Predators’ consumption of unpalatable prey does not vary as a function of bitter taste perception

Many prey species contain defensive chemicals that are described as tasting bitter. Bitter taste perception is therefore assumed to be important when predators are learning about prey defenses. However, it is not known how individuals differ in their response to bitter taste, and how this influences their foraging decisions. We conducted taste perception assays in which wild-caught great tits (Parus major) were given water with increasing concentrations of bitter-tasting chloroquine diphosphate until they showed an aversive response to bitter taste. This response threshold was found to vary considerably among individuals, ranging from chloroquine concentrations of 0.01 mmol/l to 8 mmol/l. We next investigated whether the response threshold influenced the consumption of defended prey during avoidance learning by presenting birds with novel palatable and defended prey in a random sequence until they refused to attack defended prey. We predicted that individuals with taste response thresholds at lower concentrations would consume fewer defended prey before rejecting them, but found that the response threshold had no effect on birds’ foraging choices. Instead, willingness to consume defended prey was influenced by birds’ body condition. This effect was age and sex dependent, with adult males attacking more defended prey when their body condition was poor, whereas body condition did not have an effect on the foraging choices of juveniles and females. Together, our results suggest that even though taste perception might be important for recognizing prey toxicity, other factors, such as predators’ energetic state, drive the decisions to consume chemically defended prey.This work was supported by the Academy of Finland via Finland’s Centres of Excellence Programmes (grant number 284666) and the University of Jyväskylä. LH was supported by the Finnish Cultural Foundation and Emil Aaltonen Foundation. RT is supported by an Independent Research Fellowship from the Natural Environment Research Council UK (grant number NE/K00929X/1) and a start-up grant from the Helsinki Institute of Life Science (HiLIFE), University of Helsinki. HMR was supported by a research fellowship from the Institute of Zoology, and is currently supported by the Max Plank Societ