Designation of a New Subspecies of Angola Colobus Colobus angolensis Sclater, 1860 (Primates: Cercopithecidae) Endemic to the Mahale Mountains of Western Tanzania
Primate Conservation 37
Yvonne A. de Jong and Thomas M. Butynski
Abstract: The polytypic Angola colobus Colobus angolensis is a widespread species that, in eastern Africa, is often restricted to small, highly isolated, areas. In 1966, evidence for an undescribed subspecies of C. angolensis was obtained in Mahale Mountains National Park, central west Tanzania. Mahale C. angolensis has only been observed twice by scientists (1976 and 1979) and remained unnamed. In April 2022, 43 years after the last published observation, we observed, heard, and photographed a group of Mahale C. angolensis. Given the considerable current geographic isolation (~100 km across L. Tanganyika; ~330 km across land) of this monkey from its conspecifics, together with the distinctive coloration and pattern of its pelage, we here designate this as a new subspecies. We also describe the environment in which Mahale C. angolensis lives, discuss its paleobiogeography, taxonomic arrangement, and threats, and provide recommendations for conservation and research. Mahale C. angolensis is endemic to the montane forests of Mahale Mountains National Park where it has been observed at only two sites, the south slope of Mt. Ihumo (~1,970 m asl) and on the ridge between Mt. Nkungwe and Mt. Kahoko (~2,350 m asl). In addition, bouts of ‘roar’ loud calls were heard on nearby Mt. Mhensabantu (~2,050 m asl) on two occasions. The geographic distribution of Mahale C. angolensis is likely between 10 km² and 50 km². The size of this population is probably <400 individuals, with <200 adults. This monkey appears to occur wholly within a remote and rugged part of Mahale Mountains National Park where agricultural encroachment and poaching are not major concerns at this time. The primary threats are habitat loss due to fire, and to a warming climate. With its small population and severely restricted geographic distribution, Mahale C. angolensis qualifies as a ‘Critically Endangered’ subspecies under current IUCN Red List degree of threat criteria.
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