Using Tooth Rakes to Monitor Population and Sex Differences in Aggressive Behaviour in Bottlenose Dolphins (Tursiops truncatus)

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Abstract

This study investigated intraspecific tooth rake scarring, an established indicator of received aggression by conspecifics, on bottlenose dolphins (Tursiops
truncatus) to gain knowledge of aggressive interactions. The differences in tooth rake scarring between male and female dolphins on the east coast of Scotland were examined, and overall levels of scarring were compared with dolphins on the west coast of Scotland (Sound of Barra and Hebrides). Photographs were examined for evidence of tooth rake scarring using four different methods. East
coast males displayed significantly higher scarring percentages (i.e., body area covered by tooth rake scarring), numbers of dorsal fin rake directions (i.e.,
whether tooth rake scars were vertical, horizontal, diagonal, or curved), and nick percentage (i.e., amount of the dorsal fin missing due to nicks) than females. Differences also existed between the three areas, with bottlenose dolphins around the Sound of Barra showing significantly lower levels of dorsal
fin rake directions than those on the east coast or Hebrides. Observed sex differences are likely the result of intrasexual conflict between males over
access to females. However, other factors such as sex- or age-specific behaviours or sexual coercion of females may also be involved. Such information
could potentially be used to differentiate between the sexes. The differences in dorsal fin scarring between these populations suggests differences in aggressive
interactions, possibly indicating differences in social structure. The lower scarring levels seen in the Sound of Barra group may support the suggestion
that bottlenose dolphins on the west coast belong to two communities. However, this variability in conspecific aggression may also be the result of different
social behaviours, age or sex ratios, habitat, resources, or individual behavioural differences.
Original languageEnglish
Pages (from-to)107-115
Number of pages9
JournalAquatic Mammals
Volume39
Issue number2
DOIs
Publication statusPublished - 28 May 2013

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rakes
Tursiops truncatus
dolphin
gender differences
tooth
aggression
teeth
monitoring
coast
fins
coasts
dolphins
Scotland
social structure
sex ratio
photograph
gender
photographs
habitat
resource

Keywords

  • social behaviour
  • social structure
  • cetacean
  • intraspecific aggression
  • tooth rake scarring
  • bottlenose dolphin
  • Tursiops truncates

Cite this

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title = "Using Tooth Rakes to Monitor Population and Sex Differences in Aggressive Behaviour in Bottlenose Dolphins (Tursiops truncatus)",
abstract = "This study investigated intraspecific tooth rake scarring, an established indicator of received aggression by conspecifics, on bottlenose dolphins (Tursiopstruncatus) to gain knowledge of aggressive interactions. The differences in tooth rake scarring between male and female dolphins on the east coast of Scotland were examined, and overall levels of scarring were compared with dolphins on the west coast of Scotland (Sound of Barra and Hebrides). Photographs were examined for evidence of tooth rake scarring using four different methods. Eastcoast males displayed significantly higher scarring percentages (i.e., body area covered by tooth rake scarring), numbers of dorsal fin rake directions (i.e.,whether tooth rake scars were vertical, horizontal, diagonal, or curved), and nick percentage (i.e., amount of the dorsal fin missing due to nicks) than females. Differences also existed between the three areas, with bottlenose dolphins around the Sound of Barra showing significantly lower levels of dorsalfin rake directions than those on the east coast or Hebrides. Observed sex differences are likely the result of intrasexual conflict between males overaccess to females. However, other factors such as sex- or age-specific behaviours or sexual coercion of females may also be involved. Such informationcould potentially be used to differentiate between the sexes. The differences in dorsal fin scarring between these populations suggests differences in aggressiveinteractions, possibly indicating differences in social structure. The lower scarring levels seen in the Sound of Barra group may support the suggestionthat bottlenose dolphins on the west coast belong to two communities. However, this variability in conspecific aggression may also be the result of differentsocial behaviours, age or sex ratios, habitat, resources, or individual behavioural differences.",
keywords = "social behaviour, social structure, cetacean, intraspecific aggression, tooth rake scarring, bottlenose dolphin, Tursiops truncates",
author = "Marley, {Sarah A.} and Barbara Cheney and Thompson, {Paul M.}",
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AU - Cheney, Barbara

AU - Thompson, Paul M.

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N2 - This study investigated intraspecific tooth rake scarring, an established indicator of received aggression by conspecifics, on bottlenose dolphins (Tursiopstruncatus) to gain knowledge of aggressive interactions. The differences in tooth rake scarring between male and female dolphins on the east coast of Scotland were examined, and overall levels of scarring were compared with dolphins on the west coast of Scotland (Sound of Barra and Hebrides). Photographs were examined for evidence of tooth rake scarring using four different methods. Eastcoast males displayed significantly higher scarring percentages (i.e., body area covered by tooth rake scarring), numbers of dorsal fin rake directions (i.e.,whether tooth rake scars were vertical, horizontal, diagonal, or curved), and nick percentage (i.e., amount of the dorsal fin missing due to nicks) than females. Differences also existed between the three areas, with bottlenose dolphins around the Sound of Barra showing significantly lower levels of dorsalfin rake directions than those on the east coast or Hebrides. Observed sex differences are likely the result of intrasexual conflict between males overaccess to females. However, other factors such as sex- or age-specific behaviours or sexual coercion of females may also be involved. Such informationcould potentially be used to differentiate between the sexes. The differences in dorsal fin scarring between these populations suggests differences in aggressiveinteractions, possibly indicating differences in social structure. The lower scarring levels seen in the Sound of Barra group may support the suggestionthat bottlenose dolphins on the west coast belong to two communities. However, this variability in conspecific aggression may also be the result of differentsocial behaviours, age or sex ratios, habitat, resources, or individual behavioural differences.

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