Invasive Fire Ants in Restored and Unrestored Central Valley grasslands

I mentioned earlier that I have started monitoring invasive Argentinian fire ant infestation of Sherman live traps during my rodent trapping periods. Initial data collection began in July 2014 for a subset of trapping days at two of the four locations where I am monitoring wildlife. The number of live traps infested with fire ants was used as an estimate of fire ant abundance within each site. All traps were inspected at dusk when baited for rodents, and recorded if infested. Results for the six-day survey in July revealed restored sites had a significantly lower number of infested traps (p = 0.006). Whether or not small rodents are more likely to enter invaded or uninvaded traps may also, by extension, be correlated with small rodent abundance. The likelihood of capturing a mouse in a trap infested with fire ants was significantly lower for infested traps than for non-infested traps (p < 0.0001).

Fire Ants

Fire ants have economically and ecologically detrimental impacts on native floral and faunal species, yet only recently has research been conducted on large enough spatial and temporal scales to inform management (Allen et al. 2004). While small mammal traps and trapped rodents are a convenient way to monitor levels of invasion, other taxa may also be impacted by fire ants, including reptiles and amphibians, birds, lagomorphs, and other small mammals. Fire ants eat both seeds and may kill small rodents, thereby indirectly and directly impacting rodent populations.

2014-10-23 07.19.40

Additionally, data from trapping the following morning can be used to determine if small rodents avoid infested traps (Allen et al. 1994, Holtcamp et al. 1997). Additional information characterizing interactions between small rodent species, rates of invasion, and vegetation structure will contribute to better management of affected wildlife species (Allen et al. 1994). Additionally, if small rodents avoid infested traps, this could bias trapping rates and lead to faulty conclusions (Masser and Grant 1986).

I continued to collect fire ant data across all locations and days (Days 2-7 of Trapping) in October 2014, and will post these data once they have been fully entered and analyzed.

If you have any questions, feel free to contact me at kmwolf[AT] (please replace [AT] with the @ symbol). Thanks!

References Cited

Allen, C. R., D. M. Epperson, and A. S. Garmestani 2004. Red imported fire ant impacts on wildlife: A decade of research. American Midland Naturalist 152:88-103.

Allen, C. R., S. Demarais, and R. S. Lutz 1994. Red imported fire ants impact on wildlife: An overview. The Texas Journal of Science 46:51-59.

Masser, M. P., and W. E. Grant 1986. Fire ant-induced mortality of small mammals in east-central Texas. Southwestern Association of Naturalists 31:540-542.

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