The tree lizards' dewlaps are like flags that tell other lizards how they behave. People can also use these visual signals to determine how aggressive a lizard is. This is very helpful for biologists who study tree lizard behavior. One of Moore's discoveries is that the hormones testosterone and progesterone make the male tree lizard morphs different. When they are babies, orange-blue tree lizards have lots of testosterone and progesterone.
Orange males have much less.
Because their hormone levels are different, the two types of males develop differently. High levels of these hormones cause males to develop orange-blue dewlaps, and think like fighters. In fact, Moore can change a timid orange male into a feisty orange-blue male by increasing its testosterone or progesterone levels. Moore's research team is now doing experiments to find out whether orange-blue males' brains look different from those of orange males. They are particularly interested in the areas in the brain that control aggressive behavior.