On the incidence of the breeding season in mammals after transference to a new latitude

Abstract

Ferrets, like other mammals with fixed breeding seasons in temperate latitudes, when transported to the southern hemisphere reverse their breeding seasons so as to conform to the new conditions. The change-over is very rapid, and consequently individual animals may experience two breeding seasons in one year. Ferrets taken to tropical latitudes where the seasonal conditions, at least as regards daylight duration, are comparatively uniform, experience sexual activity either at their former seasons or else come on heat irregularly. Ruminants and some other mammals inhabiting tropical areas, when taken to temperate areas, do not react to the seasonal influence of daylight duration (in the manner of species inhabiting these countries), probably because they do not possess a developed mechanism of response to seasonal influences in their own countries where conditions in regard to light duration are comparatively uniform. This is shown more particularly for various species of deer.