THE EFFECT OF INGESTED TRANSMITTERS UPON THE TEMPERATURE PREFERENCE OF THE NORTHERN WATER SNAKE, NERODIA S. SIPEDON

The mean temperature selected by post-absorptive Nerodia s. sipedon in a laboratory thermal gradient was 27.7 C (SE = 1.42, n = 5). The mean temperatures selected by the same snakes following the ingestion of natural food items and model transmitters were 36.0 C (SE = 2.33, n = 5) and 36.4 C (SE = 2.31, n = 5), respectively. A repeated measures ANOVA indicated that the substrate temperatures selected after ingestion of either food or transmitters were signif- icantly higher than those selected when post-absorptive. These results suggest that studies using ingested transmitters may bias their observations in favor of post-ingestion behavior.