Prairie dog effects on harvester ant species diversity and density
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CitationKretzer, J. E., & Cully, J. F. (2001). Prairie dog effects on harvester ant species diversity and density. Journal of Range Management, 54(1), 11-14.
PublisherSociety for Range Management
JournalJournal of Range Management
AbstractThe purpose of this study was to determine if black-tailed prairie dogs (Cynomys ludovicianus Ord) influence harvester ant nest density and species composition within the shortgrass prairie biome of southwestern Kansas. Two treatments were established: areas colonized by prairie dogs and areas not colonized by prairie dogs. We recorded 183 harvester ant nests of 3 species. Harvester ant nest density did not differ significantly between prairie dog colonies (3.08 nests ha-1) and non-colonized shortgrass prairie sites (4.54 nests ha-1), but species composition did. Pogonomyrmex rugosus Emery was the most frequent species on prairie dog colonies where it accounted for 87% of ant nests present, as opposed to 33% on sites where prairie dogs were absent. Pogonomyrmex barbatus Smith was the most abundant species on non-colonized areas, making up 49% of the ant nests sampled. Pogonomyrmex occidentalis Cresson comprised 11% of ant nests sampled, and was nearly absent from prairie dog colonies (20 nests on non-colonized sites vs. 1 nest on prairie dog colonies). The average number of harvester ant species found per site was consistently greater on sites where prairie dogs were absent.
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Soil moisture patterns below mounds of harvester antsLaundré, J. W. (Society for Range Management, 1990-01-01)Harvester ants are a major component of western rangeland. Little is known about ants' role in soil water dynamics. Annual patterns of soil moisture under mounds of the harvester ant (Pogonomyrmex owyheei, Cole) were studied in southeastern Idaho. Soil moisture at 20-cm intervals to a depth of 100 cm was estimated monthly with a neutron probe. Between 60 and 100 cm, higher levels of moisture were found below mounds than in control areas. The amount of water added to the soil during spring recharge was greater in control areas at 20 cm but greater under ant mounds at depths below 60 cm. Under ant mounds, approximately 1.3 cm more water was added to the soil between 60 and 100 cm.
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STRATEGIES OF PREDATORS AND THEIR PREY: OPTIMAL FORAGING AND HOME RANGE BEHAVIOR OF HORNED LIZARDS (PHRYNOSOMA SPP.) AND RESPONSE BY HARVESTER ANTS (POGONOMYRMEX DESERTORUM).Smith, Bob; MUNGER, JAMES CAMERON.; Heed, Bill; Michod, Rich; Chew, Bob; Rosenzweig, Mike (The University of Arizona., 1982)Tests of optimal foraging theory have shown that many predators are selective about which prey and which patches should be utilized. I hypothesize that prey species "exploit" this choosiness by evolving characteristics that cause predators to choose alternate prey. Specifically, prey should evolve traits that increase the probability of predator death, decrease the per prey or per patch nutritional intake, increase processing time, and advertise (or mimic advertisements of) undesirable traits. Predator choosiness allows prey to divert the predator instead of defeating it. The evolution of a long-term, prudent foraging strategy requires that three conditions be met: (1) The forager must use resources from a discrete subpopulation; (2) use of that subpopulation must be relatively exclusive; (3) the resource population must respond in such a way that a long-term strategy provides an economic advantage. For the horned lizard-ant system, conditions (1) and (2) were tested by tagging lizards with transmitters or radioactive tags. Horned lizards occupy home ranges much smaller than would be expected if they moved at random and home range overlap was less than expected by random placement of home ranges, thus conditions (1) and (2) were not rejected. Most techniques of home range study do not distinguish random from nonrandom movement. Condition (3) was tested by subjecting ant colonies to various levels of artificial predation. In none of five experiments was the result obtained that an increased harvest intensity led to a decrease in long-term yield; condition (3) is tentatively rejected. Ant colonies shut down in response to predation; this puts a ceiling on their losses. Short-term foraging models were tested for horned lizards foraging at ant colonies. A prediction of the marginal value theorem was not rejected: Horned lizards tended to leave colonies when their instantaneous rate of harvest at that colony had fallen to their average rate of harvest for the day. Another short-term prediction, however, was rejected: Lizards did not stay longer at the "better" of two colonies. A more liberal version of the same prediction was not rejected. Apparently, horned lizards forage adaptively but not optimally.