Optimal Foraging Ecology and Diet Choice -- The need to acquire energy to maintain homeostasis is a universal property of life -- Natural selection We expect to see adaptive behaviors that permit individuals to efficiently and effectively acquire and utilize energy

Foraging under predation risk – there is a fundamental tradeoff between acquiring energy and avoiding predation

Red Knot Calidris canutus Tidal mudflat foragers

Ruddy turnstone Arenaria interpres Inshore foragers

Differences in predator escape? Knots – advanced warning and collective flight maneuvers Turnstones – little warning, find cover, every turnstone for itself

At the Netherlands Institute for Sea Research the animal caretaker kept track of knots’ abilities to make 90 degree turns into the aviary….. > 160 g, knots compromise their flight abilities

Flight performance increases with an increase in the ratio of: Pectoral Muscle Mass/Body Mass So how do you increase flight performance?

Body Building to defy death

Red-eyed tree frog Agalychnis callidryas

Rain and snake have different vibrational signatures

Signal Detection Theory (see Box 42, p111 in your textbook)

Patchiness & The Ecology of FEAR

Quitting Harvest Rates & Giving-up Densities (GUDs)

Food left behind No significant differences Prediction #1 – Differences in initial patch quality will not influence the giving-up rule, i.e., at a constant quitting harvest rate It is a “No Regrets Strategy”

Food left behind under bush in the open vipers owls lights vipers & lights Quitting harvest rate Aug July openbush Dec - Apr rattlesnakes hibernating Prediction #2 – Increases in individual foraging costs will result in higher quitting harvest rate

Prediction #3 – As the value of energy decreases organisms should be less willing to exposed themselves to risk Exchange rate of survivorship and energy Exchange rate of time and energy QHR = P + MOC + C ____  F  e Harvest rate Predation cost Missed opportunity cost Metabolic cost P F e P F e Hazardous Duty Pay

Food left behind safe risky 10 Forest edge 10 10m 50madd 50g of sunflowers seeds

Perceived risk of predation Survivor’s Fitness The value of energy/food i.e., marginal fitness gain from foraging The Fear Equation (Joel Brown)

SignalerReceiver (‘intended’) (sender) (recipient) INFO Recipient - Eavesdropper Alarm calls and Eavesdropping Bushbuck Grey duiker

QHR = P + MOC + C ____  F  e Harvest rate Predation cost Missed opportunity cost Metabolic cost P F e P F e Hazardous Duty Pay

Islands of Fertility

Bushbuck bark Silent Rank Giving-up density

Proportion of time vigilant Mean duration of scan (sec)

COGNITION How should squirrels change their behavior in the perceived presence of a cache robber? - False-caches - Cache less often - Cache in remote/hidden locations - Frequent recaching **Reduce the Future Value of food Squirrels devalue cacheable food in the perceived presence of jays (i.e., reduce the future value of cacheable food)

Cacheable Nuts Future Value (cached 54 of 55)* Non-cacheable Nuts No Future Value (ate 52 of 55)* * Kotler et al Food spoils and ripens….hence, a food that stores well has higher future value

Detecting changes in Future Value QHR = P + MOC + C __  F  e ____  F  e  FeFe will result in  QHR or  GUD Compare GUDs on cacheable food With and Without the perceived presence of jays while holding GUD on non-cacheable food fixed (i.e., compared to a fixed currency) P = predation cost MOC = missed opportunity cost C = metabolic cost QHR = quitting harvest rate  F/  e = marginal value of energy

~75m ~100m station of two trays Speaker (jay or winter birds) ~25m Cachable food = hazelnuts in the shell Non-cachable food = hazelnuts with shell removed

~75m ~100m ~25m Jay NearJay FarCONTROL

GUD (# cachable nuts remaining) Control Blue jay AwayNear Squirrels devalue cacheable food in the perceived presence of jays Results