Foraging is the term for food-seeking behaviors, and these can include searching for food, identifying food, capturing food, and actually eating the food. So it's quite a comprehensive umbrella term for basically all things food-related. Now I want to give you an example of a very interesting genetic mechanism that controls some foraging behavior, and this involves, it's kind of gross, but fruit fly larvae. Now, they're going to have this gene called 4, for forage, and this is going to control their foraging behavior. There's going to be 2 alleles for this gene. For r, which is the rover allele as it's called, and for s, which is the sitter allele. The way this gene controls behavior is that rovers, as they're termed, individuals with these alleles will travel twice the distance for food as sitters will. And you can see a model of that here, the rovers are going to move around a lot further than the sitters will. Now, in terms of natural selection, low population densities will actually favor the 4s gene, because in low population densities you don't need to bother expending this much energy to find your food. However, rovers will do better in other situations. For example, in certain high-density population situations, foraging further will actually potentially lead to greater success in finding food because of all the competition with the other organisms.
The optimal foraging model basically says that natural selection favors foraging behavior that aims to minimize costs and maximize benefits. We're going to see organisms perform their foraging in this way. Food is going to be such a strong factor in natural selection because it's so essential to survival. So behaviors surrounding obtaining food are going to be heavily shaped by natural selection, and thus we're really going to see these patterns that optimize the foraging behaviors of organisms, allowing them to minimize their costs and maximize their benefits, and that's what this graph here is trying to represent. E is for energy, so we want to maximize the energy we obtain, and for the amount of, you know, expenditure we have to do in terms of finding that food. So that's going to involve putting yourself at risk, and actually expending energy to find the food. Like if you're a predator and you have to run, and jump, and bite this animal in the neck several times before you get to eat. So there's always really going to be this risk/reward balance between energy expenditure and energy gain for organisms. And it should be noted that predation is going to pose a great risk for a lot of animals when they're foraging, and it's going to influence their behavior. For example, there are this type of deer, mule deer. Now, you know, deer, they're like the rats of the woods. They just go eat vegetation and stuff just everywhere, and they can really eat, you know, vegetation wherever they want. They could eat it in the forest, they could eat it at the edge of the forest, but they tend to eat it in the edges because of the influence of predation. These mule deer are at a far lower risk of being eaten by mountain lions when they're on the edges of the forest, as opposed to when they're in the forest. So even though there's food in all of these places, they're actually going to selectively forage in those edge environments. The main point to take away here is that animals are always going to maximize their feeding efficiency and balance their risk, involving the risk of injury, the risk of predation, and the risk of wasting a bunch of energy, to get the optimal result.
