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The AfriCat Okonjima Predator Population Density Study : Phase 3

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Preliminary results PHASE 3: Serenjima 10 November - 29 December 2015

The third block of the study area was monitored from the 10th November 2015 until 29th December 2015. The block is located in the central-western part of the reserve (Fig. 1) and is covering an area of 34.8 km2. The area is hosting six water reservoirs of which two are artificially supplied with water and thus, perennially accessible. The area is characterized by an open grass savanna which is bordering block one in the south and a thorny bush - and scrub savanna covering the majority of the region. Elevation ranges between 1584 and 1630 meters above sea level. Due to a seasonal climate with the rainy season between October and March, the area received approximately 80 mm of precipitation during the sampling period.
Most common prey occurring in the area includes blue wildebeest (Connochaetes taurinus), common impala (Aepyceros melampus), common warthog (Phacochaerus africanus) and oryx (Oryx gazella).

19 cameras were distributed throughout the area (Fig.2). Inter-trap distances ranged from 1.12 to 2.37 kilometers (1.54 ± 0.31) to increase the likelihood that no individual could move through the study area without being detected.

fig1 overview study area leopards

Fig. 1: Overview of study area. The 200 km2 study area was divided into 5 sub-blocks of approximately 40 km2 each and will be sampled subsequently for 50 consecutive days. The third sampling block (Serenjima) is situated in the central-western part of the reserve and is measuring 34.8 km2 (yellow). The survey area was monitored by 19 camera traps for 50 consecutive days (10th November - 29th December 2015).

 

fig2 location camera traps

Fig. 2: Location of camera trap sites in the third survey block. Inter-trap distances ranged between 1.12 and 2.37 kilometers (1.54 ± 0.31) to increase the likelihood that no individual could move through the study area without being detected.

 

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Pp 4 ("Lila") showed the highest capture frequency (n=23) during the survey period. The female leopard was photographed at seven out of 19 trapping stations. Pp 4 is one of the six leopards captured in block three that is equipped with a radio collar. Pp 4 was fitted with a VHF-radio collar in July 2014.

 

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Five un-collared adult leopards (one female and four males) were recorded in block three of which three have been already captured previously in block one and/or two. (A) Pp 18 (female) was captured twice during the sampling period and was previously recorded in block two. (B) Pp 25 (male) appeared 12 times on eight different camera stations. Based on camera trap appearances he is occupying a large territory in the eastern part of the block (Fig. 5). (C) Pp 27 (male) appeared for the first time on the cameras during the entire study. He was captured a total of eight times in block three. (D) Pp 12 (male) was captured five times during the initial part of phase three. (E) Pp 11 (male) was only captured once during phase three, but was previously recorded in block one and two.

 

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Six of the 12 recorded leopards in block three were equipped with a VHF-radio collar including Pp 17 Mafuta (A), Pp 26 Isaskia (B), Pp 5 Jo Jo (C), Pp 9 Mafana (D) and Pp 13 Nkozi (E).

 

Tab. 1: Summary statistics for photographic capture-recapture data on leopards in block 3 (Serenjima) highlighted in green and comparison to previously sampled block 1 (Combretum - Okonjima Dam) and 2 (Poort - Super Highway)

  Combretum - Okonjima Dam (Block 1) Poort - Super Highway (Block 2)  Serenjima
(Block 3)
Size 3 816 ha 3 212 ha 3 480 ha
Number of camera trap stations 20 16  19
Survey period 24 July - 11 September 2015  16 September - 4 November 2015 10 November - 29 December 2015
Sampling occasions (12 pm - 12 am) 50 50 50
Sampling effort (trap nights) 966 753 910
Total number of individuals caught 15 (six females, seven males, two juveniles) 16 (six females, six males, four juveniles) 12 (five females, six males, one juvenile)
Sex ration (F:M) 0.8:1 1:1 0.8:1
Total number of captures 87 76 92
Number of individual animals caught once 5 4 1
Number of individual animals caught more than once 11 12 11
Number of individual animals caught in previous block - 7 9
Leopard density per 10 km2 3.9 4.9 3.4

The total sampling effort accumulated 910 trap nights and resulted in a total number of 12 captured leopards including 11 adult leopards (five females and six males) and one dependent juvenile leopards (≤ 18 months). Leopards were captured a total of 92 times expanded over 50 trapping occasions. Capture frequencies ranged from 1 - 23 captures per individual leopard (7.66 ± 6.01) (Fig. 3). Thereby, the sequence of photographs per individual at one trap site represents one capture event. Female leopards showed a higher capture frequency (10.0 ± 8.15) compared to male capture frequencies (6.66 ± 3.61) and showed more variations (2 - 23 captures) within their demographic class than male leopards (1 - 12captures).

Six out of the 11 adult leopards captured during the survey period were fitted with VHF radio-collar (four females: Pp 4, Pp 26, Pp 5 and Pp 17; two males: Pp 9 and Pp 13)
Leopards were photographed at 17 out of 19 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 calculated 10.2. Trap success per 100 trap nights per trapping station was 0.53 but differed significantly between single stations (SE ± 0.41) (Fig.4). Density calculated is 3.4 leopards per 10 km2 within the third sampling block.

For leopards captured at at least three different trapping stations, cameras provided data on their minimum home range size (Fig. 5). Minimal home range size obtained from camera trap data for female leopards captured at ≥ 3 trapping stations (n=3) ranged from 2.38 km2 to 7.5 km2 (5.22 ± 2.60). Male (n = 5) home range size varied between 0.8 km2 and 9.19 km2 (5.22 ± 2.95). 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.

fig1 capture sucess serenjima

Fig. 3: Capture success of leopard demographics within the third 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 are ordered by the number of captures within the demographic class.

 

fig4 leopard activity index serenjima

Fig. 4: The trap success (leopard activity index) per trapping station expresses the frequency of leopards caught per 100 days per camera trap station during the sampling period (trap events/trap nights*100). Trap success and standard error were calculated for all 19 camera stations distributed throughout the third study block.

 

fig5 home ranges serenjima

Fig. 5: Minimal home range size obtained from camera trap data recorded between the 10th November and 29th December 2015 for female (n=3) and male (n=5) leopards captured at ≥ 3 camera stations during the sampling period. Females: Pp 26 Isaskia (orange dashed line), Pp 4 Lila (purple line), Pp 5 Jo Jo (red line); males: Pp 25, un-collared (yellow line), Pp 13 Nkozi (black dashed line), Pp 12, un-collared (white dashed line), Pp 9 Mafana (blue dashed line), Pp 12, un-collared (light green line)

 

Preliminary analysis of camera trap data recorded between 24th July - 29th December 2015
A preliminary analysis of camera trap data (based on the results of phase one, two and three) revealed the presence of 27 individual leopards. 2629 active trap nights (expanded over 150 trapping occasions) resulted in a total of 255 leopard captures. Males (n=14) and females (n=13) occur in a nearly equal ratio (Fig. 6A). 14 individuals that were recorded during the study period are fitted with a VHF-radio collar while only half of the captured adult and sub-adult leopards (n=7) were found to be un-collared individuals (excluding juvenile leopards ≤ 18 months). More males were positively identified that were not equipped with a radio collar (n=6) compared to the number of males fitted with a radio collar (n=5). In contrast, the majority of females detected were collared individuals with known identity (n=9), while only one female was without a radio collar (Fig. 6B). Juvenile leopards ≤ 18 months (n=6) were included sex ratio calculations but were excluded from the analysis of collared and un-collared individuals. Leopard density for the entire sampled area (105.2km2) was calculated 2.5 leopards per 10km2.

 

fig6 ratio serenjima

Fig. 6: Ratio of males and females in percentage [%]. (A) Share of males and female leopards recorded during the study period including juvenile leopards. (B) Share of adult and sub-adult males and females recorded during the study period fitted with a VHF-radio collar and without (excluding juvenile leopards ≤ 18 months)

 

fig7 accumulation curve serenjima

Fig. 7: The accumulation curve is showing the cumulative number of individual leopards and the rate at which new individuals are discovered over time (n=50 days) for the first (blue), second (red) and third phase (green). The encounter rate of new individuals increases rapidly within the first third of the sampling period in all three blocks and is decelerating in block one and two during the second third. While the detection rate in block three is approaching an asymptote in the second third already, block one and two reaches an asymptote on the last third of the sampling period suggesting an approach of the true number of individuals occurring in the area. 14.3 individuals (±2.08) were detected per sampling block.

 

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Fig 8: Minimal home ranges of individuals captured at ≥ two blocks during phase one, two and three: Pp 12 (male, un-collared): light green line; Pp 5 (Jo Jo, female): red line; Pp 4 (Lila, female): Pp 9 (Mafana, male): blue dashed line; purple line; Pp 13 (Nkozi, male): black dashed line; Pp 17 (Mafuta, female): light blue dashed line; Pp 18(female, un-collared): light yellow line; Pp 10 (Jagu, male): white line; Pp 11 (male, un-collared): white dashed line; Pp 6 (Lundu, female): orange line; Pp 1 (Ishara, female): yellow dashed line.

 

Appendix

Tab. 2: Positively identified individuals within sampling block 1 and 2 and 3.

ID # Individual Sex Block 1 Block 2 Block 3
Pp 1 Ishara Female x x  
Pp 2 Shanti Female x    
Pp 3 MJ Female x    
Pp 4 Lila Female x x x
Pp 5 Jo Jo Female x   x
Pp 6 Lundu Female x x  
Pp 7 Un-collared male Male x x  
Pp 8 Bwana Male x    
Pp 9 Mafana Male x   x
Pp 10 Jagu Male x x  
Pp 11 Un-collared male Male x x x
Pp 12 Un-collared male Male x   x
Pp 13 Nkozi Male x x x
Pp 14 Ishara's cub Female x    
Pp 15 Jo Jo's cub Male x    
Pp 16 Electra Female   x  
Pp 17 Mafuta Female   x x
Pp 18 Un-collared female Female   x
Pp 19 Madiba Male   x  
Pp 20 Un-collared male Male   x  
Pp 21 Electra's cub Female   x  
Pp 22 Mafuta's cub Male   x x
Pp 23 Lundu's cub 1 Female   x  
Pp 24 Lundu's cub 2 Male   x  
Pp 25 Un-collared Male     x
Pp 26 Isaskia Female     x
Pp 27 Un-collared Male     x
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