INTRASPECIFIC SCARRING IN ODONTOCETE CETACEANS - AN INDICATOR OF MALEQUALITY IN AGGRESSIVE SOCIAL INTERACTIONS

The level of visible (i.e. white or unpigmented) scarring on cetaceans varies greatly between species, particularly for intraspecific scarri ng in odontocete cetaceans. In some species, unpigmented intraspecific scars may act as an indicator of male 'quality' during aggressive soc ial interactions. Evidence to support this hypothesis was found in 18 species of odontocete cetacean. These were the narwhal (Monodon monoce ros), the sperm whale (Physeter macrocephalus), the Risso's dolphin (G rampus griseus) and the family Ziphiidae (with the exception of Mesopl odon ginkgodens). The evolution of such signalling is related to the f act that teeth are not required for feeding on certain diets, primaril y cephalopod-based diets, and as a result the number of teeth has been reduced. However, some teeth have been retained, and selected, as wea pons for male-male competition. This has resulted in an increase in th e level of intraspecific scarring and the greater need for a signal of 'quality' to avoid costly and dangerous fights. As intraspecific scar ring became this signal, the repigmentation rate of scars was reduced, leading to all scars remaining permanently unpigmented in these speci es.