Predator learning differences affect the survival of chemically defended prey

Abstract

Prey animals that possess chemical defences often advertise their unprofitability to predators by a distinctive and conspicuous visual appearance known as aposematism. However, not all chemically defended species are conspicuous, and some are nearly cryptic. Differences in predator community composition and predator behaviour may explain varied levels of prey conspicuousness. We tested this hypothesis by measuring dietary wariness and learning behaviour of day-old chickens, Gallus gallus domesticus, from four strains of laying hens that have been selected for different levels of egg productivity. We used these strains as model predators to test whether predators that vary in the trade-offs associated with foraging behaviour cause differential survival of chemically defended prey with conspicuous signals. We found that strains differed in how they learned about chemically defended prey, which resulted in significant differences in prey survival. The selection pressures imposed by different types of predator could explain whether chemically defended prey evolve varied levels of conspicuousness. Predators' initial wariness of novel prey was not related to learning at the strain or individual level, but predator wariness increased after exposure to chemical defences. Our study provides support for the hypothesis that the evolution of prey defences depends on variation between ecological communities in predator learning behaviour and experience. (C) 2016 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour

The impact of life stage and pigment source on the evolution of novel warning signal traits

“…We next used our JND estimates to ask whether the conspicuousness of yellow and white larvae differed. For example, if white larvae are more conspicuous than yellow larvae, this could have facilitated the spread of white alleles due to increased signal efficacy (64,65). However, we found no evidence to suggest that white and yellow larvae differ in conspicuousness, nor did we find any evidence that shifts in host plant would affect the conspicuousness of white and yellow larvae differently.…”

Environmental complexity buffers against stress-induced negative judgement bias in female chickens

“…After initial pre-training where chicks were familiarised with the test arenas (plastic boxes covered with corrugated cardboard paper, measuring 46 W × 68 L × 42 H cm), rewards (mealworms) and handling 45 , 82 , chicks were singly trained to associate a colour cue (black or white, n white = 46, n black = 49) with a reward (1/3 of a mealworm). The colour cues were printed on photo paper and laminated.…”

Social information use about novel aposematic prey is not influenced by a predator's previous experience with toxins

“…This reduces the predation cost for aposematic prey populations and helps to explain how aposematism can evolve (Thorogood et al, 2018). However, variation in predators' physiological state (Barnett, Bateson, & Rowe, 2007;Barnett, Skelhorn, Bateson, & Rowe, 2012;Skelhorn & Rowe, 2007), dietary wariness (Exnerová et al, 2007;Marples & Mappes, 2011) or the ability to learn about prey defences (Rowland, Fulford, & Ruxton, 2017) means that predators might vary in both information use and their tendency to attack aposematic prey. Individuals are predicted to value social information more when the cost to acquire personal information is high (Kendal, Coolen, van Bergen, & Laland, 2005;Laland, 2004), and for predators, the cost of sampling novel prey could be increased when they have already ingested toxic prey.…”