Crisps and even chocolate are some of the foods being given to the deer in Dublin's Phoenix Park.
Rangers are urging people not to feed or take selfies with the animals while out on their Christmas walks.
More than 500 wild deer roam the Phoenix Park.
Terry Moore, head ranger and deer keeper, says messing with their diet can lead to malnourishment and even leave the males with smaller antlers;
"Mainly carrots.
But we’re also seeing crisps and chocolate and bread.
Sometimes they leave the plastic bags on the ground and deer eat the plastic bag.
Or even, I’ve seen a deer recently on social media eating a face mask."
People in the park are being told to keep 50 metres away. This man says there are often people getting too close:
"I’m seeing parents of young three year old or four year olds and the parents encouraging the children to walk up to reindeer to feed them."
Terry Moore says it’s a particular issue at Christmas time;
"The weekends when the weather's good then yeah, large crowds coming in just specifically to get out of the car to go over and approach the deer."
This week, especially for years, has always been a big problem.
Instead of feeding and taking pictures with the deer - post boxes for children to drop off their letters to Rudolf have been installed.
