Activity Levels and Ranging Behaviour of the Two Amazonian Tortoises, Geochelone carbonaria and Geochelone denticulata, in North-Western Brazil

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Abstract
1 Most previous studies of terrestrial ectotherms have emphasized the limitations of ectothermy by concentrating on small organisms, or ones inhabiting xeric environments. To investigate the potential plasticity of ectotherm behaviour in a benign environment, aspects of the behaviour and ecology of two species of tortoise (Testudinidae) were examined in a rain forest in north-western Brazil. 2 Activity levels were monitored by a mark-recapture study and movements were examined by radiotracking and trailing several individuals simultaneously. Fifty-six tortoises were followed over the 18-month study (1442 tortoise-days). 3 Most of the variation observed in activity levels, movement behaviour and use of area was explained at the level of individuals. The few patterns observed seemed related to reproductive biology: young individuals and adult females were active all year round, while large males were active almost exclusively during the mating season. However, except for male Geochelone carbonaria (Spix) during the mating season, individual behaviour patterns differed markedly within each species, sex and season group. 4 We argue that the low metabolic requirements of adult tortoises, along with their low vulnerability to predation and existence in a benign environ-ment, allow individuals