Tests of Antipredator and Alarm Cue Functions for Musk Gland Secretions of Northern Cottonmouths (Ag
Greene, Brian D.
Department of Biology
Missouri State University
Springfield, Missouri, USA
Paired cloacal musk glands are ubiquitous in snakes and produce aromatic substances that are secreted during defensive encounters with predators. Musk gland secretions have been mainly considered to be antipredator adaptations but have also been suggested to function as alarm cues in rattlesnakes. We conducted experiments to evaluate the effects of musk secretions of Northern Cottonmouths (Agkistrodon piscivorus) as both predator deterrents and as alarm cues. To evaluate the alarm cue hypothesis, we tested responses of captive juvenile cottonmouths in two behavioral contexts related to predation risk: foraging conflict and predatory encounters. In foraging trials, cottonmouths increased their rate of movement and tongue flick rates approximately two-fold in musk cue treatments compared to trials involving controls. Similarly, cottonmouths exposed to musk secretions exhibited a two-fold increase in defensive responses in standardized simulated predatory encounters relative to controls. We evaluated potential antipredator function of musk in palatability tests where domestic dogs were allowed to sample musk and non-musk treated food items. Test subjects spent significantly longer investigating musk-treated food than controls but did not exhibit differences in any other response variable. All dogs that consumed food ate all samples and did not consume in any pattern related to treatment. Our results provide additional support for pit viper musk acting as an alarm cue, which is particularly interesting given recent developments concerning cryptic sociality of pit vipers. However, cottonmouth musk did not seem to deter consumption by a mammalian predator, in contrast to palatability tests in some colubrid snakes.