Taste-Aversion Conditioning of Crows to Control Predation on Eggs

Abstract

Free-ranging crows (Corvus brachyrhynchos) that ate chicken eggs that were painted green and contained a nonlethal toxin subsequently avoided green eggs at various locations, whether or not they contained toxin. The crows also continued to eat unpainted and nontoxic chicken eggs. Illness-induced aversions among predators in nature may be a powerful determiner of the evolution of Batesian mimicry and, in human hands, serve as a practical tool for wildlife ecologists.

Chemical defense in pelagic octopus paralarvae: Tetrodotoxin alone does not protect individual paralarvae of the greater blue-ringed octopus (Hapalochlaena lunulata) from common reef predators

“…It may facilitate predator learning through multiple cues (e.g. Fisher 1930;Nicolaus et al 1983). In this scenario, the compound signals the onset of more detrimental symptoms of TTX.…”

Prostaglandin A2: an agent of chemical defense in the Caribbean gorgonian Plexaura homomalla

“…Therefore, the protection provided by PGA, against predation by labrids may have ecological significance. Furthermore, a wide range of organisms learn to avoid prey which produce nausea and vomiting (Nicolaus et al, 1983 and references therein). Since prostaglandins probably can induce vomiting in many different species of fish, the PGA, of P, homomalla may provide this gorgonian with an effective chemical defense against a wide range of carnivorous reef fish.…”

Fishes learn aversions to a nudibranch’s chemical defense

“…3 & 5). Similar patterns of avoidance of specific food (as opposed to specific compounds within this food) when physiological distress occurs after consumption have been documented in consumers as diverse as birds, snakes, rats, sheep and humans (Wilcoxon et al 1971, Burghardt et al 1973, Nicolaus et al 1983, Provenza et al 2003, Villalba et al 2004. Polygodial protects Doriopsilla pharpa from fish predation.…”

“…squid). Alternatively, the use of different cues may be related to how the compounds affected the consumers (Nicolaus et al 1983). C. bosquianus took a conservative strategy by associating the taste of food with physiological distress and then avoiding all food tasting or smelling like defended food, even when the food lacked aversive compounds.…”

“…Learned food aversions occur in a diverse array of consumers including insects (Berenbaum & Miliczky 1984), molluscs (Gelperin 1975), fishes (Gerhart 1991, reptiles (Burghardt et al 1973), birds (Nicolaus et al 1983), and mammals (Garcia et al 1974, Bernstein 1978, Yoerg 1991, with the majority of research focusing on terrestrial species. Fishes, a group of important, generalist consumers that co-occur with nudibranchs, are well-known for their learning ability (Thacker et al 1997, Crossland 2001, Warburton 2003 and may quickly develop aversions to food that cause regurgitation (Gerhart 1984.…”