Rodent on every continent except Antarctica. They are the only terrestrial placental mammals to have colonized Australia and New Guinea without human intervention. Humans have also allowed the animals to spread to many remote oceanic islands (e.g., the Polynesian rat). Rodents have adapted to almost every terrestrial habitat, from cold tundra (where they can live under snow) to hot deserts. Some species such as tree squirrels and New World porcupines are arboreal, while some, such as gophers, tuco-tucos, and mole rats, live almost completely underground, where they build complex burrow systems. Others dwell on the surface of the ground, but may
Arboreal locomotion its descent and prevent falling. Descent can be particularly problematic for many animals, and highly arboreal species often have specialized methods for controlling their descent. Due to the height of many branches and the potentially disastrous consequences of a fall, balance is of primary importance to arboreal animals. On horizontal and gently sloped branches, the primary problem is tipping to the side due to the narrow base of support. The narrower the branch, the greater the difficulty in balancing a given animal faces. On steep and vertical branches, tipping becomes less of an issue, and pitching backwards or slipping downwards