Check Up for Gorillas

Western Lowland Gorilla Health Evaluations
Dr. William Karesh

No one is sure,but recent estimates would suggest that I am surrounded by 50,000 or so gorillas. Not guerrillas, western lowland gorillas. I'm deep in the forest, in the middle of a park in the Congo Republic that is being re-developed under the guidance of Ecofac, a conservation group funded by the European Community. If their approved expansion plan is signed by the President, Ozdala National Park will become half as large as the country of Rwanda. Last year, the management team asked me to help with wildlife health issues and assist them with research efforts they were initiating. I made a quick trip last September to fit a forest elephant with a prototype satellite tracking collar and the system has proven itself to be quite effective.

Odzala is teaming with wildlife, and one of its remarkable qualities is the high density of western lowland gorillas. Current estimates suggest that there may be as many gorillas in this park as previously thought to exist in all of Central Africa. On this trip, I came to help ECOFAC and park managers develop a health monitoring program for the gorillas. Recent reports from neighboring Gabon, only 150 miles away, indicate that gorillas and chimpanzees disappeared from thousands of square miles of forest following the last Ebola virus outbreaks. Wildlife managers do not want to see a similar event happen here.

Gorillas are susceptible to many human diseases, from such simple things as the cold or flu to more serious diseases such as tuberculosis and Ebola. As this remote area rapidly becomes more accessible to researchers and tourists, a preventive approach to the health of the animals is needed. To accomplish this, first we need to know which diseases already exist in this "healthy looking" population of gorillas and which ones we need to ensure are not introduced by humans. For example, do they already have immunity to measles or is this something we need to make sure all of the park staff and their families are vaccinated for so they do not introduce it by accident. We can not vaccinate all of the wild gorillas living in the forest, but we could potentially vaccinate all of the park workers and their villages. This would protect them and the gorillas. The famous chimpanzee researchers at Gombe Stream in Tanzania had the misfortune to witness polio introduced to the chimpanzees by non-vaccinated or possibly improperly vaccinated humans.

To begin gathering the health information required to plan a sound program, we need to obtain blood samples from the gorillas. And of course, to do this I have to anesthetize the animals. Anesthesia of wild animals always involves some risk, not only to me and my team, but also to the gorillas. We have decided to start this project by working on solitary males to avoid disrupting a family group just for our study. Gorillas live in tight but fragile social groups. The adult males will defend his females and kids to the death, but other males sometimes try and take the whole family or some of the females. Females are known to leave a male and wander off to join another male's group if the first one is not careful. If I put a big male to sleep for four to five hours, he may lose his whole family by the time he wakes up. If I dart a female, the male may not let us work on her or he may take the rest of the family and abandon her. To avoid these problems, not only do I have to find gorillas in the forest, but I have to find solitary or bachelor males.

Working with three park guards and a few more assistants, we have staked out three small clearings in the forest and are in touch with each other by radio. We have waited several days with seeing family groups of gorillas but no single males. But on four other days, lone silverbacks (adult males with the mature silver-gray hair coat) have arrived in one of the clearings. Then it's time to run off with Saturnin, the guard I've been waiting with, slogging across the bog-like clearings, sinking down a foot or two in the mud that is disguised as a golf course by the three-inch-high, bright green sedges and phorbes that the gorillas like to eat. This is why they come to the clearings. We made a quick pace thorough the forest, running along trails made by years of elephant use, cutting across little streams, ducking and dodging liana's and overhanging branches, jumping over fallen logs, and finally arriving at the clearing with the gorilla of interest. All three have been at the far end of the clearings, neat the forest edge, pulling up the phorbes, shaking the mud off them and eating the succulent roots that look like thick white bean sprouts. They are very adept at the technique, plucking a small mat from the surface using their massive hands, 3-4 times bigger than mine, giving the veg a little shake with a few flicks of the wrist. They drag the roots back and forth across the surface of the little streams running through the clearings, shake the mat out again and then put the white roots in their mouths, closing their lips like two flaps over the whole mat and then casually pulling the green tops away with their fingers and tossing the remains on the ground.

Two of them were in the same huge bai (a wet, forest clearing), about 200 yards long and 60 yards wide. We worked our way along one side, staying in the swampy forest to avoid each animal's gaze and tried to stay as silent as possible while moving through the deep muck, dry leaf litter and countless crackling twigs and branches under foot. I leave the team behind when we get within fifty yards of the gorilla. Crawling on my hands and knees, moving the dart rifle along as carefully as I can without getting it buried in the mud or submerging it in water, moving so slowly and close to the ground with the hope of appearing as a motionless lump of insignificance. When the gorilla bends over to grab some vegetation or turns to look the other way, I slide forward a few feet, then freeze again. One gorilla was sitting in the shade of a big tree overhanging the bai and I was roasting out in the full, mid-day equatorial sun, hiding behind little clumps of scrub lining the edge of the bai. Two were in the full sun themselves, using the mats of wet phorbes to wet down their backs, shoulders and arms, while I had the luxury of laying in a flooded patch of forest nearby.

The air powered dart gun I'm using has a limited range, or more exactly, it's accuracy declines quickly with increasing range. It has the advantage of making very little noise and the light, plastic darts hit the animal with very low impact. But, I need to be within 30 yards or so to increase my odds of hitting the animal. That distance is about as close as I can get without being identified by the gorilla, usually they have already become suspicious but are still unsure of what I am. If I aim the dart rifle a foot or so above the animal, the dart arches nicely and strikes the animal in a thick muscle. So far I'm three for three in shots. In the fourth case, a Hartlaub's duck spotted me and flew off screaming, scaring away the gorilla just before I took aim. Two of the others hardly reacted to being darted, one pulled the dart out, smelled it, threw it on the ground and resumed munching on the aquatic plants. Another ran about ten feet and then started looking in my direction until he fell asleep without ever bothering to touch the dart. Most likely, African honey bees and wasps give them occasional stings more dramatic than my little plastic darts.

Within five minutes, the anesthetic agent has done its job and the animal is "sleeping." It takes four of us to carry them to a shady place for their examination. I'm trying to use a light dose of anesthesia to reduce the risk of overdosage, and two of the three gorillas have begun to wake up as we are working on them. This does cause a bit of excitement among the park guards. You can't blame them, it appears that a three hundred pound gorilla is waking up. But, there has always been enough time for me to give them a supplemental injection and get them to go to sleep again.

The examination involves a full physical examination, just as you or I would receive at our physician's office. I listen to their hearts for any sounds of abnormalities, check their lungs, and examine their eyes, ears, noses, mouths, teeth, etc. I take blood samples for laboratory testing, and fecal samples to check for internal parasites. With a cargo net, a long pole cut from a nearby sapling and two hanging scales, we weigh the animals. Of the three so far, they have ranged from 270 to 320 pounds. They have also showed evidence of interesting illnesses. The lightest one was covered from the waist down with a dermatitis that looked like a severe ringworm infection in humans. Big patches of skin were peeling off his legs and feet and his lower belly and groin had be infected for so long that the skin had lost it's normal black coloration and was now pinkish-white. Another animal had ulcers on his face that look like an infection of humans called Yaws. It's actually a common human disease in Central Africa, and probably introduced to some gorilla populations by people centuries or millennia ago. When the procedures are finished, we sit quietly nearby for several hours, waiting for the gorilla to wake up gradually from anesthesia and ensuring that he is not preyed upon by a leopard while still groggy. Later, back at camp I will process the samples using portable lab equipment and using a tank of liquid nitrogen I will keep them frozen at 280 degrees below zero (-180C).

As straightforward as the work appears to be, wild lowland gorillas have never been examined before this to determine their health status. Decades of behavioral research has been conducted to observe their social nature and feeding habits, but no comprehensive effort to learn about their health or susceptibility to human disease impact has been made until now. These three gorillas are a first and with this effort we hope to gather information to guide us in the development of rational preventive strategies and guidelines for park staff, researchers, and tourists in order to protect the health of these magnificent great apes. If conservation efforts in neighboring Cameroon continue to decline and the populations in Gabon fail to recover from their sudden disappearance in a large portion of their range, Odzala National Park may become the world's largest and most significant refuge for lowland gorillas left in the world. A population worth every effort to protect.

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