PARENT SESSION
Oral Session # 32: Herbivory II: Grasslands.
Presiding: K Suttle
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 200.

Effects of prairie dogs and banner-tailed kangaroo rats on desert grassland vegetation in the northern Chihuahuan Desert.

Davidson, Ana ^{*,1, 2}, Lightfoot, David^{1, 2}, ¹ Department of Biology, Albuquerque, NM, USA² Sevilleta Long-Term Ecological Research Program, Albuquerque, NM, USA

ABSTRACT- Prairie dogs (Cynomys spp.) and banner-tailed kangaroo rats (Dipodomys spectabilis) are keystone species in semi-arid grasslands. Their burrowing and foraging activities are known to effect community composition and structure. In the American Southwest where these species co-occur, the relative effects of their activities on grassland ecosystems are unknown. Although prairie dogs and kangaroo rats appear to have similar functional roles, these species are ecologically different and have unique effects on grassland communities. This research evaluated their comparative and interactive influences on vegetation at the Sevilleta National Wildlife Refuge (SNWR), New Mexico and near Janos, Chihuahua, Mexico. At the SNWR, Gunnison's prairie dogs (Cynomys gunnisoni) created diffuse disturbance patches on the landscape, and kangaroo rats created more intense localized disturbance patches. The overall degree of disturbance was enhanced where the species co-occurred. At the Janos research site, the effects of black-tailed prairie dogs (Cynomys ludovicianus) and kangaroo rats on vegetation were less apparent; their impacts appeared to be overridden by intensive cattle grazing. Interestingly, the exclusion of prairie dogs and kangaroo rats from plots at the SNWR resulted in a significant increase in the exotic forb species, Russian thistle (Salsola kali); this general pattern was qualitatively observed at the Janos site.

Key words: banner-tailed kangaroo rats, desert grasslands, prairire dogs, keystone species