Lagomorphs live in various habitats, ranging from forests to rocky slopes to arctic snow. Regardless of location, they often use burrows, which provide protection from weather and predators. Some species, such as rabbits, dig their own burrows, while other species colonize burrows made by others. Lagomorphs that live in rocky terrain without soft soil use crevices between rocks as burrows. Lagomorphs give birth in burrows, where young are raised until mature enough to disperse. Burrows built for individuals may be small and simple, or they may be large and branching for species that live in groups (colonially), such as pikas. Colonial lagomorphs have specialized alarm calls that can result in a mass dive for the burrows. All lagomorphs are plant-eaters (herbivores) and commonly gather and store vegetation in their burrows for future use. A lagomorph burrow is therefore a kitchen, a dining room, a master bedroom, and a nursery.

Thanks to their ability to produce milk, female mammals are able to feed their offspring for weeks, months, or even years after they are born. This sets the stage for the extended childhoods of many mammal offspring. With food and shelter taken care of (by the mother in most species), a remarkable amount of learning occurs for mammal offspring before they become independent. Elephants tend to their young for as long as 10 years, and humans for longer still. Young mammals may learn about food, shelter, migration routes, social structures, or other keys to survival from their parents. While extended childhoods support learning, they are costly, especially for the female. Lactating females must consume enough calories to feed their offspring and maintain themselves. Offspring that stay around after weaning from their mother's milk may still require protection and food. Human offspring are the most extreme case of investment, with parents usually providing intensive support until age 18 and continuing support beyond.