Mordekaiser Elder Dragon Causes Framerate to drop

Mordekaiser's elder dragon caused my framerate to cut from a constant 60 down to a constant 50 whenever he was on my screen. If I looked away my frame rate would go up to 72 (I have my frame rate capped at 60) and then go back to 60 until I looked at the dragon again. I'm using a GeForce GTX 970 Gaming 4G graphics card with the most recent drivers.