1. Changes in food consumption and fermentation capacity were examined in mole-rats housed at 23 and 30 degrees C. 2. At both temperatures animals maintained body mass. Food consumption was lower at the higher temperature and led to a similar decline in caecal mass. 3. Caecal dry matter content and fermentation efficiency were unaffected by food intake. However, gas production per animal decreased markedly with the reduced food intake. 4. The drop in fermentation in response to decreased food intake led to a concomitant decrease in heat production. This would be highly advantageous for chthonic rodents residing during summer in warm humid plugged burrows.