There's a new brand of wildlife video doing the rounds on social media - and the generally positive image enjoyed by the animals means the scenes may delight onlookers.

But many experts say the largely uncontrolled growth of Britain's deer population creates significant ecological dangers.

Without any predators, large deer populations can have a "devastating" effect on their environment, according to the Forestry Commission.

Such is the scale of the problem, that calls are increasingly being made for the reintroduction of wolves, lynx - and even bears - to Britain as a means of controlling numbers and protecting the country's nature.

How many deer are there - and what damage do they cause?

While reliable figures for deer are difficult to establish, their numbers are estimated to have risen from around 450,000 in the mid-1970s to between 1.5 million and two million today.

That could be higher than at any point in the last 1,000 years, according to the Department for Environment, Food and Rural Affairs (Defra).

Defra is among the organisations highlighting problems caused by "excessive" deer grazing, including damage to crops, woodland, trees managed for timber and our natural biodiversity.

When large numbers of deer graze in woodland, it reduces plant and animal diversity - in turn affecting soil and releasing carbon, according to the Forestry Commission.

Birds also suffer from large deer populations. Common species including robin, wren and blackbird are less likely to be in woodland areas where there are deer, research by the British Trust for Ornithology shows, and vulnerable breeds such as nightingale, nightjar and woodcock are negatively impacted.

How would wolves, lynx and bears reduce the deer population?

Dr Chris Sandom is a biology lecturer at the University of Sussex with a particular interest in rewilding, or restoring key ecological processes by reintroducing species.

He says it's hard to define how many deer is "too many" - but what happens when deer are trampling farmland or eating crops is humans and wildlife are put in competition.

Reintroduce predators to the mix and deer will face a different kind of competition.

Bears are thought to have gone extinct from Britain in medieval times, while lynx went extinct about 1,300 years ago. There are various records of the last wolf in the UK between the 15th and 18th centuries.

Bringing back wolves, lynx and bears to the UK would not just reduce the deer population by directly killing them, Dr Sandom explains.

Predators create a "landscape of fear" for their prey which can change their behaviour in a way that slows population growth.

"Large herbivores basically become wary of those big predators running around, they get more cues that they're under threat.

"When they're basically giving over more time to be vigilant, keeping an eye out for who might be creeping up on them, they're not foraging as effectively, which means they don't put on as much weight, they're not in such good breeding conditions, so that can reduce the birth rate."

Deer may also be forced to move around more if predators establish themselves in the area and make it a riskier environment.

How much would predators reduce the deer population?

It is difficult to predict how successful reintroducing predators would be as a measure of controlling the deer population, and there might be periods of time where it has a bigger or smaller impact, Dr Sandom says.

"Predators aren't managers of the prey population, they're not farming their prey species. They're not thinking 'Oh we'll kill a few more today; we don't want to kill too many'."

Research from Europe indicated the best results for reducing the deer population came from bringing in all three predators, he says.

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Dr Sandom says while there is support among the public for reintroducing predators, some people would find the animals scary and it could stop them accessing the countryside.

Other options for population control include traditional culling methods through shooting the animals with a rifle, stalking the animals for food and using reproduction control.

But there's no easy and cost-effective solution. "Trying to reduce the deer population is very challenging," Dr Sandom says.

Last year, the then Therese Coffey told farmers at a National Farmers Union (NFU) farming conference that she will not support the reintroduction of wolves and lynx.

She said at the Birmingham event: "I won't be supporting reintroductions of species like lynx and wolves."