Studies and questions about the phylogeny of an animal behavior provide us with evolutionary explanations that describe the history of the behavior. For example, these explanations can include information about:
which ancestor first possessed this trait
what was the antecedent to this behavior
what selective pressures in the past have shaped this behavior
Evolution of Food Caching
Food caching has evolved in several different species within three taxa: birds, mammals, and hymenoptera (Table 1). While the behavior appears to have evolved independently multiple times, research has identified common circumstances which preadapt animals to caching behavior (Smith and Reichman 1984).
Table 1. Food type, cache type, and time period of caching for taxa know to cache in the wild (Smith and Reichman 1984).
Acorn Woodpeckers storing their food in holes drilled in trees (left, Marie Read) and collared pika (Ochotona collaris) taking food to cache in Hatcher Pass, Alaska (right, Robert Harding Imagery).
Evolution from Provisioning of Young
In hymenoptera, caching evolved from the behavior of provisioning their young with food, and it is likely that this act of collecting and moving food from a foraging area to dependent young was the first transitional step in the evolution of food caching in other animals as well (Malyshev 1968, Smith and Reichman 1984). While all species that cache food provision their offspring, the converse is not true: relatively few animals that provision their young with food have evolved food caching behavior.
Selective Pressures Associated with Evolution of Food Caching
Pikas live in areas where the amount of food available changes drastically depending on the season, resulting in a highly variable food supply (Morrison et al. 2009, Smith and Reichman 1984). Food caching has evolved as a way for pikas to survive during periods of food shortage in return for the cost of caching when food is abundant (Smith and Reichman 1984).
In competitive environments where animals must compete with other individuals in their species for resources including food and space, some species have evolved food caching as a way to easily claim and defend resources. Pikas maintain individual territories, which saves individuals time and energy as they can claim food within their territory and avoid having to travel long distances when gathering food for their cache (Smith 1968, Smith 1981, Smith and Reichman 1984).
Climate also plays a significant role in the evolution of food caching: caching is more common in temperate regions than in tropical regions (Smith and Reichman 1984). This could be a result of selective pressure due to low predictability of food supplies in temperate regions. Additionally, food caching may have failed to evolve in tropical habitats because of the higher likelihood of food spoilage in high temperatures and humidity.