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Predation Muzvondiwa J.V. Outline • There are a variety of antipredator adaptations, which suggests that predation is important in nature • Predator–prey models can explain many outcomes • Field data suggests that predators have a large impact on prey populations Outline • Experiments involving the removal or introduction of exotic predators provide good data on the effects of predators on their prey • Field experiments involving the manipulations of native populations show predation to be a strong force Predation • Traditional view: carnivory • Differences from herbivory • Herbivory is nonlethal • Differences from parasitism • In parasitism, one individual is utilized for the development of more than one parasite • Predator–prey associations Antipredator Adaptations Aposematic or warning coloration • Advertises an unpalatable taste • Ex. Blue jays and monarch butterflies • Caterpillar obtains poison from milkweed • Blue jays suffer violent vomiting from ingesting caterpillar • Ex. Tropical frogs • Toxic skin poisons Camouflage • • • • Blending of organism into background color Ex. Grasshoppers Ex. Stick insects mimic twigs and branches Ex. Zebra stripes: blend into grassy background Mimicry • Animals that mimic other animals • Ex. Some hoverflies mimic wasps Types of mimicry • Müllerian mimicry – Fritz Müller, 1879 – Unpalatable species converge to look the same • Reinforce basic distasteful design • Ex. Wasps and some butterflies • Mimicry ring: a group of sympatric species, often different taxa, share a common warning pattern • Batesian mimicry – Henry Bates, 1862 – Mimicry of unpalatable species by palatable species • Ex. hoverflies resemble stinging bees and wasps Displays of intimidation • Ex. Toads swallow air to make themselves appear larger • Ex. Frilled lizards extend their collars to produce the same effect Polymorphism • Two or more discrete forms in the same population • Color polymorphism – Predator has a preference (usually the more abundant form) – Prey can proliferate in the rarer form – Ex. leafhopper nymphs (orange and black) – Ex. Pea aphids (red and green) • Reflexive selection – Every individual is slightly different – Examples: brittle stars, butterflies, moths, echinoderms, and gastropods – Thwart predators’ learning processes Prey phenologically separated from predator • Ex. Fruit bats – Either diurnal or nocturnal – Only nocturnal in the presence of predatory diurnal eagles Chemical defense • Used to ward off predators • Ex. Bombardier beetles – Possess a reservoir of hydroquinone and hydrogen peroxide – When threatened, eject chemicals into "explosion chamber" – Mix with peroxidase enzyme – Mixture is violently sprayed at attacker Masting • Synchronous production of many progeny by all individuals in population • Satiate predators • Allows for some progeny to survive • Common to seed herbivory
