Bioko drill facts for kids
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Quick facts for kids Bioko drill |
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| Conservation status | |
Scientific classification  |
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini |
| Infraorder: | Simiiformes |
| Family: | Cercopithecidae |
| Genus: | Mandrillus |
| Species: | |
| Subspecies: |
M. l. poensis
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| Trinomial name | |
| Mandrillus leucophaeus poensis Zukowsky, 1922
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The Bioko drill (Mandrillus leucophaeus poensis) is a type of Old World monkey. It lives only on Bioko Island in Equatorial Guinea, off the coast of Africa. Drills are among the largest monkey species. The Bioko drill is considered an endangered animal.
These drills became separate from their relatives on the mainland about 10,000 years ago. This happened when sea levels rose after the last ice age. The capital city of Equatorial Guinea, Malabo, is on Bioko Island. Sadly, hunting is the biggest danger to the Bioko drill's population. Even though hunting is banned in most protected areas, the ban is not very effective.
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What Does the Bioko Drill Look Like?
The Bioko drill looks a lot like the mainland drill. It has a green-brown coat and white fur on its belly. A key difference is its crown of fur. The Bioko drill has a yellowish crown with black tips around its face. Mainland drills usually have a white crown.
Male and female drills look very different. This is called being sexually dimorphic. Males are much larger, weighing about 20 kilograms (44 pounds) when grown. Females are smaller, usually around 8.5 kilograms (19 pounds). Their body length, not counting the tail, is similar. Males average 67 centimeters (26 inches), and females average 54 centimeters (21 inches). Male drills have a shiny black face and a long snout. They also have purple, blue, and red fur on their rear end, and white fur on their chin.
How Do Bioko Drills Behave?
Social Life of Drills
Bioko drills are very social animals. They live in groups of about 20 to 30 individuals. Most of these are adult and young females. They often gather in places with lots of food. Drills are also very noisy, which makes them easy to find by their calls. They even react to the distress calls of duikers, which are small antelopes. During the day, drills spend most of their time on the forest floor. But they climb trees to sleep at night.
How Drills Find Food
Bioko drills spend many hours each day looking for food on the forest floor. They usually do this in groups. If they feel threatened, especially by hunting dogs, they quickly climb trees. Drills are smart about how they eat. For example, they break millipedes in half to get to the insides. They also strip plant stems to eat the soft inner part, called the pith. They even search the pith for insect larvae.
Bioko drills help spread seeds. They eat tree seeds and fruits. Because they spend so much time on the ground, they eat more ripe fruits that have fallen. Their droppings then spread these seeds, helping new trees grow. When drills are hunted, it can lead to fewer hardwood trees and young plants in the forest. Recently, drills have started eating more leafy plants instead of fruits. This is likely due to hunting pressure. Because of this, they now spend more time foraging than any other primate on the island.
Where Do Bioko Drills Live?
Bioko Island has different types of forests. There are tropical rainforests in lower areas. Higher up, there are montane forests with more humidity and cooler temperatures. These areas have many tree ferns. At the highest points, there are mossy forests.
Bioko drills prefer to live in lowland forests. They form larger groups in these areas. However, some drills have been found living as high as 2,000 meters (6,500 feet) above sea level. These higher areas include grasslands and dense undergrowth. Lowland areas likely have more varied plants and fruits. Higher altitudes tend to have more fibrous foods like herbs and ferns.
More drills live in the south and east of the island. This is because there are fewer roads there, making it harder for hunters to reach them. This lack of access helps drill populations grow without as much hunting pressure. However, new roads and buildings are being built quickly. This could put these drill populations at risk. For example, a new road goes through the Gran Caldera Southern Highlands Reserve. This is a protected area where many drills live. Drills tend to avoid areas near roads, so this development could shrink their habitat.
What Do Bioko Drills Eat?
What a Bioko drill eats depends on where it lives on the island. Drills in lowland areas mostly eat fruits, just like mainland drills. Drills in mountainous areas prefer to eat leafy materials. This includes pith, leaves, and fungi. These foods are less nutritious than fruits. Drills at higher altitudes eat a wider variety of plant parts. They consume the pith, stalks, flowers, seeds, leaves, and roots of plants. They can even husk coconuts to eat them.
Drills also eat wood and mushrooms. Eating mushrooms is rare for a primate. Bioko drills are known to eat animals too. Their diet often includes beetles, land crabs, millipedes, and insects like ants, flies, and wasps. They also eat the African giant snail. Sometimes, scientists have found remains of rodents and frogs in drill droppings. Drills have also been seen looking for marine turtle eggs on beaches. Their reaction to duiker distress calls might mean they would eat duikers if they could.
Why Are Bioko Drills Endangered?
Dangers from Hunting
The Bioko drill is an endangered species. It is greatly threatened by hunting for food and money. Large monkeys like the drill, which grow slowly and spend most of their time on the ground, are especially affected by hunting. In 2009, it was thought that only about 4,000 drills lived on Bioko Island. When large animals like drills are hunted too much, the forest's health suffers. Drills cannot handle a lot of hunting pressure.
Hunting methods have changed on Bioko Island. Hunters now use shotguns more often instead of traps. Shotguns allow them to kill more animals and choose animals that sell for more money. Since the drill is the largest monkey on Bioko Island, it is also one of the most expensive. This makes it a popular target for hunters. Drills are easier to hunt with dogs and shotguns. Hunters sometimes even copy a duiker's call to find them.
Laws meant to control hunting have not worked well. When bans are announced, there's often a rush to hunt more animals before the ban starts. This is because hunters want to make money quickly. A law in 2003 banned hunting in some areas. In 2007, a law was announced to ban all hunting, selling, and eating of wild meat. After this law was announced, the market for wild meat grew rapidly. When the law officially started, the number of dead animals for sale almost disappeared. However, it quickly increased again because the law was not enforced. By 2008, the market was back to normal. By April 2010, it reached its highest point, with 37 dead animals sold per day. Hunting drills remains profitable, and their price continues to rise as their population shrinks.
Other Dangers
Drills are not often seen near farms. However, farmers sometimes shoot them to protect their crops. This happens especially with the Bubi, who are native to Bioko and often farm. They live closer to larger drill populations.
Climate change also threatens drills. Rising sea levels will affect lowland areas on Bioko Island. This is a problem because many drills live in these lowland habitats. These areas are preferred by drills and support larger groups.
There is some evidence that Bioko drills caught from the wild might be used in circuses. This is harmful to drills. In captivity, they show long-term signs of stress and can become aggressive. This makes it harder for them to mate if they are rescued. It also removes them from their natural home and population. This further reduces their already shrinking gene pool.
How Do Drills Interact with Humans?
The Culture of Wild Meat
Bioko Island has a large market for wild meat, called the Malabo market. This market is similar to those in mainland Africa. Wild meat is important for Bioko Island's economy and for feeding people. Both hunting and eating wild meat have increased as Equatorial Guinea's economy has grown. The two main ethnic groups on the island, the Bubi and the Fang, prefer wild meat over other protein sources. The Fang people especially prefer monkeys.
Modern hunting methods, like using shotguns, are more profitable. Also, new roads on Bioko Island help hunters and sellers get to the market faster. This means they can sell their catch more quickly. The Bioko drill is a popular animal for hunters. As its population goes down, its price goes up. This encourages hunters to go into even more remote areas to find them, which makes their numbers drop even further. Bioko drills are usually sold freshly killed. They are rarely smoked or sold alive. Most of the wild meat hunted on Bioko is sold in the Malabo market or elsewhere on the island. However, most of the hunters are from mainland Equatorial Guinea. Eating wild meat on Bioko has become a sign of wealth and status as its price rises. Still, it remains a common source of protein for many people.
There is also a concern that close contact between drills and humans could spread diseases. This could happen because of deforestation, hunting, and eating drills.
Drills and SIV Research
The Bioko drill has been important in studying the Simian immunodeficiency virus (SIV). This is because the Bioko drill has been isolated from mainland drills for 10,000 years. This long period of isolation has allowed SIV to evolve independently in Bioko drills. Scientists can compare this evolution with SIV in mainland drills. This helps them understand how the disease has changed over a long time. This research has also helped scientists estimate the development and age of HIV.
