Why are Some Animals so Ornate?
Throughout nature, we see that some animals have very elaborate traits, while others are more subtle in appearance. Take for example, the peacock. Why is it that male peacocks have such huge, colorful tails, but a sparrow is relatively drab in appearance and has such a short tail?
We asked the campers at Common Ground to think about this question and write down some possible answers. Here is one camper’s insightful answer:
This camper was right on the ball! It is true that in cases in which animals are very ornate this is often to attract a mate. In these animals, the more ornate you are, the more likely you are to mate. This is one component of what scientists call sexual selection. Scientists have demonstrated this phenomenon in many experiments. One of the most famous experiment involved changing the tail length of male widowbirds, birds with very long tails, and then recording which males mated the most. It turns out that in the widowbirds, females prefer males that have long tails. The scientists discovered this by changing the tail lengths of widowbirds and then recording which males mated the most, they were able to show that the males with the longer tails mated the most. To read the original study click here
But the question remains: Why are only some animals ornate, while others, like the sparrow, are so drab? To try to answer this question we played a game.
Capture the Tail
In this game, campers were assigned to play the role of a long tailed bird, a short tailed bird, or a predator. To simulate the different length tails, we clipped long and short ribbons to the campers shirts. We then played a “capture the tail” game. If the predators could pull off the tail, then the “bird” was “out.” What do you think happened?
Well, not too surprisingly, the predators had a much easier time capturing the long tails than the short tails. What does this tell us about why some animals might have long tails, while others have short tails? One reason is that, just like in the game, having a long tail makes an animal more at risk for predation.
After the game, we talked about the results with the campers and we explained that in many cases, very ornate animals tend to live in places where there are very few predators. Since these animals are at low risk of predation, they are able to evolve these ornate traits. In contrast, a sparrow, for example, is confronted with all kinds of predators: hawks, cats, dogs, etc. Therefore, it is important for the sparrow to be inconspicuous. That’s why sparrows tend to be brown and small and have short tails.
We also explained to the campers that sometimes only one of the parents is ornate, while the other is drab in appearance. These differences often have to do with which parent takes care of the babies. If the mother takes care of the babies, but the father doesn’t, it is important that she doesn’t draw too much attention to herself because this could attract predators that might not be harmful to her, but could attack the small babies. Usually, when the male and female of a species look very similar, both parents take care of the babies. Compare the pictures of the male and female bird of paradise to the male and female sea gull. Who do you think takes care of the babies in these two different types of birds?