Vegetation impacts specific to UK native and non native deer species
I find that one of the most fascinating aspects of mammal evolution and ecology is the tell tale signs or signatures that mammals leave behind in the areas in which they frequent. Whether you are a hunter, conservationist, ecologist, budding naturalist or all of the above, these tell tale animal signs can not only be fascinating to find and observe but they can also play a major part in hunting success or information needed for conservation work. Deer are elusive creatures and observing deer in the field can sometimes be very challenging. The tell tale signs left by the activities and behavior of deer are a good indicator of their presence. Deer signs come in many forms, these include: scat, antler scrapes on trees, the eating of certain types of vegetation etc. For this blog post I am going to focus on vegetation impacts caused by deer. Although it may be common knowledge that high densities of deer can have a negative impact on vegetation from overgrazing or browsing it is important to understand which species is causing the impact. This can be achieved by understanding the tell tale signs left by each species. The understanding of these signs can help aid in management decisions when trying to protect forest crops, agriculture or sensitive habitats. These signs are also as equally important to us as hunters, it gives us a better understanding of our surrounds, the species in which we hunt and a greater awareness of animals within an area.
An ancient woodland with a reasonable fallow population. You can see the browse line of the understory trees in the background of the photo.
Deer species have a predominantly herbivorous diet (apart from eating the odd ground nesting bird) and cause various direct types of damage to vegetation that can be specific or non-specific to each species. Damage can range from; browsing of saplings, grazing of vegetation and crops, stripping bark with teeth, bark (bole) scoring with antlers, thrashing at or fraying trees and shrubs, breaking tree tubes, creating racks (tracks) in vegetation, creating browse lines in woodlands and marauding crops.
On a side note it must be understood that when we talk about damage and impact we are concerned with detrimental effects to crops and vegetation. The activities of native deer and in some respects non native deer are natural evolutionary traits. These traits have many benefits to the habitats in which deer live. It is only when areas become over populated by deer that impacts become detrimental. I think I may write a blog post soon regarding the ecological benefits of deer in woodlands. Below is a few short paragraphs outlining vegetative impacts caused by the several deer species found in the UK.
Roe are selective browsers that eat the new shoots of many species of trees and some herbs. As roe are selective browsers they can cause intense damage to certain species over others. For instance, roe can come into conflict with woodland managers as they favour freshly cut coppice of hazel and ash and flowering heads of red campion. Agricultural crops are favourable when the high densities of roe put pressure on woodland vegetation. This is usual in late spring when young vegetative growth in woodlands has been depleted. Juvenile bucks are avid frayers of trees and fresh fraying can be seen throughout the summer months.
Red deer are both browsers and grazers, predating on many woodland plant and tree species. Several conifer species including; larch, Scots pine and Douglas fir are also favourable to red deer. Browsing of such species increases mortality rates in forest planting and bark stripping over winter causes growth deformities in timber crops. At peak rut males will fray bark and thrash at trees with antlers and wallow in damp areas of woodland. Red deer tend to bed up in agricultural crops creating couches and racks. Crop marauding or the creation of racks (deer tracks) from the constant walking through crops by deer can lead to wind throw. High winds can travel through the racks pushing the crop over.
Sika similar to Red, are grazers and browsers. In large numbers, predation can seriously affect heathland, salt marsh, woodland regeneration, planted woodlands and or forestry plantations. At peak rut, stags will bark strip young trees with their teeth and bole score trees with their antlers. Thrashing and bark fraying may not be as significant with sika as it is with other species such as fallow. Sika will bed up in agricultural crops creating couches and racks, a high density of racks may lead to crop wind throw.
Bark stripping of a young plantation of sweet chestnut caused by sika deer. (Image courtesy of Stuart Morrison)
Fallow are primarily grazers but browsing can also be severe and unselective. Fallow are notorious for decimating ancient woodland understory. Wild flowers, saplings, planted trees and coppice are primarily affected. As food decreases bark stripping and chewing of species such as ash and willow will occur. Rutting bucks tend to thrash at and fray semi mature trees. I have also witnessed mature bucks ripping off tree tubes to get to the bark. Fallow are also known to maraud cereal crops, as a herding species fallow tend to cross wide areas of agricultural land when transiting from woodland to woodland.
Muntjac can cause significant damage in managed ancient woodlands to: coppice, planted broadleaf and ground flora. Muntjac favor the tips of new shoots, often out of reach of browsing height. To access these out of reach parts, Muntjac will bite mid stem to fell the shoot to ground level or straddle saplings and walk them to the floor before eating the new shoots and apical bud.
Chinese Water Deer have a restricted national distribution therefore cause limited localised damage to agricultural crops. Tree damage is minimal and woodland habitats are less susceptible to browsing than other species.
A close up of bark stripping casued by sika deer (Image courtesy of Stuart Morrison)