Backyard Biology

Nature stories from my backyard and beyond

Nature Activities

Which Way Home?

Monday, Ocober 3, 2011

Instinct. It is an amazing trait, isn’t it? Think of all the happenings in nature that we attribute to instinct. Here are jut a few that quickly come to mind:

The seventeen year cicada has spent its entire live underground. Suddenly it gets the urge to climb above ground, change into and adult and search for a mate. How does it know where above ground is, or even that there is an above ground? It has never been there or seen it? Instinct.

The monarch butterfly that was born here in New England decides it is time to head south to a specific valley in central Mexico. Why does it decide that Mexico is the place to be? How does it find its way? Instinct.

Mud dauber wasps are solitary wasps. The young wasps never meet their parents, never hang out with other wasps, never are shown what to hunt and how to hunt. Yet, they are able to sting spiders in just the right spots to paralyze without killing. Fresh meat for their young. How do they know where to sting? Instinct.

Spotted salamanders, just emerging from the pond where they are born will head underground, where they will spend most of their lives. What leads them to dig? How do they know they must go down? Instinct.

Of course, when we say instinct, what we really mean is ignorance. Our ignorance, because we have no idea how animals know these things.

There are two parts to this instinct. The first part is how an animal knows instinctively what to do when it has never done it before and never had any instructions on what to do. This we may never know.
The second part is what clues tells the animal how to do whatever it is that they must do. This we can have some fun trying to figure out. As an example, let’s take a look at the snapping turtle. When the baby snapping turtle digs its way out of the nest, it makes its way to the water. It doesn’t matter that the water is hidden by the trees and is not visible, the baby snapper will always head in the right direction. What could possible tell it which way to go?
Let’s consider some of the possibilities. Each of these has at one time or another been suggested as the mechanism that turtles use to locate the water.

  • polarized light
  • smell the water
  • travel downhill
  • earth’s magnetic fields

Now let’s try some experiments that might give us some insight as to how turtles might locate the water.

Materials

  • baby snapping turtle
  • compass

Instructions

In New England, snapping turtles lay their eggs in June and hatch a few months later. So be on the lookout for baby snappers in mid September.

  1. Note the direction the baby snapper is heading. Is it heading towards the water? Is it traveling uphill or downhill?

  2. Turn the snapper around 180 degrees - away from the water - and watch what happens.

  3. Find a hill that slopes away from the water and place the snapping turtle on the hill facing downhill. What does the turtle do? Place it on the slope facing uphill, towards the water. What does it do?

  4. Place the turtle in a completely closed box so it can’t see the sun. Carry it to the other side of the water and let it out of the box, facing the direction it was originally traveling. It is now traveling away from the water. What does it do?
  5. Record all of your findings.

  6. Repeat the experiment with as many turtles as you find. A scientist always repeats an experiment many times to insure the accuracy of the results.

  7. Looking at your data, can you make some predictions about what may or may not direct the turtle to the water?