Hungry herbivores without predators deliver us the real Bambi Thug

We need to talk about Bambi.

The damage that overabundant deer cause to crops and natural ecosystems has united farmers, foresters and conservationists in calling for more effective control of deer.

Deer are herbivores – they graze in grasslands and browse on tree and shrub leaves, twigs and bark. They can kill adult trees just by stripping away the bark. A tree grows from a girdle of living cells located just underneath the bark, and removal of this precious girdle weakens and can kill a tree as it can no longer transport water and nutrients between the roots and the canopy.

All herbivores have preferences for what they eat. Some are very picky, and will delicately select individual plants from the smorgasbord available, while others will eat a wide range of different species. Very selective herbivores can change their habitat’s plant community from one with many species of tasty and attractive plants to a green desert, dominated by their least-favoured plants.

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Imagine a vegetable buffet where plates of tasty tomatoes, sweet carrots and crunchy peppers get eaten first, while the plates of Brussels sprouts lie untouched. Soon, all that’s left is Brussels sprouts. This is what takes place in our native woodlands. Deer happily munch on oak seedlings while leaving the rhododendrons untouched. Over time, this selective feeding can lead to a total replacement of oak woodland with rhododendrons.

[ Calls for larger deer culls after record 55,000 shot dead last year ]

When large herbivores such as deer are not controlled by natural predators, they are only limited by access to resources, such as the amount of food available. If enough food of good nutritional quality is not available, the old, young and weak animals die of malnutrition or are weakened and die of disease.

A forest dominated by toxic rhododendron is not much use to a population of deer, and in this way the deer and plants can cycle between over- and under-abundance, with no guarantees that an overgrazed plant species can recolonise once deer numbers naturally reduce through malnutrition. In ecology, this is termed “bottom up” control of deer numbers, as it is controlled by the plants. The cycle can take decades, centuries or even millenniums to resolve.

In Ireland we are in a phase of deer increase, there are plenty of plant resources for them in farms, forests, and restored and regenerating native woodlands. Once one area has been decimated, they can move on to another buffet location. As adult deer have no natural predators, the only way to exert “top-down” control is through hunting, a form of culling.

Deer hunting removes deer from a location and creates a landscape of fear, as hunting also deters deer from occupying certain areas and can reduce their impact. Hunting can also result in moving of deer populations into woodland refuges, where they are more difficult to find, potentially concentrating damage caused by them in sensitive locations. Hunting is therefore only part of the solution.

The Irish Deer Management Strategy Group brought together a wide range of stakeholders to provide recommendations on how to address the impacts of deer damage on agriculture, forestry and biodiversity. Top of the list of recommendations was to establish a deer management agency with local deer management units. The strategy group also looked at how the venison industry, the use of culled deer for food, could be incentivised.

Venison is lean, nutritious and very tasty, but also has connotations of elitism for some people

Venison has far lower greenhouse gas emissions associated with it than beef or lamb do, because the deer’s digestive system does not produce the same damaging methane emissions as cows and sheep. Control of deer also increases the capacity of forests to capture carbon through tree growth.

[ We're going on a Co Tipperary deerhunt ]

A trip to the local butcher to source venison was an eye-opening experience. Only expensive venison steaks were available, and when we asked for the more economical stewing venison, another customer mentioned she was looking for the same for her dogs.

Venison is lean, nutritious and very tasty, but also has connotations of elitism for some people, as the animals are perceived as too cute to eat (the Bambi effect) or as only suitable for dog food. A concerted effort is needed to make it part of a regular family diet. I can think of no other dietary or land management advice that would unite conservationists, farmers, foresters, butchers and hunters.

Yvonne Buckley is an ecologist and professor of zoology at Trinity College Dublin

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