It cannot be denied that parts of Phou Khao Kouay have been heavily logged and exploited. Still, it is home to some remarkable wildlife. With the exception of elephants, most of these animals are rarely seen though.
Some of the larger animals that inhabit the national reserve are the Asian Black Bear, Sun Bear, wild dog (Jackal and Dhole), Southern Serow, Clouded Leopard, Sambar, Mouse Deer, Phayre’s Langur, White-cheeked Gibbon, Rhesus and Pig-tailed Macaque, civets and otters. In 2001, the sighting of a Siamese Crocodile near to the Nam Leuk reservoir has been reported, but this may have been the result of an erroneous observation. Whether there are still tigers present in the park remains to be reconfirmed.
Two herds of Asian Elephant live inside the park. They have formed two groups, who apparently do not mingle or interbreed with each other. While one smaller herd is living in the north-eastern part (Nam Mang/Long Xan valley), the other group of about 40 to 50 heads is roaming near Ban Na in the southern periphery of the park.
There are many different bird species in the park. The most remarkable one is the majestic Green Peafowl. This once very common bird of the Mekong lowlands is now confined to only five tiny enclaves in southern Laos. Amongst other birds are the Blue-breasted Quail, Siamese Fireback, Red-collared Woodpecker, Coral-billed Ground Cuckoo, Grey-headed Lapwing, Jerdon’s Baza, Fish Eagle and Purple Heron. The park is also home to a large number of butterflies and countless other insect species.