Brown Hyaena Research Update
During the second half of 2018, the first ever brown hyaena population survey was conducted across Okonjima. Using 40 camera traps placed mainly at latrines, predictable areas of brown hyaena activity, individual hyaenas were identified using the unique front leg stripe patterns over an 80-day survey period.
A total of 1,002 hyaena visits were recorded during the survey and 48 individual hyaenas were identified. Using spatially-explicit capture-recapture population methods, a density of 24.01 brown hyaena/100km2 was estimated; currently the higher brown hyaena density recorded anywhere. We believe that the high-density results from a combination of protection from human persecution, the perimeter fence stopping hyaenas moving out of Okonjima, a high density of herbivores providing food resources in the form of non-violent mortalities and hyaenas stealing or scavenging kills from Okonjima’s high density leopard population. The research has recently been published in the journal Mammal Research, and we hope it will contribute to the growing field of managing wildlife in enclosed areas.
By the end of 2018, the team were able to fit GPS collars to 10 adult brown hyaenas across Okonjima, and the high resolution data we are receiving from the collars is providing detailed insights into the spatial ecology of the Okonjima brown hyaena population. Spatial data suggests a total of six clans living on Okonjima, with an average kernel density home range size of 40km2, a much smaller home range size than brown hyaenas occurring in open systems in Namibia.
When plotting all home ranges, it is clear that every part of Okonjima is occupied by brown hyaenas. One of the biggest surprises was seeing the data of OHB05 – now nicknamed ‘Johnny Walker’ – this particular male seems to be a nomadic individual, i.e. not associated with any particular clan. Johnny Walker roams across the entire reserve, with the strict exception of avoiding the Poort Clan’s territory. The reason for this is currently unclear, however the Poort Clan is the largest clan on Okonjima and perhaps the chances of running into one of its members and getting into a territorial fight is higher.
One benefit of using GPS collars on brown hyaenas is being able to locate the den sites of each clan used for raising cubs. Den sites show reliably as clusters of GPS points when plotted on a map, and these sites can be visited on the ground to set up a camera trap. Our den camera traps have shown us which females are breeding, litter sizes and cub survival rates. Being able to monitor the progress of cubs at the den and seeing them learn behaviours such as paste marking which they will need as adults, has been fascinating.
As both male and female clan members will bring food back to the dens for the cubs, we are able to monitor the diet of brown hyaenas on Okonjima using den camera traps. Along with the more common diet items such as warthog, kudu and oryx, we have seen some more unusual carrion being brought to the den; aardvark, African wild cat, black-backed jackal, baboon and even a python. As brown hyaenas are mainly scavengers, it is unknown if these animals were hunted or scavenged.
We were fortunate enough to gain funding for the purchase of 14 GPS collars and a large amount of lithium batteries for powering our camera traps from the Ernest Kleinwort Charitable Trust. We are massively grateful for this support. The GPS collars will be used to recollar our original collared hyaenas, with an additional four collars to be put on sub-adults for monitoring the dispersal behaviour of brown hyaenas on Okonjima.
As we now know from our spatial data that all of Okonijma is occupied by brown hyaena territories, the question of where young dispersing animals settle is now a major focus of our research. Do these young animals manage to integrate into new clans, do they stay within their natal clan or do they become nomadic individuals? Being able to answer these questions will aid in producing management guidelines for brown hyaenas in enclosed reserves, ultimately ensuring their long-term persistence in a world in which outside of protected areas they are ruthlessly persecuted.