What comes into your mind when you hear or read the word predator ?
What comes into your mind when you hear or read the word "predator." An image of the "Big Bad Wolf ," a snarling bear with blood shot eyes and white, blood stained fangs slashing into a helpless fawn; a hawk or falcon swooping down on a poor inoffensive dove or maybe a cloaked villain lurking in the shadows waiting for some defenseless victim to pass by? My dictionary defines predatory as: 1. Living by preying upon other animals. 2. Characterized by plundering or stealing. My thesaurus lists seven synonyms for predatory, all of which imply despicable behavior. In reality, however, it all depends on your point of view.
For example, in western culture, according to traditional beliefs, it is bad if a hawk kills a dove, a lion kills an antelope or a wolf kills a fawn, but it is even worse if a fox kills a chicken, a coyote kills a sheep or a cougar kills a calf. What makes it worse is that in the last three cases the animals being killed belong to humans who own them and therefore have the exclusive right to kill them and eat them. We raise them and buy feed for them and get them fat first and then we kill them and eat them. Of course, in our case it isn't despicable at all. We need to do this to feed ourselves. I hope you're following the logic here, because I'm a little fuzzy on it. Don't get me wrong though. I'm not saying we shouldn't eat meat. What I'm saying is your point of view makes a big difference and that maybe predators have been getting a bum rap.
In recent years we humans have begun to reexamine some of our beliefs about nature and question some of our traditional negative feelings about predatory wildlife. As we learn more about our environment and look at the overall scheme of nature, we have come to appreciate the crucial function carried out by animals that kill other animals. So critical is their role that the presence of a large spectrum of predators is a clear indicator of a healthy ecosystem. This is especially visible in the tropics where the rain forests harbor a vast diversity of species. Let's look at a couple of examples.
Manuel Antonio National Park with 682 hectares is Costa Rica's most visited National Park. According to Mario Boza's 1988 book Costa Rica National Parks, there were 184 bird species in the park at that time. Even assuming that a few new species have been registered in the last 13 years this number is surprisingly low. On Hacienda Barú National Wildlife Refuge, which is only half the size of Manuel Antonio, and is situated only 50 kilometers to the south in a similar ecosystem, ornithologists have registered 311 species. Also surprising is that none of the mammals listed in Boza's book could be considered predators. Several omnivores like the white-faced capuchin monkey and the white-nosed coati could be considered opportunistic predators, but no carnivores were listed. In contrast, Hacienda Barú has recorded twelve mammal predators, including five species of cats. At the time I didn't see a connection between the lack of predators and the lack of birds at Manuel Antonio.
Then I learned of a similar situation on Barro Colorado Island in Panama. According to John Terbrough in Requiem for Nature, one of the most intensively studied tropical habitats in the world is sixteen-hundred hectare Barro Colorado Island. Located in Gatun Lake in the central portion of the Panama Canal, Barro Colorado has been isolated from the mainland since the early 1900s when the canal was constructed. Between 1920 and 1970, 45 species of birds disappeared from the island. More than half of these local extinctions were puzzling for ornithologists.
Several researchers began seeking answers and by the early 1980s a great deal of light had been shed on the problem. It was determined that bird disappearances didn't begin until after the disappearance of top predators such as the puma and jaguar. Once these major carnivores were gone, a rapid increase occurred in populations of their prey species which included coatis and raccoons. Both of these omnivorous species are partially arboreal and often prey on bird's eggs and nestlings. The population of coatis on Barro Colorado Island was found to be about 20 times higher than in the Amazon rain forest. This clearly explains the local extinction of so many bird species.
Another example was brought to light by hunters rather than biologists. The first game preserves that appear in history belonged to feudal land lords who protected large extensions of land as hunting refuges. Many of these were for the protection of game birds such as pheasant and quail, which the owners hunted for sport. Hawks, eagles and other raptors known to prey on the game birds where routinely killed because the landlords assumed that reduced predator populations would translate into increased game populations.
Bounties were even paid for the killing of these raptors. Eventually, however, it became clear that just the opposite was true. As predatory bird populations declined so did those of the game birds. When numbers got so low that the hunters lost interest in the game bird preserve, quit hunting and quit killing predatory birds, the raptor populations would soon return to normal levels and game bird populations followed. At first the reasons weren't clear. Why would lowered numbers of predators result in lowered numbers of the prey?
A closer look at the most common prey of these raptors told the story. Most of the hawks and eagles that had been targeted really were guilty of killing a few of the game birds the hunters wanted to preserve. Their primary prey, however, were small rodents. Without the raptors to keep them under control, rodent populations increased rapidly. These included rats which kill many more nestlings and eat more bird's eggs than raptors. The solution is simple. Let the predators do their thing. Their presence signifies a healthy ecosystem.
Any animal must acquire its food as efficiently as possible. It must acquire each calorie of food energy with the expenditure of less than one calorie of bodily energy. If it does not, it will slowly decline in body weight and perish. Therefore a predator must not waste energy in attacking, subduing and killing strong, young, healthy prey, but instead go after the old, weak, sick and injured animals. This culling process keeps the prey species strong, healthy and genetically vigorous. Genes that produce physical defects are rapidly eliminated from the gene pool by the predators.
Large predators such as jaguars, pumas, ocelots and coyotes need lots of space. Estimates vary regarding the home range or territory of the large cats, but it is generally accepted that a male jaguar needs a minimum of 30 square kilometers in a tropical rain forest habitat. A female will occupy a smaller range within the male's. Pumas have territorial needs similar to the jaguar and ocelots need much less area. In order for a population of large predators to remain healthy and free of genetic defects numbers must be maintained at a viable level.
Again, we find disagreement in the scientific world over how many animals constitute a viable population, but we can safely say that it would be at least 500 over the long term. Since the male and female share a territory, we can multiply the minimum number of individual territories, 250, by the minimum size of territory, 30 square kilometers and we come up with 7,500 square kilometers. That's about 20% of the land area of Costa Rica. In short, to guarantee healthy populations of the large predatory cats that are crucial to the health of the ecosystem we would need a single large National Park or protected area that is equal to one fifth of the land area of the country. That is not going to happen, but there may be another way, wildlife corridors. If isolated natural forests are connected together by corridors, the result is the ecological equivalent of one large forest.
Jaguars may be found about 90 kilometers to the south of Dominical on the Osa Peninsula in the Corcovado National Park, an area of 470 square kilometers. Nearby Peñas Blancas National Park has about 140 square kilometers and also has jaguars. The peninsula contains another 800 square kilometers of potential jaguar habitat including the Sierpe-Térraba Mangroves. In other words the entire area could have as much as 1410 square kilometers of suitable jaguar habitat. The problem is that these areas are fragmented by farmland and pastures. There are six environmental organizations working as a coalition to create the Corcovado Biological Corridor which will connect most of these forests together. Nevertheless the total area is far short of the 7500 square kilometers we calculated as the minimum amount of habitat needed for the perpetuation of the jaguar.
Just north of the Osa Peninsula lies the Sierpe-Terraba mangrove system followed by the coastal mountain range. This is all potential jaguar territory, but much of it is badly fragmented. The Association of Amigos de la Naturaleza (ASANA) is working to restore connections between forested areas the length of the coastal range. This is an extension of nearly 100 kilometers which stretches north to the Savegre River and the Los Santos Forest Reserve where jaguars are also found. This, in turn, connects to the Tapanti National Park, Chirripo National Park and Amistad International Park. All of these protected areas combined contain more than enough land to support a vigorous population of Jaguar, Puma and other major predators. ASANAs corridor project which provides the vital link between Osa and Los Santos is called Path of the Tapir Biological Corridor. Dominical is located right in the middle.
The Path of the Tapir is named after Baird's Tapir, the largest mammal in Central America. Weighing up to 300 kg. and resembling a three-toed pig or cow with an upper lip that looks like a short trunk, the tapir was widely hunted for meat. The last one in our area was killed by hunters in 1957. Tapirs still roam in the large forested areas at both ends of the Path of the Tapir Biological Corridor and it is ASANA's hope that they will someday return to the corridor that bears their name.
The Path of the Tapir Biological Corridor project was initiated in the early 1990s. Within 10 years tangible results could already be seen. During the dry season of 2000 a biologist found puma scat with peccary hair in it at Hacienda Barú National Wildlife Refuge. He said that other evidence, including tracks and near personal encounters, indicated that there were at least two of the large cats. A neighbor later sighted a young puma, possibly a recently weaned cub. Another biologist was surprised to find himself practically in the middle of about a dozen white-lipped peccary, a species of wild pig that had been hunted to extinction in this area around 40 years ago. In 1998 a lone male spider monkey appeared mysteriously on Hacienda Barú. Six months later a female appeared. A year after that four of them were sighted by visitors and their guide. Spider monkeys haven't been seen here since 1947.
The return of all these species clearly indicates that the corridor is functioning and that it can work to give large predators the vital connecting link and freedom of movement they need to maintain viable populations. By creating corridors we are giving a helping hand to the "bad guys," the major predators, and thereby insuring the health of the entire system. Every species has its own niche. In nature there are no good guys and bad guys. They all play their part in the overall scheme of things and work in harmony as an intricately coordinated ecosystem with an infinite number of checks and balances. The only bad guys are those who have figured out how to beat the system.
Under natural conditions predators kill only for food or to protect territory. Well fed domestic cats and dogs will sometimes kill for fun. There is one predator that will kill anything that bothers it, gets in its way. This predator will kill any other living thing that competes for the same food. It has even been known to use chemical warfare in an attempt to completely annihilate other species that create problems for it. As a result of this strategy, the predator in mention has become so numerous that it has been estimated that it appropriates for its own use between 20% and 40% of all the solar energy stored in land plants on the face of the earth. This of course has been to the detriment of the millions of other species on the planet which, at this time, are going extinct at a rate of over 10,000 per year, according to Paul Hawken author of The Ecology of Commerce.
Fortunately the predatory species to which I am referring can, when properly stimulated, use its intelligence in a positive manner and is capable of recognizing and correcting its own errors. That species, of course is us, Homo sapiens.
Recommended Reading: Requiem for Nature by John Terbrough, The Ecology of Commerce by Paul Hawken and any of the Daniel Quinn series, which should be read in the following order: Ishmael, The Story of B, My Ishmael, Beyond Civilization.
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