Updated: Nov 15, 2020
Habitat loss is a major issue to wildlife populations around the world. When humans seek land for use in agriculture and to build infrastructure such as roads, much of the habitat left is often fragmented areas. For those who travel through the canopy of tall rainforest trees, this can have a detrimental effect. Species of primate will find themselves unable to occupy previous home ranges and find it difficult to access certain resources such as food, shelter and mates. Those who dare to cross between fragments may risk sprinting across busy roads or balancing bravely along powerlines to reach the other side. Sanctuaries around the world may well have treated primates for injuries sustained by vehicle collisions or primates with severe burns from being electrocuted by powerlines. Many primates do not survive this. Although sad, there is a solution many conservationists are using to mitigate these issues. Canopy bridges. Here I cover three species of primate that has benefited hugely from artificial bridges and mention the conservation organisations devoting their time to making this happen.
The Dusky langur (Trachypithecus obscurus): Langur Project Penang
Dusky langurs (Trachypithecus obscurus) are a bold species. You can often see them flying between trees to access shelter or desired food. So, when it comes to crossing busy roads for these resources dusky langurs will risk their lives. Dusky langurs are frequently seen balancing along powerlines above busy roads in parts of Malaysia, some even carrying baby. These dare devils are therefore at high risk of both electrocution and becoming ‘roadkill’. One organisation that has successfully addressed this growing issue is the Langur Project Penang (LPP). Many of you may have seen David Attenborough’s ‘Primates’ documentary staring the brave langurs of this project as they defied gravity, balancing delicately along powerlines above a busy Penang road. LPP constructed the first urban setting firehose canopy bridge in Malaysia, calling it the “Ah Lai’s Crossing” project. The bridge was completed on 28th February 2019 on a busy road at their coastal site of Teluk Bahang, Penang. This project has bloomed and has seen three arboreal species using the bridge including Ducky langur’s, plantain squirrels (Callosciurus notatus) and long-tailed macaques (Macaca fascicularis). Since the bridge was erected the LPP team has had no record of roadkill and has reported more than 500 individuals crossing the firehose bridge. The Langur Project Penang continue to monitor the ecology and behaviour of the langur groups and aim to expand this initiative to other parts of Penang and Peninsular Malaysia through research, conservation and education.
Photo credit: Langur Penang Project
The Javan slow loris (Nycticebus javanicus)- Little Fireface Project
Lorises are small arboreal primates traveling through trees in a delicate and precise manner. When loris habitat is destroyed to make way for agriculture and road construction they are forced to find alternative ways of traveling through the fragmented rainforests. Unlike the dusky langurs’, Javan slow lorises (Nycticebus javanicus) can’t leap from tree to tree and being a small bodied primate, they are extremely vulnerable if they were to descend to the ground for travel. Javan slow lorises use powerlines as a way of moving which result in electrocution and even death. So, what could be the solution for this? Slow loris bridges of course! A project devoted to the mitigation of this problem is the Little Fireface Project (LFP) based on the Indonesian island of Java. LFP constructed a number of waterline and rubber bridges for Javan slow lorises in Cipagnti, West Java. The bridges comprised of simple ladder-like structures connecting patches of trees in Javan slow lorises fragmented habitat. With a study published in the American Journal of Primatology at the end of 2019 these bridges have shown to be a popular tool for slow lorises. An incredible success for the Little Fireface project as the lorises home range size almost doubled once the bridges were built (2.57 ha before, 4.11 ha after) and after there was a decrease in ground use by the Javan slow loris. The Little Fireface Project continue to aid lorises in their survival as well as focusing heavily on local education and empowerment.
Photo credit: Little Fireface Project
The Black and White Colobus (Colobus angolensis)- Colobus Conservation
Roads and powerlines are also a threat to primate species in Africa. The black and white colobus monkey (Colobus angolensis) can be seen in areas of Kenya risking themselves and their families by sprinting across busy tourist roads and balancing precariously along powerline to reach necessary resources. These African primates are frequently injured and killed by vehicle collisions and electrocution. To tackle this problem a solution was designed in the form of colobus bridges. Building bridges for primates isn’t necessarily a new innovation. The NGO Colobus Conservation located in Diani, Kenya, erected their first colobus bridge (also known as colobridges) across Diani’s Beach Road in 1997. In 1997 the bridges were a simple rope and wooden rung design. Since, Colobus Conservation has evolved tactile and sturdy ladder bridges which can with stand harsh Kenyan rain and humidity, as well as the weight of a colobus monkey. Amazingly, since 1997 this project has now installed 32 bridges across Diani beach Road. These bridges have allowed this charismatic primate species to thrive in the tourist areas of Diani. The colobridge doesn’t just aid the species it’s intended for. The Colobus Conservation’s long-term project has given a route to other species of monkey too, for example the sykes’ monkey (Cercopithecus albogularis). The Colobus Conservation team continue to monitor and provide more bridges to mitigate the injury and loss of colobus monkey to vehicle collisions.
Photo Credit: Colobus Conservation
It is clear that one initiative can be implemented across a number of species to aid conservation. However, is it critical to preserve the habitat left for these primates and not to assume bridges are the answer to all fragmented habitats caused by human development. I think it is also important here to address who took part in each of these projects. Throughout the years of conservation so many projects devote themselves to, it is clear that the solution to a successful project is involving the communities in surrounding areas by empowering and educating the local population.
Rope Bridge update - 15/11/2020
On the 15th October 2020 the first ever article discussing the usage of rope bridges by Hainan gibbons (Nomascus hainanus) was published. The Hainan gibbon has received a lot of attention due to its rarity. This species of gibbon is the worlds rarest ape, rarest primate and possibly the world rarest mammal. With their population at only about 30 individuals, the Hainan gibbon is need of innovative conservation strategies.
Landslides in the area of the gibbons forest of Bawangling three months after Super Typhoon Rammasun. Photo credit: Chan. et al., 2020.
On the island of Hainan a natural landslide in 2014 carved a large gully between two habitats. With large leaps the gibbons could just about make it to the otherwise. However, as gibbons continually used this route, the natural foliage used by the gibbons started to give away potentially preventing them from crossing. Researchers rushed in to aid the gibbons and provide them with an alternative route.
In 2015, a team of researchers constructed a rope bridge made of two ropes that was installed across the 15-metre gap. Although slow to adapt, after 176 days gibbons were caught on camera traps successfully using the rope bridge. Camera traps placed by the researchers on nearby trees to monitor how the gibbons used the bridge and who was most likely to utilise it.
Hainan gibbons were caught on camera traps placed by the researchers. They were observed utilising the rope bridge in a number of ways. Photo credit: Chan, et al., 2020.
Read the full published article here: https://www.nature.com/articles/s41598-020-72641-z
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