Aspects of comparative thermal ecology of sympatric hinge‐back tortoises (Kinixys homeana and Kinixys erosa) in the Niger Delta, southern Nigeria

Abstract

AbstractAspects of the thermal ecology of two sympatric hinge‐back tortoises, Kinixys erosa and Kinixys homeana, were studied in the rainforest zone of south‐eastern Nigeria (West Africa). There were no significant differences in mean body temperatures (Tb) among K. homeana males, K. homeana females, K. erosa males and K. erosa females. In both species, there was a significant correlation between Tb and air temperature (Ta), and the regression line of Ta plotted against Tb differed significantly from the line of ideal poikilothermy. These regressions did not differ significantly between sexes in either species. There were no significant differences in terms of mean Tb in K. homeana during the various day‐hour intervals, whereas the mean Tb of K. erosa varied significantly among the various daytime intervals, attaining the higher values at 11.01–15.00 and 15.01–19.00 hours. In both species, Tbs were nearly always below Tas, and the negative difference ‘Tb ‐ Ta’ increased with increasing Ta. The hourly‐time course of the difference between Tb and Ta showed significant differences in K. homeana (with the higher negative differences at 11.01–15.00 and 15.01–19.00 hours), whereas no such difference was observed in K. erosa. In general, tortoises of both species showed behavioural thermoregulation in their avoidance of overheating in tropical environments, taking advantage of shady forest environments.