The old man showed me the small wound on the back of his neck.
The old man showed me the small wound on the back of his neck. It didn't look too bad. The edges were crusted with dried blood, but it wasn't inflamed. The round cut looked like a small piece of flesh had been scooped out. It would probably leave a tiny scar similar to a pock mark. I dabbed some iodine on it for him. Don Rafael wasn't concerned. "If it weren't for the blood on the sheets," he said, "I probably wouldn't have noticed the cut." The next day he had a second wound less than a centimeter from the first. Like the one from the night before Don Rafael didn't know how he had acquired it.
That night another blood encrusted hole appeared about 5 centimeters from the first two. The area around the wounds was showing signs of a low grade infection. In addition to the tincture of iodine from the medicine cabinet, I applied some neosporin to combat the infection. Don Rafael was starting to get worried. He told me that he was afraid to sleep at night. Later that day I took Don Rafael a mosquito net. That night he slept under the net with the edges tucked under his mattress. No new wounds appeared for the next two nights. Then, on the sixth night he failed to tuck the net under the mattress. He awoke the next morning with another wound on his neck and the culprit was trapped inside the mosquito net with him.
The common vampire bat, (Desmodus rotundus,) was dead when Don Rafael showed it to me. It was small, no bigger than a house mouse and weighed less than an ounce. The hair was reddish-brown. I opened its mouth with a pencil. The incisors were long and sharp. Obviously, this tiny flying mammal was what had been biting the old man while he slept. It had probably landed on his bed, crawled up to his neck and made a small cut with the razor sharp end of an incisor. The level of sharpness was so keen that Don Rafael didn't feel it and didn't wake up. As blood oozed from the wound the vampire bat lapped it up with its long tongue. The anticoagulant in its saliva made the blood flow freely. Once the bat was satiated, it flew away and left Don Rafael sleeping, his blood dripping onto the sheets.
I took Don Rafael to the local health center in Hatillo. Rolando, the paramedic wasn't alarmed by the bites. The infection was under control. I asked about rabies, but Rolando just shrugged and said that wasn't a concern. In the last couple of weeks there had been one other case of vampire bat wound reported. Rolando said he would report both cases to the Health Ministry in Quepos. Later, I learned that there had been several cases in Dominicalito as well.
A couple of weeks after Don Rafael's experience, a veterinarian from the Ministry of Agriculture stopped by Hacienda Barú. She asked if the vampires had been bothering the cattle much. That was in 1983 when we still had cattle at Hacienda Barú. I pointed out a number of animals with vampire wounds and told her about Don Rafael and the other reports of attacks on humans. Teresa, the veterinarian, explained that under natural conditions the common vampire bats aren't very abundant. Their population is limited by their food supply, or lack of it.
They have to work hard just to find a meal. When the environment is shared with humans and their domesticated animals, especially cattle and horses, food is abundant. With nearly unlimited supplies of blood, populations of common vampire bats expand. Fortunately, Desmodus rotundus have only one offspring per year, so their numbers don't increase rapidly. They are normally quite wary of humans and houses. But when their population density reaches extremely high levels, they do enter homes and prey on the people sleeping there.
Teresa told me that vampire bats can carry rabies, but that no cases had been reported recently and Don Rafael was unlikely to be in any danger. Nevertheless, it was time to get the Desmodus population back under control. She said she would return in a few days.
True to her word the young veterinarian returned with an assistant about a week later. Teresa asked us to sort out all the cattle with bat wounds. Late that afternoon we separated about two dozen cows and calves from the rest of the herd and enclosed them in the corral. Most of the bloody bites were on their necks and shoulders, but there were a few in other places, including the ears. Then the young veterinarian and her assistant strung very fine threaded nets, called mist nets, in several locations around the corral. The bats tend to return to the same cattle night after night she explained. She presumed that they smelled the dried blood that had spilled from previous wounds leaving red strains on the cattle's necks and sides.
Shortly after dark the first common vampire bat became entangled in the mist net. With gloved hands Jorge, the assistant, carefully removed it from the thin threads and held it by the wings. Teresa painted the small furry mammal with a jelly like substance she called vampiricida or vampirecide in English. Then Jorge released it. Teresa explained that the vampire bat would return to the roost where its companions would groom it, licking off the toxic jell. She estimated that for each bat they painted, between 20 and 30 would die. That night they caught, painted and released 9 common vampire bats.
Teresa estimated that during the night, about 25 bats of several other species became trapped in the mist nets. Only the vampires were painted with the jell. The rest were released unharmed.
Rabies epidemics aren't common in Costa Rica, but when there is one the vampire bats play a major role in spreading the disease. Apparently they are naturally resistant to rabies infections, easily surviving the disease and from then on acting as carriers. Most domestic mammals are vulnerable to rabies, as are humans. When vampire populations are high, the danger of a rabies epidemic is much greater.
This episode of overpopulation of Desmodus rotundus reminds me of a similar situation with another blood feeder, the mosquito. Worldwide, mosquitos cause more human deaths (over one million annually,) than any other animal, by spreading diseases like malaria, dengue fever, yellow fever and encephalitis. When I arrived at Hacienda Barú in 1972, the coastal plain had already seen a couple of decades of rice farming and cattle ranching. We continued cultivating rice at the hacienda until 1984. I remember the hordes of mosquitos we had to endure at that time. They were so bad that repellent often didn't work.
Some nights we had to dress in long sleeved shirts, long pants and boots in order to endure the onslaught. Soon after we quit farming rice, the mosquito population diminished to a tolerable level. At the time I didn't make the connection between rice farming and mosquito populations, but it's really pretty simple. Fish, frogs, birds, lizards and bats all eat mosquitos. Conventional rice farming requires aerial fumigation that kills many of these natural predators. The fast breeding insects develop a genetic resistance to the agrochemicals much quicker than their enemies, and mosquito populations skyrocket. When we quit farming and stopped the massive use of pesticides, populations of the mosquitos' enemies rebounded. This, of course, was good news for us and bad news for the mosquitos. Nowadays at Hacienda Barú National Wildlife Refuge, mosquitos are a very minor bother. Many visitors comment on the lack of them.
Under natural conditions, neither the mosquito nor the vampire bat is a serious pest. But in the examples above, human beings had killed off the natural prey of the vampires, and the natural enemies of the mosquito. In both cases it was our quest for food to feed ourselves that made it possible for these species to increase in population until they became pests. This is one tiny example of how our agricultural practices and lack of respect for the other living things, has come back to haunt us.
In the words of Daniel Quinn in Beyond Civilization:
"This is what happens when we clear a piece of land of wildlife and replant it with human crops. This land was supporting a biomass comprising hundreds of thousands of species and tens of millions of individuals. Now all the productivity of that land is being turned into human mass, literally into human flesh. Everyday all over the world diversity is disappearing as more and more of our planet´s biomass is being turned into human mass."
How much longer can the earth support our activities? How much longer before the stack of cards comes tumbling down? Since 1983, when that common vampire bat bit Don Rafael and the mosquitos were driving me insane, the human population of earth has increased by about one-third. That's over a billion more people to feed in less than 20 years. We are supposedly the most intelligent life form on this planet. We can learn from our mistakes, and we urgently need to learn better ways to interact with our environment.
The truth is that many people are learning and taking action. Things are changing in the region where we live. Land is being restored to natural habitat. Manuel Antonio National Park has been expanded to provide it with a corridor to the Savegre River. A group called COBISPA is working on an Interoceanic Biological Corridor between there and the Caribbean coast. A little farther south a group called ASANA is creating a Biological Corridor called The Path of the Tapir. And that connects to the Osa Peninsula Biological Corridor. All of these form part of an international project called the Mesoamerican Biological Corridor. You can picture it as a mega park with all the formally protected areas connect by rainforest corridors.
In recent years we have restored much forest cover to Hacienda Barú National Wildlife Refuge. I haven't heard of any bat bites on humans since Don Rafael fell victim to Desmodus rotundus. Mosquitos are now quite tolerable. If you want to live better and in harmony with your environment, work to restore natural habitat. When we restore natural habitat, everything gradually comes back into balance. In a healthy ecosystem there are no major pests. Vampire bats, mosquitos and other wildlife that can harm humans are still around, but their populations remain at levels we can live with. Of course the Biological Corridor projects mentioned above weren't designed with the objective of getting vampire and mosquito populations under control. That's just one of the hundreds of extra added bonuses that happen when you give Mother Nature a free hand. Try it and see for yourself.
Recommended reading: Beyond Civilization, by Daniel Quinn. This is the fourth book in a series. Preceding it are Ishmael, The Story of B and My Ishmael, all by Daniel Quinn.
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