Rabbits and Bergmann's rule: How cold was Portugal during the last glaciation?

Abstract

Osteometric data from > 450 modern wild rabbits, mostly from Portugal, Spain and France, show an inverse correlation between their size and the temperature of the environment, in accordance with Bergmann's rule. Similar measurements made on some 1660 rabbit bones from 14 Portuguese late Pleistocene and Holocene archaeological sites indicate that rabbits became considerably smaller at the Pleistocene-Holocene boundary. Thus, rabbit size varies or varied with temperature both today and in the past. A direct temperature-size relationship was assumed, and the regression of modern rabbit bone size on temperature was then used to calibrate the temperature equivalent for the change of size of rabbit bones in the past. The result indicates a Last Glacial Maximum to present-day difference, Δt°, of 7 or 8 °C. An alternative interpretation that does not assume a direct temperature-size relationship would indicate that the environment in Portugal 15 000-30 000 years ago was similar to that in northern France today.