Depends on what he feeds them.
If they eat mexican, then there will be a hazardous trail of methane gas around the globe
Feeds them peanuts, then the sound you will hear would NOT be santa and his reindeer landing on your roof. The sound would infact be turds chock full of peanuts landing on your roof (no billy, those arent cookies your eating....)
I cant think of any others, feel free to add more