Behavioral ecology - Original research

Oecologia

, Volume 169, Issue 4, pp 965-973

Ontogenetic shifts in a prey’s chemical defences influence feeding responses of a snake predator

  • John LlewelynAffiliated withSchool of Biological Sciences, University of SydneySchool of Marine and Tropical Biology, James Cook University Email author 
  • , Kris BellAffiliated withSchool of Marine and Tropical Biology, James Cook University
  • , Lin SchwarzkopfAffiliated withSchool of Marine and Tropical Biology, James Cook University
  • , Ross A. AlfordAffiliated withSchool of Marine and Tropical Biology, James Cook University
  • , Richard ShineAffiliated withSchool of Biological Sciences, University of Sydney

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Abstract

Foraging theory suggests that predator responses to potential prey should be influenced by prey chemical defences, but the effects of ontogenetic variation in such defences on prey vulnerability to predators remain unclear. Cane toads (Rhinella marina) are toxic to anurophagous snakes, including the keelback (Tropidonophis mairii, a natricine colubrid that occurs within the toads’ invasive range in Australia). Toxin levels and diversity change through toad ontogeny, decreasing from the egg stage to metamorphosis, then increasing in postmetamorphic toads. If the toxin content of a prey item influences predator responses, we predict that keelbacks should exhibit selective predation on toads close to metamorphosis. The results of our laboratory trials on adult (field-collected, and thus toad-experienced) and hatchling (laboratory-incubated, and thus toad-naive) keelbacks supported this prediction. The snakes selectively consumed later-stage rather than earlier-stage tadpoles, and earlier-stage rather than later-stage metamorphs. Our data are thus consistent with the hypothesis that ontogenetic changes in toxin content can affect individuals’ vulnerability to predation.

Keywords

Chemical defence Ontogeny Optimal foraging Bufo marinus