PUB - Publikationen an der Universität Bielefeld

Small mammals in the tropics and subtropics usually rely opportunistically on favorable environmental conditions for breeding rather than base their breeding decision on prediction from photoperiodic cues as most high-latitude species do. Species producing precocial young may be more likely to reproduce aseasonally than species with altricial young. For female wild guinea pigs (Cavia aperea) from Argentina (35 degrees S) that produce extremely precocial young, these hypotheses would predict moderate responsiveness of female reproduction to photoperiod. These predictions were tested in a series of laboratory experiments. Guinea pigs reproduced aseasonally when kept under natural photoperiod and temperatures at Bielefeld (52 degrees 01'N, 8 degrees 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 on female reproduction was noted. A shift from long day length (14L:10D) to short day length (9L:15D) did not stop reproduction. Increasing energy expenditure for thermoregulation at low temperature (5 degrees C) under long-day (14L:10D) conditions also did not inhibit reproduction. Wild guinea pigs thus reproduce throughout the year without respect to photoperiod as long as food and temperature conditions allow reproduction.