Playing back animal distress calls (call-ins) is a common technique used by scientists to attract study animals, making it possible to monitor more elusive mammals that could otherwise be difficult to see.
What this means for our team on South Africa's Brown Hyenas is sitting in a vehicle in the dark, waiting while the grunting snarl of a hyena pounds out around us. I scan the landscape in the darkness, making out the shapes of distant hills and scrubby bushes in the moonlight. Behind me I can see the mountain ridge we had driven over earlier, on our way to our call-in site in Pilanesberg National Park, South Africa. Our research team is one of the few groups privileged enough to be able to participate in this form of scientific research within the park.
Pilanesberg is just one of the study sites used on the Earthwatch expedition South Africa's Brown Hyenas. The main site for the project is Mankwe Wildlife Reserve, a semi-protected area. The reserve has been lovingly managed by Dougal MacTavish for the last 25 years and is home to a variety of species, from antelope such as impala, to larger mammals such as white rhino. The reserve is also home to a small population of brown hyena. While many of the herbivores are stocked in the reserve (a common practice in South Africa), others, like the hyena, are free to roam in and out of the reserve, making use of the holes dug by warthogs under the boundary fences.
A research technique that Earthwatch teams conduct are transects (both in vehicles and on foot) to look for hyena spoor, and other carnivores' spoor. The most identifiable hyena spoor is dung, which progressively whitens as it ages due to the high content of bone in a hyena diet. The other form of spoor we are looking for are footprints. A hyena has an incredibly large foot - up to 7.5 centimetres across - and easily distinguishable from most of the other predator footprints in the area. The final form of spoor (which sadly, we don't manage to see up close) is the double pasting on foliage from a hyena's anal scent pouch. We spend a lot of time looking nonetheless!
In Mankwe we are able to carry out these transects on foot and Dougal and Lynne (co-Principal Investigator) quickly demonstrate how our senses become dulled from sitting in offices all day when they show us what we are missing. We quickly become adept at spotting piles of dung by the road sides, recording 22 individual hyena latrines on our phase. Dougal gives us several lessons in how our sense of smell is dulled, and I am amazed when he points out scents that are often only very subtle to me; the smell of a leopard, rhino urine, and my personal favourite, the rubbing of a hartebeest's eye gland into the soil. The antelope has rubbed its horns on the roadside and on inspecting it closely (on hands and knees), even with my dulled sense of smell I am struck by the strong animal aroma.
The research in the Pilanesberg National Park is necessarily confined to vehicle based latrine surveys due to the high density of predators (including lion, leopard, hyena, elephant and black rhino) which make it unsafe to walk in the park. After completing a latrine survey one day we sit in the van in silence as Nick carefully re-positions the speakers for another three minutes of mournful grunting and calling from our tape-recorded hyena. Sitting in the dark you can't help but wonder what the call means as it projects out into the long grass; one hyena calling to another "grub's up!" or two males fighting over territory? Either way the small pile of smelly sardines we leave out to attract the hyena close enough to be recorded, photographed and counted can hardly be called appetising. However, research has revealed that the hyena is attracted to this pile of canned fish more than traditional baits.
I look around again, camera at the ready - surely out there in the darkness there is a hyena scavenging. I glance back down the road and there it is - a menacing silhouette standing on the horizon, the moon just illuminating its sloping back and shaggy mane. Ears alert and erect it stares straight back at me before slipping into the grass alongside the van. Our call-back over, we flick the spotlight on and there again, standing on the road in front of us, is the brown hyena we've been waiting for, with slightly torn ears and a healthy golden mane. I carefully lean out of the car window and grab a shot of it staring straight back at us as if to ask "Is this pathetic pile of smelly fish all you have called me here for?"
Our call-ins prove extremely successful with almost 50 per cent of night call-ins recording brown hyena, proving the brown hyena call to be more effective than the more traditional pig squeal (a rather testing sound of a pig's distress call). What the hyena is saying to us, we still do not know.
Niall Riddell is an award winning photographer who joined South Africa's Brown Hyenas in January 2008. More of his photographs can be seen on his website: http://www.lyonimages.co.uk/