Optimality Theory

  • The highest benefit to cost trait is the adaptation
  • Optimal Covey size for northern bobwhite quail is a function of the costs and benefits of belonging to groups of different sizes.

Reto Zach’s observations of foraging crows:

  • The crows only picked up large whelks
  • The flew up about 5 meters before dropping
  • The kept trying until the whelk was broken, even if many flights were required

If crows are foraging optimally, then…

  • Large whelks should be more likely than small ones to shatter after a drop of 5 meters
  • Drops of less than 5 meters should have lower breakage rates
  • Drops of more than 5 meters should not greatly improve the chances of opening a whelk
  • The probability of breaking should be independent of the # of drops

Optimal foraging theory predicts that an animal should behave in a way that…

  • Maximizes benefits
  • Minimizes costs
    • So maximize net energy gain
    • The central assumption is the more net energy an individual gains, the greater the reproductive success

Profitability of prey = energy gained per unit handling time

Whether or not an animal can forage optimally, may be influenced by other factors such as predators and parasites

Alternative Foraging Strategies

  • Genetically based strategies maintained by frequency-dependent selection
  • Conditional strategies based on environmental conditions
  • Geographical separation and divergence

Conditional Strategy

  • An inherited mechanism that gives the individual the ability to be flexible
    • EX. Ruddy Turnstone
      • Push strands of seaweed to one side
      • Turn stones over
      • Probe in the mud