Rats are various rodents with long, medium-sized tails. Although the genus Rattus is home to the typical rat, species of rats can be found throughout the order Rodentia. Neotoma (pack rats), Bandicota (bandicoot rats), and Dipodomys (kangaroo rats) are three additional rat genera.

Typically, rats and mice are distinguished by size. The common name for a large muroid rodent typically includes the word “rat,” whereas the name for a smaller muroid rodent typically includes the word “mouse.” The terms “rat” and “mouse” in common usage are not taxonomically distinct.

The black rat (Rattus rattus) and the brown rat (Rattus norvegicus) are the most well-known rat species. This species, which is also known as the true rats or Old World rats, originated in Asia.

By measuring heat conduction through test organisms and subjecting them to various levels of physical activity, numerous studies have investigated the thermoregulatory capacity of rodent tails. According to one study, rat tail heat loss is significantly lower than abdomen heat loss.