Effects of low temperature and photoperiod on reproduction in the female wild guinea pig (Cavia aperea)

Small mammals in the tropics and subtropics usually rely opportunistically on favorable environmental conditions for breeding rather than base their b reeding decision on prediction from photoperiodic cues as most high-latitud e species do. Species producing precocial young may be more likely to repro duce aseasonally than species with altricial young. For female wild guinea pigs (Cavia aperea) from Argentina (35 degrees S) that produce extremely pr ecocial young, these hypotheses would predict moderate responsiveness of fe male reproduction to photoperiod. These predictions were tested in a series of laboratory experiments. Guinea pigs reproduced aseasonally when kept un der natural photoperiod and temperatures at Bielefeld (52 degrees 01'N, 8 d egrees 32'E). When given short days (9L:15D) and long days (14L:10D) under indoor temperature conditions (20-23 degrees C), no effect of photoperiod o n female reproduction was noted. A shift from long day length (14L:10D) to short day length (9L:15D) did not stop reproduction. Increasing energy expe nditure for thermoregulation at low temperature (5 degrees C) under long-da y (14L:10D) conditions also did not inhibit reproduction. Wild guinea pigs thus reproduce throughout the year without respect to photoperiod as long a s food and temperature conditions allow reproduction.