PILOT SURVEY USING CAMERA TRAPS; (Reconyx Rapidfire camera RM45) Introduction Estimating the population abundance of solitary, cryptic carnivores is a challenge for biologists and most studies have employed a variety of direct sampling measures that yield unreliable estimates. Camera-trap method developed by Karanth & Nichols (1998) to calculate tiger (Panthera tigris) densities in India, has emerged as an accurate and cost-effective method for estimating individually recognizable felid species. Ecological monitoring department (EMD) has therefore adopted the use of reconyx IR 45 infrared camera traps to assay carnivore activity and abundance in Ol Pejeta Conservancy (OPC). The main objective is to estimate the density of sympatric carnivore species that are individually recognizable from spot patterns; spotted hyena, cheetah and leopard. These carnivores especially hyenas are also the apex predator in OPC, fulfilling a vital role in the ecosystem. This data therefore, will generate accurate information especially on the status of the hyena population in OPC which is critical for establishing a management plan that is economically and ecologically sustainable. Method The conservation area was stratified into three blocks and divided into 2 km2 grids (standard spatial sampling 2 x 2 grids). The centroid of each grid was located using Arcmap 10, and designated as potential trap points (Figure 1). Actual trap points were strategically located at ecologically suitable sites within 50 meters from the centroid, typically near a road or active game trail. The camera traps were located approximately 2 km apart to decrease the likelihood that an individual could move through the block without being detected. Hence, there were at least two camera-trap stations in each grid ensuring that every individual using the survey block had an opportunity to be captured.
Figure 1: Camera trapping points
Density estimation of sympatric carnivores; Compiled by Caroline and Haron
As part of pilot survey, cameras were deployed in the Eastern sector and left active for 10 days; trapping intervals of 24 hours. Camera traps were mounted on metallic posts and some tied on trees which were selected carefully considering spoor, sightings, kills, habitat, road and game path networks (Plate 1).
Plate 1: Deploying cameras in the field A total of 38 camera traps (two camera traps mounted on posts approximately 6–10 m apart at each trap point, to photograph both sides of carnivores passing in between thus allow unambiguous identification of spot patterns necessary for individual identification). Sampling will take place sequentially in the three blocks of 19, 22 and 31 paired camera stations for Eastern, Northern and Southern blocks respectively. From the sequential camera arrays all carnivore photographs will be independently assessed and later develop regular capture histories matrix to represent captures during the 10 days sampling interval. Consequently the individual matrices will be joined into a detection matrix of each individual geo-referenced to a trap location which can be used to estimate densities using the software package DENSITY 4.4. Preliminary results Of the nineteen camera stations, only four carnivores were captured with the lion and leopard being re-captured on two occasions. Other carnivores also captured during the period include hyena and silver backed jackal (see plate 2 a – d).
a) Camera located at Oryx plain with female lion showing its whisker spots though difficult to discern the spots
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Density estimation of sympatric carnivores; Compiled by Caroline and Haron
b)Leopard (Panthera pardus)
c) Spotted hyena (Crocuta crocuta)
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Density estimation of sympatric carnivores; Compiled by Caroline and Haron
d) Silver backed jackal (Canis mesomelas) Plate 2 a – d: Carnivores captured Several images of other species captured included; Black rhino, plain zebra, grevy zebra, buffaloe, infant impala, elephant calf, aardvark among other species (see plate 3 a - g).
a) Black rhino (Dicerous bicornis)
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Density estimation of sympatric carnivores; Compiled by Caroline and Haron
b) Plain zebra (Equus burchelli)
c) Grevy zebra (Equus grevyi)
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Density estimation of sympatric carnivores; Compiled by Caroline and Haron
d) Buffalo (Syncerus caffer)
e) Elephant calf (Loxodonta africana)
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Density estimation of sympatric carnivores; Compiled by Caroline and Haron
f) Infant Impala (Aepyceros melampus)
g) Aardvark (Orycteropus afer) Plate 3 a - g: Other species captured
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Density estimation of sympatric carnivores; Compiled by Caroline and Haron
Cameras located on dense bush land captured more diverse animals compared to those in open grasslands. From the photographs it is clear that most carnivores were captured in the evening to night hours and early mornings. Also, two cameras (cameras E13 and R19) were found not mounted in position probably interrupted by elephants.
Challenge on camera traps Inadequate camera stands posed a major challenge especially on trap points that were on open grounds with few or no trees to mount the cameras. In addition, given the lack of cages the cameras are at risk (Plate 4). Despite raising a work requisition 14528 on 27th February 2012; requesting for construction of 50 camera trap cages, we have only received 10 from workshop.
Plate 4: A lion pulling the cable from a camera mounted on a tree In regards to camera settings we found that rapid fire setting was very sensitive since any slight movement of vegetation (e.g. by wind) triggered the cameras to take photographs. This however, will be solved by changing the sensitivity from high to medium.
Conclusion and recommendations Camera-trap surveys, when combined with capture–recapture models, are an accurate and cost-effective method for estimating the abundance of individually identifiable carnivore species although we were not quite successful in capturing many predators during the ten days survey. This might be attributed to a brief sampling effort of only ten days; we therefore recommended a 21 day sampling interval and also observe for tracks and signs of predators within the 50 meter radius from the centroid.
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