Usually seen foraging alone, brown hyaena are often assumed to be solitary animals, however they been described as ‘obviously solitary, but secretly social’ due to their highly social lives which are played out at hidden dens away from sight.
The Okonjima/AfriCat brown hyaena research project has been gaining insights into the secret social lives of brown hyaenas using camera traps, which is greatly enhancing our understanding of the study
population. Brown hyaena dens are not easy to find, being deliberately hidden away, often in thick bush far away
from roads or areas of human activity. However, GPS collars fitted to adult individuals makes locating dens much easier. As dens are the centre point of brown hyaena society, with all clan members visiting
them, dens reliably show up on plotted GPS collar data as clusters of points. Once a cluster of points is detected, it then usually requires a field visit to confirm the presence of the den and setting a camera trap up at the den if no adults are present.
The primary function of a brown hyaena den is to provide protection for the cubs, which spend the first 12-15 months of the lives almost exclusively at the den. As such, dens are selected which have narrow tunnels, too small for adult brown hyaena, or other carnivore species, to fit down. Young cubs usually only emerge from the den when an adult is present, and the mother usually brings the cubs out when at the den by softly calling down the tunnel to them. Brown hyaena do not dig the dens themselves, but
rather take over disused aardvark, porcupine or warthog burrows.
Brown hyaenas are born after a three month gestation period, with the eyes shut and ears folded tightly forward. Cubs are born away from the clan, in a small, natal den and brought the main den at around three months of age. Average cub birth weight is 693 grams, which is just 1.9% of adult weight. Litter size can range between one to four cubs, with an average of three cubs. At four months old, the cubs are left alone at the den for considerable period of time, with an average of one visit per 24 hours from the mother. By 10 months old cubs spend more time away from the den and may go 24 hours away from its safety, and by 15 months they are considered sub-adults. At 30 months old a brown hyaena is considered an adult and may leave its natal clan to become either nomadic or attempt to integrate into
a new clan.
Being social animals, all clan members of a brown hyaena clan help to raise the cubs by bringing food back to the den. If more than one female has cubs simultaneously, they will suckle each other’s young. A cub’s diet is supplemented with meat from around 12 weeks of age, although they are not weaned until 12-16 months old. Therefore, the presence of old bones and skin around a burrow entrance is a key feature of brown hyaena dens.
We are currently monitoring four brown hyaena dens across the Okonjima Nature Reserve, each of which have cubs of different ages belonging to our different clans. The Northwest den has the oldest cubs which are still spending the vast majority of their time at the riverbank den, but have been weaned.
Clan adults are regularly bringing food to them, which has included steenbok, oryx calves, ostrich, eland legs and even a dead aardvark. When an adult arrives at the den with food it usually causes great excitement to all present at the den, who usually rush up to the adult with raised hair, eager to investigate the new meal. Scavenged prey are usually placed into the large main tunnel and taken in and out by all individuals to feed on.
The den within the Poort area currently has three older and three younger cubs, which all suckle from our collared female ‘Ed’ who seems a caring and patient mother. This den is located on a mountain and the cubs seek shelter in rocky caves. We have another den at the base of North Mountain with three larger cubs who are often seen exploring the surrounding camera traps and seem to be in the process of weaning from one of our collared females. Our most recently found den belongs to the Northeastern clan who currently have a small, single cub belonging to our collared female who is currently coming to suckle the cub once or twice a day.
All dens have been visited by a number of other species, especially since the recent rains and we presume the burrowing species may be checking out potential new burrow locations after their burrows collapsed during the rain. It is very nerve wracking to see the photos and videos of other carnivore species at the dens, especially the spotted hyaena which chased the cubs of the Northwest clan down the tunnels and which tried to climb down into the tunnel at the Northeast den whilst the cub was inside.
Luckily, no mortalities have occurred, but the incidents clearly demonstrate the risk posed to brown hyaena cubs living in an area with other large carnivore species.
By monitoring the dens the inter-birth intervals, litter sizes and cub mortality can be analysed which will ultimately help in estimating population growth rates and in developing an effective management plan for brown hyaenas not only in the Okonjima Nature Reserve, but for the many enclosed reserves now established throughout southern Africa.