Ambient Temperature and Reproductive Success in Rodents Living at Different Latitudes 1

Abstract

The susceptibility of rodent reproduction to latitudinal acclimatization was investigated, specifically, the relationship between ambient temperature and reproductive success in house mice and deer mice whose ancestors had been trapped in northern vs. (southern climates (Alberta [Canada] vs. Texas [USA]). Third generation adults of each of these 4 populations were paired and challenged to breed at -6.degree., 3.degree., 23.degree. or 34.degree. C. A 50-day period of gradual temperature adaptation preceded pairing. House mice, regardless of their geographic origin, were relatively insensitive to extreme temperatures. Many pairs of both the Alberta and Texas stocks of this species still produced offspring when maintained at the experimental extremes of -6.degree. and 34.degree. C. In marked contrast, both northern and southern deer mice exhibited relatively narrow temperature ranges within which maximum breeding occurred: -6.degree. to 3.degree. for Texas deer mice and only at 23.degree. C for Alberta deer mice. Thus, there is no evidence in either species that reproduction is either less sensitive to cold in northern latitudes or less sensitive to heat in southern latitudes; indeed, somewhat the reverse situation exists in deer mice. Evolutionarily, latitudinal considerations seem to have been of secondary rather than of primary importance in shaping the relationship between ambient temperature and reproduction in these 2 spp.