March, if you get a calm sunny day, is a lovely time to be in a broadleaved wood. They are just beginning to wake up, with celandines, primroses, the first dog-violets and wood anemones, all reminding us that colour is coming again. It is also the month that we begin our deer impact surveys.

Rich and regenerating woods are a home to host of specialist species from bluebells, marsh tits and dormice, down to fungi and deadwood invertebrates. But woodland habitats are facing a range of long-term pressures including climate change, fragmentation and especially in recent years, ash dieback disease.

Yet another significant factor for woodland health is the increase in deer populations. At the start of the 20^th century, wild deer were basically absent from our three counties; but during the last century, and particularly in the last 50 years, deer numbers have boomed, and they are now a common sight in fields and woods.

In Berkshire, Buckinghamshire and Oxfordshire, we have three species of deer to consider in relation to woods – the native roe deer and the introduced fallow and (Reeve’s) muntjac. All three are species that live in woods, but each has a different impact.

Roe and muntjac are mostly solitary, holding loose territories all year round within the woods, whereas fallow are herd animals, roving around large habitat patches, so that they might not re-visit an individual woodland for many months. Roe and fallow browse woody vegetation, leaves, growing twigs and saplings (large herds of fallow can eat a lot!); muntjac are smaller and take more soft vegetation, leaves and ground flora species such as bluebells, sedges, and ferns. 

The collective impact can be a reduction in ground flora abundance and diversity; a reduction in the density and productivity of the undestorey – giving rise to an “opening up” of the wood; and in the longer-term, a lack of replacement young trees jeopardising the future of the wood itself. All of which has consequences for the whole spectrum of woodland wildlife.   

Within the land management team, we routinely monitor the condition of the woods, looking at health, structure and diversity, as well as key species including birds, butterflies, bats and dormice, but a big part of the survey programme is the deer impact and activity assessment.  

We follow a methodology, developed by the Deer Initiative to get a balanced picture of the effect of the deer present. We survey in early spring so that there is good visibility of the ground and the ground layer of vegetation. The survey requires us to follow a set route through representative areas of the wood covering different blocks and variations in habitats.

On the route we record any deer seen (or if barking is heard for muntjac), but usually the more obvious signs are footprints, “slots” – parallel elongated tear-drop impressions; trackways, “racks” snaking across the woodland floor; and piles of dung. There may also be flattened, cleared “couches”, where deer lay-up; or scrapes in the soil and leaf litter, and frayed bark at the base of young trees – although badgers do both of these too, so the presence of hairs that kink, rather than coil when bent, is a good clue that deer are responsible.

We also look at what and how much has been nibbled, which species of ground flora (deer have their likes and dislikes), the number of shoots on hazel coppice, the presence of tree seedlings, and the effect on bramble and ivy, which are two favourite foods. Ivy leaves starting at about 1.5m up a tree trunk, or bramble with bare stems below a similar height are a sure sign of deer. If many deer are present, there may be almost no bramble present at all.

With all monitoring, the aim is to feed back into site management to make best use of our resources to get good outcomes for wildlife. The results of the deer impact surveys lead to decisions about if and how to protect new planting or coppice coupes. Where re-stocking is required after ash dieback works, the survey results may make the difference between allowing natural regeneration, or the taking the decision to plant and protect new trees.

Volunteers have been busy protecting newly coppiced hazel, with tall dead hedges made from the left-over brash, to allow new shoots to explode from the stools and reach a height above deer mouths, before they naturally decay and rot back into the woodland soils. This example is from Moor Copse, but similar work takes place at our other superb woodland reserves including Rushbeds Wood, Little Linford Wood and Warburg Nature Reserve.

At smaller scales individual stumps can be protected by building brash baskets or erecting temporary fencing cages, but in some cases whole woodland blocks are deer fenced for a longer-term solution.