Habitat separation in tortoises and the consequences for activity and thermoregulation

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Abstract
Habitat use, daily activity times, and body temperatures of sympatric Testudo hermanni and Testudo graeca in summer were studied at four coastal sites in northeastern Greece. There was significant habitat separation at each site, with T. graeca occupying more open habitat. The two species had similar daily activity periods and body temperatures in habitats of similar structural complexity, coastal heath and mixed heath. Testudo hermanni occupying pine plantations and broadleafed woodland had lower body temperatures, and morning and evening activity periods shifted towards midday, compared with sympatric T. graeca in coastal heath. Habitat separation was studied throughout the year at one site, where T. hermanni were absent from coastal heath in spring; however, some T. hermanni moved into this habitat in summer. Testudo graeca occupied only coastal heath all year, so that habitat separation was least in summer. Less movement of T. hermanni into coastal heath occurred in a dry year, decreasing competition during periods of low food supply. The distribution of T. graeca in northern Greece is described. It is an eastern species which occupies a variety of habitats in Asia Minor, where it is the only tortoise. There is a cline of habitat use, such that moving westwards, T. graeca becomes progressively limited to more open habitats; the other habitats are occupied by T. hermanni. This pattern is discussed in relation to the evolutionary history of Mediterranean tortoises.