|Kerley, Graham - UNIV OF PORT ELIZABETH|
|Kay, Fenton - NEW MEXICO STATE UNIV|
Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 26, 1997
Publication Date: N/A
Interpretive Summary: We investigated the role of grass consumption by kangaroo rats in affecting changes in desert grasslands. Ord's kangaroo rats cut and consumed a large proportion of the tillers of three Chihuahuan Desert tussock forming grass species. Observations on sites where all rodents, medium-sized kangaroo rats or only large kangaroo rats were excluded indicated that the medium sized kangaroo rat species were responsible for cutting grasses. Up to 7% of grasses at a site may be cut by these rodents. Only the grass bush muhly was not affected by the kangaroo rats. Thus kangaroo rats may play an important role in desert grassland ecosystems.
Technical Abstract: Graminivory by kangaroo rats (Dipodomys spp.) was investigated as a potential mechanism for the keystone role of these rodents in the dynamics of desert grasslands. Experiments confirmed that Ord's kangaroo rats (Dipodomys ordii) cut and consumed a large proportion of the tillers of three Chihuahuan Desert tussock-forming grass species. Field observations indicated that the characteristically cut grass tillers were absent from all-rodent and medium-sized kangaroo rat exclosures, but were frequent in large-sized kangaroo rat and rabbit exclosures, indicating that the medium-sized kangaroo rat (D. Ordii, D. merriami) were responsible for grass cutting. Tiller waste as a percentage of peak standing crop ranged from 7% in grassland habitats to 0.7% in Flourensia cernua shrubland. Of the 13 species of perennial, tussock-forming grasses measured, only one, Muhlenbergia porteri, had no tillers cut by kangaroo rats. This study demonstrates that the keystone role of kangaroo rats in Chihuahuan Desert grassland ecosystems is probably the result of their graminivory.