Why is Mr. Ranger shooting Bambi?

shooting bambi
Exotic deer have worn out their welcome at Point Reyes National Seashore, and the National Park Service has decided it's time to wipe them out...

The alternatives range from doing nothing to shooting the deer. The park service's preferred option involves killing most of them and treating the remainder with a special vaccine that would sterilize does for up to three years...
Pt. Reyes is located in... Marin County, the same place that spawned these beasts.