engleski

Craniometry of bottlenose dolphins (Tursiops truncatus) from the Adriatic Sea

The bottlenose dolphin (Tursiops truncatus) is a cetacean distributed worldwide with an external morphology that varies between different populations. An endangered population of bottlenose dolphins inhabits the Adriatic Sea and is legally protected. The skulls of 95 adult bottlenose dolphins (47 females and 43 males, 5 of unknown sex) were morphometrically analyzed. They originated from bottlenose dolphins stranded dead from 1990 to 2011 in the Croatian part of the Adriatic Sea. For each animal a total of up to 53 skull measurements and meristic characters were taken using slide calipers to the nearest 0.01 cm. Sexual dimorphism within the Adriatic population was analyzed while the average morphometric values of Adriatic specimens were compared with published values for the genus Tursiops from different geographical areas. Male Adriatic bottlenose dolphins were signifi cantly larger in terms of 19 craniometric characteristics compared to females. The male skull is wider along the rostrum, at the level of the braincase and at the orbital region. Their braincase is higher and longer and their teeth are higher. Comparison of morphometrical values between Adriatic bottlenose dolphins and populations from other seas confi rms geographical polymorphism within the species T. truncatus. Our study showed that the skull size follows Bergmann’s rule, with larger skulls found in colder waters, while smaller skulls are found in populations from temperate and tropical seas. Our results represent referent craniometrical values for the Adriatic bottlenose dolphin and should be used when implementing morphometry in population conservation.

bottlenose dolphin; Tursiops truncatus; Adriatic Sea; geographical polymorphism; cranial morphometry

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