Non-human primates, including apes, monkeys, and galagos, are increasingly threatened by human activities in sub-Saharan Africa. Habitat loss, the wild animal trade, hunting, and human infrastructure, including roads, electric power lines and fences, are some of the factors that endanger these animals. In South Africa, the expanding urban areas, extensive road networks, use of electrification and guard dogs to protect properties, and traditional hunting practices are taking a large toll on the remaining populations of these primates.
Two recent collaborative studies between the University of Colorado Boulder and three South Africa-based institutions (the University of Venda, Lajuma Research Center and the Endangered Wildlife Trust (EWT) conservation organization) have taken an in-depth look at the effects of roads, power lines and dogs on non-human primates in a study area in the northeastern part of the country.
South Africa has five species of endemic non-human primates, including greater (Otolemur crassicaudatus) and southern lesser (Galago moholis) bushbabies. These nocturnal primates spend most of their lives in trees, and some are so small they can fit in the palm of your hand. In addition, samango monkeys (Cercopithecus albogularis), vervet monkeys (Chlorocebus pygerythrus) and chacma baboons (Papio ursinus) are present.
All of these species are listed in the IUCN red list as being of least concern in terms of conservation status, except for the samango monkey which has a status of vulnerable or threatened, depending on the subspecies. However, the findings arising from these two studies indicate that the threats facing these species are not always easy to see, especially if the species have not been intensely researched or monitored
In one study, scientists led by Birthe Linden at Lajuma analyzed hundreds of cases in which non-human primates were killed on roads or around power lines across the country. In a companion paper, the researchers explored the growing risks that domestic dogs pose to the animals.
Primatologist Linden first became interested in the many dangers facing primates on her almost daily drives to the University of Venda in South Africa’s Soutpansberg Mountains. She kept seeing samango monkeys that had been run over and killed by motorists, and wondered how often this was happening to primate species across the country. These monkeys are listed in the “Red List of Mammals of South Africa, Swaziland and Lesotho” as vulnerable, and the roadkill represented another threat to their already fragile populations.
“It’s one stretch where the road is quite close to indigenous forest, which is where samango monkeys typically live,” Linden said..She wondered whether road fatalities represented more of a threat to non-human primates than researchers suspected. South Africa is home to more than 675,000 miles (1,090,000 kilometers) of roads and power lines – and the number keeps climbing.
To explore the extent of this pervasive threat, Linden and her colleagues drew from a wide range of data sources. They include Road Watch, a citizen science app released by the EWT that allows anyone in South Africa to upload reports of roadkill. In all, the team gathered 483 examples of primates killed on roads or around power lines, some dating back to the late 1990s. All five species of primates were represented in the database.
In the second study, Frank Cuozzo of the Lajuma Research Centre and a research fellow at the University of Pretoria’s Mammal Research Institute, led researchers in exploring the impact of domestic dog kills on greater bushbabies. In fact, the team gathered data opportunistically during the course of their research on bushbabies in the mountains of the Limpopo Province in South Africa. They recorded the deaths of greater bushbabies, regardless of the cause – whether by domestic dogs, road kills, electrocutions, or natural predation.
“Bushbabies, especially, are an example of species that may be having problems, but we don’t know what they are until we go looking,” said Michelle Sauther, co-author of the two studies and professor of anthropology at CU Boulder.
Their information was also derived using the broad network of citizen scientists, along with newspaper articles and reports on social media, and their own experiences in the study area. In particular, they recorded 13 known incidents since 2014 where greater bushbabies were killed by dogs. In one instance, people intentionally sent their hunting dogs out to kill a bushbaby that had ventured too close to town and that was considered the embodiment of an evil spirit.
In another instance, a greater bushbaby that was personally known at the Lajuma Research Center was killed by a dog. This bushbaby had been captured and measured four times between 2015 and 2018. It was not in a good shape, having lost one eye and also showing signs of significant dental decay and tooth abscesses. The researchers nicknamed it “Bruiser” because it reminded them of a prize fighter. In 2019, Bruiser was caught and killed by a domestic dog. It seems that the bushbaby came down from the trees and was walking on the ground when the pet dog found and killed him.
“These are small stories,” said Sauther, who has studied bushbabies for a decade. “They’re not the big stories of conservation, but they really do matter, especially as we have no good data on bushbaby mortality and thus cannot easily judge their conservation status.”
They may be small stories, but they probably represent the situation for almost all non-human primate species across the continent, not just in South Africa. And the data that has been collected by the researchers in these two studies is likely to underrepresent the situation considerably because to most people the deaths of these animals are considered insignificant and not worthy of recording.
“These reports are clearly a sliver of what’s actually happening,” said Cuozzo who earned his doctorate in biological anthropology from CU Boulder in 2000. “It’s happening in the towns and suburban areas, in the rural areas, the reserve areas, and it’s happening far more than anyone would think.”
The researchers do not know whether fatalities from roads, power lines and domestic dogs are significant in terms of non-human primate numbers in South Africa, mostly because the population status of each species is not known. However, they argue that it is important to monitor these deaths, especially since all of the species are already suffering the consequences of climate change and habitat loss.
Wendy Collinson-Jonker, co-author of the infrastructure study and a researcher at the EWT, noted that these problems are widespread, but may be surprisingly simple to rectify. Studies have shown, for example, that monkeys and other forest climbers can hop across roads safely on a “canopy bridge,” such as a rope suspended between trees.
Humans can also keep dogs away from primates by being careful not to leave food out, especially at night. Leftover dog or cat food, or even fruit left out on bird feeders, can attract bushbabies and monkeys into areas where they are then vulnerable to attack by dogs.
“We know the solutions,” Collinson-Jonker said. “It’s a case of now getting them implemented.”
As for Bruiser the bushbaby, Sauther noted that his story ended with a small bit of consolation. The team was able to recover his body and collected X-rays that helped reveal a deeper picture of his more than a decade of life, right down to the arthritis building up between his joints that likely led him to climb down to the ground rather than leap through the trees in search of food.
“We were able to document his whole life story,” Sauther said. “We knew him right to the end.”
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