Mountain Gorilla (Gorilla beringei) Influenced Landscapes in Equatorial Africa

Gorilla costumes are popular on Halloween.  There is something frightening about a gorilla.  They resemble humans but are bigger, much more powerful, and hairy.  Moreover, they’re armed with sharp canine teeth.  For tens of thousands of years gorillas were better adapted to some environments than technologically primitive humans.  Gorillas can survive with more success than naked unarmed humans (See the tv series Naked and Afraid on Discovery Channel) in lowland tropical jungles and cold vegetated highlands.  But the human population has exploded in recent centuries, and people are infringing on gorilla habitat.  Though no physical match for a gorilla, humans do use projectile weapons to slaughter their cousin apes.  I think a man who would enjoy hunting a gorilla would also have no qualms about shooting his neighbor for the hell of it.  In reality humans are much scarier than gorillas.

Mountain gorillas significantly modify their environment.

Gorillas are much more powerful than humans.  An unarmed human would stand no chance in a fight with one.  They could literally tear the arms off the top human MMA fighter.  I mean pulling the arms off at the shoulder socket and tearing them off with the skin attached.

Mountain gorilla habitat is shaped by many forces.  They live between 7200-14,000 feet in elevation, an environment known as equatorial highland.  The high elevation keeps temperatures cool and catches rain clouds, resulting in moist conditions, but the location near the equator is frost free, fostering the year round green vegetation gorillas need because their diet is almost completely vegetarian.  Volcanic activity, rocky landslides, bamboo die-offs, fire, and gorilla and elephant foraging create conditions favorable for the low level plant growth that can support gorilla populations.  According to Jonathan Kingdon, gorillas chase duikers, buffalo, and elephants away from their favorite feeding grounds.  Before they learned to fear men with projectile weapons, I suspect they chased humans away too.  Just imagine Pleistocene humans encountering gorillas for the first time.  It’s likely these people were walking along with just spears.  If the gorillas felt threatened and attacked quickly enough, the first humans to see them  probably fled for their lives.  Alas, today there are only 620 mountain gorillas left in the wild.

 

Mountain gorilla habitat.  Lots of low level vegetation due to the variety of factors mentioned above.

Mountain gorillas (Gorilla beringei) diverged from western lowland gorillas (G. gorilla) during the early to mid Pleistocene Ice Ages when savannah habitat expanded and isolated gorillas into forest refugia.  Gorillas can’t survive on savannahs because those environments are subject to long droughts and won’t support the plants gorillas need to eat.  Genetic studies suggest this divergence occurred at least 261,000 years ago during the Illinois Ice Age.  Eastern lowland gorillas expanded their range following the end of the last Ice Age ~15,000 BP when forest habitat expanded.  Eastern lowland gorillas are the same species as mountain gorillas.  There are 4000 eastern lowland gorillas left in the wild.  Western lowland gorillas still have an healthy population of an estimated 100,000.

Reference:

Anthony, Nicola; et. al.

“The Role of Pleistocene Refugia and Rivers in Shaping Gorilla Genetic Diversity in Central Africa”

PNAS 2007

Advertisement

Carvers Creek State Park in South Central North Carolina

Last Saturday, we visited my nephew who is stationed at Fort Bragg in North Carolina.  This gave me the opportunity to hike around Carvers Creek State Park located nearby.  Past the entrance, a long wide path borders an old field on one side and a woodland of shortleaf pine with an understory of blackjack oak and sweetgum saplings on the other side.  I heard a constant chirping of crickets in the field, and grasshoppers were also abundant.  This is ideal habitat for loggerhead shrikes (Lanius ludovicianus), a species in decline.  They nest in short trees but hunt for large insects (such as grasshoppers), mice, lizards, amphibians, and even juvenile venomous snakes; all of which can be found in this old field.  I’ve never seen a loggerhead shrike, and it’s high on my birding wish list.  I asked a park ranger where the shrikes were.  She told me they could usually be seen behind a fence where they keep their maintenance equipment, and birders using binoculars could stand near the fence and see them.  I didn’t have binoculars with me, so shrikes are still on my wish list.

The first part of the trail borders an old field humming with crickets and grasshoppers.  Loggerhead shrikes inhabit this park.

Much of the park is open woodland/savannah type environments.

Big loblolly pine.

This path leads to the former winter house of one of the Rockefellers, but it is not yet open to the public.  The state park service probably needs to renovate it, so it’s safe for visitors.  Rotten floor boards can be hazardous.  It overlooks a millpond and has glassed-in porches on the 2nd floor of both the front and the back.

The front of the WWI era Rockefeller winter home.

Back of the Rockefeller winter home.  Most of the wildlife I did see was here behind the fence.  Note the glassed-in porch.  Nice.  It overlooks the millpond.

Cypress trees ring the millpond.

Millpond.

A live oak tree grows near the Rockefeller house.  Live oak is not native to North Carolina this far inland, though it does grow near the coast.  This specimen must have been transplanted here over a century ago.  I saw gray squirrels, chipping sparrows, and blue jays foraging on acorns under the tree.  One of the squirrels was rather large, and at first I thought it might be a fox squirrel, but I caught a glimpse of white underbelly.  Gray squirrels usually have white bellies, while fox squirrels are solid-colored.  The ranger told me fox squirrels can be seen on the loop trail around the millpond, but I didn’t see them.

Live oak.

The loop trail goes through a savannah.

More open woodland/savannah.

I was surprised to see cypress trees growing this far inland.  Cypress trees grow on the edges of the millpond here.  I checked the range map and learned this site is about as far inland as they can normally be found.

The loop trail threads through open pine savannah.  I noticed fire marks on some of the pines.  This park must be managed with fire.

The millpond is u-shaped. Note the cypress trees in the water.

Carvers Creek Park is a recent and valuable addition to North Carolina’s state park system.  Much of the area around the park has been transmogrified into pine tree farms, an environment that supports almost no wildlife at all.

 

Hitchcock Woods in Aiken, South Carolina

I visited Hitchcock Woods in 1990 and was not impressed then.  I considered it a boring pine-dominated woods.  However, South Carolina Educational Television recently showed episodes of Naturescene and Expeditions with Patrick McMillan that both featured this park, and I learned more about it and what to look for.  I revisited Hitchcock Woods this past Sunday and with more knowledge of the site, I had a much more favorable impression than I did 25 years ago.

William Hitchcock donated a 1200 acre stretch of woods to the city of Aiken, S.C. in 1939.  The Hitchcock Foundation has since added nearly 800 acres, so that there is about 3 square miles of wilderness in the middle of Aiken.  The trails are wide and sandy and littered with horse manure.  Horseback riding is popular in this town.

The soils consist of sand and kaolin clay that formed during the Cretaceous Age over 66 million years ago when this region was seashore.  The sandy clay soil is unproductive for agriculture and most of Hitchcock Woods has never been under cultivation.  It has also never been clear cut, though selective logging is part of the management plan for the woods.  I saw a great variety of trees here including southern red oak, post oak, water oak, black oak, white oak, overcup oak, red maple, silver maple, hickory, magnolia, persimmon, dogwood, loblolly pine, shortleaf pine, longleaf pine, slash pine, and Virginia pine.

The soil here is sandy with nodules of kaolin clay.

Tall old growth trees grow in these woods.

A great variety of trees grow here.

The trails are wide and sandy and littered with horse manure.

More old growth hardwoods.

There are several interesting disjunct species here that are relics from earlier climatic phases.  The poor soils that prevail are a condition favorable for their continued existence at this locality, since they’ve disappeared from the rest of the region. Sandhill rosemary (Ceratiola ericoides) currently grows on the sandhills of Florida.  A relic disjunct population occurs in Hitchcock Woods.  This species likely was more widespread throughout southeastern North America during the late Pliocene/early Pleistocene when the region suffered through an especially arid climatic phase.  However, it may also have been more widespread during the most recent Ice Age Maximum about 20,000 years ago because climatic conditions were quite dry then as well.  Disjunct populations of Virginia pine (Pinus virginiana) and mountain laurel (Kalmia latifolia) are also Ice Age relics that likely occurred throughout the region during colder climatic stages.

Virginia pine growing around the chalk cliffs is a disjunct species normally found in the mountains.

Many of the trees in Hitchcock Woods are at least 200 years old.  Some longleaf pine trees (Pinus palustris) have red-cockaded woodpecker (Dryobates borealis) nesting cavities.  This species is the only woodpecker that makes nesting cavities in live longleaf pine trees.  The oozing sap repels predatory snakes seeking to eat nestling birds.  After years of fire suppression red-cockaded woodpeckers disappeared from Hitchcock Woods.  They require open conditions.  The Hitchcock Foundation began managing prescribed fires 20 years ago, and the red-cockaded woodpeckers could be re-established here some day.  For now the park’s 5 other species of woodpeckers use these cavities.

I think this is a longleaf pine.  Some longleaf pines in Hitchcock Woods may be more than 200 years old and have red-cockaded woodpecker nesting cavities, though the birds have been extirpated from this area.

A population of fox squirrels (Scirius niger) lives in Hitchcock Woods.  The gray color phase predominates here.  Fox squirrels are uncommon and local in Georgia and South Carolina.  I hypothesize fox squirrels have difficulty recolonizing forests that have been clear cut.  The young dense forests that resprout following clear cuts are more favorable for gray squirrels (Scirius carolinensis).  Gray squirrels are more nimble and can escape predators by jumping from tree top to tree top.  Fox squirrels prefer racing across the forest floor to escape predation.  The presence of fox squirrels in Hitchcock Woods suggests they were formerly more common in southern forests before they were clear cut. I was hoping to see a fox squirrel, but they are more active in the morning, and my hiking companion doesn’t get out of bed until nearly noon.

Rain has eroded the clay and sand here into chalk cliffs.  This is where I found Virginia pine trees.

Chalk cliffs are a naturally eroded environment.

Another view of the chalk cliffs.

The Sand River is another interesting geological anomaly in Hitchcock Woods.  Water flows down this creek following a rainy spell, but normally it’s just a river of sand.  It’s located on the other side of Hitchcock Woods from the chalk cliffs.  I’ll visit that part of the park another time.

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.

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.

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

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

Ecological Islands within the Continent of Africa (Part 3–The Forests of Biafra)

The bight of Biafra, the “armpit” shaped region of western Africa, hosts the wettest rainforests on the continent.  Over 6000 species of plants grow here including oil date palms, and many species of cassia trees, liana vines, and orchids that sprout in organic matter deposited on the crooks of tree branches.  Before humans deforested the greater part of the region, it was a lush, green, and shady environment.  Species such as the giant ginger plant (Aframomum gigantea) exist as long-lived roots until a tree falls, allowing sunlight to reach the forest floor.  Then the ginger plant sprouts up to 18 feet tall to benefit from life-giving photosynthesis.  The spicy hot compounds in the root protects the ginger from foraging animals, insects, and microbes for decades while the plant awaits its chance to sprout.  The stems, however, are a favorite food of the gorilla.  Ginger is used in human cuisine, but try taking a bite of raw ginger root and find out why animals avoid eating it.

Illustration of the giant ginger plant.

Primates and squirrels like to eat the nuts of the 20 species of colas that grow here.  Yes, this is the nut that flavors Coca-Cola.  The caffeine in the nuts is poison to some animals but many species, including humans eat them.

Cola nuts are native to Africa.  Extract from the caffeine-laden nuts is used to flavor Coca-Cola.

The American persimmon (Diospyros virginianus) is 1 of just 2 species of ebony trees native to North America.  Africa has 40 species in this genus.  They produce a heavy valuable wood, a trait that has led to deforestation of the region.  The fruit of ebony trees resemble those of American persimmons and are edible, but the leaves are toxic.  An area of Biafra, known as the Sanaga Delta, experiences heavy rains and has sandy soils.  Ebony trees thrive on these poor soils and dominate the forest canopy.  The toxins in the ebony tree leaves help the trees conserve nutrients by discouraging animals from eating them.  Most colobus monkeys primarily eat leaves but can’t eat the toxic ebony tree leaves.  Therefore, most species of colobus monkeys live in lower densities on the Sanaga Delta than elsewhere in Biafra.  But the satanic colobus monkey (Colobus satana) evolved the ability to eat seeds and do better here with reduced competition from other monkeys.

Ebony trees are endangered because of the high quality dense wood they produce.  Most fruits are edible, similar to American persimmons, but the leaves are toxic.

The satanic or black and white colobus monkey.

The mandrill (Mandrillus leucopheus) evolved from a ground dwelling baboon-like monkey.  It became adapted to more forested conditions.  The colorful faces and genitals of the males is likely an adaptation to communal living in the forest.

Male mandrill.

Over 1000 species of butterflies live in Biafra–the richest diversity in the world–and over 500 species of birds occur here, rivaling the Amazon basin’s diversity.  There are 8 endemic genera of frogs as well.  The goliath frog (Conraua goliath), weighing over 7 pounds, is the largest frog in the world.  This species occurs in a small range within Biafra.  Its large size and slow rate of reproduction make it vulnerable to predation, yet it has found a survivable niche in this rich region.

The goliath frog is endemic to this region.  It can weigh over 7 pounds.

Reference:

Kingdon, Jonathan

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

Princeton University Press 1989

Ecological Islands within the Continent of Africa (Part 2-The Guinea and Ivory Coast)

The tropical forests of Guinea and Ivory Coast are separated from Central African tropical forests by a wide belt of savannah that stretches all the way to the Atlantic Ocean.  This zone of grassland is known as the Dahomey Gap.  The 2 regions of tropical forest share many of the same species, showing they were formerly connected, but they host different species as well–evidence they’ve been isolated for long enough that speciation occurred.  The Sahara Desert, located to the north of Guinea, has expanded during past climatic cycles, compressing this region of tropical forest into a smaller pocket.  Even today, sandstorms and desert winds deposit sand and spread fires in this region.  These factors exert a differing influence on this tropical forest than on Central African forests.  This may explain differences in floral and faunal composition between the 2 regions.

 

 

 

 

 

 

 

 

 

 

 

 

 

The Dahomey Gap is a savannah that isolates the tropical forest of Guinea from the forests of Biafria to the southeast. This gap and rivers isolate chimpanzees into different subspecies.

Forest elephants (Loxodonta africana) had the greatest impact on the environment here until man nearly extirpated them.  Elephants were formerly so abundant they influenced the names of the nations.  Ivory Coast was named for the trade in elephant tusks, and the Guinea–a gold piece with an elephant image stamped on it–was used as money in the British Empire for centuries.  The decline in the elephant population caused a corresponding decline in white breasted guinea fowl (Agelastes meleagrides) numbers.  This species prefers open forest floors created by elephant trampling and foraging.  Without elephants, dense undergrowth covers the forest floor, a condition that favors a different species of guinea fowl–the crested (Guttera pucherani).

The white-breasted guinea fowl is in decline because it prefers open forest floors created by elephants which have been extirpated from many places within this region.

Over 140 species of mammals live in this region, including 11 species of primates.  There are 7 species of small forest antelopes known as duikers, 2 species of wild hogs, forest buffaloes, pygmy hippos, chimpanzees, colobus monkeys, Liberian mongoose, genets, and large leopards.  The jungle leopards grow larger than savannah leopards, probably because they don’t face competition from lions and are the king cat in this region.

When most people think of African wildlife, they don’t think of squirrels, but this region is home to 6 different species.  All African squirrel species originated from ground dwellers that invaded the continent 10 million years ago.  They later adapted to life in the trees.  The most primitive local species is the western palm squirrel (Epixarus ebii)–a large squirrel that spends considerable time on the ground and can gnaw through the hardest of nut shells.  By contrast the giant squirrel (Prototoxerus strangeri) is the most arboreal species.  The slender-tailed squirrel (Allosciurius aubinni)prefers swamp forests where it avoids  2 species of crocodiles by staying in the tree tops.  The red-legged squirrel (Heliosciurus rufobrachim) is completely arboreal and evolved in tropical forests, while the Gambian sun squirrel (H. gambianus) evolved on savannahs and still occurs there but has adapted to forests as well.  Pel’s flying squirrel (Anomalurus peli) glides between the trees.

The Gambian sun squirrel lives within the Guinea/Ivory Coast forests.  It also occurs on savannah habitat and is a relic from when savannah was more prevalent here.

 Pel’s flying squirrel.

Zebra duiker.

Giant forest hogs are aggressive and dangerous and will attack people.

Western red colobus monkeys are endemic to this region.

 

 

 

 

 

 

 

 

 

 

 

 

 

The rufous fishing owl (Scotopelia ussheri) is another unique species endemic to the region.

All this spectacular wildlife can be found in Tai National Park, but unfortunately this is where the Ebola virus originated.  Chimpanzees contracted Ebola from hunting colobus monkeys.  People eating bush meat then became exposed to the deadly disease.  Though I’d enjoy seeing this diverse fauna, I think I’ll skip the chance that I might catch Ebola.

Reference:

Kingdon, Jonathan

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

Princeton University Press 1989

 

Ecological Islands within the Continent of Africa (Part-1, the Cape of Good Hope)

I scour the latest scientific journals, looking for material I can write about on my blog.  The focus of my blog is meant to be on the paleoecology of southeastern North America during the late Pleistocene.  My writing output, however, is more prolific than the number of new studies being published.  I wish there was an army of scientists researching ancient evidence of plants and animals in the region, but instead there are probably less than a platoon’s worth.  So I’m forced to delve outside the region for blog fodder.

Recently, while researching something else, I discovered a wonderful book published in 1989 by Jonathan Kingdon entitled Island Africa: The Evolution of Africa’s Rare Animals and Plants.  The premise of the book is that climate and geography have worked together in Africa to isolate many different natural communities into ecologically diverse islands.  For example climate change has caused deserts and savannahs to expand, thus isolating regions with tropical forest that were once connected.  Closely related organisms of the forest then evolved into different species because of this isolation.  Conversely, tropical forests grow between deserts and savannahs and isolate organisms that prefer dry open environments, resulting in speciation of grassland organisms.

While reading this book, I learned about many species of plants and animals that I did not know about.  Because I’ve so thoroughly studied and speculated about the flora and fauna of Pleistocene North America, I thought it would be a refreshing change to cover Africa’s paleoecology for awhile.  Pleistocene North America was a great untouched wilderness until man colonized the continent about 15,000 years ago, and it’s fauna has often been compared to Africa’s.  This is a misguided perception because Africa’s wildlife is much more diverse than that of North America during the Pleistocene.  (See: https://markgelbart.wordpress.com/2013/12/09/the-faunal-diversity-of-pleistocene-north-america-was-less-than-that-of-modern-day-africa/ )  South Africa, the first “ecological island” I’m writing about has 30 species of antelope alone.

Several physical barriers isolate South Africa from the rest of the continent.  Cold mountains block the exchange of tropical species.  Deserts are an insurmountable obstacle for forest species.  And wide rivers are an impediment for animals that avoid swimming.  The Cape of Good Hope includes a wide range of environments including desert, savannah, montane grassland, evergreen heath, woodland, and coastal forest.  Antarctic and tropical currents offshore create an unusual climate consisting of dry summers with frequent fires and cool moist winters that mostly stay frost free (though snow and frost do occur in the mountains) so that plants can grow well then.

Many interesting plants that are fire tolerant and can take advantage of winter precipitation grow in this region  Over 20 species of cycads, a primitive gymnosperm, grow here.  Sugar bushes are also endemic.

 

 

 

 

 

 

 

 

 

 

Cycads are common in South Africa.  They are primitive gymnosperms that first evolved 250 million years ago.

Many species of sugarbush are native to South Africa.

Flowering plants such as geraniums and gladiolus originated in South Africa, but ironically are now rare in their original environments though they are commonly cultivated in flower gardens around the world.

Wild geranium in its native habitat.

South Africa is home to several species of primitive antelopes that formerly were widespread throughout the African continent during the Pleistocene.  Other more advanced species of antelope outcompeted them on most of the rest of the continent, but for various reasons grysbok (Raphizera melanotis), rhebok (Pelea capreolus), bluebuck (Hyppotragus leucophaeus), and white-tailed gnu (Connochaetes gnou) held their ground in South Africa until European settlers overhunted the latter 2 species.  Bluebuck became extinct in 1798.  Conservationists saved white-tailed gnus, and this species is making a comeback.

White-tailed gnu are native to South Africa.

Rhebok with a broken right horn.

European settlers also overhunted the quagga (Equus quagga quagga) into extinction.  Zebras that live farther away from the equator have fewer stripes.  A species of zebra lived in North America until the early Pleistocene.  It likely resembled the quagga.

The only specimen of the quagga ever photographed.  It is now extinct.

The golden  mole (Neamblysomos julianac) is also a primitive species unique to South Africa.

The golden mole is endemic to South Africa.

The ground-nesting woodpecker (Geocolaptes olivaceoc) nests in underground burrows dug into sandbanks. This is very unusual behavior for a woodpecker.  It’s also one of the largest species of woodpeckers in the world.

The ground-nesting woodpecker is endemic to South Africa’s montane grasslands.

Reference:

Kingdon, Jonathan

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

Princeton University Press 1989