The family Ailuridae includes just a single living species, the Red Panda (Ailurus fulgens), which occurs in a narrow range extending west to Nepal and east to southwestern China. The evolutionary affinities of this species remain uncertain, with morphological and molecular phylogenetic data having led various researchers to conclude that it is most closely related to Procyonidae (raccoon family), Ursidae (bears), or ursids plus seals, among other possibilities. As of 2013, it appears that Ailuridae is sister to a clade consisting of (Procyonidae + Mustelidae), with Mephitidae basal to (Ailuridae + Procyonidae + Mustelidae) (Eizirik et al. 2010; Nyakatura and Bininda-Emonds 2012; Sato et al. 2012). The Red Panda is no longer believed to be closely related to the Giant Panda (Ailuropoda melanoleuca), whose placement in the bear family (Ursidae) is now well established, although it shares with the Giant Panda a bamboo diet and certain associated morphological peculiarities (bamboo leaves constitute around 80 to 90% of the Red Panda's diet).
Red Pandas are found in temperate forests of the Himalayas and in the mountains of northern Burma and western Sichuan and Yunnan at elevations of 1500 to 4800 meters (and even up to the snowline at 5000 meters in summer). In Meghalaya (northeastern India), they have been found in tropical forests at much lower elevations, between 1700 and 1400 meters. Red Pandas are found in forests with a thick bamboo understory. Around half of the geographic range falls within China.
Except during the mating season, Red Pandas are generally solitary. They are well adapted for climbing and spend much of their time off the ground.
At least in China, Red Panda populations declined dramatically in the latter part of the 20th century. The greatest threats to Red Panda populations are habitat loss and fragmentation, poaching, and trade in live animals, although Red Pandas are legally protected in China, India, Bhutan, and Nepal and protected areas with Red Pandas have been established in all these countries.