Anti-predator behavior Chapter 5

Mobbing behavior Seen in birds like ground nesting black headed gulls Scare off predators, protect young chicks Flapping, kicking, droppings, screaming Is it adaptive? Does it occur because natural selection has acted on genes that allow/promote this behavior Is it hereditary and does it lead to increased reproductive success?

Adaptations Hereditary traits that give rise to a fitness benefit (genetic success) Spread through the population in the past and is maintained by natural selection Is currently spreading relative to alternative traits because of natural selection

Constraints on adaptation Failure of mutations to occur Can only select upon what is available Particularly a problem for man-made environmental changes Pleiotropy Any gene may have >1 role in development and/or behavior Allow maintenance of slightly negative trait (misdirected parental care) Disallow positive trait if it leads to negative in another realm Coevolution The predator is undergoing selection too

Cost-Benefit analysis of mobbing Cost: time and energy, loss of life, attract more predators Benefits: prevent attacks on offspring Predict: mobbing should be especially effective against predators that don’t attack adults (crows) Mobbing should result in fewer attacks

Comparative testing of adaptations If a behavior is an adaptation, it should be selected for in species with similar circumstances

Mobbing behavior in mammals These squirrels can adjust their mobbing behavior based on the threat assessment of the rattler—size and body temp of the snake signals its venomous danger levels to the squirrels and they are less likely to mob larger, warmer snakes which can move faster and inject more venom if they get a chance to bite their prey. Siberian Jays will mob a model hawk more often during the day than a model owl, based on their knowledge of day vs night predators, risk assessment!

Dilution effect Another group strategy for survival.

Swarming The flip side of the dilution strategy. An organized defensive attack.

DQ Explain the behavior of these sleeping bees Sleeping bees clustered together. Come up with 3 hypotheses about the anti-predator value of the sleeping clusters. What predictions does each hypothesis lead to?

Eggshell dispersal Costs? Benefits?

Camouflage Adaptive for solitary animals, but only against the right background

The black moth has almost completely taken over the population in the peppered moth (urbanization theory). Indeed, the most conspicuous moth to us is eaten most often by birds.

Is perch selection an adaptation? Natural perch of the peppered moth is in shaded limb joints—if this perch is an adaptation, moths in limb joints ought to be more protected. Also, the typical (light) moth survives better in unpolluted woods, whereas the melanized (dark) moth survives better in the polluted woods. Frequency dependent selection: the light form is coming back as pollution controls reduce the amount of soot in the air

How effective is cryptic perching? Blue jays recognize only 80-90% of moths perched on their preferred substrate (birch) in their preferred, head up orientation. 100% on a darker substrate are detected.

Why does it work? Conspicuous edges are used by inedible or poisonous prey so that predators can see and avoid eating them.

Receptive fields

Odor cue detection Squirrels roll in shed snake skins to hide their odor Snakes spend less time investigating squirrel+ snake odors vs. squirrel odor alone Caterpillar larvae expel their waste far away from their leaf shelter to avoid detection by means of scent Evolved to combat visual deception by prey

Predator is the paper wasp, who will find and kill a larva with its waste pellets over one without about 85% of the time.

Conspicuous behavior: a puzzle Monarch butterfly: consumes toxic milkweed. Any bird that eats it will become sick and learn to avoid it. Blister beetles (B) and this moth in C also harbor poisonous toxins. Is learning inherited/selected on in predators? Or is this an example of indirect selection?

Starlings adjust feeding behavior based on toxicity perception Grey-water injected worms, White-quinine injected worms Toxicity determined by visual cues Skelhorn and Rowe, 2010

More anti-predator strategies Look like your enemy. Particularly, a threatening version of your enemy that will elicit its own innate escape response. Experimentally, exchanging wings for clear ones reduces the benefit of jumping around, and placing tephritid wings on houseflies (who don’t jump) does not protect them. Need both the marked wings and the jumping behavior to deceive the real spider.

Conspicuous mammalian behavior

Solitary gazelles do stot, rule out 1 and 3 They also orient the rump at the predator, ruling out 2

Unprofitability hypothesis is supported Two points: Is it an honest signal of escape probability? Hasn’t been tested, but probably, otherwise cheetahs would ignore it Is it true for all members of the order Artiodactyla? No, all bovidae (gazelles are members) that have stalking predators stot, but deer (family cervidae) do not.

Optimality and Game Theories of anti-predatory behavior Take into account benefit-cost, not just benefit Both attempt to show that the behavior is better than the alternatives Difficult to measure in nature

Comparing alternatives using optimality theory

Optimality theory applied to quail Groups of 11 are superior in every way—survival, least movement, fastest response to predator silhouette, and maximal vigilance (watching for predators with head up)

Game theory of anti-predator behavior “Winning” depends upon what strategy others are using In a sparse population, a social mutant arises and clusters with another animal, using it as defense against predators—hide behind strategy Social animal is successful, trait spreads Might make herd more conspicuous Individuals jockey for best positions

A selfish herd of penguins Winners won’t be first or last into the water in case a seal is lying in wait.