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Peer-reviewedCC BY 4.0Royal Society Open Science

Ontogeny of rake mark scarring on common dolphins ( Delphinus delphis ): insights to aggression and affiliation?

  • Hannah R. Crisp1
  • Katharina J. Peters2
  • Emily I. Palmer1
  • Frédérik Saltré3,4
  • Emma L. Betty1
  • Eva-Maria F. Hanninger1
  • Karen A. Stockin1
4 affiliations
  1. 1Cetacean Pathology Unit, New Zealand Institute for Advanced Study, Massey University 1 , Auckland, New Zealand
  2. 2Marine Vertebrate Ecology Lab, Environmental Futures, School of Science, University of Wollongong 2 , Wollongong, New South Wales, Australia
  3. 3Biogeography Ecology and Modelling | Ngura Nandamari, School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, 3 Australia
  4. 4Australian Museum Research Institute, Australian Museum 4 , Sydney, New South Wales 2010, Australia
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Abstract

Aggressive and affiliative interactions shape resource allocation, social structure and reproduction in social species. In delphinids, rake marks (parallel scars from tooth raking) indicate social interactions. When examined alongside ontogeny, demographic traits and scar position, rake marks can inform social dynamics. We assessed rake marks on common dolphins (Delphinus delphis) in Aotearoa New Zealand (2006–2024; n = 102) during post-mortem examinations to explore drivers of social behaviour. Using a zero-inflated generalized linear mixed model, we assessed rake mark occurrence (probability of rake density > 0) and prevalence (rake density, rake marks dm−2) across the body (n = 101; dorsal/ventral, cranial/caudal, left/right) in relation to sex, age, total body length (TBL), sexual maturity, body condition (n = 101) and female reproductive status (n = 51), to infer confrontation, avoidance and lateralization. Females showed higher rake mark prevalence but lower occurrence than males, suggesting infrequent but prolonged interactions, possibly sexual coercion. Rake prevalence and occurrence increased with TBL, potentially related to increased social interactions and surface area in larger individuals. Age, sexual maturity, body condition, and female reproductive status were not strong predictors of rake mark occurrence or prevalence. Our findings highlight rake marks as potential indicators of social dynamics.

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Cite

BibTeXRIS
BibTeX
@article{crisp2026ontogeny,
  title = {{Ontogeny of rake mark scarring on common dolphins ( Delphinus delphis ): insights to aggression and affiliation?}},
  author = {Hannah R. Crisp and Katharina J. Peters and Emily I. Palmer and Frédérik Saltré and Emma L. Betty and Eva-Maria F. Hanninger and Karen A. Stockin},
  journal = {Royal Society Open Science},
  year = {2026},
  month = oct,
  doi = {10.1098/rsos.252175},
  url = {https://royalsocietypublishing.org/rsos/article/13/10/252175/483609/Ontogeny-of-rake-mark-scarring-on-common-dolphins},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Ontogeny of rake mark scarring on common dolphins ( Delphinus delphis ): insights to aggression and affiliation?
AU  - Hannah R. Crisp
AU  - Katharina J. Peters
AU  - Emily I. Palmer
AU  - Frédérik Saltré
AU  - Emma L. Betty
AU  - Eva-Maria F. Hanninger
AU  - Karen A. Stockin
PY  - 2026
DA  - 2026/10/14
JO  - Royal Society Open Science
DO  - 10.1098/rsos.252175
UR  - https://royalsocietypublishing.org/rsos/article/13/10/252175/483609/Ontogeny-of-rake-mark-scarring-on-common-dolphins
AB  - Aggressive and affiliative interactions shape resource allocation, social structure and reproduction in social species. In delphinids, rake marks (parallel scars from tooth raking) indicate social interactions. When examined alongside ontogeny, demographic traits and scar position, rake marks can inform social dynamics. We assessed rake marks on common dolphins (Delphinus delphis) in Aotearoa New Zealand (2006–2024; n = 102) during post-mortem examinations to explore drivers of social behaviour. Using a zero-inflated generalized linear mixed model, we assessed rake mark occurrence (probability of rake density > 0) and prevalence (rake density, rake marks dm−2) across the body (n = 101; dorsal/ventral, cranial/caudal, left/right) in relation to sex, age, total body length (TBL), sexual maturity, body condition (n = 101) and female reproductive status (n = 51), to infer confrontation, avoidance and lateralization. Females showed higher rake mark prevalence but lower occurrence than males, suggesting infrequent but prolonged interactions, possibly sexual coercion. Rake prevalence and occurrence increased with TBL, potentially related to increased social interactions and surface area in larger individuals. Age, sexual maturity, body condition, and female reproductive status were not strong predictors of rake mark occurrence or prevalence. Our findings highlight rake marks as potential indicators of social dynamics.
SN  - 2054-5703
ER  -