Cheetahs are spotted cats best known for being the fastest land animal, sprinting at speeds of about 120 kilometers (75 miles) per hour. They can accelerate from zero to 97 kilometers (60 miles) per hour in three seconds, making them faster than most sports cars. Cheetahs use their acceleration and speed to chase down and catch their prey, like gazelles, on the Sub-Saharan savannas of Africa. Cheetahs have small heads, lean bodies, and long legs. They have a yellowish-tan coat with distinctive black spots. And they are facing extinction.

 

Pressure from climate change, hunting by humans, and habitat destruction are reducing their populations. Cheetahs also face problems from their own genes. Cheetahs have a low rate of reproductive success meaning that, as a species, they are not always able to reproduce. With fewer offspring, the population can neither grow nor adapt to changes in the environment. 

 

Evolution of Cheetahs 

 

Cheetahs originally evolved from mountain lions in North America. About 100,000 years ago, cheetahs began migrating out of North America across the Beringian Land Bridge to Asia and then into Europe and Africa. About 10,000 to 12,000 years ago, at the end of the last ice age, an extinction event took place that wiped out many large mammal species around the world. The cheetah species in North America and Europe became extinct, leaving only the Asian and African species of cheetahs. Since then, stress from climate change, habitat loss, and human activities have put pressure on the remaining two species. Today, one cheetah species is found in eastern, central, and southwestern Africa, while a tiny population of another species, the Asiatic cheetah, is found in Iran. Scientists estimate that less than 8,000 African cheetahs are living in the wild, and there may be less than 50 Asian cheetahs left in the world. 

 

Bottleneck Events


Cheetahs today are heading toward extinction. However, this is not the first time that cheetahs have faced extinction. Genetic analysis of wild cheetahs shows that they have survived at least two bottleneck events. In biology, a bottleneck event occurs when something happens to sharply reduce the size of the population. When this happens, the few remaining individuals end up mating with relatives; this is called inbreeding. This reduces the size of the gene pool and can lead to problems such as decreased genetic variability and the persistence of potentially harmful mutations. When genetic variability is reduced in a population, it is harder for the remaining population to adapt to changes in their environment. In a very small population, any mutations that occur are much more likely to be passed on to offspring.

 

The first bottleneck event that cheetahs underwent occurred around 100,000 years ago when cheetahs expanded their range into Asia, Europe, and Africa. This range expansion took place rapidly, spreading out cheetahs over a very large area. Because the cheetah populations were spread out across the continents, they were isolated from one another, unable to exchange genes. This first bottleneck event affected the populations of cheetahs, but they were able to bounce back. Over the next 90,000 years, their gene pools expanded as the populations grew to a large size.

 

The second bottleneck event occurred about 10,000 to 12,000 years ago, at the end of the last ice age. The cheetahs in North America and Europe became extinct, leaving only the Asian and African species. As large mammals died out across the world, the number of surviving cheetahs dwindled. Some scientists estimate that as few as seven African cheetahs survived this bottleneck event. This led to extreme inbreeding among cheetahs. Even though the population of cheetahs in Africa grew into the hundreds of thousands by the 19th century, their genetic variability remained low due to the extreme bottleneck event that took place thousands of years previously. 

 

Cheetah Genes Today


Wild cheetahs today are almost all genetically identical and heavily inbred. Evidence for this comes from several different indicators. One way to test for the degree of inbreeding is to perform a skin graft. This involves transplanting a piece of skin from one cheetah onto another to see if the receiving cheetah accepts or rejects the graft. In inbred populations, skin grafts are easily accepted among unrelated cheetahs. This occurs because cheetahs seem to have lost some of the genes that affect their immune responses. Another sign of inbreeding is shown in skull development. In inbred animals, the skull is more asymmetrically shaped. A study of cheetah skulls in museum collections showed that their skulls are asymmetrical. 

 

The third line of evidence for inbreeding comes from the enzymes that cheetahs produce. Enzymes are important because they act as a catalyst and speed up chemical reactions in the body. Enzymes are a kind of protein, and as such, they are built from coded instructions in an organism’s DNA. Among cheetahs, their enzymes are about 97 percent identical throughout the population. Laboratory rats that have been inbred for at least 20 generations will also have about 97 percent identical enzymes. By comparison, human enzymes are about 70 percent identical.

 

Cheetahs are facing extinction from many different factors. Humans are threatening the population by infringing on their habitats, hunting, and perpetuating climate change. Cheetahs are unable to cope with these pressures because, in part, they lack the genetic variability to respond to these pressures. Cheetahs have faced at least two genetic bottlenecks in the past and survived. As the population of wild cheetahs dwindles, only time will tell if they can survive the current genetic bottleneck.

 

Cheetahs: On the Brink of Extinction, Again

Cheetah's struggle to reproduce, which along with human-caused pressures to their population, puts their species in jeopardy. The IUCN Red List classifies this big cat species as vulnerable.

bottleneck
Noun

event that drastically reduces the size of a breeding population resulting in less genetic diversity

catalyst
Noun

substance that causes or quickens a chemical reaction, without being affected by it.

DNA
Noun

(deoxyribonucleic acid) molecule in every living organism that contains specific genetic information on that organism.

enzyme
Noun

proteins produced in living cells that act as catalysts to accelerate the vital processes of an organism.

Noun

process of complete disappearance of a species from Earth.

gene
Noun

part of DNA that is the basic unit of heredity.

gene pool
Noun

all the available genes in a breeding population

genetic diversity
Noun

difference or variety of units of inheritance (genes) in a species.

Noun

differences in the genes among individual members of a species.

inbreeding
Noun

breeding animals that are closely related genetically

Noun

sudden variation in one or more characteristics caused by a change in a gene or chromosome.

organism
Noun

living or once-living thing.

population
Noun

total number of people or organisms in a particular area.

protein
Noun

one of many complex compounds, made of chains of amino acids, that make up the majority of all cellular structures and are necessary for biological processes.

reproductive success
Noun

passing genes on to the next generation