Witten Effect

Abstract

Whitten was breeding laboratory mice for his research at the Australian National University when he noted that females housed in a dense group showed prolonged periods of anestrus, some as long as 40 days (Whitten 1959). Isolated females cycled with a 4 or 5 day periodicity. He then found that by placing a male confined to a wire basket into the group, the formally anestrous females exhibited estrus 3 or 4 days later. Normally about 20 % of females with a regular cycle of 5 days would be expected to conceive each night. However when the females where individually paired with a male, over 50% conceived on the third night after pairing thus revealing a synchronous estrus among the females. Whitten's discovery and the almost simultaneous report that pregnancy in mice can be blocked by olfactory stimuli from strange males stimulated a number of studies on the role of olfaction in reproduction. The mechanisms involved in mediating the Whitten effect, it ecological implications, and its generalizability to other species have been explored by Whitten and others, and will be briefly reviewed here.