In captivity, red pandas live well in mixed-sex groups, but in the wild, they remain solitary.
At birth, the eyes and ears of the red panda are closed, and head, body, and tail are covered with thick, woolly, gray-buff fur approximately 25 millimeters long. The skin is pink, plantar surfaces of the feet are unfurred, mystaceal vibrissae are about 20 millimeters long, and the pelage lacks adult coloration and markings. The tail is proportionately shorter in young than in adults, averaging about 70 millimeters or 25% of the total length in contrast to about 40% of the total length in adults. Total length is about 280 millimeters and weigth is 110 to 130 grams.
By day 14, long reddish guard hairs appear giving a slightly reddish tinge. Eyes and ears open by day 18. Premolars, both upper and lower, first appear at about 30 days and complete dentition appears by 6 months. Adult coloration and coat pattern are discernable at about day 50; the tail is ringed, the face white with a dark track from the eye to the corner of the mouth, and the soles of the feet are fully furred. Adult coloration and patterning essentially are complete by day 70. Adult size and mass are attained by 12 months of age.