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.
Highlights
IntroductionPrimates are threatened across their range (Estrada et al 2017), with species loss driven by direct (e.g., hunting and live capture) and indirect (e.g., habitat degradation and disease mortality) threats (Gillespie and Chapman 2008; Plumptre and Johns 2001; Wich and Marshall 2016)
Primates are threatened across their range (Estrada et al 2017), with species loss driven by direct and indirect threats (Gillespie and Chapman 2008; Plumptre and Johns 2001; Wich and Marshall 2016)
Except for blue monkeys, which we observed at only one site (Ntakata), we observed each species at a minimum of two survey sites
Summary
Primates are threatened across their range (Estrada et al 2017), with species loss driven by direct (e.g., hunting and live capture) and indirect (e.g., habitat degradation and disease mortality) threats (Gillespie and Chapman 2008; Plumptre and Johns 2001; Wich and Marshall 2016). Most data on primate abundance come from protected areas, which are often selected for surveying owing to high primate densities or the presence of charismatic taxa (e.g., great apes; Chapman and Peres 2001; Tranquilli et al 2014). Assessing only a subset of a species’ distribution may overestimate the importance of protected areas and underrepresent the role of unprotected areas that host large, often unmonitored populations. This risk is especially pertinent for relatively uncharismatic animals or species that live naturally at low densities (Cronon 1996; Gardner et al 2007). To account for spatial heterogeneity of primate abundance and threats, data collected from landscape-scale surveys and protected area-level gradients should better reflect species distribution and conservation status (Arroyo-Rodriguez and Fahrig 2014; Caro 1999; Cavada et al 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
