Monitoring mammal populations for sustainable hunting
As part of a community-based conservation effort, monitoring the sustainability of hunting levels within the Pacaya-Samiria National Reserve, Peru, is proving successful in maintaining stable populations of animals taken as bush meat whilst ensuring the needs of the local Cocama Indian communities are met.
At first appearances, the attitudes of conservationists and indigenous communities towards the large mammals found in the Amazon basin seem at odds. Conventional approaches to conservation management have focussed on preserving wildlife by preventing access to protected sites for commercial hunters and local people alike. In contrast the local communities, who for centuries have utilised the rainforest for resources, are reliant upon the hunting of forest ungulates and other mammals for sustenance. Such opposing needs have led to confrontation and often violent conflict, and unsustainable levels of opportunistic hunting.
A community-based conservation approach
The Pacaya-Samiria National Reserve in the Loreto region of Peru is pioneering an alternative, community-based conservation strategy to manage the populations of large mammals within the rainforests. As the local Cocama Indian people want to protect their food sources, with support from NGOs these communities are working with the reserve authorities to ensure their hunting levels are leaving sufficient numbers of animals for the populations to be stable. Since this move away from a ‘parks without people’ management approach at the beginning of the 21st century, populations of tapir, agouti and other mammals within the reserve have rebounded.
Different reproductive strategies mean not all animals are equally suited as bush meat. Tapir, for example, produce only a single calf every two years, and so small populations increase slowly. Other mammals like peccary, agouti and red brocket deer, however, exhibit density-dependent rates of increase; when populations are below that of carrying capacity their rate of offspring production increases. Hunters have therefore shifted their focus to those species whose populations recover relatively quickly, and drastically reduced hunting of less suitable species.
Monitoring large mammal populations
The various communities have areas where they will not hunt based on cultural respect for ancestors, and these act as source areas that can replenish the more heavily hunted areas when population levels are reduced. Each year students from Operation Wallacea, in conjunction with the NGO FundAmazonia, survey both source (scarcely hunted) and sink (regularly hunted) areas to obtain population density estimates of large mammals within the Pacaya-Samiria National Reserve. For non-hunted areas, the population densities are used to approximate the current maximum carrying capacity (K) of the environment. The proportion of the population being taken for bush meat in hunted areas can then be estimated.
Hunters have shifted their focus to those species whose populations recover relatively quickly, and drastically reduced hunting of less suitable species
For mammals that are large, gregarious, conspicuous or that favour open habitats, population sizes can be estimated from direct observations. Line transects are used to survey ground-dwelling mammals like tayra, paca, black agouti and South America coati as well as primates such as howler monkeys and brown capuchins. The software programme DISTANCE is then used to estimate population densities from this data, based on the rate at which sightings decrease with distance from the transect.
To count rare, shy or elusive mammals or mammals that are predominantly crepuscular or nocturnal requires less direct means, such as the use of camera traps. From the frequency at which images are captured, counts of mammals such as red brocket deer, lowland tapir, giant anteater and collared and white-lipped peccary can be estimated.
Modelling sustainable hunting levels
Various models are used to determine the long-term impact on bush meat species of subsistence hunting by the local Cocama Indian people. These combine information on potential and actual population sizes, current hunting levels and life history characteristics of each mammal, such as number of offspring produced each year and development times. A common assessment of whether hunting levels are sustainable uses the stock recruitment model, which produces a maximum sustainable yield (MSY) estimate for a given animal based on its reproductive strategy and the carrying capacity of the environment. Only if population sizes are greater than the MSY is the current hunting level likely to be sustainable. For agouti and other rodents, peccaries and deer, all of which show density-dependent reproductive rates, the MSY in set at 60% of carrying capacity (K). For slower-reproducing animals such as tapir and many primates, the MSY is set at 80% of K.
A myriad of factors affect populations of bush meat species
Hunting alone is not the only threat to forest ungulates and other mammals however, with populations also vulnerable to intensive weather events, varying levels of predation and outbreaks of disease. For example, the ecology of the Pacaya Samiria National Reserve is driven by the dramatic and prolonged annual flooding that occurs as a result of seasonal rainfall changes over the Andes; as the water levels rise so the amount of available land decreases. In recent years the extent of the waters have become more extreme, with unprecedented high water levels in 2009, a prolonged drought period in 2010, and even higher flood waters in 2011 and 2012.
At the beginning of the 21st century hunting levels of collared peccary, white-lipped peccary and red brocket deer were sustainable and populations of these mammals were steady. However, the extreme variation in water levels have dramatically reduced terrestrial mammal populations, bringing the number of individuals closer to the minimum required for a population to be stable. In 2010 the diminished population of collared peccary meant hunting levels that had previously been sustainable were now putting the population at risk, with levels of hunting of the white-lipped peccary, red brocket deer and black agouti deemed unsustainable the following year. Once again, hunters from the local communities are actively implementing conservation strategies to ameliorate the decline in health of the populations of bush meat species. Density estimates will be monitored in coming years to confirm the efficacy of these actions.
Overall, the shift in conservation strategy within the Pacaya Samiria National Reserve to allow a limited amount of sustenance hunting by the local communities has been successful, resulting in a reduction in hunting pressure and a general increase in wildlife populations. By creating local management groups, the Cocama Indian people are no longer viewed as poachers but are integral to the long-term success of the Reserve, maintaining hunting at a sustainable level and preventing other groups from illegally exploiting the area.
Similarly, with the socio-economic benefits of such strategies becoming apparent, the attitudes of the indigenous people to the reserve authorities have changed. As impacts from extreme climatic events threaten the sustainability of local resource use, the collaborative efforts of the reserve authorities and the Cocama Indians, in combination with data collected from the field by voluntary organisations, will become increasingly important for conserving both the wildlife of the Reserve whilst ensuring the needs of the communities are met.