Hybrid orangutan

A hybrid orangutan or cocktail orangutan is a usually captive-born orangutan derived from interbreeding between Bornean (Pongo pygmaeus) and Sumatran (Pongo abelii) orangutans. The topic of orangutan speciation was poorly understood until the 1980s, when genetics revealed that orangutans actually comprise these two genetically distinct species. Before this was known, orangutans from differing species were paired in captivity, and in some cases produced hybrid offspring. Subsequently, the government of Indonesia and the organization that oversees zoo programs in the United States suggested to stop interbreeding of Sumatran and Bornean orangutans and called for disallowing hybrids to reproduce.

From 1971 to 1985, 90 orphaned or displaced orangutans rescued from illegal animal trade were released into Tanjung Puting National Park in Central Kalimantan. A subsequent genetic survey determined that at least two orangutans, captured in a different region and therefore not native to the park, had prolifically interbred with the local native apes, and produced at least 22 hybridized descendents. Their offspring contributes to fears that interbreeding of subspecies leads to "hybrid vigor", in which "offspring reap the benefits of their parents' individual qualities", but  "offspring born to parents from two genetically distinct populations, which have not been in genetic contact for significant periods of time, have also been shown to suffer poor health and reproductive success in a range of different species." This is thought to lead to "outbreeding depression", where hybrid individuals die earlier than non-hybrids, thereby contributing to a diminishing ornagutan population.