Burrowing rodents increase landscape heterogeneity in a desert grassland

Animals that modify their environment through engineering and herbivory have important impacts on ecosystems, yet the interactive roles of such species have rarely been studied. We studied the comparative and interactive effects of two burrowing herbivorous rodents, Gunnison's prairie dogs (Cynomys gunnisoni) and banner-tailed kangaroo rats (Dipodomys spectabilis), on vegetation where they co-occurred in a Chihuahuan Desert grassland. We found that their effects remained distinct and, thus, non-substitutable, where they co-occurred. The rodents differentially altered plant community structure relative to their different mound types, herbivory, and spatial scales of disturbance. Vegetation structure and plant species assemblages differed between mound and landscape patches occupied by prairie dogs and kangaroo rats. Where both species co-occurred, there was more soil disturbance, organic material from-their fecal pellets, forb cover, and activity by other animals. The combined effect of these rodents increased the landscape heterogeneity and plant species richness by creating a mosaic of different habitat patches on the landscape. Our results demonstrate that these rodents had complementary, additive effects where they co-occurred, and suggest that multiple habitat-modifying species, especially those that play large ecological roles, can have important interactive effects on community structure and biodiversity. (c) 2007 Elsevier Ltd. All rights reserved.