Selection and Intake of Carbohydrates by Wild and Domesticated Rats.

Summary Domestication has altered the response of rats to sweet solutions. Fluid intake with all the sweeteners was lower and relatively constant for the wild rats. However, both wild and domesticated rats exhibited a qualitatively similar preference for the carbohydrate solutions. The domestic rat selected non-nutritive saccharin to a significantly greater degree, while the wild rat responded to toxic xylose with a reduced preference. Although the caloric intake of the wild rats was larger and was obtained to a greater degree from the ration, they gained no more weight than did the domesticated rat. Since body weights were similar, and the wild rat consumed less water and more food it follows that the wild rat functions with a lower ratio of water to caloric intake. Under the conditions of the experiment the domestic rat was indulgent with the sweet solutions, responding less to the nutritional and toxic consequences than did its wild counterpart.