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The AfriCat Okonjima Predator Population Density Study : Phase 2

leopards mother and cub africatb2 camera trap leopards b

Preliminary results PHASE 2: Poort - Super Highway 16 Sep - 4 Nov 2015

The second block within the entire study area (20 000 ha) was monitored from the 16th September 2015 - 4th November 2015 and measures 3 242 hectares (32.42 km2) in size (Fig. 1). The block is situated in the south-east, east of the reserve and includes the main road (5.19 km) used to enter and leave the reserve.

The area consists of six water sources of which five are permanently installed and perennially accessible. The vegetation mainly consists of thorny bush - and scrub savannah in the northern part of the area and a mountainous area in the southern part with an altitudinal range from 1550 to 1860 meters above sea level.

Prey assemblage includes oryx (Oryx gazella), greater kudu (Tragelaphus strepsiceros) and common warthog (Phacochoerus africanus).

16 cameras were distributed throughout the area (Fig.2). Inter-trap distances ranged from 0.62 to 2.52 kilometers (1.59 ± 0.42) to increase the likelihood that no individual could move through the study area without being detected.
Due to the mountainous environment trapping stations in the southern part of the sampled area were spaced further apart than the pre-set distance of 1.5 kilometers (1.81 ± 0.61).

fig1 b2 map  study area

Fig. 1: Overview of study area. The 20 000 hectares study area was divided into 5 sub-blocks of approximately 4 000 hectares each and will be sampled subsequently for 50 consecutive days. The second sampling block (Poort - Super Highway), situated in the south-east of the reserve and measuring 3 242 hectares (blue), was monitored by 16 camera traps for 50 consecutive days.

 

(16th September - 4th November 2015).

The total sampling effort accumulated 753 trap nights and resulted in a total of 12 individual adult leopards (six females and six males) and four dependent juvenile leopards (≤ 18 months) that were captured a total of 69 times expanded over 50 trapping occasions. Capture frequencies ranged from 1 - 20 captures per individual leopard (4.75 ± 4.90) (Fig. 3). Thereby, the sequence of photographs per individual represents one capture event. No significant differences in female (5.5 ± 3.27) and male capture frequencies (5.16 ± 7.44) were found, but male leopards showed more variations (1 - 20 captures) within their demographic class than female leopards (2 - 10 captures).

Leopards were photographed at 14 out of 16 camera stations. Overall trap success (leopard activity index) for all 16 traps per 100 trap nights (frequency of leopards caught per 100 trap nights) was 10.1. Trap success per camera-trap station was 0.08 but differed significantly between single stations (SE ± 0.06) (Fig.4).

Eight out of the 12 captured adult leopards during the survey period were collared individuals. Three of the six captured males were un-collared individuals, while only one female was found to be un-collared.
Density was 4.9 leopards per 10 km2 within the second sampling block.

For leopards captured at at least three different trapping stations, cameras provided data on their minimum home range size. Minimal home range size obtained from camera trap data of the two female leopards captured at ≥ 3 trapping stations ranged from 1.14 to 3.28 km2. Male home range size (n = 2) varied between 1.14 and 18.6 km2. Minimal home range size of radio-collared individuals as displayed by the movement between camera stations will be compared to home range size established via the use of VHF-telemetry technology after completion of the entire study period of 250 days.

The dependent juvenile leopards (n = 4) that were recorded during the sampling period could be allocated to three collared females (Pp16, Pp17 and Pp6). The age of Pp 21 and Pp 22 was found to be < 12 months (approximately eight months and five months, respectively). Both cubs have exclusively been captured with their mother. Pp 23 and Pp 24 (both approx. 15 months of age) are both sub-adult cubs of Pp 6. Pp 24 was only captured once during the sampling period (together with Pp 6), while Pp 23 was captured alone (n = 1) and independently from Pp 6 (n = 1) (Fig. 6).

b2 camera trap 2 leopardsb2 camera trap leopards b2 camera trap leopards b2 camera trap leopards

Four juvenile leopards (≤ 18 months) were recorded during the second sampling block (16 September 2015 - 4 November 2015) ranging from approximately five months to 15 months of age. (A) Pp 17 with five months old cub (Pp 22). (B) Pp 6 with sub-adult cubs Pp 23 and Pp 24 (approximately 15 months of age). (C) Pp 16 with dependent cub Pp 21 (approximately eight months of age). (D) Pp 23 captured without its mother during one sampling occasion.

 

b2 camera trap leopardb2 camera trap leopard b2 camera trap leopards

Four un-collared individual leopards (three males, one female) were recorded within sampling block 2. (A) Pp 20 (male) was captured only once during the sampling period in the eastern corner of the reserve (2CT10). (B) Pp 7 (male) was caught three times on two different trapping stations (2CT5 and 2CT6) and was also captured in the first sampling block (Combretum - Okonjima Dam). (C) Pp 18 is the only un-collared female that was documented by the camera traps. She was captured three times at two different trap stations (2CT2 and 2CT3).

 

b2 camera trap leopardsb2 camera trap leopards b2 camera trap leopardsb2 camera trap leopards

Pp 19 - a collared male leopard (collared on 25 September 2014) - was the most captured individual within sampling block 2. He was captured on 20 occasions at 10 out of 16 trapping stations (see Fig. 5).

 

map closeup block 2 leopards

Fig. 2: Location of camera trap sites within the second monitored block. Inter-trap distances ranged from 0.62 to 2.52 kilometers (1.59 ± 0.42) to increase the likelihood that no individuals could move through the study area without being detected. The mountainous area didn’t allow for a continuous spacing of the cameras of approximately 1.6 kilometers, thus distances between varied more within this block compared to the previous sampled block (1.59 ± 0.27). The white area is displaying the 2 000 hectares lodge area that is surrounded by a predator-proof fence and thus, notionally inaccessible for leopards or other carnivores.

 

fig3 capture success block2

Fig. 3: Capture success of leopard demographics within the second sampling block. Each number on the x-axis refers to a positively identified leopard within the corresponding demographic class: F = female, M = male, C = cub. Data is ordered by the number of captures within the demographic class.

 

fig4 leopard activity index block2

Fig. 4: Trap success (leopard activity index) expresses the frequency of leopards caught per day per camera-trap station during the sampling period (trap events/trap nights). Trap success and standard error was calculated for all 16 camera stations distributed throughout the second study block.

 

fig5 home range block 2

Fig. 5: Minimal home range size obtained from camera trap data from the 16th September - 4th November 2015 for female (n=2) and male (n=2) leopards captured at least ≥ 3 camera stations during sampling period. Pp 19 Madiba (blue polygon) is occupying large areas of the sampled block. Home ranges of the females Pp16 Electra and Pp 6 Lundu as well as male leopard Pp 10 Jagu (white outline polygon) are overlapping with that of Pp 19.

 

fig6 capture frequencies block 2

 

Fig. 6: Capture frequencies of dependent juvenile leopards ≤ 18 months with and without mother during trap events.

 

Comparison BLOCK 1 (Combretum - Okonjima Dam) and BLOCK 2 (Poort - Super Highway)

Tab. 2: Summary statistics for photographic capture-recapture data on leopards in block 1 (Combretum - Okonjima Dam) and block 2 (Poort - Super Highway)

  Combretum - Okonjima Dam (Block 1) Poort - Super Highway (Block 2) 
Size 3 816 ha 3 212 ha
Number of camera trap stations 20 16 
Survey period 24 July - 11 September 2015  16 September - 4 November 2015
Sampling occasions (12 pm - 12 am) 50 50
Sampling effort (trap nights) 966 753
Total number of individuals caught 15 (six females, seven males, two juveniles) 16 (six females, six males, four juveniles)
Sex ration (F:M) 0.8:1 1:1
Total number of captures 87 76
Number of individual animals caught once 5 4
Number of individual animals caught more than once 11 12
Number of individual animals caught in previous block - 7
Leopard density per 10 km2 3.9 4.9

 fig 7 comparison leopards block 1 2

Fig. 7: Comparison block 1 and 2: (A) Overall trap success including all camera trap stations (frequency of leopard caught per 100 trap nights). (B) Total number of individual leopards captured during study period arranged within their demographic class.

 

block 2 fig 8 leopards comparison chart

Fig. 8: Cumulative number of individual leopards captured over time (n = 50 days) in the first (blue) and second sampling block (red).

 

The accumulation curve (Fig. 8) is showing the cumulative number of individual leopards encountered in block one and block two and the rate at which new individuals are discovered over time. The accumulation of new individuals increases rapidly within the first half of the sampling period and decelerates in the second half. The rate of new encounters is showing an asymptote at day 38 (block 1) and day 36 (block 2), respectively suggesting an approach of the true number of individuals occurring in the area.

 

Appendix

Tab. 2: Positively identified individuals within sampling block 1 and 2

ID # Individual Block 1 Block 2
Pp 1 Ishara x x
Pp 2 Shanti x  
Pp 3 MJ x  
Pp 4 Lila x x
Pp 5 Jo Jo x  
Pp 6 Lundu x x
Pp 7 Un-collared male x x
Pp 8 Bwana x  
Pp 9 Mafana x  
Pp 10 Jagu x x
Pp 11 Un-collared male x x
Pp 12 Un-collared male x  
Pp 13 Nkozi x x
Pp 14 Ishara's cub x  
Pp 15 Jo Jo's cub x  
Pp 16 Electra   x
Pp 17 Mafuta   x
Pp 18 Un-collared female   x
Pp 19 Madiba   x
Pp 20 Un-collared male   x
Pp 21 Electra's cub (female)   x
Pp 22 Mafuta's cub (male)   x
Pp 23 Lundu's cub 1 (female)   x
Pp 24 Lundu's cub 2 (male)   x
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