Incredibly varied in both size, type and variety, there are more than 100 different species of snakes in North America alone, according to information from the University of Pittsburgh. Despite this great level of diversity and salient characteristics, the diets of snakes are not quite as varied as snakes themselves. All snakes are carnivores, which means that they exclusively consume meat, forgoing plant-based sources of nutrition altogether.
The main limiting factor in the range of items consumed in a snake's diet is governed only by the size of the snake itself. Snakes subsist only on items that are smaller than themselves because all snakes have the disconcerting tendency of consuming their meals whole. According to the website EnchantedLearning.com, snakes consume all manner of small mammals, rodents, other reptiles, birds, insects, amphibians (such as frogs), fish and even whole eggs stolen from the nest. In all of these cases, snakes feed by quickly striking the prey with their fangs (or rendering it unconscious by squeezing it in the case of the boa constrictor), and then proceed to consume the animal whole. This is possible due to the extreme elasticity of a snake's body; the snake is able to expand and contort its throat to accommodate all manner of items. Many types of snakes (such as pythons) are nocturnal, which means that they feed only during the night.
A snake's frequency of feeding is much less than warm-blooded creatures such as mammals due to their slower metabolism. Generally speaking, a growing snake needs to eat only about once a week, with a fully grown snake requiring food every seven to 14 days. The behavior of a snake changes when it is prepared to feed. It becomes increasingly active (going into "hunter" mode), looking for the aforementioned food types to satiate its needs for the next week or so. Beyond solid food requirements, snakes also require a fresh source of water, preferring to drink by becoming completely submerged in the liquid.