|Wiens, J. - THE NATURE CONSERVANCY|
Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 6, 2002
Publication Date: March 1, 2003
Citation: BESTELMEYER, B.T., WIENS, J.A. SCAVENGING ANT FORAGING BEHAVIOR AND VARIATION IN THE SCALE OF NUTRIENT REDISTRIBUTION IN SEMIARID GRASSLANDS. JOURNAL OF ARID ENVIRONMENTS. 2003. V. 53(3). P. 373-386. Interpretive Summary: This paper addresses the role of ants in removing nutrients to their nests in three different grassland settings (shortgrass steppe and two desert grasslands). Ants are important scavengers and remove much of the dead (and living) animal tissue that falls to the ground. Ants in these grasslands typically live in nests and forage away from the nests so their activities tend to concentrate animal material and put it underground. Thi may have important consequences for nutrient cycling. Because the grasslands differ in the kinds of ants found in them and in their ground cover, we asked whether ants concentrate nutrients differently in each grassland and, if so,why. Ants in the Chihuahuan Desert grassland of southern New Mexico concentrated nutrients over an area that is on average seven times greater than such areas in the shortgrass steppe of Colorado. This seems to be due primarily to the greater activity of thermophilic (heat-loving) ants in the Chihuahuan Desert. These ants move faster and farther than their heat-intolerant counterparts.
Technical Abstract: The scavenging of arthropod carrion by ants is an important mechanism of nutrient redistribution in grasslands. But, the foraging activities of scavenging ants have been scarcely documented. We examine variation in overall ant foraging activity among grassland regions differing in species composition and how this creates differences in the distances that scavenged material is redistributed among three semiarid grassland ecosystems. In order to consider the effects of the ant community as a whole on the disposition of nutrient resources, we focused on the fate of baits that appeared under different environmental conditions. Specifically, we asked 1) which ant species are the dominant scavengers in each grassland, 2) what ant characteristics determine the distance that baits are removed to nests, and 3) how do these patterns come together to create differences among grassland ecosystems in the distance that scavenged resources are removed? Species at a site differed widely in the microclimatic conditions that they removed baits and in the average distances they were removed. Generally, species with large-bodied workers and thermophilic species removed baits the farthest. Overall, this resulted in a positive relationship between removal distance and vapor pressure deficit (VPD). Controlling for intersite variation in habitat types and VPD, mean removal distance across all ants increased from the shortgrass steppe to the Chihuahuan Desert grassland. We conclude that differences in the foraging ecology and body size of the dominant scavengers among these grasslands can create a seven-fold variation in the spatial scale of nutrient concentration by ants. These species are little-known when compared to the harvester ants emphasized in ecosystem studies.