18.1.1: Current Conservation of Nonhuman Primates

Diversity of Primates

The order Primates is one of the most diverse groups of mammals on the planet, with 504 species in 79 different genera currently recognized (Figure B.2; Estrada et al. 2017). Recently new genera, species, and subspecies of nonhuman primates (henceforth, simply “primates” ) have been recognized, in some cases as a result of new discoveries and new data, but also because of revisions to taxonomic classification systems based on different species concepts (Groves 2014; Lynch Alfaro et al. 2012; Rylands and Mittermeier 2014).

Figure \(\PageIndex{1}\): The global distribution and species richness of primates and the percentage of those threatened with extinction and declining populations. The numbers next to each geographic area indicate the current species present in that location. The bars below show the percentage of species threatened with extinction (in green) and the percentage of species with declining populations in each region (in red).

Figure \(\PageIndex{2}\): Mountain gorilla (Gorilla beringei beringei) in Bwindi Impenetrable National Park, Uganda. Mountain gorillas are classified as endangered and are only found in the Virungas area of Rwanda and the Democratic Republic of Congo and the Bwindi forest of Uganda (Hickey et al. 2018; Kalpers et al. 2003). This species has suffered tremendously due to habitat destruction, poaching, political unrest, and war (Kalpers et al. 2003).

Figure \(\PageIndex{3}\): A female northern muriqui (Brachyteles hypoxanthus) with infant at the Feliciano Miguel Abdala Private Natural Heritage Reserve outside of Caratinga, Brazil. Muriquis are found exclusively in the Atlantic Forest of southeastern Brazil. The destruction and fragmentation of these forests have caused this species to be listed as Critically Endangered (Strier et al. 2017). Although still threatened, the continued efforts of the Muriqui Project of Caratinga have brought this species back from the brink of extinction.

Wild primates occur in 90 countries around the world, but two-thirds of all species are found in only four countries: Brazil, Madagascar, Democratic Republic of Congo, and Indonesia (Estrada et al. 2017; Estrada et al. 2018). An estimated 60% of primate species are threatened with extinction and 75% are experiencing population declines (Estrada et al. 2017, see Figure B.2). Yet despite these discouraging statistics, there are a growing number of populations recovering as a result of research and conservation efforts. For example, the population of mountain gorillas (Figure B.3) initially studied by Dian Fossey in Rwanda in 1967 has increased from 250 gorillas in 1981 to 339 in 2008 as a result of ongoing research and conservation efforts that include highly controlled ecotourism (Robbins et al. 2011). Similarly, one population of northern muriqui monkeys (Figure B.4) inhabiting a small privately owned forest fragment in southeastern Brazil’s Atlantic Forest increased from about 50 individuals to nearly 350 individuals as a result of increased habitat protection over the course of the Muriqui Project of Caratinga, a long-term field study initiated more than 35 years ago by one of the authors of this appendix (Strier and Mendes 2012).

International Union for the Conservation of Nature (IUCN)

In conservation, it is crucial to have a global standard to assess and recognize the conservation status of species. The International Union for the Conservation of Nature (IUCN) formed the Red List for Threatened Species in 1994 to determine species extinction risks (IUCN 2017). Scientists submit assessments of species to the IUCN, which are subsequently categorized based on the size and distribution of species’ numbers and available habitat. The categories range from “data deficient,” when not enough is known, to “least concern,” “near threatened,” “vulnerable,” “endangered,” “critically endangered,” “extinct in the wild,” and “extinct.” Threatened species are classified as “vulnerable,” “endangered,” or “critically endangered,” with the most critically endangered species being those whose numbers are fewer than 250 mature individuals and continuing to decline or whose habitats are severely fragmented (Figure B.5; IUCN 2017).

Table 18.1.1: International Union for Conservation of Nature (IUCN) Criteria for Threatened Taxa. Updated from Strier 2011a. Source: Simplified and condensed from IUCN Species Survival Commission, 2012.

Critically Endangered (CR): Facing an extremely high risk of extinction in the wild due to any of the following: A. Reduction in population size of 80%–90% over the last ten years or three generations, depending on the causes and reversibility of the reductions; B. Extent of occurrence <100 km2 or area of occupancy <10 km2 or both; C. Population size estimated to number fewer than 250 mature individuals and to be declining or unevenly distributed; D. Population size estimated to number fewer than 50 mature individuals; E. Probability of extinction within ten years or three generations is at least 50%. Endangered (EN): Facing a very high risk of extinction in the wild due to any of the following: A. Reduction in population size of 50%–70% over the last ten years or three generations, depending on the causes and reversibility of the reductions; B. Extent of occurrence <5000 km2 or area of occupancy <500 km2 or both; C. Population size estimated to number fewer than 2,500 mature individuals and to be declining or unevenly distributed; D. Population size estimated to number fewer than 250 mature individuals; E. Probability of extinction within 20 years or five generations is at least 20%. Vulnerable (VU): Facing a high risk of extinction in the wild due to any of the following: A. Reduction in population size of 30%–50% over the last ten years or three generations, depending on the causes and reversibility of the reductions; B. Extent of occurrence <20,000 km2 or area of occupancy <2000 km2 or both; C. Population size estimated to number fewer than 10,000 mature individuals and to be declining or unevenly distributed; D. Population size estimated to number fewer than 1,000 mature individuals; E. Probability of extinction within 100 years is at least 10%.

The IUCN has a committee specifically dedicated to primates, the IUCN Species Survival Commission (SSC) Primate Specialist Group. This group collaborates with the International Primatological Society (IPS), Conservation International (CI), and the Bristol Zoological Society (BZS) every two years to publish “Primates in Peril: The World’s 25 Most Endangered Primates.” These lists are created at IPS open meetings and are intended to focus attention on all endangered primates by highlighting the plights of some of the most critically endangered (Schwitzer et al. 2017).

Identifying Priorities in Primate Conservation

It is important to consider extinction risk in making conservation decisions, thus the IUCN Red list and the “Primates in Peril” reports are factors in deciding how to allocate resources and funding. Some primate species are found only in biodiversity hot spots, or areas that contain high levels of species diversity and include primates that are endemic to the area and genetically unique (Sechrest et al. 2002). Hot spots are often considered conservation priorities because protecting these areas can result in the protection of large numbers of species. In addition, some conservation organizations focus on highly charismatic primate species (e.g., primates that are large, closely related to humans, or well-known from zoos, such as the golden lion tamarin) to garner attention and resources for conservation (Figure B.6). However, dramatic declines of charismatic species indicate that charisma is not enough (Estrada et al. 2017). For example, it is estimated that the population of Bornean orangutans (Pongo pygmaeus) decreased by 100,000 individuals between 1999 and 2015, despite being very popular with the general public (Voigt et al. 2018). In making conservation decisions, primatologists may also consider the importance of genetically unique primates, such as the aye-aye (Daubentonia madagascariensis), the last remaining species within its genus in order to preserve evolutionary history (Strier 2011a).