behaviour below the surface), and this study aims to examine how these modes differ in functionality and costs for whale sharks (Rhincodon typus). Analysis of data from animal-attached tags recording acceleration, heading, temperature and depth from 20 animals indicated that the two modes were distinct in energetic costs and amount of time allocated to them. Surface swimming was more tortuous and required significantly more energy than diving, and diving accounted for a greater proportion of time (on average 65%) and feeding events. The allocation of time to each mode varied between day and night, with personality thought to play a role since individuals differed significantly. This study refutes the common assumption that surface swimming is entirely a thermoregulatory behaviour since depth and temperature were not correlated, yet bimodality was still shown. It also highlights a gap in our understanding of whale shark behaviour, since they perform energy expensive, tortuous movements even when not feeding – a behaviour that is not often discussed in the literature. Although surface swimming and diving have broadly similar functions in whale sharks, systematic differences in behaviour metrics imply that there are subtle behaviour differences between the two modes. We also highlight the need for a novel focus on the behavioural plasticity between individuals and different populations, considering the factors that contribute to behavioural variations. E-Thesis Swansea, Wales, UK Tortuosity, Energy efficiency, Feeding, Biologging, Vertical velocity 20 3 2023 2023-03-20 COLLEGE NANME COLLEGE CODE Swansea University Wilson, Rory P. Master of Research MRes 2023-10-27T15:15:44.0723686 2023-04-28T10:54:37.6407828 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Biosciences SIENA MCQUADE 1 63273__27261__179fa30e82d24491993f27df26d96108.pdf 2023_McQuade_S.final.63273.pdf 2023-04-28T11:08:08.4725714 Output 1318138 application/pdf E-Thesis – open access true Copyright: The Author, Siena McQuade, 2023. true eng
title Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus)
spellingShingle Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus)
SIENA MCQUADE
title_short Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus)
title_full Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus)
title_fullStr Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus)
title_full_unstemmed Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus)
title_sort Bimodality in depth use by sharks reflects bimodality in behaviour - a case study with Whale Sharks (Rhincodon typus)
author_id_str_mv cdd016b654ebf37b3d776620d71afc2f
author_id_fullname_str_mv cdd016b654ebf37b3d776620d71afc2f_***_SIENA MCQUADE
author SIENA MCQUADE
author2 SIENA MCQUADE
format E-Thesis
publishDate 2023
institution Swansea University
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Biosciences{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Biosciences
document_store_str 1
active_str 0
description Movement (body translocation) is a fundamental aspect of life for many animals and tends to have a clear purpose that enhances lifetime reproductive success. Obligate ram-ventilated sharks must move continuously to respire, making their patterns of movement less defined by clear behaviours. Among other functions, sharks must feed and behaviourally regulate their body temperature, and their position in the water column can play a key role in both. Sharks display bimodality in their use of depth, either ‘surface swimming’ or ‘diving’ (term used to encompass all behaviour below the surface), and this study aims to examine how these modes differ in functionality and costs for whale sharks (Rhincodon typus). Analysis of data from animal-attached tags recording acceleration, heading, temperature and depth from 20 animals indicated that the two modes were distinct in energetic costs and amount of time allocated to them. Surface swimming was more tortuous and required significantly more energy than diving, and diving accounted for a greater proportion of time (on average 65%) and feeding events. The allocation of time to each mode varied between day and night, with personality thought to play a role since individuals differed significantly. This study refutes the common assumption that surface swimming is entirely a thermoregulatory behaviour since depth and temperature were not correlated, yet bimodality was still shown. It also highlights a gap in our understanding of whale shark behaviour, since they perform energy expensive, tortuous movements even when not feeding – a behaviour that is not often discussed in the literature. Although surface swimming and diving have broadly similar functions in whale sharks, systematic differences in behaviour metrics imply that there are subtle behaviour differences between the two modes. We also highlight the need for a novel focus on the behavioural plasticity between individuals and different populations, considering the factors that contribute to behavioural variations.
published_date 2023-03-20T15:15:42Z
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score 11.016235

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