The samango monkey (Cercopithecus albogularis) is South Africa's only exclusively forest dwelling primate representing the southernmost extent of the range of arboreal guenons in Africa. In South Africa the species distribution is closely correlated with distribution of Afromontane, Coastal and Scarp forests. Forests are South Africa’s smallest, most fragmented and most vulnerable biome and samango monkeys play an important role dispersing seeds of many forest plants. In the Red Data Book of the Mammals of South Africa, the samango is listed as Vulnerable and is considered rare. The samango population in the study area represents the northernmost population of the species in the country and is considered to be completely isolated from samango populations further south.
A threat assessment has shown that one major threat to samangos in the area are provincial roads, specifically one stretch of ~30 km tar road. Forests in that particular area extend down the southern slopes of the mountain and are bisected by this road. Since June 2012 17 road killed samangos of all age and sex classes were collected and more than a dozen road crossings were observed.
A solution to this problem could be the establishment of road crossing structures, more specifically canopy bridges that allow safe road crossing for samangos. Canopy bridges for arboreal animals have been trialed in Australia, Brazil, Kenya and Madagascar and have shown promising results for primates, porcupines and opossum species.
In order to establish a suitable bridge design for samango monkeys we are conducting experiments on habituated samangos at the Lajuma Research Centre. Parameters tested are 1) solid pole bridge versus flexible rope bridge and 2) different levels of vegetation cover over the bridges. The effectiveness of the bridges is evaluated through direct behavioural observations. Preliminary results show that the samangos prefer using a solid pole canopy bridge design (99.6% of crossings) over a flexible rope bridge design. Results of behavioural data collected show that sub-adult individuals and adult females were most likely to use bridges when crossing the road, juvenile samangos preferred crossing the road in the tree canopy and adult male samango monkeys mostly crossed roads on the ground. Further, the results showed that bridges partially covered with vegetation were used more frequently than uncovered bridges and that the more vegetation cover over the bridges, the more likely the monkeys were to cross the roads using the forest canopy. Results from the experiments will be used to design the most suitable and cost-effective bridge prototype for erection at the actual road kill hot spots.
samango monkey, road kill, mitigation, canopy bridges, South Africa