Logo

The AfriCat Okonjima Predator Population Density Study: Phase 4

p4 mafutaleopard

Preliminary results PHASE 4: Dam Lise - Buffalo Dam 26 January - 15 March 2016

The fourth block of the study area was monitored from the 26th January 2016 until 15th March 2016. The block is located in the north-eastern part of the reserve (Fig. 1) and is covering an area of 34.9 km2. The area is hosting four water reservoirs which are all artificially supplied with water during the dry season (April - October) and thus, perennially accessible. The area is mainly characterized by a thorny bush- and scrub savanna interspersed with patches of open grass savanna and a dry river system in the central part of the area. Elevation ranges between 1580 and 1640 meters above sea level.

Most common prey occurring in the area includes oryx (Oryx gazella), common eland (Tragelaphus eland), greater kudu (Tragelaphus strepsiceros) and common warthog (Phacochaerus africanus).

20 cameras were distributed throughout the area (Fig.2). Inter-trap distances ranged from 0.84 to 2.13 kilometers (1.47 ± 0.23) to increase the likelihood that no individual could move through the study area without being detected (Fig. 2).

p4 fig1 overview map

Fig. 1: Overview of study area. The 200 km2 hectares study area was divided into 5 sub-blocks of approximately 40 km2 each and will be sampled subsequently for 50 consecutive days. The fourth sampling block (Dam Lise - Buffalo Dam) is situated in the north-eastern part of the reserve and is measuring 34.9 km2 (orange). The survey area was monitored by 20 camera traps for 50 consecutive days (26th January - 15th March 2016).

p4 fig2 camera stations

Fig. 2: Location of camera trap sites in the third survey block. Inter-trap distances ranged between 0.84 and 2.13 kilometers (1.47 ± 0.23). A close inter-trap distance is supposed to increase the likelihood that in theory no individual is able to move in between trap sights without being detected on at least on camera.

leopardleopardleopard

We were able to monitor three new, un-collared individuals that didn’t appear on the cameras in one of the previous sampled block. Top: Pp 30: A young male that was captured 25 times on the cameras in the northern-central part of the study block. Bottom left: Pp 28 "Sefu" only appeared five times on cameras, as Pp 30 mainly in the northern-central part of the reserve. Bottom right: Pp 29 - a female of approximately 7 - 8 years was captured 11 times on the cameras. Based on camera trap data her range extends from the central part of the survey area until the northern boundary fence line (Fig. 5).

leopardleopardleopardleopardleopard

Five un-collared additional adult leopard (four males, one female) were recorded during the study period that have been previously captured in at least one of the previously sampled blocks. Top: Pp 11(male); middle left: Pp 27 (male); middle right: Pp 25 "Nuka" (male); bottom left: Pp 7 (male); bottom right: Pp 18 (female).

p4 electrap4 leopardp4 isaskiap4 nkozip4 madiba

Five out of the recorded 15 individuals were equipped with a VHF-radio collar: Top left: Pp 16 "Electra"; top right: Pp 17 "Mafuta"; Middle: Pp 26 "Isaskia"; bottom left: Pp 13 “Nkozi”; bottom right: Pp 19 "Madiba"

leopardp4 p21leopard

Two juvenile cubs were recording during the study period: Left: Pp 22; right: Pp 21 "Nandi"

 

Tab. 1: Summary statistics for photographic capture-recapture data on leopards in block 4 (Dam Lise - Buffalo Dam) highlighted in green and comparison to previously sampled block 1 (Combretum - Okonjima Dam) block 2 (Poort - Super Highway) and block 3 (Serenjima).

  Combretum - Okonjima Dam
(Block 1)
Poort - Super Highway (Block 2)  Serenjima
(Block 3)
Dam Lise - Buffalo Dam (Block 4)
Size 38.1 km2 32.1 km2 34.8 km2 34.9 km2
Number of camera trap stations 20 16  19 20
Survey period 24 July - 11 September 2015  16 September - 4 November 2015 10 November - 29 December 2015 26 January - 15 March
Sampling occasions (12 pm - 12 am) 50 50 50 50
Sampling effort (trap nights) 966 753 910 974
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) 15 (five females, eight males, two juveniles)
Sex ration (F:M) 0.8:1 1:1 0.8:1 0.625:1
Total number of captures 87 76 92 103
Number of individual animals caught once 5 4 1 12
Number of individual animals caught more than once 11 12 11 3
Number of individual animals caught in previous block - 7 9 12
Leopard density per 10 km2 3.9 4.9 3.4 4.3

The total sampling effort accumulated 974 trap nights and resulted in a total number of 15 captured leopards including 13 adult leopards (five females and eight males) and two dependent juvenile leopards (≤ 18 months). Leopards were captured a total of 103 times expanded over 50 trapping occasions. Capture frequencies ranged from 1 - 25 captures per individual leopard (6.8 ± 6.62) (Fig. 3). Thereby, the sequence of photographs per individual at one trap site represents one capture event. Male leopards showed a slightly higher capture frequency (8 ± 8.22) compared to female capture frequencies (7.2 ± 3.9) but showed more variations (1 - 25 captures) within their demographic class than female leopards (2 - 11 captures).

Five out of the 13 adult leopards captured during the survey period were fitted with VHF radio-collar (three females: Pp 16, Pp 17, Pp 26; two males: Pp 13 and Pp 19)

Leopards were photographed at all 20 camera stations. Overall trap success (leopard activity index) for all 20 traps per 100 trap nights (frequency of leopards caught per 100 trap nights) was calculated 10.6. Trap success per 100 trap nights per trapping station was calculated 0.53 but differed significantly between single stations (SE ± 0.31) (Fig.4). Density was calculated 4.3 leopards per 10 km2 within the fourth 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=4) within sampling block four ranged from 0.67 km2 to 7.76 km2 (2.57 ± 3.46). Male (n = 6) home range size varied between 2.82 km2 and 7.46 km2 (4.68 ± 2.01). 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.

p4 fig3 capture success

Fig 3: Capture success of leopard demographics within the fourth 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 each demographic class.


p4 fig4 leopard activity index

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 20 camera stations distributed throughout the fourth study block.


p4 fig5 min home ranges

Fig. 5: Minimal home range size obtained from camera trap data recorded between the 26th January and 15th March 2016 for female (n=4) and male (n=6) leopards captured at ≥ 3 camera stations during the sampling period. Females: Pp 26 Isaskia (pink line); Pp 29, un-collared (orange line); Pp 17 Mafuta (purple line); Pp 16 Electra (red line); males: Pp 7, un-collared (blue dashed line); Pp 28 Sefu, un-collared (black dashed line); Pp 30, un-collared (green dashed line); Pp 27, un-collared (yellow dashed line); Pp 11, un-collared (light green line); Pp 25 Nuka, un-collared (White dashed line)

 

 

Preliminary analysis of camera trap data recorded from 24th July 2015 - 15th March 2016

A preliminary analysis of camera trap data (based on the results of phase one, two and three) revealed the presence of 30 individual leopards. 360 active trap nights (expanded over 200 trapping occasions) resulted in a total of 358 leopard captures. Males (n=16) and females (n=14) occur in a nearly equal ratio (Fig. 6A). 58% of all recorded adult and sub-adult individuals (n=24) are fitted with a VHF-radio collar while 42 % were found to be un-collared individuals (excluding the six juvenile leopards ≤ 18 months).

More males were positively identified that were not equipped with a radio collar (n=8) 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 two females without a radio collar were recorded (Fig. 6B). Juvenile leopards ≤ 18 months (n=6) were included in sex ratio calculations but were excluded from the analysis of collared and un-collared individuals.

Leopard density for the entire sampled area (140 km2) was calculated 2.1 leopards per 10km2.


p4 fig6 ratio male female leopards

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)


p4 fig7 accumulation curve

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) third (green) and fourth phase (yellow). The encounter rate of new individuals increases rapidly within the first third of the sampling period in all four 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 during the last third of the sampling period suggesting an approach of the true number of individuals occurring in the area. The detection rate of new individuals in block four is highest during the first third and is decelerating at day 19. 14.5 individuals (±1.73) were detected per sampling block.


p4 fig8 female homeranges

Fig 8: Minimal home ranges of female leopards captured at ≥ two blocks during phase one, two, three and four: Pp 1 (Ishara): light purple line; Pp 2 (Shanti): white line; Pp 3 (MJ): orange line; Pp 4 (Lila): pink line; Pp 5 (Jo Jo): yellow line; Pp 6 (Lundu): white line; Pp 16 (Electra): red line; Pp 17 (Mafuta): purple line; Pp 18 (un-collared): dark red; Pp 26 (Isaskia): light pink line; Pp 29 (un-collared): light orange line.


p4 fig9 male homeranges

Fig 9: Minimal home ranges of male leopards captured at ≥ two blocks during phase one, two, three and four: Pp 8 (Bwana): red line; Pp 9 (Mafana): yellow line; Pp 10 (Jagu): dark blue line; Pp 11 (un-collared): dark green line; Pp 12 (un-collared): green line; Pp 13 (Nkozi): light blue line; Pp 19 (Madiba): grey line; Pp 25 (un-collared): white line; Pp 27 (un-collared): black line; Pp 28 (un-collared): orange line; Pp 30 (un-collared): dark blue.

 

Appendix

Tab. 2: Positively identified individuals within sampling block 1, 2, 3 and 4.

ID # Individual Sex
Block 1 Block 2 Block 3
Block 4
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   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 x
Pp 12 Un-collared male Male x   x  
Pp 13 Nkozi Male x x x x
Pp 14 Ishara's cub Female x      
Pp 15 Jo Jo's cub Male x      
Pp 16 Electra Female   x   x
Pp 17 Mafuta Female   x x x
Pp 18 Un-collared female Female   x x
Pp 19 Madiba Male   x   x
Pp 20 Un-collared male Male   x    
Pp 21 Electra's cub Female   x   x
Pp 22 Mafuta's cub Male   x x x
Pp 23 Lundu's cub 1 Female   x    
Pp 24 Lundu's cub 2 Male   x    
Pp 25 Un-collared Male     x x
Pp 26 Isaskia Female     x x
Pp 27 Un-collared Male     x x
Pp 28 Un-collared Male       x
Pp 29 Un-collared Female       x
Pp30 Un-collared Male       x
Copyright AfriCat All rights reserved Copying of images is prohibited