Apr 13 2021

Monitoring the Herd

When the medieval inhabitants of the Teign valley introduced a herd of fallow deer to Whiddon Deer park, they could scarcely have imagined that 500 years later, we would be counting their descendants as they wander through Fingle Woods at night. It would be even less likely that they would have been able to comprehend the lithium powered, GPS-guided flying machine, equipped with high resolution digital cameras that could see in the dark. What is this witchcraft? Such flying sorcery!

Though the deer are now considered a part of today’s ecosystem, it helps the task of restoring Fingle Woods if we know how many there are. Groups of large herbivores have an impact on regrowth of vegetation as they roam. In some cases, is it an impact that is beneficial but frequently, it can be unhelpful to the restoration cause. Before widespread human intervention and with big cats and wolves on the scene, the fence-free landscape would have found a way to balance these large beasts whether they were early relatives of the cattle, ponies or even deer we see in the countryside today. The effects of grazing herds can be significant, and at Fingle, the historic herd of fallow deer are being carefully watched.

Fallow deer on the steep slope facing Fingle Woods

Since the rows of conifers were planted, the woodlands along the Teign gorge have been making a gradual transition to become a bit wilder, but with excessive nibbling of shoots and saplings, browsing of branches of larger trees and grazing the wildflower sward, there could be a problem. While the herd-forming fallow and a few small groups of roe deer are here to stay, ecologists have been monitoring the vegetation across Fingle to find out whether the way they graze might create subtle differences in the patterns of growth and the key to understanding this pattern needs accurate knowledge of numbers – how many deer are actively moving around the site? A walking survey is the traditional way but that can be time consuming, sitting patiently, waiting. A visual count may have questionable accuracy as it would be done over a period of days to cover the vast expanse of woodland resulting in double counting some while completely missing others.

So, to get a view of the deer in and around Fingle in one night, a team of nocturnal surveyors set out one evening in early March. Ben Harrower, the Woodland Trust’s lead on wildlife management, was setting up his gadget-laden drone saying, “March is an important time of year for this. We need to do it before the vegetation is up. I’ll be mapping everything we count so we will have a good understanding of the number of deer and their utilisation of the site. From that, we can build up a picture of the health of the woodland and its optimum carrying capacity for the deer.”


Ben with the survey drone                                                                    The drone prepares for take off

Assisting Ben and bringing local knowledge and more drone piloting experience, Tom Williams explained how the complex and valuable piece of equipment worked. “It’s a base drone, an airframe with bolt-on options. In this case, we are using a thermal imaging camera giving us high resolution daylight and night time views. We will be able to pick out individual deer and record them.”


A daylight camera and thermal imaging camera are used to count deer

There was no time to waste and once the drone was set up, the survey began as evening drew in. The plan was to push on quickly as some approaching stormy weather was in the forecast and to get the job done in time, they would need to stay up through the night to capture the most accurate record of Fingle’s deer yet. As the drone set off on its first flight it immediately picked up some movement; the first group of fallow deer was counted without even disturbing them. Watching them on the hand-held screen, the methodical grazing patterns could be observed. Dave Rickwood also joined the survey team and explained from the Woodland Manager’s point of view that, “we need a picture of the deer numbers here and in the other sites across eastern Dartmoor. It’s the start of an overall impact assessment so we can look at regeneration of vegetation and the woodland’s ability to recover.”


Tom planning for the next launch site                                                            The drone at sunset


The survey carried on after dark with a break to catch up on a few hours of sleep and to recharge the battery pack before they were back out in the woods again before dawn. Tired but excited, Tom reported later that, “The resolution of the camera is incredible. We could see a grey squirrel feeding on a pine cone from 500 metres away!” During the night the team discussed the potential for surveying other nocturnal mammals including bats and dormice. In some areas, large swarms of insects in decaying trees were spotted so there was also the suggestion of being able to use this drone to record valuable dead wood habitats. This deer survey will be repeated in the future, but the team were pleased with their results this time round; around 180 deer were recorded in a little over 12 hours. Using this drone is clearly cost-effective too. Even though there is some expensive equipment involved, the survey was quick and very efficient. It is the kind of new technology that not only provides a 21st Century view of a medieval legacy but a rapid head count of one of the crucial limiting factors in woodland restoration.

by Matt Parkins

Note: Flying drones requires skilled a pilot (or in this case two) and is only done where genuine conservation benefit is gained. Due to the complexities of land ownership and regulations from the Civil Aviation Authority and Dartmoor National Park, a significant amount of licensing and preparation work was done in the lead up to this survey.


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