Ecological Islands within the Continent of Africa (Part 4–the Zaire Basin)

The Ndoki forest, located in the Zaire basin, was probably untouched by man until about 25 years ago.  Archaeologists believe it was never inhabited by modern man (Homo sapiens).  Local tribes avoided the forest because they feared a monster described as being similar in appearance to a pre-historic plesiosaur.  Witnesses weren’t lying, but what they likely saw were forest elephants (Loxodonta cyclotis) walking across deep river bottoms with their heads and trunks exposed.  This would resemble a plesiosaur.  When lumber companies began exploring the forest, the animals were naive and unafraid of people.  The Ndoki forest is now protected but selective logging is allowed in the areas around the park.  This park is rich in wildlife–elephants, buffalo, antelope, hogs, and primates abound.

The okapi (Okapi johnstoni) is only found in this region.  It is a giraffid, a family of ungulates that were formerly more widespread.  There were 17 genera of giraffids during the Miocene about 20 million years ago, but today there are 2 genera of just 1 species each–the okapi and the giraffe (Giraffa camelopardalis). Giraffids have long dark tongues, skin-covered horns, and lobed canine teeth.  Okapis were more widespread in Africa during the Pleistocene.  Anthropogenic fires and hunting, along with competiton from antelopes, may have driven them to relic status.  As a whole, deer and antelope have ecologically replaced giraffids in Eurasia and Africa respectively.

Image of an okapi

The okapi is a relic of the giraffid family.  They were once widespread over Eurasia.  Giraffids have been ecologically replaced by antelope and deer.

Alternating wet and dry climate cycles have influenced evolution and caused the speciation of many new organisms in this region.  Bush babies (Galongo sp.) are tiny primates adapted to eating sap and insects.  They likely evolved from fruit-eating primates during dry climate cycles when trees didn’t produce enough fruit to eat.

Bush babies are adorable little primates.

There are over 20 species of guenon monkeys in this region.  These tree-dwelling primates evolved from ground-dwelling primates during wet climate cycles when forests replaced savannah.  Dry climate cycles limited forests to isolated areas along the river and isolated populations of monkeys evolved into different species.  Following a return to wet conditions and expanded forests, these new species of monkeys came into contact with each other.  Some hybridized, creating still new species, while others did not.  This explains why this region hosts so many species of monkeys that occupy similar ecological niches.

GenettaVictoriaeSmit.jpg

The giant genet is endemic to the Zaire basin.  I could not find a good photo of this species online.

File:Cercopithecus wolfi at the Bronx Zoo 004.jpg

Wolf’s monkey (Cercopethicus wolfi) is 1 of many species of guenon monkeys that live in the Zaire basin.

This region is also home to the bonobo (Pan paniscus), a chimpanzee that is more peaceful than its violent warlike cousin (Pan trogolodytes).  They would likely be wiped out, if P. trogolodytes invaded their range.

Small parakeets, known as lovebirds, have also evolved into new species here in response to climate changes.  There are 7 species in this region.

The collared lovebird (Agapornis swindernianus) evolved from an Asian species that crossed savannah then became adapted to tropical forest.

Reference:

Kingdon, Jonathan

Island Africa: The Evolution of Africa’s Rare Animals and Plants

Princeton University Press 1989

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