What does it mean to be green?

Green anoles have an amazing ability that humans don’t. Can you guess what it is? They can change the color of their body! And they can do this in a quickly as three seconds! The usual color of a green anole’s body, as their name suggests, is green. When they are interacting with other anoles or when they become stressed (from being chased, or being cold) they often turn brown. To me, this is very interesting, and I wanted to learn more about it. So, last summer I asked two big questions and did experiments to answer them.

1. Are some lizards usually green, and other lizards usually brown?

To answer this, I caught 24 green anole lizards (12 males and 12 females) at the beginning of the summer. Each lizard spent about half the summer living alone and the other half living with a lizard of the opposite sex. Every day I recorded their body color, and I found that some lizards were regularly green, and others were most often brown. And, for some lizards, this depended on whether they were living alone or with a roommate.

A brown green anole!

For most males, body color didn’t depend on having a roommate – those who were most often green when they were living alone, were usually green when they lived with a female. Females, on the other hand, were most often brown, but only after moving in with a male. This could mean that for females living with a roommate is more stressful than living alone, especially if that roommate is a male. (I can definitely relate to female anoles – in my experience, living with boys can be a headache, with all the farting, eating, and making messes. If I were a green anole I would be brown ALL the time!)

Female lizards are usually smaller and less aggressive, while males are bigger and fight more often with other males. We also saw that the body color of a green anole changed depending on whether they won or lost a fight; winners will usually stay green after a fight, while losers turn brown. This led me to ask my second question:

2. If males are regularly green or brown, does this change if they win a fight against another male?

To test this, I randomly paired two males and watched them interact for 10 minutes. During these trials, lizards would display at each other using their dewlaps and by doing push-ups, and sometimes they would chase each other around the cage. (So, the lizards didn’t actually fight or hurt each other.) After 10 minutes, we determined who won and who lost – the winner was the lizard who displayed more. All males got to “fight” with four other males. Interestingly, I found that males who were most often green were more likely to be winners. Other scientists had already shown that during an anole fight, the winner was more often green, and the loser was more often brown.  But my study helped us learn that what a lizard’s regular body color is over a long time plays a role in winning in a fight.  This suggests that our lizards have personalities that are connected to their body color!

So, what does it mean to be green? For females, we’re not sure yet – we will have to do more experiments to find out. But if you are a male anole, being green means you may be more aggressive and dominant.  So, if you paint your body green, will you become the most feared and popular kid in school? Probably not, unless you are a green anole!