Better the devil you know: avian predators find variation in prey toxicity aversive.
Toxic prey that signal their defences to predators using conspicuous warning signals are called 'aposematic'. Predators learn about the toxic content of aposematic prey and reduce their attacks on them. However, through regulating their toxin intake, predators will include aposematic prey in their diets when the benefits of gaining the nutrients they contain outweigh the costs of ingesting the prey's toxins. Predators face a problem when managing their toxin intake: prey sharing the same warning signal often vary in their toxicities. Given that predators should avoid uncertainty when managing their toxin intake, we tested whether European starlings (Sturnus vulgaris) preferred to eat fixed-defence prey (where all prey contained a 2% quinine solution) to mixed-defence prey (where half the prey contained a 4% quinine solution and the other half contained only water). Our results support the idea that predators should be more 'risk-averse' when foraging on variably defended prey and suggest that variation in toxicity levels could be a form of defence.
Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK optimalforager@hotmail.com.
Craig A
CA
Barnett
Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
Melissa
http://orcid.org/0000-0002-0861-0191
M
Bateson
Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
Candy
http://orcid.org/0000-0001-5379-843X
C
Rowe
D000818:Animals; D001362:Avoidance Learning; D004032:Diet; D004305:Dose-Response Relationship, Drug; D020387:Food Chain; D007814:Larva / Q000502:physiology; D008297:Male; D011235:Predatory Behavior; D011803:Quinine / Q000737:chemistry; D012306:Risk; D046749:Starlings / Q000502:physiology*; D013712:Tenebrio / Q000254:growth & development / Q000502:physiology*
D011803:Quinine
European starling; Sturnus vulgaris; aposematism; chemical defence; mimicry; variability