Tropical Grassland Ecosystems

Tropical Grasslands are found in Central Africa, Australia, Brazil and India, with an average rainfall from 51 to 127 cm annually.

Tropical grasslands are also known as savanna or veldt, are found close to the equator and are hot all year round, with distinctive dry and wet seasons. Rain is generally concentrated in 6-8 months and the remaining months have drought conditions.

Animal Adaptations

Savanna mammals tend to reproduce during the hospitable wet season when food is plentiful, affording sufficient nutrition for mothers to nurse their young. If the rains do not arrive on time, it is not uncommon for antelope calves to die.

The rainy season provides an abundance of food for the birds, insects, large and small mammals but the remaining dry season brings with it a competition for survival. Water becomes very scarce.

Many birds and large mammals migrate to find water, sometimes needing only to move a few miles away because of the variation in rainfall in different nearby areas. Many burrowing animals go into a state of dormancy during this period.

Giraffes are an example of an animal who drinks water when it is available, but who is capable of surviving for weeks if no water is available, drinking morning dew and deriving water from their food.

Because of the giraffe’s long neck, it is capable of reaching leaves that are too high for other mammals, and is it also able to see any potential predators from a distance.

The African hedgehog can manipulate its backbone in order to curl up into a ball when faced with a predator so that only its spiny armour is exposed. Coupled with this adaptation, the animal has acute auditory (hearing) and olfactory (smelling) senses.

Elephants utilize their long trunks to pull off tender leaves above their heads, and move them to their mouths to chew.

The Australian wallaroo has furry pads that allow it to climb on rocks and to dig for underground sources of water.

Plant Adaptations

In order to prevent the areas from becoming rainforests, most tropical grasslands are maintained by frequent fires (both natural and man-made) during the dry season, beginning in October. Fires provide opportunistic meals for birds and other animals, who feed off the insects, mice and lizards killed by the fire. The fires produce a fine ash providing nutrients for the new growth of grass.

Different plants have adapted to grow in specific savanna areas, depending on how much rainfall occurs.

Grasses in these areas have very deep roots that remain unharmed during fires, rapidly sending up new shoots once the rains return. Shrubs survive on the subterranean food reserves in their roots until the rainy season. Some trees survive the fires because of their fire-resistant bark.

In the protected parks of Africa, elephants can be responsible for creating savannas by destroying trees, thereby paving the way for fires to maintain the grasses that sprout up.

Large mammals also contribute to the low density of trees by eating the seedlings.

Acacia trees are capable of emitting a foul-tasting poisonous alkaloid, in order to discourage giraffes from eating its leaves. These trees have the amazing ability to communicate danger to their neighbouring acacia trees, which respond by emitting this same chemical into their own leaves.

Overgrazing and plowing over of grasslands lead to erosion of the soil during droughts. The loose soil left behind is picked up by strong winds, causing dust storms for miles and the loss of fertility in the earth.

See also:

• Grassland Ecosystems
• Temperate Grassland Ecosystems