This is a list of the mammal species recorded in Guam. There are fifteen mammal species in and around Guam, of which two are endangered and one is considered to be extinct.[1]
The following tags are used to highlight each species' conservation status as assessed by the International Union for Conservation of Nature:
| Extinct | No reasonable doubt that the last individual has died. | ||
| Extinct in the wild | Known only to survive in captivity or as a naturalized populations well outside its previous range. | ||
| Critically endangered | The species is in imminent risk of extinction in the wild. | ||
| Endangered | The species is facing an extremely high risk of extinction in the wild. | ||
| Vulnerable | The species is facing a high risk of extinction in the wild. | ||
| Near threatened | The species does not meet any of the criteria that would categorise it as risking extinction but it is likely to do so in the future. | ||
| Least concern | There are no current identifiable risks to the species. | ||
| Data deficient | There is inadequate information to make an assessment of the risks to this species. |
The bats' most distinguishing feature is that their forelimbs are developed as wings, making them the only mammals capable of flight. Bat species account for about 20% of all mammals.
The order Cetacea includes whales, dolphins and porpoises. They are the mammals most fully adapted to aquatic life with a spindle-shaped nearly hairless body, protected by a thick layer of blubber, forelimbs, and tails modified to provide propulsion underwater.