Rewriting the Unassessed, Discredited and Long-Forgotten History of the Pygmy Hippopotamus in Guinea-Bissau

Despite its small area and the loss of forest cover, Guinea-Bissau still is an environmentally diverse and biodiversity-rich country with a high percentage of protected areas. However, its biodiversity is still poorly known and is under threat from land conversion. Therefore, several rare or declining species may soon disappear before they are studied or even before their former presence or persistence in the country can be confirmed. One of these species was the pygmy hippopotamus (Choeropsis liberiensis), as reported in the journal Mammalia in 1958. With no subsequent data, its former presence in the country was later discredited. Considering that this was not based on an in-depth review of the information and further surveys, we analysed in detail the author identity, the circumstances of the sightings, the existence of other supporting information, and searched for new data through interviews in the rural countryside. We conclude that credit for the past occurrence of the species in the country was justified, but our new data suggest it went extinct, presumably in association with the anticolonial war (1963–1974).