Because they are a prey animal.
12% skittish
Skittish was created in 2000.
Skittish is an adjective.
Wild deer are usually very skittish animals and must be stalked and killed quietly to avoid alerting the deer and any others nearby. Though now with deer having so much contact with humans they are often quite unafraid of people. Their behavior really depends of where you live and the population density of deer as well as humans.
Raccoons are skittish and definitely not apathetic.
The skittish cat darted away at the sound of footsteps.
After hearing a loud noise, the skittish deer quickly ran away into the forest.
Kevin has a skittish personality so she has trouble making friends.
The cat appeared skittish, racing around the house and jumping up on the bookcase.
British
shy
You just have to keep petting and playing with them. They will remain skittish if you don't handle them quiet frequently.