grasslands of Botswana in south-central Africa and of Colorado in the central
United States exist on opposite sides of the globe, yet they are eerily similar
in appearance and function; a testament to the forces of evolution. When faced
with similar environmental conditions like soil type and levels of
precipitation, and similar ecology like the patterns of how and when
precipitation falls, natural selection opts for plants and animals that tend
towards similarity in their behaviors and sometimes even appearance. Can you
tell which of the following images is from Botswana and which from Colorado?
photo is of the African savanna and the second is of
the Colorado steppe. The grasses and plant associations are very similar. And
below are close up images of fruiting grasses, with the African savanna
on the left and Colorado steppe on the right.
prairies of central North America are classified as temperate grassland, while
those of Africa are tropical savanna. What makes grassland temperate? First,
rain falls in spring and early summer, and is limited usually to about 20
inches per year. This lack of rainfall coupled with the relatively thin soils
found in temperate grassland prevents trees or shrubs from establishing.
Second, temperate grassland experiences tremendous seasonal variations in
temperature; temperate grasslands have a winter that limits the growing season.
Savanna grassland is the tropical version of the temperate grassland and in contrast to
temperate grasslands they usually receive more rainfall and have some trees and
shrubs scattered in the landscape. Savannas don’t experience a winter and are
caused by a distinctive climate pattern that includes a wet season followed by
a long dry season without rain. Fires frequent the dry season and thin the
trees and shrubs that would otherwise invade the grassland. In both, it is the
rains that bring another cycle of life to the grassland. In North America it is
an awakening that follows a long cold winter, in Africa it’s the blood
that breaths life back into the parched, dry and fire prone savanna.
large animals inhabiting the plains of both continents, either did, or still
undergo extensive migrations as they follow along behind the rains, engorging
themselves on the grasses that respond almost immediately to the sudden
abundance of moisture. In North America, it was bison, elk, and pronghorn that
occupied the landscape in the 10,000s or even millions in the case of bison,
moving like a silent army, tracking the rainfall across the landscape. In
Africa, it is the wildebeest, impala, buffalo, and other antelope that still
remain today, following the rains across the landscape and giving birth to a
new generation of offspring as they move.
Bison on the North American plains, left, and buffalo on the African savanna, right.
with the large herds of roaming animals there exists robust populations of
predators feeding off this cornucopia of wildlife. In Africa there are the wild
dog, jackal, lion, leopard, cheetah, caracal, hyena, and honey badger. In North
America there are or were the wolf, coyote, fox, cougar, bobcat, grizzly bear, and
badger. It is striking how similar these predators are, there are canids, cats,
badgers, and miscellaneous other predators in each grassland type. Can you tell
me what is in the picture below? Is it from Africa or North America?
No this isn’t a coyote, it’s a jackal on the African savanna
As an ecologist, I find all of this fascinating, something that is almost visceral and meaningful at a very deep level. I would encourage all of you who are reading this to contact us and start planning your trip to Africa today to witness these majestic predators and the magnificent migrations for yourself. Migrations that persist today as they have for eons in a landscape capable of making one think they were in a far off time, experiencing something long sense lost to our modern way of life.