Cloacal evaporation: an important and previously undescribed mechanism for avian thermoregulation.

We present the first experimental evidence that a bird is capable of evaporating enough water from the cloaca to be important for thermoregulation. We measured rates of evaporation occurring from the mouth, the skin, and the cloaca of Inca doves Columbina inca Lesson and Eurasian quail Coturnix coturnix Linnaeus. Inca doves showed no significant increase in cutaneous evaporation in response to curtailment of buccopharyngeal evaporation.

Using direct calorimetry to test the accuracy of indirect calorimetry in an ectotherm.

We previously demonstrated that the relationship between respiratory gas exchange and metabolic heat production is unexpectedly variable and that conventional approaches to estimating energy expenditure by indirect calorimetry can incorporate large errors. Prior studies, however, comparing direct and indirect calorimetry of animals focused only on endothermic organisms. Given that endothermy and ectothermy represent a fundamental dichotomy of animal energetics, in this analysis we explore how these contrasting physiologies correlate with the relationship between heat production and respiratory gas exchange.

Direct calorimetry reveals large errors in respirometric estimates of energy expenditure.

Knowledge of animal energetics is based largely upon indirect calorimetry, which is estimation of metabolic heat production by an organism from measurement of indices such as oxygen consumption or carbon dioxide production. Remarkably, indirect calorimetry has been validated by comparison to direct measurements of metabolic heat production (direct calorimetry) only for highly restricted conditions, primarily with a few species of medium-to-large mammals. Taxa with differing physiologies are little studied.

Body temperature and locomotor capacity in a heterothermic rodent.

We quantify the locomotor capacity of the round-tailed ground squirrel (Spermophilus tereticaudus), a mammal that can lower energetic costs by relaxing thermoregulatory limits without becoming inactive. We measured maximum sprint speed, maximum limb cycling frequency and maximum force production in animals at body temperatures ranging from 31 degrees C to 41 degrees C. We found no thermal dependence in any of these parameters of locomotion.

Kangaroo rats revisited: re-evaluating a classic case of desert survival.

Kangaroo rats are the archetypical organisms for mammalian survival in North American deserts, yet there are contradictions in the data surrounding their physiology and ecology. The traditional view has been that these nocturnal rodents have little tolerance to high temperatures (e.g.

Effect of environmental temperature on body temperature and metabolic heat production in a heterothermic rodent, Spermophilus tereticaudus.

This study quantifies the thermoregulatory ability and energetics of a mammal, the round-tailed ground squirrel Spermophilus tereticaudus, that can relax thermoregulatory limits without becoming inactive. We measured body temperature and metabolic rate in animals exposed for short periods (1 h) to air temperatures ranging from 10 to 45 degrees C and for long periods (8 h) to air temperatures ranging from 10 to 30 degrees C. Within 45 min of exposure to air temperatures ranging from 10 to 45 degrees C, the mean body temperatures of alert and responsive animals ranged from 32.