Can pseudo entrainment explain the synchrony of estrous cycles among golden hamsters (Mesocricetus auratus)?

Synchrony among golden hamsters is often cited in the menstrual-cycle synch rony literature and has recently become a paradigm for explaining menstrual synchrony in humans (L. Weller, A. Weller, and S. Roizman (1999), J. Comp. Psychol. 113, 261-268). It has also stimulated further research on synchro ny in Djungarian hamsters, for which no evidence of synchrony was found (G. E. Erb, H. E. Edwards, K. L. Jenkins, L. C. Mucklow, and K. E. Wynne-Edwar ds (1993), Physiol. Behav. 54, 955-959). The case for synchrony in the gold en hamster is reexamined in this paper. It is demonstrated, with the help o f computer simulation experiments, that the experimental method used by G. Handelmann, R. Ravizza, and W. J. Ray (1980, Horm. Behav. 14, 107-115) for detecting synchrony has a critical flaw. It does not distinguish synchrony that can occur by chance (pseudo entrainment) from synchrony due to a proce ss of entrainment. It is suggested that the apparent entrainment of estrous cycles in hamsters and the role of social dominance may be due to the stre ss caused by moving animals to different rooms or grouping them. Thus, beca use we cannot reject the possibility of pseudo entrainment as an explanatio n for these results, it must be concluded that there is no evidence that go lden hamsters synchronize their estrous cycles. Finally, an approach is bri efly outlined for testing synchrony in golden hamsters. (C) 2000 Academic P ress.