A new study using camera traps in mongabay.com’s open-access journal Tropical Conservation Science has surveyed the diversity of medium and large-sized predators in the San Juan-La Selva biological corridor in Costa Rica, whilst also demonstrating how alteration of habitat is affecting the use of this corridor.
A large amount of the land within the Costa Rican corridor is private, with many groups creating reserves or eco-lodges to alleviate the effects of small-scale agriculture. By monitoring the diversity of species and the frequency with which they use the corridor, conservationists can better understand the effects alteration of the landscape is having on the behavior and richness of species.
Tayras on camera trap. Photo courtesy of Cove et al.
The researchers set up camera traps across 16 sites in the fragmented corridor, within or adjacent to four different types of habitat—eco-lodge forest reserves, tree plantations/general reforestation, cattle ranches, or pineapple/agricultural plantations—to monitor which species are traveling through the corridors. The camera traps were set up low to the ground so species such as primates and arboreal marsupials, which rarely travel terrestrially, were not included in the species count. Camera traps were baited with a secured can of sardines, and in subsets, some small portions of carpet scented with cologne, to attract felid species.
In total, the model-averaged estimate for species richness was 20 species, roughly 5 species less than predicted. Species such as ocelots, tayras, white-nosed coatis, opossums and the nine-banded armadillo were found at each of the four sites monitored. Others including the northern tamandua were found only near pineapple plantations, and the Baird’s tapir was found adjacent to all the study areas except for those near pineapple plantations.
Top: pineapple plantation. Bottom: tapir caught on camera trap. Photos courtesy of: Cove et al.
The 20 species catalogued in the study represent only two thirds of the medium and large mammals native to that area, suggesting that the human disruption and conversion of the landscape is affecting the frequency with which some mammal species are seen in the corridor. Pineapple plantations showed the highest species richness, but other sites have more forest cover, and therefore a higher potential for connectivity between the different areas of land. Whilst the production of pineapples may support more medium-sized mammals, the fragmentations “severely limit[s] the habitat for large herbivorous/frugivorous mammals that are often responsible for maintain natural plant communities.” Moreover, the easily accessible roads into the corridor make the forest areas more open, putting species such as collared peccaries and pacas at risk to poachers and hunters.
Species that were either rarely or not at all found in this study, such as tapirs and jaguars, are usually those that hold highest interest for people, so further surveys need to be carried out to increase the detection of individuals, and to help the conservation of these areas by becoming flagship species. The fact that jaguars and other species were not spotted may just be an indicator of their true rarity in this area, where they exist in low numbers and are thus more elusive and difficult to detect.
The research paper concludes that although the pineapple plantations have the highest observed medium and large-sized mammal estimates, it doesn’t mean that the mammal community in these patches is healthy. The majority of these species were opportunists or invasive, which have “less community value” than more iconic species such as felids, Baird’s tapirs and peccaries. To better understand the effects of the fragmentation of the biological corridor, the scientists say further research has to be carried out to evaluate the effects of the agricultural expansion, farming, and the loss of connectivity between the different habitats. If the connectivity between the areas is reduced, migration of species between these will decrease, and as a result, local extinctions may be on the rise.
- Michael V. Cove, R. Manuel Spínola, Victoria L. Jackson, Joel C. Sáenz and Oliver Chassot. Integrating occupancy modelling and camera-trap data to estimate medium and large mammal detection and richness in a Central American biological corridor, 2013. Tropical Conservation Science Vol. 6(6): 781-795.
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