Cercopithecine and Colobine Abundance Across Protected and Unprotected Land in the Greater Mahale Ecosystem, Western Tanzania

Abstract

Most primates live in unprotected land where abundances and threats may differ from those in protected areas. We therefore need to establish population densities in both unprotected and protected areas to effectively inform conservation planning. The Greater Mahale Ecosystem in western Tanzania is a region of mixed protected status with seven cercopithecine and colobine species: blue (Cercopithecus mitis doggetti), red-tailed (C. ascanius schmidi), and vervet (Chlorocebus pygerythrus) monkeys; ashy red colobus (Piliocolobus tephrosceles); black-and-white colobus (Colobus angolensis); and olive (Papio anubis) and yellow (P. cynocephalus) baboons. These species may be threatened by increasing human activity; however, except for ashy red colobus, no data on local abundances are available. We walked over 350 km of line transects in legally protected (Village Forest Reserves) and unprotected general land between August 2011 and October 2012 to estimate densities of primates and human activity. Primate densities were consistently low across the Greater Mahale Ecosystem. Blue and red-tailed monkey and ashy red colobus densities were especially low compared to populations in predominantly forested landscapes. Primate and human activity densities did not differ significantly inside and outside of reserves. Low primate densities could be natural responses to the lower proportions and quality of riparian forest habitat in the region. High levels of human activity and the absence of significantly higher primate densities in reserves suggest unprotected land could provide important refuges for primates in the Greater Mahale Ecosystem. This result further reinforces a broad need to include unprotected areas in primate conservation strategies.

Population dynamics of the Manyara monkey (Cercopithecus mitismanyaraensis) and vervet monkey (Chlorocebus pygerythrus) in Lake Manyara National Park, Tanzania

“…Furthermore, comparative studies on olive baboon survey methods in LMNP provide evidence that distance sampling along roads yields biased absolute population density estimates (Kiffner et al, 2022). Manyara monkey densities (average of 13.0 individuals km −2 ; 95 % CI: 10.2-16.7) for LMNP are, at least, well within the range of densities for gentle monkeys at other sites in central Africa and eastern Africa (Butynski, 1990;Thomas, 1991;Plumptre and Reynolds, 1994;Fashing and Cords, 2000;Hall et al, 2003;Uehara, 2003;Fashing et al, 2012;McLester et al, 2019).…”

“…Population densities of gentle monkeys and vervet monkeys have been estimated at various sites in eastern Africa (Struhsaker, 1967;Butynski, 1990;Isbell et al, 1990Isbell et al, , 1999Thomas, 1991;Plumptre and Reynolds, 1994;Lee and Hauser, 1998;Fashing and Cords, 2000;Hall et al, 2003;Uehara, 2003;Fashing et al, 2012;McLester et al, 2019).…”

Chewing stems of Asparagus buchananii (Asparagaceae) and Aloe sp. (Aloaceae) and spitting them out after extracting fluids may be an evidence of self‐medication in common duikers (Sylvicapra grimmia) in the Greater Mahale Ecosystem, Tanzania

“…Rainfall is highly variable across the landscape, ranging from 600 to 1500 mm per year (Kweka, 2014). There are at least 50 mammal species in the region, including wild dog ( Lycaon pictus ), elephant ( Loxodonta africana ), lions ( Panthera leo ), roan antelope ( Hippotragus equinus ) and several species of non‐human primates including chimpanzee ( Pan troglodytes ) (Iida et al, 2012; McLester et al, 2019).…”

Combining Deforestation and Species Distribution Models to Improve Measures of Chimpanzee Conservation Impacts of REDD: A Case Study from Ntakata Mountains, Western Tanzania

“…The region is characterized by forest lined hills, miombo woodlands and thin strips of gallery forest, typically in valley bottoms. There are also patches of seasonally inundated grasslands, wooded grasslands, rocky outcrops and expansive tracts of native bamboo woodlands, especially along the eastern border of MMNP [35]. The Greater Mahale Ecosystem is framed by Lake Tanganyika in the west and by major rivers-Malagarasi in the north, Ugalla in the east-as well as smaller riverine systems that flow into Lake Tanganyika.…”