Need for speed

The fastest animal that we know of is the peregrine falcon, which can reach 349 kilometres per hour as it dives for the kill. We have also been told that the fastest mammal is the cheetah at 112 kph, and - get this - the fastest insect is the Deer Botfly at 1,287 kph - which is faster than the speed of sound!

However, it seems that someone has been cheating on the cheetah figures, and that the stats for the botfly have been badly botched. Just like bad science, once a wrong speed record is published, it takes a long time to die.

The botfly story began back in 1927, when the entomologist, Charles H. T. Townsend published an article in the Journal of the New York Entomological Society. Right at the end of his article, he included this very interesting paragraph:

"On 12,000-foot summits in New Mexico I have seen pass me at an incredible velocity what were quite certainly the males of (the deer botfly). I could barely distinguish that something had passed, only a brownish blur in the air of about the right size for these flies and without sense of form. As closely as I can estimate, their speed must have approximated 400 yards per second [800 miles per hour]."- (actually closer to 818 mph)

In 1938, Irving Langmuir, an American chemist and Nobel Prize winner, demolished this astounding claim.

First, at 1,287 kph the air pressure against the head of the fly would have been about half an atmosphere, which would have been enough to crush the poor little fly. Second, the energy needed to fly at that speed meant the deer botfly would have to eat one-and-a-half times its own weight in food every second! Third, at what speed does a flying insect turn into a blur? Langmuir just got a lump of metal the size of a deer botfly, tied it to a thread and swung it around. At 20 kph, it was a blur - "the shape could not be seen, but it could be recognised as a small object of about the correct size". At 41 kph, "the fly was barely visible as a moving object". So Townsend probably saw deer botflys cruising at around 40 kays, which is a lot less than 1,287 kph.

Also, you would get an extremely nasty injury from a supersonic botfly running into you - but there are none on record. The fastest insect on record, that has been reliably measured, is the Australian dragon fly - which has a top speed of around 57 kph.

So what about the cheetah? The claim that it can travel at 112 kph (70 mph) originally came from an article by Kurt Severin published in the magazine 'Outdoor Life' in April 1957.

The cheetah's trainer marked out a course 80 yards long. He attached a bag that was scented with meat to the wheel of an upside down bicycle, and then hand-cranked the pedals like crazy. The trainer called out 'GO' and started his stopwatch, and then the cheetah took off. An assistant fired a pistol when the cheetah crossed the finish line, at which point the trainer stopped his stopwatch. Severin then wrote an article saying that "from a deep crouch ... (the cheetah) .. spurted to the end of the 80-yard course in 2.25 seconds, for an average speed of about 114 km (71 mph)".

But there are a few problems with this measurement.

First, there was a mathematical error! 80 yards in 2.25 seconds works out to 117 kph, not 114 kph. Second, it turns out that the track was only 65 yards long, not 80 yards long. Thirdly, there's a lot of room for human reaction time error in measuring a time as short as 2.25 seconds. Fourthly of course, the animal was timed from a standing start, not once it had got up to speed.

The best measurement on record was made in 1965 by N. C. Craig Sharp, who was at that time a veterinary surgeon in Kenya. He had access to a tame cheetah that had been raised on a farm. He wanted to see how fast this cheetah could go, so he measured out a 201 metre (220-yard) course. He was sensible enough to realise that the animal needed a bit of acceleration time, so the cheetah began some 20 yards behind the starting line. Sharp was in the back of a Land Rover, trailing a lump of meat in the path of the cheetah. The Land Rover took off with the meaty lure, and the cheetah chased. Sharp simply clicked his stopwatch on and off, as the cheetah crossed the start and finish lines.

He did only three runs, which is not a very large or statistically significant sample size, but he did measure times of 7.0, 6.9 and 7.2 seconds. This works out to around 102 kph. Now Sharp didn't bother publishing his results, because he thought that other people had done more scientifically rigorous measurements of the speed of a running cheetah. But eventually he realised that there were no really accurate speeds published for the cheetah, so he released his results in 1997, in the Journal of Zoology.

With rickety results like these, can we really believe that the cockroach has been clocked at a top speed of only 2.9 kph, when they get out of your way so rapidly when you enter the kitchen at midnight?