Extensive scaring observed on female or juvenile male sperm whales off the Galápagos Islands.

Sascha K. Hooker. 1998.

Mammalia 62: 134-139.


Scarring on sperm whales (Physeter macrocephalus), has been previously noted on mature males, but not on female or juvenile male sperm whales. In the Galapágos during 1995, two female or juvenile male sperm whales were observed with extensive scarring on the head and anterior dorsal surface of their bodies. This note describes the unusual degree and nature of scarring on one of these females / juvenile males (based on photographs) and discusses the possible causes.

Scarring was observed over a large portion of the head and anterior dorsal surface, arranged in at least twenty "groups". Each scar group was composed of between 1 and 6 parallel scars (average 3.75), although groups were not always straight and often showed s-shapes or distinct changes of direction. Assuming a head size of approximately 2.2 - 2.8 m, it was possible to approximate the dimensions of the scarring and infer the dimensions required to cause this. A comparison of the inter-dental or inter-hook measurements for selected other odontocetes, sharks and cephalopods showed that scar dimensions were best fit by either another sperm whale or a giant squid, but that the apparent depth of the scars was more suggestive of a sperm whale cause.

While previous accounts of intra-specific aggression in sperm whales have been between adult males, the interscar spacing observed corresponds instead to the interdental spacing of a female or juvenile sperm whale. This encounter is therefore suggestive of intra-specific aggression between smaller sperm whales than has previously been recorded.

Fig. 1. - Extensive scarring observed on a female or juvenile male sperm whale off the Galápagos Islands, 7 May 1995. Photograph by Sascha Hooker.

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