Richardson’s ground squirrel, Urocitellus richardsonii, adaptive sex allocation

Abstract

Trivers and Willard proposed that female mammals should adjust their investment in male versus female offspring relative to the effect of their underlying body condition on their ability to produce high quality offspring. I conducted studies testing whether litter size-sex ratio tradeoffs predicted by adaptive sex allocation (ASA) theory occur among Richardson’s ground squirrel (Urocitellus richardsonii) dams, and whether circulating plasma glucose levels of those dams influence offspring sex ratio as predicted by Cameron’s glucose metabolism hypothesis. The results of these studies validate the use of the Roche Diagnostics Accu-chek® Aviva glucometer in measuring Richardson’s ground squirrel plasma glucose concentration, inform future studies attempting to test the glucose metabolism hypothesis, and provide evidence from long-term data of litter size-sex ratio tradeoffs supporting earlier reports of ASA among Richardson’s ground squirrels from the same study population that have been called into question owing to small sample sizes derived over single breeding seasons.