Monday, August 3, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Background/Question/Methods
Overexploitation of game populations occurs across the humid tropics and is a significant threat to large-bodied mammalian and primate populations. Consequently, high levels of hunting can dramatically reduce large-bodied primate abundance in tropical forests, which is of conservation concern as globally, up to one third of primate species are threatened with extinction. In order to investigate the effects of harvesting and the role of unhunted reserve areas on primate populations, a spatially explicit, individual-based model was developed in a landscape that included hunted and unhunted areas. Alouatta seniculus, the red howler monkey, was used as a case study species; it is a large-bodied neotropical primate that can be heavily harvested due to its size. The influence of hunting intensity and the proportion of area dedicated to reserves on population persistence, population size, and harvest yields of red howler monkeys was tested.
Results/Conclusions
Results indicated that moderate hunting rates caused large declines in the hunted subpopulation numbers after 100 years, and, at all levels of hunting pressure, as a greater percentage of the landscape was hunted, the overall population size steadily declined. However, regardless of hunting pressure, the unhunted population maintained a fairly constant density, which allowed the overall population to persist. The population was quite resilient to extinction as long as reserves were maintained in the model, only in scenarios with no unhunted areas did the population go extinct. Finally, harvests (kgs of biomass) increased as a larger proportion of the overall area was hunted at a moderate hunting intensity and with increasing harvest intensities if less than 55% of the landscape was hunted. However, if more than 55% of the landscape was hunted at a high intensity, harvests were lower than those obtained from moderate levels of hunting and population sizes in reserve areas increased from baseline levels. This suggests that in landscapes with little reserve area, populations are less resilient to heavy exploitation which causes a decline in the harvest. The results from this study indicate that unhunted areas may be acting as important buffers in hunted landscapes, can enhance harvest rates, and can play an important role in population persistence. Furthermore, it appears that sustainable harvesting and population persistence is a function of both harvest rates and larger landscape level factors.
Overexploitation of game populations occurs across the humid tropics and is a significant threat to large-bodied mammalian and primate populations. Consequently, high levels of hunting can dramatically reduce large-bodied primate abundance in tropical forests, which is of conservation concern as globally, up to one third of primate species are threatened with extinction. In order to investigate the effects of harvesting and the role of unhunted reserve areas on primate populations, a spatially explicit, individual-based model was developed in a landscape that included hunted and unhunted areas. Alouatta seniculus, the red howler monkey, was used as a case study species; it is a large-bodied neotropical primate that can be heavily harvested due to its size. The influence of hunting intensity and the proportion of area dedicated to reserves on population persistence, population size, and harvest yields of red howler monkeys was tested.
Results/Conclusions
Results indicated that moderate hunting rates caused large declines in the hunted subpopulation numbers after 100 years, and, at all levels of hunting pressure, as a greater percentage of the landscape was hunted, the overall population size steadily declined. However, regardless of hunting pressure, the unhunted population maintained a fairly constant density, which allowed the overall population to persist. The population was quite resilient to extinction as long as reserves were maintained in the model, only in scenarios with no unhunted areas did the population go extinct. Finally, harvests (kgs of biomass) increased as a larger proportion of the overall area was hunted at a moderate hunting intensity and with increasing harvest intensities if less than 55% of the landscape was hunted. However, if more than 55% of the landscape was hunted at a high intensity, harvests were lower than those obtained from moderate levels of hunting and population sizes in reserve areas increased from baseline levels. This suggests that in landscapes with little reserve area, populations are less resilient to heavy exploitation which causes a decline in the harvest. The results from this study indicate that unhunted areas may be acting as important buffers in hunted landscapes, can enhance harvest rates, and can play an important role in population persistence. Furthermore, it appears that sustainable harvesting and population persistence is a function of both harvest rates and larger landscape level factors.
