Biology 301


Optimal Foraging



Optimal Foraging theory is an application of evolutionary thinking to the behaviors of consumers (choice of patches of food, or individual items of food).


The assumptions are that organisms maximize their fitness by maximizing their energy intake, and by minimizing their risk of exposure to enemies.


On a foraging trip, an organism spends time traveling between patches of food (travel time), and spends time in each patch of food (search time). 


The choice of individual food items is analyzed in a similar way


The average rate of energy gain for an animal  is


E/T  where E is the total energy gained and T is the total time spent foraging.


For each food item, the time spent is divided into Search Time Ts and Handling Time Th.


An animal encounters a food item and must decide whether to eat it or not.  It already has found the item, so the only further time it must spend is Th, the handling time necessary to eat it.  The animal should add the item if E/Th for that item is greater than E/(Ts+Th) for its preferred item.  In order to get the preferred item, it must search and then handle and consume the preferred item.  In order to consume the item in hand, it only has to handle it.