Does immune challenge affect torpor duration?

1. Hibernation may alter the relationship between pathogens and their hosts ; low host temperatures can prevent pathogen replication. Therefore, manipu lating the timing and duration of torpor bouts could allow animals to gain an advantage over pathogens. 2, Thirty-two Turkish Hamsters (Mesocricetus brandti) were placed in short- day cold conditions. After 10 weeks, 20 animals were challenged with an ant igen to simulate a pathogen infection. Ten of these animals were returned t o the cold ('cold-challenged'). The other 10 animals were placed in warm co nditions ('warm-challenged'). Twelve animals received saline injections and were returned to the cold ('cold-control'). Cold-challenged animals spent significantly more time in torpor than did cold-control animals. 3, After 6.5 weeks, all animals were housed in warm conditions and ceased t orpor. Both cold-challenged and warm-challenged animals received a second i njection of antigen. There was no correlation between time spent euthermic and level of secondary humoral response of cold-challenged animals. The sec ondary humoral response of the cold-challenged animals was significantly lo wer than that of warm-challenged animals. 4. Ln this study immune status influenced torpor duration, and torpor cause d immunosuppression. Hibernators may manipulate body temperature in order t o combat pathogens while their own immune systems are suppressed.