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Temperature and the tropical tortoise Kinixys spekii: constraints on activity level and body temperature
Author(s) -
Hailey A.,
Coulson I. M.
Publication year - 1996
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1996.tb05303.x
Subject(s) - relative humidity , biology , maximum temperature , thermoregulation , tortoise , zoology , atmospheric sciences , mean radiant temperature , operative temperature , overheating (electricity) , air temperature , humidity , ecology , sympatric speciation , climate change , meteorology , geography , physics , quantum mechanics , thermal
Movements of five Kinixys spekii were measured continuously during six weeks of their activity season, by thread‐trailing. The mean daily movement distance was negatively correlated with maximum shade air temperature, but not significantly related to minimum temperature, rainfall, or humidity. There was a midday period of inactivity of increasing length as maximum air temperature exceeded 29° C. Temperatures of models suggest that lower activity on hot days was due to the risk of overheating in this small (mean mass 617 g) tortoise. Kinixys spekii had a mean field body temperature (T b ) of 27° C, which is low compared to other tortoises (including sympatric Geochelone pardulis, mean T b = 32.5° C), but salivated at a similar T b (38.4° C). This pattern also occurs in other small species; mean and maximum field T b s of tortoises are positively correlated with body mass, but salivation and critical maximum T b s do not vary with body mass. Low field T b provides a wide safety margin before evaporation of water becomes necessary. Kinixys sprkii had a short annual activity period, with about 95% of sightings in four months (December to March). Monthly sightings of K. spekii were correlated with rainfall, but not significantly related to temperature or humidity. Seasonal activity is therefore related to rainfall, but within the rainy season the level and pattern of daily activity is related to temperature.