Eight animals in a flock of 20 Merino sheep were observed during four 24-h periods in summer (T(a)max 31-37-degrees-C) to see whether their voluntary use of shade was related to patterns of foraging and posture. Observations were made at 15-min intervals on the 4 animals that used shade most (31% of the day) and the 4 animals that used shade least (12%). A related experiment revealed no significant differences in body core or skin temperatures or in respiratory rates between the groups.Feeding times, ruminating times and drinks per day were no different in groups making most and least use of shade; day-night patterns of these variables were also indistinguishable. Sheep in the shade stood for 2 h longer per day than sheep in the sun, though they behaved similarly at night. Thus shade use by sheep was not apparently related to patterns of feeding or watering, but was associated with postural modifications that probably have thermoregulatory consequences.

1. A group of six rats, living at thermoneutrality, but with access to food only under a high heat load, was compared with a similar group living and eating at thermoneutrality. 2. Animals eating in the heat reduced total food intake, meal duration, total feeding time, and rate of weight gain; they increased frequency of feeding and had higher water intakes. 3. Identifiable behavioral and nutritional responses explained some of the difference in adaptation between the groups through other factors may also have played a role.

The temperature and humidity of expired air from three adult Merino sheep were measured at air temperatures of 20, 30 and 40 degrees C before and after the animals were shorn. Expired air was apparently always saturated with water vapour. At the higher air temperatures the temperature of expired air was close to deep body temperature; at lower air temperatures, expired air had been significantly cooled, e.g. to 32.3 degrees C in shorn sheep at 20 degrees C air temperature. Expired air was cooler from shorn than from unshorn animals at 20 and 30 degrees C air temperature, possibly due to thermally induced vasomotor changes in the upper respiratory tract. Cooling of expired air would be expected to lead to recovery of some of the water evaporated during inspiration; at 20 degrees C air temperature, this fraction was estimated to be 25% in unshorn sheep and 36% in shorn sheep.