Feeding behavior and an oropharyngeal component of satiety in a two-headed snake

Abstract

We studied the feeding behavior of a dicephalous Black Rat Snake ( Elaphe o. obsoleta) whose heads attack and ingest prey independently. Both heads were given satiation feedings with mouse prey at either 5-day intervals (1989, n = 16 feedings) or 9–11 day intervals (1990, n = 4 feedings). In 1989, a meal pattern was manifested as a negative correlation between total (left + right) meal size (g) and total size of the last meal. Meal sizes of the heads were consistently different (L > R) despite their apparently identical genotypes. We confirmed tongue-flicking rate and swallowing time as indices of satiety/hunger in each head. In order to test whether oropharyngeal stimulation is involved in satiation, we analyzed three measures: willingness to feed, and intrameal changes in swallowing, and tongue-flicking rates. Data for these tests were taken from experimental feedings in which one head was fed to satiation (first head) before the other head (second head) was fed. The second head generally did eat (8 of 10 experimental feedings) after the first head had become satiated. In addition, while the time to swallow a mouse generally increased as the snake neared satiety, swallowing time decreased significantly ( p = 0.04) from the first head's last mouse to the second head's first mouse. Finally, in two of three feedings, the first head's tongue-flicking rate decreased before the second head's. These results, which take advantage of this unique animal, indicate that oropharyngeal stimulation is involved in meal termination.