Nepal is emerging as a major hub for criminal gangs moving wildlife and animal parts around the globe. In recent years, the authorities here have arrested hundreds of smugglers who have taken advantage of Nepal’s porous borders with India and China, corrupt law enforcement and loose customs rules to illegally transport rhinoceros horns, wool from Tibetan antelopes and live, rare owls and endangered apes.

But for seized animals, problems continue after they have been intercepted. In Nepal, the two chimpanzees rescued on Oct. 17 are now at the center of a spat between the Nigerian government, which is calling for them to be returned, and local wildlife officials, who have named the animals Champa and Chimpu and are trying to keep them at Nepal’s Central Zoo.

The Convention on International Trade in Endangered Species of Wild Fauna and Flora, a multinational treaty, states that the authorities are required to send confiscated animals back to their country of origin or to an accredited rescue center.

But enforcement of the treaty is not easy, said Doug Cress, the head of the World Association of Zoos and Aquariums, an organization that provides support to animal shelters. Most countries lack proper rehabilitation clinics for trafficked animals, he said, and for places that do have facilities, the cost of providing food and medical care to wildlife is high. He said repatriation could take years.