Miranda Davis

Research

Introduction

Carnivores, and particularly felids, have long been singled out as potential keystone species which exert a critical stabilizing influence on their respective communities and yet very little is known about carnivore ecology due to the difficulties involved in conducting research on such rare, wide-ranging species (Terborgh 1988, Terborgh et al. 1999, Miller et al. 2001). Small felids such as the ocelot (Leopardus pardalis) can prove even more challenging to conserve than their large cousins: they are difficult to study not only due to their elusive nature, but also because they may be overlooked in research projects due to their geographic overlap with other, larger and better known flagship felid species such as jaguars (Panthera onca).

An ocelot captured by the Reconyx digital camera system

Due to the highly competitive nature of felids, both within and between species, sympatric carnivore communities can potentially be upset by population shifts among its members. For example, cheetahs and wild dogs are influenced by lions where high lion numbers result in reduced cheetah recruitment (Kelly and Durant 2001) and the extirpation of wild dogs (Ginsberg et al. 1995, Creel and Creel 1996) -- even within protected areas. Wildlife reserves established based upon the ecological needs of one flagship predator, therefore, may not be sufficient to protect the other carnivore species in the community. An understanding of the interplay between the densities of sympatric carnivores is necessary to enact conservation measures which simultaneously preserve both small and large predators, and maintain the ecological integrity of the community.

Brushing off the daily dirt

Mesopredator release theory proposes that with the decline of large predators, smaller "mesopredators" experience less competition and increase in abundance resulting in a cascade of population shifts down the food chain (Brown and Wilson 1956, Crooks and Soule 1999). The findings of several studies support this theory but research has largely been restricted to temperate communities of small carnivores (Crooks and Soule 1999, Gehrt and Clark 2003, Schmidt 2003) and to the guilds of large predators in the open landscapes of Africa (Kelly et al. 1998, Durant et al. 2004). Terborgh (1990) suggests that the effects of carnivores on their communities are equally, if not more, pervasive in the neotropics even though the direct observation of interactions in these dense forests is often impossible. Terborgh (1992) detailed how ocelots likely benefited from an increase in prey due to a low density of top predators and, recently, Moreno et al. (2006) showed that ocelots exhibited changes in diet due to mesopredator release in the absence of jaguars. But to date, all of these studies have taken place on Barro Colorado Island a 6 km² island created by the construction of the Panama Canal.

This raises doubt as to whether mesopredator release is widely applicable across the neotropics. My project will investigate the ecology of an understudied small carnivore, the ocelot, and its density in relation to the populations of larger sympatric felids, namely the jaguar and puma (Puma concolor).

Objectives:

1.    Estimate the densities of ocelots across five sites in Belize.

2.    Compare the densities of ocelots to those of other, sympatric predators, namely the jaguar and the puma, across the five reserves to examine the ecology of predator co-existence and potential effects of mesopredator release.

3.    Examine the correlates of ocelot camera-trap success and density across and within each site including: climatic conditions, landscape characteristics, microhabitat features and trap success of other felids, prey species, and humans.


Miranda collects habitat data in the vicinity of a camera trap station

Methods and Analysis

Remote camera surveys will be used to estimate the densities of ocelot populations across five sites in Belize (the Cockscomb Basin Wildlife Sanctuary, the Mounatain Pine Ridge Forest Reserve, the Gallon Jug/Rio Bravo Conservation Area, the Golden Stream Corridor Reserve and the Chiquibul Forest Reserve and National Park) known from previous remote cameras studies to contain differing densities of jaguars (ranging 3.1 - 11.4 per 100km²; Miller per comm.; Kelly per comm.). If mesopredator release occurs in this predator community ocelot densities should be higher in areas of lower jaguar and/or puma densities. The camera surveys will follow standardized techniques found to be successful at trapping ocelots, jaguars, and pumas in previous studies (Silver et al 2004, Maffei et al 2005, Dillon and Kelly In press). Jaguar camera trapping surveys have been already established at the four sites. Within these grids, smaller nested grids for the estimation of ocelot density will be established following Dillon and Kelly (In press) in order to accommodate the smaller home ranges maintained by ocelots. Cameras will be operational for at least 60 days at each site. Jaguars and ocelots will be identified by their distinct spot patterns while pumas will be identified using a variety of characteristics including individual differences such as scars, tail rings, undercoat patterns and other subtle markings (Kelly et al. under review). Data will be analyzed in the computer program CAPTURE which will calculate abundance estimates based on the number of individuals captured and the frequency with which they are recaptured (Otis et al. 1978, White et al. 1982, Rexstad and Burnham 1991). The ocelot, jaguar and puma abundances produced by this program will then be divided by the effective area (km²) sampled to generate density estimates. These densities will be compared at each study site to determine the influence of top predators on ocelots.

mprmap

Map of the camera grid established in the Mountain Pine Ridge Forest Reserve (depicted in yellow). Two cameras were located just outside reserve boundaries on forested private land. The camera survey ran from June to August of 2007. Each Camera station is represented by one red dot and is made up of 2 remote sensing cameras set up on opposing sides of roads or trails. To the south you can see the Chiquibul Forest Reserve and National Park that contains broadleaf forests where ocelots have been recorded at much higher densities than are found in the pine forest reserve.

Correlatives of trap success will be considered at each trapping site in order to identify niche shifts which may be related to variations among the population densities of these three carnivores. The trap success for ocelots, jaguars and pumas will be measured as the number of captures at each separate camera station and across all camera stations within the five studies sites. From this it is possible to determine through linear regression of trap success if ocelots appear to be spatially avoiding the larger carnivores. Additionally, estimates will be made of the trap success of different species and compared to ocelot trap success and density.

Having fallen into a cenote, Miranda puts on a brave face

Lastly, habitat will be characterized across and within the studies using GIS in combination with manual habitat sampling. Each of the trapping stations will be marked using a GPS unit and those points will plotted on pre-existing digital vegetation maps of the area. This will allow the measurement of landscape features such as the distance to nearest water source, elevation, slope and aspect at each camera station and to measure the percent composition of land cover around each trap location. Vegetation within a 50 meter radius of each camera station will be sampled from the ground. This investigation will concentrate on aspects of habitat structure which ocelots are known to be sensitive to, namely understory thickness and canopy cover (Ludlow and Sunquist 1987, Haines et al. 2006).

Miranda and a local bodybuilder check cameras in the field

These data will be examined to help quantify the characteristics of the five study sites and to identify possible correlates of the previously determined felid densities at those locations. Significant correlations may be indicative of what landscape features lead to higher or lower densities of these three species across sites and, therefore, influence levels of competition and the effects of mesopredator release within this predator guild. Secondly these data will be analyzed for correlation with the individual measure of trap success at each trapping station within each site. Any significant relationships may help us discover if competition or avoidance between felid species is resulting in habitat niche differentiation and if ocelots are relegated to lower quality habitat (featuring less appealing vegetation or lower prey abundances) by their desire to avoid larger felids.

On a wider scale this may demonstrate how small predators in general could be affected when reserves are designed purely to maintain high densities of top carnivore species.

Field research in Belize will be completed in two separate periods. I will collect data at the Mountain Pine Ridge Reserve during June, July, and August of 2007 and will complete the research at the other four sites from January to August 2008. Data will be analyzed during the fall of 2008.

References:

Brown, W. L., and E. O. Wilson. 1956. Character displacement. Systematic Zoology 5: 49-64.

Creel, S., and N. M. Creel. 1996. Limitation of African wild dogs by competition with larger carnivores. Conservation Biology 10: 526-538.

Crooks, K. R., and M. E. Soule. 1999. Mesopredator release and avifaunal extinctions in a fragmented system. Nature 400: 563-566.

Dillon, A., and M. J. Kelly. In press. Ocelot activity, trap success, and density in Belize: the impact of trap spacing and distance moved on density estimates.

Durant et al. Factors affecting life and death in Serengeti cheetahs: Environment, age, and sociality. Behavioral Ecology 15: 11 -22.

Gehrt, S. D. and W. R. Clark. 2003. Raccoons, coyotes and reflections on the mesopredator release hypothesis. Wildlife Society Bulletin 31: 836-842.

Ginsberg et al. 1995. Local extinction in a small and declining population: wild dogs in the Serengeti. Proceedings: Biological Sciences 262: 221-228.

Haines et al. 2006. First ocelot (Leopardus pardalis) monitored with GPS telemetry. European Journal of Wildlife Research 52: 216-218.

Kelly et al. 1998. Demography of the Serengeti cheetah (Acinonyx jubatus) population: the first 25 years. Journal of Zoology 244: 473-488.

Kelly et al. Under review. Estimating puma densities from camera trapping across three study sites: Bolivia, Argentina, Belize. Journal of Mammalogy.

Ludlow M. E. and M. E. Sunquist. 1987. Ecology and behavior of ocelots in Venezuela. National Geographic Research 3: 447-461.

Maffei et al. 2005. Ocelot (Felis pardalis) population densities, activity, and ranging behavior in the dry forests of eastern Bolivia: data from camera trapping. Journal of Tropical Ecology 21: 349-353.

Miller et al. 2001. The importance of large carnivores to healthy ecosystems. University of Michigan, School of Natural Resources.

Moreno et al. 2006. Competitive release in diets of ocelot (Leopardus pardalis) and puma (Puma concolor) after jaguar (Panthera onca) decline. Journal of Mammalogy 87: 808-816.

Otis et al. 1978. Statistical- inference from capture data on closed animal populations. Wildlife Monographs: 7-135.

Rexstad, E., and K. P. Burnham. 1991. User's guide for interactive program CAPTURE: Abundance estimation of closed animal populations, Colorado Cooperative Fish and Wildlife Research Unit, Fort Collins, CO; Colorado, United States.

Schmidt, K. A. 2003. Nest predation and population declines in Illinois songbirds: A case of mesopredator effects. Conservation Biology 17: 1141-1150. Terborgh J. 1988. The big things that run the world -- a sequel to E. O. Wilson. Conservation Biology 2: 1988.

Terborgh J. 1990. The role of felid predators in neotropical forests. Vida Silvestre Neotropical 2: 3-5.

Terborgh J. 1992. Maintenance of diversity in tropical forests. Biotropica 24: 283-292.

Terborgh et al. 1999. The role of top carnivores in regulating terrestrial ecosystems. Wild Earth: 42-56.

White et al. 1982. Capture-recapture and Removal Methods for Sampling Closed Populations Los Alamos National Laboratory, Los Alamos, USA.

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