I think we can all agree that dogs are great at everything. Except being bad friends, they’re terrible at that. They’re especially great at having jobs, and increasingly, researchers are realising their potential as wildlife scouts to help them track down the struggling species that (understandably) are doing their best to stay hidden.
In New Zealand, specially trained dogs are seeking out the dwindling populations of native, flightless kiwis and kakapos, and across the Mojave and Sonoran deserts in the US and Mexico, they’re sniffing out the threatened desert tortoises. A very pretty girl called Maya is tracking koalas in Brisbane, Australia, and a shiny black lab named Tucker is sailing the eastern North Pacific Ocean in search of orcas.
And now they’re helping scientists figure out the population numbers of the world’s rarest gorilla, the Cross River gorilla (Gorilla gorilla diehli).
This critically endangered subspecies keeps to about 12,000 sq km of dense, highland forests on the border between Nigeria and Cameroon, where they’re forced to endure the constant pressures of hunters, habitat loss, and population fragmentation. And because of the combination of their stubborn elusiveness - you can’t really blame them for being wary of humans - and the crazy-difficult terrain they choose to live in, traditional population census methods for Cross River gorillas aren’t working. Population estimates have remained frustratingly vague for years, now thought to be anywhere between 200 and 300 individuals.
So a team of researchers from Germany and the US set out to find a better way of tracking the gorillas, and figured dogs were as good as anyone to help them do it. The team, led by Richard A. Bergl from the North Carolina Zoo took a handful of specially trained dogs to two Cameroonian Cross River sites, and compared their faeces-finding skills to their own. They wanted to see who offered the most effective solution to the problem of studying one of the rarest primates on Earth.
And where do you find the right dogs for the job? Shelters, because these researchers are on the hunt for a very particular set of skills. "We select high-drive dogs, meaning they are high energy, most people would say is excessively, object obsessed,” one of the team, Megan Parker from Working Dogs for Conservation in Montana, says. "This allows us to train them as detection dogs, and since these traits in a dog tend to make them poor pets, we select dogs from shelters, specifically for these characteristics. These dogs also have to have high focus and a desire to work with a handler, as well as being able to focus while working, ignoring all the distractions that would normally tempt a dog to explore.”
The team trained the dogs to track specific odours through increasingly complex training scenarios over several weeks. They were sent dung from wild western lowland gorillas (Gorilla gorilla gorilla) to figure out if the dogs were good with that kind of scent, and once they knew they could trust them to scout across great distances, the dogs were ready to be flown to Cameroon. It takes several weeks for a veteran dog to get to this point, says Parker, while a dog that’s completely new to the training will take between nine and 12 weeks to get up to speed.
Once in Cameroon, the dogs participated in simulated Cross River gorilla searches using fresh faecal samples over a four-day period in the coastal town of Limbé. Following this, they moved to the Kagwene Gorilla Sanctuary - a national park built by the local government to protect the remaining Cross River gorilla populations - and the northern portion of Mone River Forest Reserve, where their final field training was conducted.
Around the same time, teams of researchers with years of experience in tracking were also having their skills tested, as they tried to find as many samples as they could in the designated areas. Faeces that were between one and three days old were the most valuable find, because at four days old, the genetic information within would have been rendered useless.
While the dog teams struggled with some of the most difficult and rugged terrain - held back by their less-nimble handlers, it must be said - they still came out on top, with 43 fresh samples and 288 old samples found over 44 days. Those 43 useable samples equate to 0.97 samples a day, which is not too shabby, when you consider that the human teams could only manage 75 fresh samples over 175 days, equating to 0.43 samples a team. And they found a total of zero old pieces of dung, the researchers report in the Royal Society Open Science.
Of the faeces the teams collected, 76 samples contained sufficient DNA for analysis, and were sent to the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany for processing. Here they were used to figure out the grouping patterns of the wild gorillas, and the movements of individuals based on records from 10 years prior. Individuals were identified by their specific genotypes - determined thanks to the intestinal cells they pooped out - and local population estimates were made using a technique called capture-recapture. Used commonly by ecologists in situations where it’s impossible to count each individual in a population, this method involves identifying a portion of a population, and seeing how often they reoccur, to come up with a total population estimate.
"By determining how many individuals we actually identified and how many are missing, we can roughly estimate the population size and how confident we are in that estimate,” says one of the team, Mimi Arandjelovic from Max Planck. "Since we record the geographic location of each faecal sample we find, we can link the location of the gorilla that produced a faecal sample to those of others nearby in order to figure out which individuals are in the same group and where they range."
"From that, we can then see how much overlap the groups have with each other and how much of the forest they are using,” she adds. "If we monitor populations over a long enough time with this method, we can also detect individuals moving between groups, identify when new groups form, and even uncover how the individuals are related to one another. We can also use faeces to determine the pathogens the gorillas might be carrying, as well as look at the types of food they are eating.”
While three dogs is all the team could afford to get to Cameroon from the US, the study was a proof of concept that this kind of technique could work better than what’s currently being deployed in the area to track Cross River gorillas. Not only could they work with researchers interested in gorillas, says Parker from Working Dogs for Conservation, but they could be taught to sniff out a range of endangered species all at once, making them even more cost effective. And thanks to the strength of the conservation efforts being undertaken in both Cameroon and Nigeria, there’s a good chance something like this will be adopted in the region.
"The most critical thing is anti-poaching focused law enforcement, in order to prevent the killing of gorillas,” Bergl said.
Researchers from the Zoo and the US Wildlife Conservation Society are working together in the region to support these efforts, while also trying to ensure the various smaller populations of the Cross River gorillas stay connected for breeding purposes. "We have used sophisticated analysis of satellite images in order to identify and map gorilla habitat, and are promoting a variety of approaches to protect this habitat (e.g., strictly protected areas, community-run reserves),” says Bergl.
Their details action plan for Cross River gorilla conservation can be accessed here.