Which group of animals typically has a more complex digestive system, including multiple stomach compartments?

Ruminants are a group of animals characterized by their unique digestive system, which includes multiple stomach compartments—commonly four in species such as cattle, sheep, and deer. This complex digestive structure allows them to efficiently break down fibrous plant material found in their herbivorous diet. The first compartment, the rumen, serves as a fermentation vat where microorganisms help digest cellulose and other complex carbohydrates, breaking them down into simpler compounds that can be absorbed by the body.

In contrast, monogastrics (like pigs and humans) possess a single-chambered stomach that is more suited for a varied diet that does not require such extensive fermentation. Herbivores can include both ruminants and non-ruminants (like horses) but do not necessarily have the same multi-chambered stomach structure. Omnivores have a simple stomach suited for digesting both plant and animal matter, but again, this does not equate to the complex multi-compartment system found in ruminants. Therefore, the complexity and efficiency of the ruminant digestive system are specifically designed for their dietary needs, making them the correct answer to the question.