Foraging Risk and Variation shortened

Foraging Risk and Variation shortened - Diet and Foraging...

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Diet and Foraging Behavior Part 2: When economics goes bad Optimal foraging theory – how the previous lecture was framed; it’s basically an economics approach It assumes that maximizing something (like E/T) is what’s important. - variation in that “something” is not important - variation among individuals is not important Size of prey Energy / Time Optimal Foraging : birds always try to maximize; everything else is “error” Size of prey Might variation be important, too?
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Importance of Variation The basic idea : when a bird is easily able to attain the maximum, it will behave differently than when variation in food is great and it can rarely attain that maximum. But how might this work ? A hypothetical example : Assume a bird needs 10 units of food per day to survive It has 2 choices on where to forage 1. It will always get 9.5 units/day; no variation 2. It will get an average of 9.0 units/day; much variation What’s more important, the average or the variation?
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Do birds really respond to variation? Juncos need 2 seeds/minute Tom Caraco Junco 2 2 2 2 2 2 2 2 2 2 0 4 0 0 0 0 0 4 4 4 4 4 Average = 2 seeds/min No variation Average = 2 seeds/min High variation Juncos always chose this side. “Risk Averse”
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Change the average, not the variation 1 1 1 1 1 1 1 1 1 1 0 2 0 0 0 0 0 2 2 2 2 2 Average = 1 seed/min No variation Average = 1 seeds/min High variation Juncos always chose this side. “Risk Prone”
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Foraging Risk and Variation shortened - Diet and Foraging...

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