Current invasive species research being conducted at MSU
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Project 18

Project Title: Direct and indirect effects of a novel predator, the invasive fire ant (Solenopsis invicta), on the life history evolution of vertebrates, including the black-capped vireo (Vireo atricapilla).
Investigators: Jennifer E. Smith, Christopher W. Whelan, Steven J. Taylor, Michael L. Denight, Mike M. Stake
Contact: Jennifer Smith (smith780@msu.edu)

Whether a species responds appropriately when faced with a novel environmental insult or stress is fundamentally important to evolutionary ecology and conservation biology. We study the response of a federally endangered passerine, called the black-capped vireo (Vireo atricapilla), to the introduction of the novel predator species, the fire ant (Solenopsis invicta). The fire ant is an invasive species, native to South America. It preys upon a variety of taxa and is expanding its range globally. Its current distribution within the U.S. appears to be restricted by extreme heat, aridity, and cold temperatures. Fire ants inject venom to immobilize and kill their prey. Although unable to depredate adult vireos, fire ants are effective predators of vireo nestlings.

We are currently investigating the behavioral response and energetic consequences of adult black-capped vireos to nest predation by fire ants. Our study is at Fort Hood, Texas on an 88,500-hectare US military installation. Previous work suggests that this newly introduced predator imposes the obvious cost of nest loss upon its vertebrate prey (Stake and Cimprich 2003). Our most recent findings suggest that fire ants also impose indirect effects (positive and negative) on nest predators (Smith et al. 2004) and influence the life-history trade-offs in adult vireos (Smith et al. 2007).

We are finding that fire ants usually attack vireo nests near midnight as parents sleep. All attacked nests – whether with eggs or nestlings – failed despite energetically expensive defense of the nest by adult vireos. Nest defense was prolonged, with a mean duration of 7.7 +/- 1.5 hours (25 times longer than that against native snake predators). Compared with brooding or incubation, nest defense is energetically expensive, depleting an estimated 59% of fat stores. Fire ants are effective nest predators on this low-nesting bird species.

The behavioral response of vireos to this novel predator is wholly inappropriate, with no benefits and considerable costs. Besides the energetic costs, defense results in numerous bites and venomous stings. Vireos ought to abandon their nests when first attacked by fire ants but fail to do so. We hypothesize (Smith et al. 2007) that other newly introduced species likely evoke inappropriate behavioral and physiological responses from their prey. We suspect that novel perturbations of this sort are particularly potent because new prey species lack co-evolved strategies typically perpetuated by the well-documented ‘races’ between native predators and their prey.

Recent Publications:
Smith, J.E., C.W. Whelan, S.J. Taylor, M.L. Denight, & M.M. Stake. 2007. Novel predator-prey
interactions: is resistance futile? Evolutionary Ecology Research 9:433-446.         
Smith, J.E., S.J. Taylor, C.W. Whelan, M.L. Denight, & M.M. Stake. 2004. Behavioral interactions
between fire ants and vertebrate nest predators at two black-capped vireo nests. Wilson Bulletin
116:163-166.
Stake, M.M. and Cimprich, D.A. 2003. Using video to monitor predation at Black-capped Vireo
nests. Condor, 105: 348–357.

For more information:
Jennifer E. Smith, Ph.D. Candidate, Michigan State University: http://www.msu.edu/user/smith780/
Steven J. Taylor, Ph.D., Illinois Natural History Survey: http://www.inhs.uiuc.edu/~sjtaylor/home.html
Texas Imported Fire Ant Research and Management Project: http://fireant.tamu.edu/research/
The Nature Conservancy in Texas: http://www.nature.org/wherewework/northamerica/states/texas/
Frequently Asked Questions about Fire Ants: http://uts.cc.utexas.edu/~gilbert/research/fireants/faq.html