My name is Claudia Ibeth Torres and I am an undergraduate student at ASU West.  Under the guidance of Dr. J, I am conducting a study of the anti-predator behavior of the beloved black widow spider (Latrodectus hesperus).  Specifically, I am interested in understanding their death feigning behavior (thanatosis).  Black widow spiders are infamous for their red hour glass, big cob webs and nasty bites, but very little is known about thanatosis in black widows despite our observation that it is a frequent behavior that can last as long as 6-8 hours in some individuals.  In particular, I am interested in understanding variation in this anti-predator reaction amongst individuals, and I hope ultimately to compare population variation between urban and desert populations. 

We have recently completed data gathering in a study designed to test the role of harassment and feeding history on death feigning behavior.  To control for family effects, two sisters (full siblings) from each of 15 families were studied.  One sister from each family was placed in a harassed treatment, and the other sister in a no harassment treatment.  The harassment manipulation occurred 3 times weekly and consisted of tapping the spider at a steady rate on the dorsal side of their abdomen until either death feigning behavior occurred or the trial was truncated at 3 minutes.  Sisters in the no harassment treatment experienced no such manipulation.  Two days following harassment manipulations, spiders in each treatment were scored in anti-predator trials.  Here we measured the duration of harassment required to elicit death feigning and the duration of death feigning before the spider returned to its foraging posture.  We also noted other responses to harassment (e.g. refuge use, attack and wrapping of the stick used for harassment).  All spiders were fed weekly, and in these foraging trials we measured location before a feeding trial, time to first attack of prey, and the time it took to wrap and kill the prey.    

While we are just now beginning to compile and analyze our data, our expectation is that spiders in the harassment treatment will, over time, begin to habituate to harassment and show greater reluctance to feign death.  In addition, we entered the study with the expectation that if death feigning has energetic costs, perhaps only spiders in good feeding condition could afford to employ this anti-predator behavior.  Alternatively, we may find that harassment and food limitation do not predictably deter death feigning, but instead that individuals exhibit consistent variation across harassment and foraging trials.  This idea, that animals commonly display suites of correlated behaviors, or behavioral syndromes (a.k.a. animal personalities), is currently a hot topic in behavioral ecology and our repeated measures design will allow us to evaluate this hypothesis in black widows.  In particular, if sisters in different harassment treatments behave similarly this will be suggestive of a family effect and will warrant more intensive study to quantify family differences in this behavior with a larger sample size.  Finally, I would like to thank the Salt River Project, and ASU Tempe’s SOLUR and MARC fellowship programs for their support throughout my work.