Browsing by Subject "prey"
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(2020)Hypotheses to explain the emergence and maintenance of trichromacy in primates have long focused on the role of diet, often suggesting trichromats are better able to detect ripe fruits and nutritious leaves. However, many neotropical primate species also need to avoid eating conspicuous food items like insects that have evolved to warn potential predators of their unprofitability. This factor has largely been ignored in work on primate colour vision. We suggest here that dichromatic and trichromatic individuals vary in their ability to learn about conspicuous but unprofitable food and that trichromats could be more effective than dichromats at detecting conspicuous unprofitable prey. To test this hypothesis, three females and one male white-faced saki (Pithecia pithecia) participated in behavioral experiments at Korkeasaari zoo (Helsinki, Finland) where choice boxes were presented marked with two symbols against a green background. Only trichromats could discriminate orange symbols that provided an unprofitable food reward from the more profitable green symbols. Each saki made 80 choices over 10 trials. While we did not detect any evidence for learning about symbol profitability, we found two females significantly avoided the conspicuous prey meaning they received greater food rewards than the dichromat male and one putative dichromat female. Further analysis is needed of the opsin genes of the females in this study to confirm the role of unprofitable food in Saki colour vision.
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(2021)Prey defend themselves from predators using a range of tactics, including evolving distasteful compounds and advertising their unprofitability with aposematic warning signals. Therefore, before attacking a potential prey, predators need to assess whether it is palatable and profitable to consume. Previous studies have demonstrated that predators can rely on personal experience (personal information) and/or observe the foraging behaviour of others (social information) to assess prey profitability. ‘Social avoidance learning’, where predators observe a negative foraging experience associated with beak wiping, has been suggested to be important to explain how novel warning signals evolve. However, in previous studies observers saw a very strong “disgust response” of the demonstrators, when in fact there is variation in how strongly birds respond to unpalatable food. Therefore, to understand how social avoidance learning can work in nature I investigated how blue tits (Cyanistes caeruleus) use social information from demonstrators that show a weaker response to unpalatable food. I provided social information to observers using video playback of a demonstrator bird consuming a novel conspicuous prey item and showing: (1) a strong disgust response (65-95 beak wipes) as in previous studies, (2) a weak disgust response (12-25 beak wipes), or (3) no disgust response (control, no beak wiping). Next, I investigated birds’ foraging choices using a miniature novel world protocol where birds encountered novel aposematic (conspicuous and unpalatable) and cryptic (camouflaged and palatable) prey. Tested individuals consumed fewer aposematic prey after seeing a strong response but seeing a weak response did not influence their foraging choices. My results, therefore, suggest that information about novel aposematic prey may be less likely to spread socially than previously thought. However, more work is needed to determine both the availability and salience of graded social information.
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