IntroductionThe African wild dog is southern Africa’s most endangered large carnivore with approximately less than 6 000 free-ranging individuals surviving in subpopulations across a decreasing range. There is a need to understand the wild dog’s dispersal patterns and demographic consequences of dispersal which can have far-reaching conservation and management implications.
The goal of the project is to study the viability and connectivity of African wild dog subpopulations in Botswana and across the Kavango-Zambezi Transfrontier Conservation Area (KAZA TFCA) landscapes in particular, by providing new empirical evidence and novel information on dispersal and its demographics. The project will enable measuring the population viability and extinction risks under changing environmental and anthropogenic scenarios helping identify key conservation actions.
Ultimately this study aims to reveal complex ecological processes and mechanisms at present unknown, and which are critical for the conservation of the species nationally and internationally.
Researcher: Gabriele CozziRegion: Botswana
Partner Organisation: Botswana Predator Conservation Trust
BackgroundOver the past three decades there has been a substantial increase in knowledge on behaviour, ecology and life history of the species; however the empirical work that has been done focused on a few established packs and omitted between-pack processes, specifically the dispersal of individuals. Dispersal is, however, intimately intertwined with population demographic processes.
The project targets several major threats to African wild dog populations, including:
- Habitat loss and fragmentation, which thus calls for the urgent need to understand how wild dogs respond to and move through degraded and scattered suitable patches.
- The encroachment into human activities outside protected areas as a result of long-distance dispersal events, which can exacerbate conflict due to predation on livestock and expose wild dog to infectious diseases and fatal road accidents.
- The viability and reproductive success of newly-formed packs, and their consequent potential to rescue small populations and recolonise unoccupied territories to create new subpopulations.
As a result of these threats wild dogs are forced to live in isolated, small subpopulations, which are particularly vulnerable to extinction. Through emigration and immigration, dispersing individuals lead to the formation of new groups, can rescue small subpopulations, and recolonise unoccupied areas. Understanding how and where wild dogs disperse and assessing the connectivity between subpopulations is thus fundamental for the management and conservation of the species across large wildlife landscapes such as KAZA TFCA, for which wild dogs have been identified as a flagship species. Moreover, wild dog dispersal and the fate of dispersers is still largely unknown mainly due to technological limitations.
ObjectivesThe main goal of the proposed project is to improve the long-term viability and connectivity of African wild dog subpopulations nationally and across the KAZA TFCA landscapes. In addition the project also aims:
- To identify the influence of ecological, environmental and social factors on patterns of emigration from the natal group.
- To investigate the ecological, environmental, social and anthropogenic determinants that influence dispersal movement patterns and habitat selection during dispersal and quantify the degree of connectivity among subpopulations by determining the landscape features which facilitate or prevent wild dog movements.
- To evaluate how dispersing coalition characteristics, dispersal distance and time, and environmental and anthropogenic factors influence dispersal success, i.e. survival rate during movement, new pack formation, settlement likelihood in a new territory, and reproductive success after settlement.
- To combine novel information on dispersing individuals with 25 years of long-term demographic information on resident groups, ultimately to create a unified population demographic model. This model will allow the assessment of population viability and extinction risks under changing environmental and anthropogenic scenarios, thus helping identify key conservation actions for the species.
Results will be of great interest to scientists from a range of disciplines, the general public, conservationists and policy makers, particularly in management of wildlife populations.
MethodologyTwenty dogs between 18 and 36 months of age are being considered as candidate dispersing individuals and fitted with state of the art GPS/ satellite radio collars over a two-year period.
Candidate dispersers will be sedated while still in the natal pack, following protocols and procedures developed at Botswana Predator Conservation Trust (BPCT) during 25 years of activity. The collars record and store several high-resolution GPS coordinates daily and send them to a base station via the Iridium satellite system. This allows the researcher to continuously follow the movements and fate of dispersing individuals, from emigration until settlement in a new territory.
Each collar is equipped with a VHF beacon that allows the researcher to locate individuals on the ground. Information such as dispersing coalition size, body condition, injuries, association with opposite-sex coalitions, and reproductive success after settlement will be collected at each sighting. Each collar is equipped with a drop-off mechanism.
During the first phase of the project, short-distance (within the study area) and long-distance dispersal events (Figure 1), five mortality events, and the formation of new packs were observed and studied. For instance, one male dispersing coalition circumvented the Okavango Delta and covered a cumulative distance of 370 km in 17 days prior to settlement in a new area. Four additional dispersal events of coalitions were recorded that left the study area and moved between 60 and 120 km (straight line) from their natal territory.
Data show that African wild dogs cover an average distance of 20 km each day during dispersal; this is 2.5 times more than the distance covered by resident individuals. Wild dogs that emigrate from the Okavango region can thus be expected to easily reach the Namibian and Zimbabwean border in 10-15 days, when moving along a fairly straight line. The data in hand also shows that the Moremi ecosystem is intimately linked with the Savute-Linyanti ecosystems. Furthermore, several movements across water bodies were observed, suggesting that water may be more permeable to dispersing individuals than it is for resident packs. This finding could have important implications for connectivity of landscapes across a wet ecosystem.
April – June 2018
The collars attached to Karasimbi and his brother were retrieved from the ground in the second quarter of the year. At present we do not know whether the dogs are still in the swamp or have moved on to dry ground. Neither have returned to their natal pack so we assume they have successfully dispersed.
Denali and her littermate sister Gahinga emigrated mid-May 2018, following the typical pattern of long distance dispersers, they covered over 100 km in a few days. After hitting Maun they looped back north along the Tamalakane River and crossed the southern buffalo fence. They are currently moving along the eastern banks of the Gomoti River in what appears to be an attempt, obstructed by rising water, to return to their natal pack.
Kalahari, who settled in southern Moremi Game Reserve in 2017, recently took exploratory trips around the Gomoti River and eastwards to Sankuyo village. Such trips anticipate emigration from the pack and may be the result of Kalahari’s inability to take over dominance in her newly-formed pack. The pack has started denning, which increases Kalahari’s emigration likelihood.
We have received an increasing number of reports and wild dog pictures from tour operators and self-drivers, due to the posters we put at the entrances of the park. These posters have the dual benefit of informing the public about wild dogs and helping us collect information. We have also started fruitful communication with the lodges and tour operators likely to come into contact with any of the collared wild dogs. We regularly update them on the fate of the collared dogs so they can engage with their clients and in turn, make their experience more memorable.
The majority of the females emigrate at 21 months of age while males tend to stay longer with the natal pack and emigrate at 27 months of age. While females tend to emigrate between December and March, males show two very distinct emigration periods in December and July. The December peak in male dispersal may trigger subsequent dispersal events in females later in the season.
The July peak may be related to the emergence of new-born pups and the change within the pack hierarchical structure. As reproduction is highly seasonal in northern Botswana and peaks in June, emigration between December and March appears like the best strategy to allow timely formation of new packs, establishment of within-pack hierarchy, and mating. It is not yet clear what the benefits of the male peak emigration in July are, since these individuals have to survive an entire year without the benefits of their natal pack before being able to reproduce.
Jan – Mar 2018
During the first quarter of 2018 we recorded the formation of a new dispersing coalition and two mortality events. We closely monitored a newly-formed pack which established itself in the Black Pools area of Moremi Game Reserve.
Dalwhinnie and her sister emigrated south across the southern Buffalo Fence. The roaming phase of the dispersal trajectory, between emigration from the natal group and settlement in what appears to be the new territory, lasted 11 days in which the females covered 110 km. They were stationary in an area of approximately 520 km² with neither of them joining with unrelated males.
Liuwa emigrated with her sister from their natal pack in the Santawani area and reached the Savuti area. They first headed south across the buffalo fence and moved 120 km reaching Maun in four days before looping back across the fence where they rejoined their pack for six days. They eventually emigrated again towards the north, covering 290 km in nine days, of which 70 km was covered in just 20 hours before reaching their final destination in Savuti. In January, they were stationery in Savuti – moving in an area of approximately 280 km².
On the 5th of February, the collar sent a mortality signal. We retrieved the collar on the ground, undamaged, but we were not able to locate the body. Two weeks later, Liuwa’s sister was back with her natal pack in the Santawani area, a clear indication that Liuwa was dead. Given the location of the casualty and the movement patterns immediately before the mortality signal, we speculate that Liuwa died a sudden death that points to an aggressive encounter with other carnivores.
Karisimbi and his littermate brother left their pack resident in the northern top of the Chitabe peninsula mid-December 2017, dispersing 60 km north into the swamp in three days. They settled 55 km from the centre of the territory of their natal pack, south of Desert & Delta’s Camp Okavango on Nxaragha.
During the first trimester of the 2018 they moved over a small area of 50 km², composed of small dry islands, their movement largely restricted by the surrounding water. Due to inaccessibility of the terrain we do not know whether Karisimbi associated with unrelated females.
On the 21st of March 2018 the collar sent a mortality signal. As in Liuwa’s case, the movement patterns immediately before the mortality event suggest a sudden death. However, the collar may have also simply detached from the animal.