Degradation of chemical alarm cues under natural conditions: risk assessment by larval woodfrogs |
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Authors: | Maud C O Ferrari François Messier Douglas P Chivers |
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Institution: | (1) Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada |
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Abstract: | Summary. Many aquatic species use chemosensory information to assess predation risk. The cues used in such risk assessment can come
either from the predator (predator odour) or from injured prey (alarm cues). The information conveyed through chemicals may,
however, be inaccurate both spatially and temporally, as chemicals may persist in the environment long after the predator
is gone. Thus, the level of accuracy of the cues for risk assessment may depend on the persistency of the chemicals in the
habitat. Here, we investigated the persistency of alarm cues of a larval amphibian, the woodfrog (Rana sylvatica) in a ephemeral pond, their natural habitat. We introduced either alarm cues or control water in enclosed sleeves (~10 L)
installed in the pond. The sleeve water was then sampled after 5 min and every two hours for eight hours. We used the behavioural
response of woodfrog tadpoles to alarm cues as a bioassay to assess how long the alarm cues persisted in the environment.
We found that tadpoles responded with an antipredator response to the pond water containing alarm cues 5 min after the injection
of the cues in the sleeves but did not respond to that same pond water after two hours. Our results indicate that biodegradation
and/or photodegradation of alarm cues in natural habitats might occur relatively quickly as the loss of a response to the
cues in our experiment was independent of a dilution effect. This contrasts with previous laboratory results indicating that
chemicals may be active after several hours. |
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Keywords: | Alarm cues degradation persistency field experiment risk assessment larval woodfrog Rana sylvatica |
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