It’s a hot summer night in Davis, one of the rare few where the delta breeze fails to bring relief from the scorching daytime highs. Tossing and turning in bed, you decide the effort is futile and you might as well engage in a little nocturnal foraging bout. You drag yourself from bed, bleary-eyed, and stumble towards the kitchen in search of ice cream. Standing in the kitchen, fumbling for the light switch, the hairs on the back of your neck perk up. You’re not alone. You throw the switch, and in the blinding fluorescent flash, a dozen chitinous bodies scurry from sight! You let out a little shriek as the cat looks at you from the couch with an air of condescension at the sight of your cowardice.

Pests are all around us: in our homes, our yards, our fields, our forests. In fact, pests are defined by their connection to us; the very word deems the relationship adversarial. This can actually make defining “pests” a challenge, since “they’re really annoying” isn’t exactly a scientific delineation. The National Pesticide Information Center defines pests as “…unwanted plants, animals, insects, germs or other organisms that interfere with human activity.” This is an extremely broad definition, but insects and mammals include some of the more commonly recognized (and loathed) pests.

As many pests as there are, there are almost as many pest control methods. We use a wide variety of traps, chemical and physical pesticides, and mechanical removal techniques, usually tailored to our specific pest of interest. Some of these are relatively non-invasive to the homeowner, such as mouse traps, while some are considerably more annoying, such as tenting and fumigation.

Believe it or not, the effectiveness of these techniques may be dependent on the personalities of your pest.  Many pests are able to express consistent behavioral differences among individuals.  For instance, both the brown rat and the American cockroach (common pests in domestic households) exhibit personalities in their tendency to seek shelter (Franks B. et al 2013, Planas-Sitjà et al 2015). Some rats are even more reward driven than others (Franks B. et al 2013), meaning they will be much more determined to get into your delicious food stores. These behavioral differences result in some individuals that are bolder and won’t shy away easily, while others will scatter as soon as the lights come on. These personalities may affect the way that the pest interacts with certain pest control methods. Placing mouse traps in the garage may only catch individuals who are bold enough to venture there in search of food, but the individuals that hide in the safety of the attic remain unaffected. This is where methods like fumigation may prove useful, where noxious chemicals can fill every crevice, reaching even the most timid of individuals.

What kind of cockroach are you?

What about ways to control pests that are both non-invasive and also control all of the individuals in a population? A European project, LEURRE, is aiming to produce miniature robotic cockroaches that are able to integrate and potentially even manipulate cockroach populations. This “Insbot” smells and even behaves like a cockroach, causing natural cockroaches to accept it as their own. It can then influence collective decision-making of the population by causing other members to herd nearby (Sempo G. et al 2006). A big part of controlling pest populations is figuring out where they are located or directing their movement. For example, by moving cockroaches to a specific area, pesticide applications could be smaller and more precise, reducing the harmful side effects of pesticides and increasing their effectiveness.

Author Michael Culshaw-Maurer is a 3rd year PhD candidate in the Graduate Group in Ecology.

Author Daniel Martinez is a UC Davis graduate with a degree in Animal Biology.

References Cited

Franks, B., E. T. Higgins, and F. a Champagne. 2013. Evidence for individual differences in regulatory focus in rats, Rattus norvegicus. Journal of Comparative Psychology 126:347–354.

Planas-Sitja I, Deneubourg J-L, Gibon C, S. G. 2015. Group personality during collective decision-making : a multi-level approach. Proceedings of the Royal Society B 282:20142515.

Sempo, G., S. Depickere, J.-M. Ame, C. Detrain, J. Halloy, and J.-L. Deneubourg. 2006. Integration of an autonomous artificial agent in an insect society: Experimental validation. From Animals To Animats 9, Proceedings 4095:703–712.

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