Animals in nature use many strategies to evade or deter their predators. Within venomous snake mimicry, stereotyped anti-predator behaviours are hypothesized to be effective warning signals under strong selection for independent convergence across species. However, no studies have systematically quantified snake anti-predator displays across taxonomically broad clades to examine how these behaviours evolve within a comparative methods framework. Here we describe a new high-throughput approach for collecting and quantifying anti-predator displays in snakes that demonstrates both low observer bias and infinite extension. Then, we show this method’s utility by comparing 20 species spanning six taxonomic families from Peru. We found that a simple experimental set-up varying simulated predator cues was successful in eliciting displays across species and that high-speed videography captured a great diversity of anti-predator responses. Although display components show complicated patterns of covariance, we found support for behavioural convergence in anti-predator displays among elapid coral snakes and their distantly related mimics. Our approach provides new analytical opportunities for both behaviour and kinematics, especially macroevolutionary analyses across clades with similar difficulty in observing or comparing trait diversity.

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An animal's internal state can shift its behavior. Animals that would typically avoid dangerous foraging conditions may choose to forego safety when food is restricted. Furthermore, physiological demands such as gravidness can drive sex differences in foraging behavior among individuals of the same species. In bats, moonlight can impose risk: some bat species decrease or completely avoid foraging on full moon nights when visually oriented predators are most active. In this study, we tested the hypothesis that hunger increases risky foraging behavior. Previous work with the Jamaican fruit bat, Artibeus jamaicensis, demonstrated that this species shifts its foraging behavior in moonlight by increasing latency to land. In this experiment, bats trained to feed from a food platform were then observed landing in conditions of satiation and food-restriction, with and without the presence of artificial full moonlight. As predicted, we found that bats forage significantly more quickly when food-restricted than when satiated. We found that bats showed a nonsignificant trend to avoid moonlight via increased latencies to land on the food platform. Males—but not females—were significantly slower to land in the presence of moonlight when satiated but not when food-restricted. Our results demonstrate that internal state influences foraging decisions, with individuals landing faster when hungry than when satiated, but that the increased foraging risks associated with moonlight affect male bats more than females.

Animals in nature use diverse strategies to evade or deter their predators, including many vivid behavioural displays only qualitatively described from field encounters with natural predators or humans. Within venomous snake mimicry, stereotyped anti-predator displays are suggested to be a critical component of the warning signal given by toxic models and thus under strong selection for independent convergence in mimetic species. However, no studies have systematically quantified variation in snake anti-predator displays across taxonomically broad clades to test how these behaviours evolve across species within a phylogenetic comparative methods framework. Here we describe a new, high-throughput approach for collecting and scoring snake anti-predator displays in the field that demonstrates both low observer bias and infinite extension across any species. Then, we show our method’s utility in quantitatively comparing the behaviour of 20 highly-divergent snake species from the Amazonian lowlands of Peru. We found that a simple experimental setup varying simulated predator cues was very successful in eliciting anti-predator displays across species and that high-speed videography captured a greater diversity of behavioural responses than described in the literature. We also found that although different display components evolve at different rates with complicated patterns of covariance, there is clear evidence of evolutionary convergence in anti-predator displays among distantly related elapid coral snakes and their colubrid mimics. We conclude that our approach provides new opportunity for analyses of snake behaviour, kinematics, and the evolution of anti-predator signals more generally, especially macroevolutionary analyses across clades with similarly intractable behavioural diversity.