Have you ever seen animals walking on top of the water? A few small animals do that very well, and I find that amazing.

Water striders spend much of their lives standing on the water surface, supported by surface tension. Their weight pushes their legs or feet down and stretches the water surface. This makes a dimple in the surface, just the way your finger makes a dimple in the surface of a balloon when you push on it.

Water striders catch insects that land on the water. Sometimes, though, these water-walking animals are themselves eaten by fish. I've been trying to learn more about how water striders avoid being caught by fish.

I know from my investigations that water striders can jump straight up from the water surface, sometimes as high as 3 or 4 centimeters. I suspect that this jumping is their way of protecting themselves against being eaten.

I have seen lots of jumping, but I've never observed one of these creatures jumping to avoid a predator that I could see. So I think that actually being attacked must be a very rare event, but it must be common enough so that these animals still jump for the slightest reason--just in case.

The Challenge: Help me figure out how often water striders jump "for no visible reason," and how often they jump in response to something you can see, like a fish attack or bumping against another water strider. Just fill out the data sheet below. Thanks for your help!

1. Find a pond that has water striders near the edge, so that you can see them easily.

2. Make yourself comfortable: Remember you'll have to sit very still for 15 minutes so you don't frighten the water striders.

3. Watch the striders for 15 minutes. Don't watch more than four striders at a time, because you don't want to miss a jump. Every time you see a strider jump, put a check mark on the data sheet. If you could see why it jumped, write down the reason it jumped next to the check mark. If you could not see why it jumped, use only a check mark.

4. Add up the total number of check marks, and put the number in the first box.

5. Add up the number of check marks with "known causes," and put the total in the second box.

6. Add up the number of check marks with "no known causes," and put the total in the third box.

If you have time to do this study more than once, that would be great! Please visit this page separately for each 15 minutes of strider observations.

Fill out the data sheet below for as many jumps as you see. Remember only to fill out the "cause" if you actually saw something that caused the water strider to jump straight up into the air.

See if you can tell what caused the jump you see (but only report something as the cause of the jump if you actually saw the cause).

Total number of jumps observed in the 15 minute observation period.

Number of jumps observed in the 15 minute observation period with known causes.

Number of jumps with observed in the 15 minute observation period with no known causes.

If you saw any jumps with known causes, enter the causes you observed here. Then click on the submit button.