Legally protect primate habitat
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 8
Background information and definitions
Efforts to reduce habitat destruction rely heavily on the establishment of protected areas. However, conventional methods of evaluating the effectiveness of protected areas can be biased, because protection is not randomly assigned and because humans can respond to protection in one location by changing land uses in neighboring locations, and thereofore protection can induce habitat destruction of neighboring forests. Such ‘spillovers’ can also be positive, for example enhanced law enforcement on private lands or establishment of private reserves nearby (Andam et al. 2008). Andam and colleagues (2008) controlled for these biases and found that in 1960-1997 about 10% of the protected forests in Costa Rica would have been deforested had they not been protected. Protection therefore seems to reduce deforestation, but does it also protect primate populations? A correlative study in northern Republic of Congo by Stokes et al. (2010) compared wildlife densities and distributions among areas with varying degrees of conservation management. The authors found that both elephant Loxodonta africana and chimpanzee Pan troglodytes troglodytes density decreased with increasing distance to Nouabalé-Ndoki National Park, the only protected area included in their study. The study found no permanent human habitation or roads and no sign of poaching in the national park during their survey. Furthermore, a modelling and decision analysis study that compared two conservation strategies for orangutans Pongo spp., namely rehabilitation and reintroduction of ex-captive or displaced individuals; and protection of their forest habitat, found that reintroduction, which costs twelve times as much per animal as compared to protection of forest, was only a cost-effective strategy at very short timescales. For time scales longer than 10-20 years, forest protection was the more cost-efficient strategy for maintaining wild orangutan populations (Wilson et al. 2014).
Andam K.S., Ferraro P.J., Pfaff A., Sanchez-Azofeifa G.A. & Robalino J.A. (2008) Measuring the effectiveness of protected area networks in reducing deforestation. Proceedings of the National Academy of Sciences, 105, 16089–16094.
Stokes E.J., Strindberg S., Bakabana P.C., Elkan P.W., Iyenguet F.C., Madzoke B., Malanda G.A.F., Mowawa B.S., Moukoumbou C., Ouakabadio F.K. & Rainey H.J. (2010) Monitoring great ape and elephant abundance at large spatial scales: measuring effectiveness of a conservation landscape. PLoS ONE, 5, e10294.
Wilson H.B., Meijaard E., Venter O., Ancrenaz M. & Possingham H.P. (2014) Conservation strategies for orangutans: reintroduction versus habitat preservation and the benefits of sustainably logged forest. PLoS ONE 9, e102174.
Supporting evidence from individual studies
A review on the status of rhesus monkeys Macaca mulatta in 1976-1983 in tropical montane forest in Nanwan Nature Reserve, China found that their population increased in numbers by more than 90% over seven years after the area was proclaimed an internationally protected nature reserve along with provisioning monkeys with supplementary food. Their numbers increased from ‘a few dozen’ in 1976 to 600-700 individuals by 1983, excluding the >100 monkeys that were captured and supplied to scientific and medical institutions. However, no statistical tests were carried out to determine whether this difference was significant. The study does not distinguish between the effects of the different interventions mentioned above.Study and other actions tested
A review on the status of grey snub-nosed monkeys Rhinopithecus brelichi in 1978-1985 in tropical montane forest in Fanjingshan Nature Reserve, China found that no individuals were killed or captured in the area after it was proclaimed a provincial nature reserve in 1978, although 13 individuals were trapped and/or killed by poachers in 1962-1977. The population was reported to be young or sub-adult, further indicating that it was increasing in size. The reserve administration appeared to be preserving the virgin forests effectively. The area also represents a sacred mountain for pilgrims, which forbids the killing of wildlife. There were few killings (<1 individual annually) of grey snub-nosed monkeys reported in the area even before it was proclaimed a nature reserve. Surveys conducted in 1981-1983 had discovered eight groups totalling 450-500 monkeys, and estimates of the total population in the area were as high as 2,000-3,000 animals.Study and other actions tested
A before-and-after trial in 1975-1985 in swamp and riverine forest in Tana River Primate Reserve, Kenya found that after proclaiming the study area a National Reserve alongside other interventions, resident populations of Tana River red colobus Colobus badius rufomitratus and crested mangabeys Cercocebus galeritus galeritus decreased over ten years. Overall population size decreased from 1,200-1,800 to 200-300 individuals (83% decrease) for colobus and from 1,100-1,500 to 800-1,100 (25% decrease) individuals for mangabeys. In addition, the number of forest patches inhabited by these two species also decreased over time. No statistical tests were carried out to determine whether these decreases were significant. Results of total counts in 1985 and in 1973-1975 were compared to estimated population changes. A permanent ranger post was built in 1976 and from 1977-1981, a tourism enterprise with a permanent lodge was established in the reserve. The study does not distinguish between the effects of the different interventions mentioned above.Study and other actions tested
A before-and-after trial in 1978-1987 in tropical montane forest on Hainan Island, China found that the population of the Hainan gibbon Hylobates concolor hainanus increased from 7-8 individuals to 22 gibbons (34% increase) over nine years after the area was proclaimed the Bawanglin Nature Reserve. However, no statistical tests were carried out to determine whether this increase was significant. The total breeding population consisted of four adult males and seven adult females. In 1980, an area of 13 km2 was declared protected from hunting and logging activities. Three of the four remaining groups had a composition that was unusual for this species; they consisted of one adult male and two adult females with 2-4 young per group. The authors suggested that this may be a result of the small size of the group’s habitat, which may have encouraged individuals to remain in their natal group instead of dispersing to establish new territories.Study and other actions tested
A before-and-after trial in 1984-1991 in coastal forest in Poço das Antas Reserve, Brazil, which was proclaimed a protected area in 1983 alongside 14 other interventions, found that the majority of reintroduced golden lion tamarins Leontopithecus rosalia, did not survive over seven years. Fifty-eight out of 91 (64%) reintroduced tamarins did not survive in the wild. However, 57 infants were born (reproductive rate=63%) during the study period, of which 38 (67%) survived. The Reserve falls into the IUCN category 1a and has the protective status of a ‘Strict Nature Reserve’. Different groups of captive-bred or orphaned tamarins were introduced in different years into habitat already occupied by the species and predators. Groups were provided with supplementary food, water and nesting boxes, and allowed to adapt to local habitat conditions before release. Tamarins were quarantined, underwent veterinary checks and were treated for parasites before release. Sick or injured animals were rescued, treated and rereleased. In 1983, a long-term research study was implemented. The study does not distinguish between the effects of the different interventions mentioned above.Study and other actions tested
A before-and-after trial in 1994-1999 in mixed tropical forest in Conkouati-Douli National Park, Republic of Congo, which was upgraded from reserve to national park in 1999 alongside 16 other interventions, found that the majority of reintroduced central chimpanzees Pan troglodytes troglodytes survived over five years. Out of 20 reintroduced chimpanzees released into the legally protected area, 14 (70%) survived. No statistical tests were carried out to determine whether the population decrease was significant. Individuals were radio-collared. Rehabilitated orphaned chimpanzees underwent vaccination, parasite treatments and veterinary screens before being translocated in four subgroups from the sanctuary to the release site where resident conspecifics occurred. Staff members were permanently present to monitor primate health, provide animals with additional food if necessary and detect and examine dead animals. Local people were relocated from the release site to a nearby village. TV and radio advertisements were used to raise chimpanzee conservation awareness and local people were provided monetary and non-monetary benefits in exchange for their conservation support. The study does not distinguish between the effects of the different interventions mentioned above.Study and other actions tested
A before-and-after site comparison study in 1996-2006 in tropical forests of Lesio-Louna Wildlife Reserve, Republic of Congo (Congo) and Batéké Plateau National Park, Gabon found that the majority of reintroduced western lowland gorillas Gorilla gorilla gorilla that were released into regions that received protected status alongside other interventions, survived for at least four years. Twenty-one of 25 gorillas (84%) released in Congo and 22 of 26 gorillas (85%) released in Gabon survived for at least four years. Nine females gave birth to 11 infants, of which nine survived. Released gorillas underwent disease screening and vaccinations during quarantine. Gorillas were released in groups, allowed to adapt to the local environment and supplemented with food prior to release. Gorillas were released into habitat with no resident gorillas to re-establish populations. Released gorillas were treated for parasites and when sick. So-called ‘problem-animals’ were removed and relocated and bodies of dead gorillas were examined to determine their cause of death. Forty-three individuals were rehabilitated wild-born orphaned gorillas and eight gorillas were ex-situ captive-borns. Both sites were proclaimed protected areas before reintroduction procedures commenced. The study does not distinguish between the effects of the different interventions mentioned above.Study and other actions tested
Referenced paperKing T., Chamberlan C. & Courage A. (2012) Assessing initial reintroduction success in long-lived primates by quantifying survival, reproduction, and dispersal parameters: western lowland gorillas (Gorilla gorilla gorilla) in Congo and Gabon. International Journal of Primatology, 33, 134-149.
A controlled, site comparison study in 2006-2007 in tropical forest in Campeche State, Mexico found that stress levels of black howler monkeys Alouatta pigra that lived in protected areas were lower than of those living in highly fragmented and unprotected forest patches. Overall mean stress levels, measured by faecal glucocorticoid metabolite (FGM), of individuals living in unprotected habitats were about 20% higher (338.9 ng/g) than those of individuals living in protected habitats (266.2 ng/g). However, agonistic interactions among group members occurred at similar frequencies during sampling weeks in both habitats (protected: 57.1%, unprotected: 62%). Furthermore, seasonal variation in FGM concentrations was only detected in protected habitats. The results of this study were based on 371 faecal samples from 21 adults belonging to five groups, two from protected habitats and three from unprotected habitats. FGM concentrations were determined with radioimmunoassays and 1,200 h of agonistic within-group and between-group interactions were recorded in total.Study and other actions tested