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Photo of Rodger Kram Ultimate Speed

By studying the motion of cheetas at the Phoenix Zoo, Rodger Kram is learning that this species has several key adaptations that allow it to achieve speeds of more than 40 miles an hour in less than two seconds. Following the premiere of this Scientific American Frontiers Special Going to Extremes, Rodger answered viewers' questions about the cheetah in an Ask the Scientists forum. Here are viewers' questions and his answers:

QDuring the program the question arose concerning the assertion that cheetah once lived in North America, but around 10,000 years ago they became extinct. Since the pronghorns and cheetah evolved similar speeds, why would one die out and the other thrive? I can only speculate that maybe the cheetah had to work harder for a meal than the pronghorn and along with the mini ice ages couldn't cut it. I don't know. What do you know or think caused the extinction?

That is really out of my expertise. However, I am aware of a new book published by Dr. John A. Byers at University of Idaho @ Moscow. The title is "American Pronghorn: Social Adaptations and the Ghosts of Predators Past." It is published by University of Chicago Press. This book is highly controversial.

Cheetahs in Africa today survive on a narrow edge. It appears that as a species they went through a "genetic bottleneck". That is, their population was very small and near extinct recently. All living cheetahs are offspring of a relatively small population. Thus, they have relatively little genetic variation. A single disease could wipe them out pretty easily. For more on cheetah's genetics, look at an article by S.J. O'brien in Scientific American, May 1986 issue. Hopefully your library has kept their back issues! Saying anything about why the North American cheetah went extinct is speculation.

QHow long do cheetahs live and at what age can the cheetah run its fastest?

According to one source, the average life span is 6.9 years for radio-collared females in the wild (11.7 years in captivity). Lots of other cheetah "facts" are available at:

We don't have good information about the relationship between age and speed. However, it is clear that very young cheetahs are not so fast and very old cheetahs are not very fast. Perhaps this is reflected in the relatively short lifespans quoted above. Being a cheetah is not an easy lifestyle and many prey get away from even the fastest cheetahs. Since cheetahs rarely eat carrion (prey killed by others), once a cheetah can't catch prey it can't live too long.

However, I am very skeptical of the speeds reported for any animal unless they are based on careful scientific measurements. Many animal speeds sound like people describing how big of a fish they caught. :)

QWhat other adaptations in the cheetah's body, besides its flexible backbone, allow it to reach such high speeds?

Cheetahs carry relatively little "extra baggage." They are rather slender and lightweight. However, they do have long legs with lots of muscle mass. We suspect that their muscles are capable of contracting very fast. To really know for sure, we plan to do experiments on muscle fibers extracted from living cheetahs that are involved in a captive breeding program. We suspect that cheetahs also have muscles that are adapted for supplying energy very quickly (via anaerobic glycolosis rather than aerobic oxidation).

QDo you know of any programs in the USA to help the endangered cheetah through captive breeding programs? Are they successful?

Perhaps the best source is:

In general the programs are successful in that they have lots of offspring. Will this really save the cheetah? Not until we all figure out how to conserve enough land in Africa for wild cheetahs. Breeding programs are at best an insurance policy.

Our research on cheetah locomotion will hopefully help these breeding programs. Breeding animal should be healthy and fit and regular exercise is part of that. Cheetahs, being kind of lazy cats, will not exercise much on their own. We have ideas of how to lure cheetahs into running; however, to know how much exercise is safe for a cheetah we need to measure things like how much their temperatures rise while sprinting, how hard they hit the ground with their legs etc.

QIt seemed like a lot of trouble (and a lot of rabbit feet!) for you to get a video of the cheetah while running. I was wondering why you didn't do your video analysis using the footage (possibly from a nature show) that was shown on this story. Just curious.

Curiosity and cats, eh? Like most cats, I am also lazy, and if I could just use such films I would. However, I don't analyze such footage for a couple for reasons. First, to know speed one must know distance and time. To determine a distance from video or film images, one must calibrate the field of view so that you know what the scale is. No nature shows would ever have that information and also they zoom in and out so that the scale changes. Alternatively, if I knew the size of the cheetah, perhaps I could use that as a scale. To do that, someone would have to catch the cheetah and measure him or her.

Timing is another problem. Video is shot at 60 fields or 30 frames per second in the USA and Japan etc. However it is 50 /25 frames per second in Europe. Video is often transferred from one speed to another and back again etc. There is also some commercial slow-motion video but it is not easy to ascertain what speed it is shot at. Traditional cine film can be many different rates and can be increased or decreased for a slow-motion effect. I would never trust the rates of a camera without being there myself and calibrating it somehow. Prof. Milton Hildebrand studied cheetah locomotion in the early 1960's. He began by analyzing a clip from a Walt Disney movie and assumed the film rate was 64 frames/second and it turned out later to be 48 frames/sec (don't hold me to those numbers, the point is he assumed the wrong rate). As a result, he published an article about the top speed of the animal that he later had to re-count. In fact, his mistaken speed is often quoted by others.

In my research I use high speed video (>200 frames/second) and I know that framing rate for certain. Before an experimental run, I put markers in the space where the cheetah will run. I measure the distance between these points using a tape measure and then later, I can convert the images and distances I see on the video screen to real units like inches or centimeters.

Some other reasons I don't analyze Nature TV show footage: I want to know exactly how big the cheetah is in order to make measurements of the torques about the joints, changes in back angles etc. Again, to do so I would need the individual cheetah that had been filmed.

Finally, I measure simultaneously the motion of the cheetah and the forces that they exert on the ground with their feet. In a controlled situation like a zoo, the animal will run across the force platforms I use to measure force. In the wild, they would be very unlikely to run in the right spot.

By the way, the cheetahs in the zoo really seem to enjoy chasing rabbits feet etc. In the show, scenes were shot of the exhibit at the Phoenix Zoo. They run their cheetahs several times per week to give them exercise and to keep them from being bored. After they chase a rabbit foot, they play a great deal. You can go see them run for yourself if you are in Phoenix. The National Zoo in Washington DC also has a cheetah running exhibit. Seeing a cheetah run in person is a breathtaking experience! If you went on a trip to Africa, if you were really, really lucky you might see a cheetah run. If you go to one of these zoos on the right day, you are sure to see them run.

QOur class would like to know why you first decided to do your experiments with cheetahs, and what it's like to work with them. Do these big cats become tame when they get to know you?

Like the shows title, I go to "extremes" to study things. I want to understand what limits the speeds that all animals can run, so I decided to study the fastest animal - the cheetah. I could have chosen to study goats, for example, but I would not learn what sets the ultimate limit for speed. Part of my decision was that it is great fun to watch these amazing animals run! In other experiments I have studied extreme animals. For example, I studied why beetles are the strongest animals (in terms of how many times their body weight they can carry). I have also studied elephants to understand what physical limits are placed on very large animals. I hope to study really slow animals like tortoises someday. All of these extreme animals can teach us something.

I don't really handle the animals myself. Instead, the zoo keepers interact with the cheetahs. However, I do get to go behind the scenes. Some days the animals are fed big meaty bones. The animals are behind strong cage bars but it is really scary in a fun way to watch and listen to them chew and crack open big bones with their jaws and teeth. Because I am unfamiliar to them, I get a lot of intense stares from the cheetahs. After they eat, they lay around like pussy cats but they remain potentially very dangerous animals. I am very careful to not be in a situation where they could hurt me. The cheetahs do get to know the zoo keepers but not like your pet cats do.

QYour research is fascinating but there wasn't much information given on the program about how you, or others, may apply your findings. Can you fill us in on how the results of your research may ultimately be used?

Not everything worth doing has an application -- poetry for example. Also, the study of many things that seem to have no application end up being very useful. For example, someone once wondered why certain jellyfish glow in the dark. After figuring that out, the chemicals that allow jellyfish to glow are now used to study many organic chemical reactions. The glowing chemicals allow for the energy released to be measured etc.

So back to your question, we think that the cheetah's muscles are very specialized for generating power, but we really don't understand that yet. Understanding how muscles of a cheetah work will probably give us insight into how all muscles work. Understanding how genes and nerve input determine the power output of a muscle could be important in treating or curing a lot of diseases. Cheetahs also develop an enormous amount of heat when they sprint and their body temperatures rise quickly. In fact, we think that cheetahs stop running more because they are too hot than because they are tired. Their muscles may be specially adapted to withstand these high temperatures. Something like that might be useful for treating a person who has an extremely high fever. Understanding how cheetahs run so fast might tell us something about the limitations to human athletic performance also. Maybe those secrets could be used to train faster runners for the Olympics etc. Many of these applications are impossible to foresee. If we knew the answers, we wouldn't do the experiments! :)


Scientific American Frontiers
Fall 1990 to Spring 2000
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