A study shows visitors feeding the deer at Dublin's Phoenix Park is having a huge negative impact on the wild herd.

Laura Griffin, who is running the project, has seen firsthand the harmful foods the deer are fed.

She has been recording these interactions for the past four summers.

The observation fieldwork is park of her PhD study with the Laboratory of Wildlife Ecology and Behaviour at UCD and is funded by the Office of Public Works (OPW).

Laura Griffin is investigating the interactions between visitors and deer at Phoenix Park

She said: "We have seen them being fed chocolate, biscuits, crisps, popcorn. Even sandwiches with ham and chicken in them have been fed to the deer. All of which - 100% - should not be fed to them.

"A lot of people who come into the park think they are doing something beneficial for the deer. They love the deer. They could be bringing in carrots, and apples and oats. They think this is part of the deer's natural diet but it's not, especially not in the quantities that they are getting it."

Feeding the deer at Phoenix Park is prohibited by the OPW. The pandemic has seen an increase in the numbers visiting the park and interacting with the deer. Laura said the health and welfare implications of feeding the deer are many.

There are around 600 fallow deer at Phoenix Park in Dublin

She said: "There are physiological effects such the deer that are fed by people, they actually produce smaller antler sizes after their antlers have finished growing.

"The implication for that during the rut could be huge because they use their antlers for sexual competition. So, when they are fighting. If your antlers are smaller you are more likely to lose which means you are going to have less mating opportunities. You're actually putting them at a disadvantage.

"Deers are ruminants. They are like cattle. They have a four-chambered stomach. They need to sit and ruminate or digest to extract all the nutrition from their food. We actually found that the deer that accept food from people have ended up changing the internal structure of their gastrointestinal tract.

"As well as that, with the female herd, we found that people approaching them to feed results in a lot of stress behaviours. Particularly at this time of the year because the fawns are coming out to join the herd for the first time."

Amy Haigh said getting a selfie for social media is driving people to get closer with the deer

Often the reason people feed the deer is to draw them closer for a 'selfie', said Amy Haigh, a technical officer with UCD who assists Laura with her fieldwork.

She said: "I think social media has a huge impact on it. When we see pictures of people incredibly close to the deer and think, 'oh, that would be an amazing photograph for my Facebook profile'. And then I think when you do get that close people think, 'can I just get that step closer?'"

OPW guidelines say to keep a 50-metre distance from the deer at Phoenix Park. 'Selfies' are not allowed.

Laura Griffin said if you "let the deer be deer" you can have a much more enriching viewing experience.

She said: "If you just keep a safe distance - we recommend 50 metres - if you keep that distance and watch the deer, you'll see some incredible natural behaviours. You get some fabulous photo opportunities from that. At this time of the year, you can see the fawns come out into the open. You get to see them playing, suckling off their moms. The deer socialising, grooming each other.

"Keep the wildlife wild. Admire them from a distance and let the deer be deer".