Heterocephalus glaber, more commonly known as the naked mole rat, is an obviously strange species of rodent in the mole family. These odd animals live most of their lives in underground tunnels, protecting their bare, vulnerable (and wrinkly) skin from the sun and feasting upon all sorts of grubs and insects. Here are five of the strangest facts about naked mole rats.

Uniquely cold-blooded

One of the most intriguing facts about naked mole rats is the fact that they are the only cold-blooded animal that is considered a mammal. Being warm-blooded is one of the defining characteristics of a mammal in all other cases, but naked mole rats meet so many of the other requirements to be defined a mammal that scientists made an exception for the naked mole rat’s cold blood.

Hard to suffocate

A human deprived of oxygen will suffer brain damage in as little as a minute. Naked mole rats, on the other hand, can be active in an oxygen-free environment for 18 minutes before suffering any harm from it. These rodents can also survive in an environment much higher in carbon dioxide than many other creatures.

Extremely social

Naked mole rats are incredibly social creatures, having far more complex social structures than other rodents. They are classified as “eusocial” animals by scientists, meaning that naked mole rats live in colonies formed of more than one generation working together, they share the responsibilities of raising young, and they divide labor into specific jobs.

Cannot feel pain

The skin of a naked mole rat lacks a neurotransmitter known as “substance P,” which is necessary for the transmission of pain signals. This means that the mole rats cannot feel pain at all (nor can they feel itchy). They are also unaware of temperature-related discomfort. Scientists believe these are adaptations to the environmental hazards naked mole rats must survive.

Immortal and cancer free

Naked mole rats do not follow the normal aging process for animals. While they can be killed, they will not die of old age, nor will they grow decrepit as they get older. Also, no matter how long a naked mole rat may live, it is highly unlikely to ever grow tumors, as they are extremely resistant, though not entirely immune, to cancers.