Deer Survey 2022 – a bird’s eye view
Deer, as with everything in the world of wildlife, can be complicated. At Fingle Woods, we spend a lot of time considering how hundreds of large herbivores might be responsible for browsing woodland regrowth. We often consider what their damaging impact on the regeneration of woodland plants might be, but we also ask ourselves questions about their positive impacts too. We know that their selective feeding and disturbance of soil may have beneficial effects on the diversity of wild woodland flora. As we walk through the woods, it is always a pleasure to see these beautiful beasts going about their business and displaying natural behaviours. They are, after all, an important group of species within the ecosystem and quite magnificent too. The real crux of the question we must contend with is around their uncontrolled numbers, and it is a man-made problem. Before humans hunted predators to extinction, deer used to be in balance with the other species and habitats around them but now, as they continue their high reproduction levels in the absence of predators, we ask, what can we do to restore the balance?
The British Deer Society states that, “In the absence of natural predation it falls to people to manage the ever-growing deer populations, but to manage them with care, with respect and with deference to scientific knowledge and research.” Going on to say that “deer management usually means culling to a plan which replicates a similar impact to that of natural predation.” But first, we need to know where they are, what species are there locally and in what numbers? So, stage one of this delicate operation is to survey the deer across the Dartmoor landscape. Fallow, red and roe deer are the three well established species in the woods around Dartmoor, though more recent introductions have increased the nation’s species list to six (including sika, muntjac and Chinese water deer).
Traditionally, a survey would have started by walking the fields and woods in the areas where deer are likely to be present, looking for hoof prints (slots), droppings and overnight ‘scrapes’. Other signs such as hairs caught on barbed wire or the seasonal bark stripping or ‘fraying’ of trees also fill in pieces of the picture but it is difficult to put a number on the local population from these clues alone. In recent years, technology has moved on and the development of cameras mounted on drones has provided a new window into the activities of these elusive animals.
Tom Williams is our local licensed drone pilot and, with a team of assistants, alarms were set for the middle of the night so we could meet up at a series of sites around the eastern wooded valleys of Dartmoor. These sites covered the river valleys of the Dart, Bovey and the Teign where Woodland Trust sites and interested neighbours would contribute to a nocturnal count of deer in the landscape. As deer are frequently active through the night and the early hours of the morning, the drone survey team had to do the same over a period of weeks before winter turned to spring. With the tree canopies bare of foliage, a high-powered drone could pick up activity over half a kilometre (500m) away at night. So far, in fact, that the deer were not often disturbed by the presence of an eye in the sky. Using both thermal imaging and daytime, colour photography, the drone had the ability to capture both videos and still frames before and after sunrise. The accuracy of the camera equipment can be quite astonishing, particularly as thermal imaging cameras work best during hours of darkness, using the contrasting heat signature of a warm body in the cold night. When the weather was favourably dry and with a clear sky, wild creatures as small as a squirrel or a woodland bird could be seen and sometimes identified.
With Tom flying the drone, the job of the assistant was to cover safety checks, listen out for other aircraft and record data. Results were plotted on a hand-held tablet in as much detail as possible, including the species and sex of the deer if it was possible to determine. Adding all the data together, a map of the landscape shows some interesting patterns. Tom commented that, “the survey largely confirmed that Roe are present across all sites in relatively low numbers, with Fallow absent from Ausewell, present in low numbers in the Bovey and numerous in the Teign Valley. Red deer were present at Ausewell only”. This summary shows a correlation with a recent vegetation impact survey that provides a measure of the effects of deer browsing. Tom added that, “it looks like it broadly tracks the variance in population we observed with the drone with the Dart and Bovey being lower impact than the Teign Valley where there are larger herds of fallow deer”.
The use of trial cameras backs up the findings of the drone survey and are useful as a way to verify those results. These fixed-position cameras have confirmed that there are large herds of fallow, smaller groups of roe deer and the occasional fox at Fingle. Trail cameras are useful but are only effective in a small area compared to a drone that can cover several kilometres in one night. The full picture of deer monitoring does provide us with some areas to focus on with some sensitive deer control but, as British Deer Society says, “Deer management is more than just culling and can take into account a number of factors and methods to ensure deer populations remain healthy and in balance with their environment.”
by Matt Parkins
Aerial photography: Tom Williams
