After working as an engineer in New York for four years, he moved to the University of Wisconsin–Madison to study wildlife ecology under Stanley Temple, and received a Master of Science degree in 1995.

He then worked for the Okanagen-Wenatchee National Forest for three years, before beginning a PhD at Northern Arizona University.

This model allowed gene flow to occur across multiple paths in the landscape in proportion to their "resistance", calculated in an electrical circuit using Kirchhoff's laws.

This model was different from the paradigm at the time, which assumed that gene flow would occur along the single "least cost" path.

McRae's model, published chiefly in three papers between 2006 and 2008, became influential within wildlife population genetics and conservation biology.