The AfriCat Okonjima Predator Population Density Study: Phase 5
12 Aug The AfriCat Okonjima Predator Population Density Study: Phase 5
Preliminary results PHASE 5: Eland Dam – North Dam 23 March – 11 May 2016
The fifth block of the study area was monitored from the 23rd March 2016 until 11th May 2016. The block is located in the north-western part of the reserve (Fig. 1) and is covering an area of 44.7 km2. The area is hosting three water reservoirs which are 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 newly opened patches of open grass savanna. Elevation ranges between 1580 and 1640 meters above sea level.
Most common prey occurring in the area includes oryx (Oryx gazella), plain zebra (Equus quagga), common eland (Tragelaphus eland) and common warthog (Phacochaerus africanus).
20 cameras were distributed throughout the area (Fig.2). Inter-trap distances ranged from 1.3 to 2.3 kilometers (1.60 ± 0.23) to increase the likelihood that no individual could move through the study area without being detected (Fig. 2).
Fig. 1: Overview of study area. The 200 km2 study area was divided into 5 sub-blocks of approximately 40 km2 each which were sampled subsequently for 50 consecutive days. The fifth sampling block (Eland Dam – North Dam) is situated in the north-western part of the reserve and is measuring 44.7 km2 (light green). The survey area was monitored by 20 camera traps for 50 consecutive days (23 March – 11 May 2016).
Fig. 2: Location of camera trap sites in the fifth survey block. Inter-trap distances ranged between 1.3 and 2.3 kilometers (1.60 ± 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 one camera.
Eight un-collared adult and sub-adult leopards were positively identified during the sampling period of which four individuals appeared on the cameras for the first time and haven’t previously been detected in any other sampling block.
Top left Pp 31: A sub-adult male that appeared 21 times on the cameras and whose range is extending over the central part of the study block. Top middle Pp 32: A female leopard, detected 19 times on camera. Her range is overlapping Pp 31’s area to a large extent (Fig. 5).
Top right: The relation between Pp 31 and Pp 32 can’t be entirely clarified but both individuals have been seen together on cameras during a few occasions (n=5). Bottom left Pp 33: A female leopard that is accompanied by a dependent cub (Pp 35). Her range mainly covers the northern part of the sampling block. Bottom right Pp 34: Another female leopard that appeared regularly (n=15) on the cameras. Her range is strongly overlapping with those of Pp 31 and Pp 32.
Another four un-collared adult leopard (three males, one female) were recorded during the sampling period that have been captured in at least one of the previously four sampled blocks. Top left Pp 25 “Nuka” (male); top right Pp 28 “Sefu” (male); bottom left: Pp 29 (female); bottom right Pp 30 (male).
Only three of the recorded 13 individuals were equipped with a VHF-radio collar: Top left Pp 17 “Mafuta” (female) was only captured once during the sampling period; top right Pp 26 “Isaskia” (female); bottom Pp 13 “Nkozi” (male)
Two juvenile leopards (≤18 months) were recorded during the study period. While Pp 22 (middle) (male) already appeared on the cameras in block two, three and four, Pp 35 (left) (male) exclusively occurred in block number five. Right: Pp 35 captured together with its mother Pp 33.
Tab. 1: Summary statistics for photographic capture-recapture data on leopards in block 5 (Eland Dam – North Dam) highlighted in green and comparison to previously sampled block 1 (Combretum – Okonjima Dam) block 2 (Poort – Super Highway), block 3 (Serenjima) and block 4 (Dam Lise – Buffalo Dam).
|Combretum – Okonjima Dam
|Poort – Super Highway (Block 2)||Serenjima
|Dam Lise – Buffalo Dam (Block 4)
||Eland Dam – North Dam (Block 5)|
|Size||38.1 km2||32.1 km2||34.8 km2||34.9 km2||44.7km2|
|Number of camera trap stations||20||16||19||20||20|
|Survey period||24 July – 11 September 2015||16 September – 4 November 2015||10 November – 29 December 2015||26 January – 15 March||23 March – 11 May 2016|
|Sampling occasions (12 pm – 12 am)||50||50||50||50||50|
|Sampling effort (trap nights)||966||753||910||974||963|
|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)||13 (six females, five males, two juveniles)|
|Sex ration (F:M)||0.8:1||1:1||0.8:1||0.625:1||1.2:1|
|Total number of captures||87||76||92||103||99|
|Number of individual animals caught once||5||4||1||12||2|
|Number of individual animals caught more than once||11||12||11||3||11|
|Number of individual animals caught in previous block||–||7||9||12||8|
|Leopard density per 10 km2||3.9||4.9||3.4||4.3||2.9|
The total sampling effort accumulated 963 trap nights and resulted in a total number of 13 captured leopards including 11 adult leopards (six females and five males) and two dependent juvenile leopards (≤ 18 months). Leopards were captured a total of 99 times expanded over 50 trapping occasions. Capture frequencies ranged from 1 – 21 captures per individual leopard (7.6 ± 7.55) (Fig. 3). Thereby, the sequence of photographs per individual at one trap site represents one capture event. Pp 31 (male) showed the highest capture frequency (n=21) during the sampling period, but female leopards showed an overall higher capture frequency (10.1 ± 7.7) within their demographic class when compared to male capture frequencies (5.8 ± 8.5).
Only three of the 11 adult leopards captured during the survey period were fitted with VHF radio-collar (two females: Pp 17 and Pp 26; one male: Pp 13).
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 9.5. Trap success per 100 trap nights per trapping station was calculated 0.47 but differed significantly between single stations (SD ± 0.26) (Fig.4). Density was calculated 2.9 leopards per 10 km2 within the fifth sampling block.
For leopards captured on 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) within sampling block five ranged from 7.45 km2 to 15.9 km2 (11.12 ± 4.33). Male (n = 2) home range size varied between 7.0 km2 and 15.7 km2 (11.35 ± 6.15).
Home range analysis of male leopards includes data of one juvenile individual (Pp 35).
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.
Fig. 3: Capture success of leopard demographics within the fifth 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.
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 fifth study block.
Fig. 5: Minimal home range size obtained from camera trap data recorded between the 23th March and 11th May 2016 for female (n=3) and male (n=2) leopards captured at ≥ 3 camera stations during the sampling period. Home range analysis of male leopards includes data of one juvenile individual (Pp 35). Females: Pp 32 (un-collared): yellow line; Pp 33 (un-collared): purple line; Pp 34 (un-collared): blue line. Males: Pp 31 (un-collared): black dashed line; Pp 35 (un-collared): white dashed line.
Tab. 2: Positively identified individuals in sampling block one, two, three, four and five.
||Block 1||Block 2||Block 3
|Pp 5||Jo Jo||Female||x||x|
|Pp 7||Un-collared male||Male||x||x||x|
|Pp 11||Un-collared male||Male||x||x||x||x|
|Pp 12||Un-collared male||Male||x||x|
|Pp 14||Ishara’s cub||Female||x|
|Pp 15||Jo Jo’s cub||Male||x|
|Pp 18||Un-collared female||Female||x||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||x|
|Pp 23||Lundu’s cub 1||Female||x|
|Pp 24||Lundu’s cub 2||Male||x|
|Pp 35||Un-collared (J)||Male||x|