What is the only snake species known to build a nest for its eggs?

The king cobra is the only snake species known to build a nest for its eggs.

A female king cobra gathers dry leaves and other vegetation into a mound, creating a nest that protects the eggs and helps regulate their conditions. She may remain near the nest and defend it until the young hatch. This is unusual because most snakes lay eggs or give birth without constructing and guarding a nest.

King cobras live in South and Southeast Asia and are specialized snake-eaters. Their scientific name, Ophiophagus hannah, reflects that diet. Although they are often called cobras, they are classified in the separate genus Ophiophagus rather than Naja, the genus containing many familiar true cobras.

The hatchlings are venomous from birth and can raise their heads and spread small hoods. Their independence soon after hatching is typical of snakes, even though the mother provides unusually extensive protection before that stage.