Dietary Restrictions

An animal diet typically requires a wide range of different nutrients for survival, but not all these nutrients are readily and equally available. The scarcity or relative difficulty to obtain some critical nutrients can lead to specialized foraging behavior for many animals.

A good example is the mineral form of sodium for herbivores on Earth. Plants typically contain a low amount of sodium, so herbivores have to find an alternative source to complete their diet. This results in animals living around a few available patches of crystallized salt, insects gathering at the edge of puddles where evaporated water lead to crystallization of salt, and moose spending a large part of their summer foraging eating energy-poor, but sodium-rich, aquatic plants that are not available in winter.

Another example in carnivores is the lack of abundance of vitamin A. This nutrient is found almost exclusively in the liver of their preys, making it an important part of their food consumption habits.

The scarcity of specific resources could lead to a forager having to spend additional energy to search and feed on those resources. This extra cost could mean they are energetically unfavorable, leading the foraging having to compensate by spending additional time to forage for higher energy content preys to compensate. This is why these dietary restrictions are very important to understand a foraging strategy. to define an appropriate foraging currency and for the Daily Energy Budget rule.