# Thread: What is the fastest land animal ...?

1. ## What is the fastest land animal ...?

I think everybody would agree that the cheetah is the fastest animal, at around 70 mph = 31 m.sec-1. But I was wondering which was the fastest relative to body size.

I've just calculated that the cheetah at a size of (say) 140 cms has a maximum speed of 22 m.sec-1.metrebodylength-1.

This question came into my head because a spider just ran across my desk, at a speed of at least 0.5 m.sec-1. Not that fast really, except that I estimate its size at 3mm before flattening (I have quick reactions, and besides, it came back again). Relative to body size, this makes 166 m.sec-1.metrebodylength-1, eight times faster than a cheetah.

Fleas don't qualify because they jump. But can anybody think of an animal that runs faster than my spider before it became an ex-spider?

2. Cockroaches always seemed really fast to me for body size, but I haven't done the measurements nor the math. I would guess the winner would be some sort of insect or "bug". This answers.com webpage says it is the tiger beetle, without evidence or references.

3. Mechanically assisted humans? 600m/h = 288m/s. 288/2 (for a tall human) = 144m/s per meter of length.

4. Steve Austin, a man barely alive...we can rebuild him...although does he still count as an animal?

Actually I think relative to body size it's some sort of bug that wins relative to body size. Oddly enough, there was a show about this a while back, comparing all the animals in different ways relative to body size. As I recall, insects fared quite well. In the speed category, some sort of bug won easily.

5. Originally Posted by Swift
This answers.com webpage says it is the tiger beetle, without evidence or references.
Perhaps he was basing it on this.

6. Originally Posted by PetersCreek
Perhaps he was basing it on this.
Huh - the tiger beetle comes nowhere near my spider - that link gives roughly the same scale as mine, and the beetle is only 125 compared with my spider's 166.

7. Originally Posted by Perikles
This question came into my head because a spider just ran across my desk....
We have a certain kind of spider around here that doesn't just run, but seems to quantum leap from one location to another a few inches away. Makes them darn hard to squash. ("Huh? How'd he get over there?") I swear, these spiders do not traverse the distance between one location and the other; they just instantaneously appear in the new location.

OK, I know that's physically impossible (for macroscopic things), but it sure seems like that's what this spider is doing. It's just got to take the record for fastest land animal, regardless of size.

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Ah, so that's where the metabelan phase spiders went.

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The tiger beetle I believe is the fastest animal with body size in account. The cheetah is the fastest animal using it's legs, yet with body size in account a household cat would beat it. But the short answer would be Tiger beetle.

10. Originally Posted by Cougar
We have a certain kind of spider around here that doesn't just run, but seems to quantum leap from one location to another a few inches away. ... It's just got to take the record for fastest land animal, regardless of size.
Yes, but these are jumping spiders, we've got them here as well, the only venomous species in Tenerife, I think, with a nasty bite. Fortunately they are usually too small to be a problem. But if we are counting jumping as well as running, then perhaps fleas are even faster.

11. I believe a sidewinder snake can move pretty fast and is aggresive, so it will chase you and can go faster than you can. I further heard that funnel web spiders will also chase you, so which do you prefer to challenge?

12. Originally Posted by profloater
I believe a sidewinder snake can move pretty fast and is aggresive, so it will chase you and can go faster than you can. I further heard that funnel web spiders will also chase you, so which do you prefer to challenge?
I moved to where we are so as not to have to encounter either. But the spider is much faster than the snake in terms of relative to body size.

13. Spiders must be faster than insects, with eight legs to six.

I hope I never encounter one of those millipedes.

14. Aha, I looked up bacteria which can move at 100 times their body length per second! Vibrio Comma for example hares along at 200 microm/s.

15. Originally Posted by profloater
Aha, I looked up bacteria which can move at 100 times their body length per second! Vibrio Comma for example hares along at 200 microm/s.
Hey - did you read my OP? My spider did 166 times body length per sec!

16. Originally Posted by Perikles
Hey - did you read my OP? My spider did 166 times body length per sec!
Did you account for her getting foreshortened as she approached the speed of light?

17. Originally Posted by DonM435
Did you account for her getting foreshortened as she approached the speed of light?
Of course - I originally calculated 166.00000001 and adjusted accordingly.

18. Just thinking about unassisted humans:
Body length, as defined by dimension in the direction of travel, for a human is only about .25m. (Because our long dimension is vertical!) Sprinters cover 100m in about 10 sec, from a standing start no less, so 10m/sec. That gives a sprinter 40m/sec per unit of body length, better than the cheetah. As long as you use my definition of length!

My personal body length is greater and my speed much slower. The cheetah would have me for lunch.

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Too bad it's "land animal," as the mantis shrimp's strike hits around 23 m/s (about 50 mph). Relative to it's size, I think that would have been a winner.

Naturally, in addition to not being a land animal, it's also only it's claw, not it's whole body.

20. Originally Posted by Trebuchet
Just thinking about unassisted humans:
Body length, as defined by dimension in the direction of travel, for a human is only about .25m. (Because our long dimension is vertical!) Sprinters cover 100m in about 10 sec, from a standing start no less, so 10m/sec. That gives a sprinter 40m/sec per unit of body length, better than the cheetah. As long as you use my definition of length!

My personal body length is greater and my speed much slower. The cheetah would have me for lunch.
You probably wouldn't be happy, but I believe you would probably persevere in a confrontation with a cheetah. Every person I've every heard of being killed by a cheetah has been a woman 5'5" or under.

21. I suspect it depend in the willingness to sacrifice one arm to hold its teeth off and the ability to inflict enough harm with the other hand and the legs to make it want to stop.

22. Originally Posted by HenrikOlsen
I suspect it depend in the willingness to sacrifice one arm to hold its teeth off and the ability to inflict enough harm with the other hand and the legs to make it want to stop.
The alternative being let it kill you?

23. Unwillingness to sacrifice parts of the body occasionally gets in the way of survival.

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Originally Posted by HenrikOlsen
Unwillingness to sacrifice parts of the body occasionally gets in the way of survival.
I have no problem sacrificing parts of the body, provided they're parts of the body of the animal attacking me.

BigDon, I think you're right about human survival rates with cheetahs. Adults weigh from about 70 lbs to 160 lbs. That's less than a mountain lion's 115 lbs to 220 lbs, and they've been successfully defended against by humans with a wild hair of their own.

We "puny" humans are tougher than we look.

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Originally Posted by Cougar
We have a certain kind of spider around here that doesn't just run, but seems to quantum leap from one location to another a few inches away.
I read yesterday about someone who has researched how cockroaches seem to disappear. It turns out that our perception is sufficiently slow that an animal that suddenly does something in less than about 0.2s we can't spot it and that does seem like quantum transportation to us. The particular trick that cockroaches achieve in less than 0.2 seconds is, on arriving at an overhang, to hook themselves onto the underside of the overhang, lifting themselves off the floor. Thus they seem to disappear on arriving at their lair.

26. I seem to recall reading that cockroaches have these sensory hairs on the sides of their body that are effectively "wired" directly to their leg musculature (or whatever it is) such that when touched, they can begin running well before their "brain" (or whatever passes for one) is aware of the contact.

So for the bug, it's "What the -- ? Why am I running? Oh, I get it, someone's trying to squish me! Might as well keep going!"

Small wonder they're difficult to catch.

27. Originally Posted by DonM435
I seem to recall reading that cockroaches have these sensory hairs on the sides of their body that are effectively "wired" directly to their leg musculature (or whatever it is) such that when touched, they can begin running well before their "brain" (or whatever passes for one) is aware of the contact.

So for the bug, it's "What the -- ? Why am I running? Oh, I get it, someone's trying to squish me! Might as well keep going!"

Small wonder they're difficult to catch.
I also recall this.

If you think about it, this is not an unusual neurological wiring; it is found in humans. When you touch a hot object, you pull your hand away because of wiring through your spinal column, not because your brain tells your hand to pull away.

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Originally Posted by Swift
I also recall this.

If you think about it, this is not an unusual neurological wiring; it is found in humans. When you touch a hot object, you pull your hand away because of wiring through your spinal column, not because your brain tells your hand to pull away.
A lot of reflexes are wired this way, including the familiar knee-jerk reflex.

Nick

29. The solifugae are pretty cool spiders. I've heard a lot about them, but it seems that a lot of it (bring down small animals, attack humans) is a bunch of poppycock.

"Solifuges vary from a few millimeters to 10 centimeters in length"

"able to run at extremely fast speeds (53 cm/sec)"

A small sun spider would match your .5m/s and 3mm long parameters, so your estimation of the spidey-speed could be accurate.

30. Two small felines who realize that it is breakfast time and you are going to fill the food bowls, racing passed you down the hall, when you are still 3/4s asleep, appear to be just about the fastest creatures on the Earth.

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