My son's odd behavior at the zoo has me worried?

I recently took my children to the zoo. We all had a great time and I suspected nothing out of the ordinary. Before we went in I thought it would be fun to give all of my kids a disposable camera to take pictures of their favorite animals. A few days later I went to get them developed and when I started looking at the pictures I noticed that my youngest son used all of his pictures on the elephants genitalia. The camera held 50 pictures and the majority were all of the elephants "thing". Naturally as a mother this has me extremely worried. Please help me through this.