The geographical distribution of rodent granivory and cheek pouches across North America

Abstract

Aim: One of the specializations that many granivorous rodents exhibit to increase their efficiency in harvesting seeds is cheek pouches. We propose that the presence or absence of cheek pouches is related to seed size and the productivity of the habitat where those rodents reside. Location: North America – United States and Canada. Taxon: Granivorous rodents. Methods: We divided granivorous rodents into those species with and without cheek pouches. We then compiled a list of plant species (n = 389) that are known or suspected to be dispersed by these rodents by scatter hoarding the seeds in soil and compared the richness distributions of small (≤10 mm) and large seeds (>10 mm) to the distributions of rodents with and without cheek pouches. Results: Most rodents with cheek pouches live in the arid southwestern North America, whereas most rodents that lack cheek pouches live in the mesic southeastern North America. The richness distribution of rodents with cheek pouches was more similar to the richness distribution of small seeds, and the richness distribution of rodents that lack cheek pouches was more similar to the richness distribution of large seeds (nuts). Rodents with cheek pouches (mean = 59.5 g) are smaller than rodents that lack cheek pouches (592.6 g). Main conclusions: Large rodents that lack cheek pouches live mostly in the more productive southeastern North America where there are many trees that produce large nuts. Small rodent with cheek pouches live mostly in the less productive southwestern North America where there are many shrubs, forbs, and grasses that produce small seeds.