Predators and prey

1. Predators and prey • Predation = capture and consumption of one organism by another (includes herbivory) • Predation provides strong selective pressure on prey populations • Favors adaptations to evade capture in prey and counter adaptations in predators (i.e.coevolution) Where have all the sea otters gone?

2. Predators and prey • Morphological defenses: • Thorns, spines and prickles • Plant defenses against herbivory • Hairs (deter insect herbivores) • Grasses incorporate silica into cells Where have all the sea otters gone?

3. Predators and prey • Chemical defenses: • Called secondary chemical compounds because not part of major metabolic pathways • Plant defenses against herbivory • Effects of secondary chemical compounds: • toxic (e.g. cardiac glycosides of milkweed) • interfere with digestion (e.g. tannins of oaks) or interrupt development of insects • interrupt development of insects • Secondary chemicals can be maintained in tissues at all times or released after damage by herbivores Where have all the sea otters gone?

4. Predators and prey • Chemical defenses: • Some herbivores able to feed on plants protected with a certain secondary chemical compound (e.g. monarch butterfly larvae) • Plant defenses against herbivory Where have all the sea otters gone?

5. Predators and prey • Chemical defenses: • Larvae of monarch butterflies feed on milkweeds and incorporate cardiac glycosides as own defense • Animal defenses against predators • Most predators learn not to eat monarchs Where have all the sea otters gone?

6. Predators and prey • Chemical defenses: • Many species produce toxic chemical to deter predators • Animal defenses against predators • Poison-dart frogs produce toxic alkaloids in mucus covering skin • Bombardier beetle shoots 100oC irritant from abdomen Where have all the sea otters gone?

7. Predators and prey • Defensive coloration: • Many species advertise their chemical defense through aposematic coloration • Animal defenses against predators • Yellows, reds, oranges and blacks (e.g. monarch butterflies) • Other species rely on cryptic coloration to avoid detection by predators Where have all the sea otters gone?

8. Predators and prey • Behavioral defenses: • Dilution effect • Animal defenses against predators • Stay in large groups to overwhelm predator and reduce one’s own risk of capture (e.g. mayflies swarms) • Startle effect • Reveal coloration to cause hesitation by predator (e.g. Io moth) Where have all the sea otters gone?

9. Predators and prey • Mimicry = evolution of coloration to resemble other species • Animal defenses against predators • Two general types: • Batesianmimicry: poisonous model and palatable mimic Wasp (model) Mantid (mimic) Moth (mimic) Where have all the sea otters gone?

10. Predators and prey • Mimicry • Müllerianmimicry: several unrelated, poisonous species with similar aposematic coloration • Animal defenses against predators Where have all the sea otters gone?