Marginal value theorem
It is assumed that evolution by natural selection results in animals utilizing the most economic and efficient strategy to balance energy gain and consumption.
When an animal is foraging in a system where food sources are patchily distributed, the MVT can be used to predict how much time an individual will spend searching for a particular patch before moving on to a new one.
Optimal foraging time is modeled by connecting this point on the x-axis tangentially to the resource intake curve.
The optimal time spent picking apples in each tree is thus a compromise between these two strategies, which can be quantitatively found using the MVT.
As predicted, in both cases birds spent more time in one area when the patches were farther away or yielded more benefits, regardless of the environment.
Experimental evidence has shown that screaming hairy armadillos and guinea pigs qualitatively follow MVT when foraging.
While the qualitative foraging trend was shown to follow MVT in each case, the quantitative analysis indicated that each patch was exploited further than expected.
Plants have been shown to preferentially place their roots, which are their foraging organs, in areas of higher resource concentration.
Recall that the MVT predicts that animals will forage for longer in patches with higher resource quality.
Thus, plants grow roots into patches of soil according to their wealth of resources in a manner consistent with the MVT.
In the dung fly mating system, males gather on fresh cow droppings and wait for females to arrive in smaller groups to lay their eggs.
Thus, males change their copulation time to maximize their fitness, but they are doing so in response to selection imposed by female morphology.
Even with these variations, male dung flies do exhibit close-to-optimal copulation time relative to their body size, as predicted by the MVT.
[8] Many studies, such as the examples presented above, have shown good qualitative support for predictions generated by the Marginal Value Theorem.
