Chapter 5 Deer management
5.1 History of deer management at Glenveagh
Deer management at Glenveagh began with various introductions of red deer (Cervus elaphus) from different European sources in the mid- to late 19th century. A deer fence was erected around the perimeter of the estate in the late 19th century and this is largely still in place, although since the dissolution of the dedicated fencing team (early-mid 2000s) it has become ineffective, with multiple breach points along its 45 km length. Historically, deer management has been associated with sporting rather than ecological interests, although a series of woodland exclosures have been erected over the last 50 years with the intention of excluding deer from areas of woodland (see Fig. 17). While many of these fences are still largely in place, they have all been breached and are in various stages of disrepair due to a variety of causes including rotting of stakes, falling of branches, deer pressure and snow drift, and require ongoing management, which has been entirely lacking in the past 15-20 years.
5.2 The need for deer control
There are no longer any natural predators for deer in Ireland due to an absence of apex predators such as wolves, lynx and bears. This has led to an increase in the number of deer ranging through the Park, and the development of behaviour and feeding patterns that are damaging to the woodlands, such as animals spending longer periods browsing in one place. There is therefore a requirement for humans to take on a role that mimics the actions of predators. This takes the form of directly controlling population numbers by culling, or of influencing where and how quickly individuals and herds move through areas of woodland, using methods such as fencing (to limit access to some areas) or non-lethal hunting (to keep animals on the move to reduce browsing time).
A recent study and deer management plan for Glenveagh (Burkitt, 2017, 2018) reports deer densities of approximately 5.0–6.0 / km2 (range of 2.55 to 8.99 / km2). Notwithstanding these low estimates there is widespread evidence throughout the Park of significant deer impacts which are rendering the existing woodlands unsustainable in the long term. There are very few areas or cases of woodland regeneration surviving the browsing impact of deer except where deer have been excluded by fences or by natural topography such as steep gullies or by occasional orientations of fallen timber. These provide direct evidence of the impact deer are having on the ecology of the National Park. Further evidence is provided from assessments within historic exclosures where there are cohorts of natural regeneration that were afforded temporary protection from deer and that have progressed to thicket and semi-mature stages as a result of that period of protection (Höna, 2009; pers. obs., June 2021). New woodland establishment and, potentially, expansion of existing woodland (for example, by higher levels of tree regeneration at woodland margins) will achieve greater success with an implemented deer management plan.
5.3 Points to consider with regard to deer fencing
The historic perimeter fence is not proposed as a viable resource for deer management in the Strategy. Evidence from Glenveagh’s 100 years of deer fence management, and other similar estates worldwide, indicates that large fenced areas neither effectively exclude deer nor prevent their escape. Additionally, large fenced areas are not cost effective and resources are more efficiently deployed when they are focused on smaller fenced areas and active management (such as culling) over a larger area, rather than passive infrastructure (fencing). This also simulates a more natural environment with regard to deer use of cover in response to hunting pressures. Indeed, open range control of deer is considered closer to natural processes and more effective over a wider landscape where change is to be effected through natural regeneration. Newman et al. (2014b) recommend that large-scale, long-term fencing of oak woodlands be replaced by large herbivore management programmes, in order to ensure the conservation of diverse native woodland ecosystems, monitoring and adjusting large herbivore impacts through localised culling, to achieve specific long-term management objectives.
Ultimately, it is the level of grazing impact that is important in determining the sustainability of the woodlands at Glenveagh rather than deer density or numbers. From the survey work completed as part of this Strategy (unpublished results) it is evident that current impact levels are locally high, that woodland condition is generally poor, and that the woods are in an unsustainable state. The successful implementation of a revised deer management strategy, whereby deer densities are significantly reduced, will allow much of the natural tree regeneration to progress.
The gradual release of currently regenerating native trees over a 10 to 20-year period would leave a legacy for 100 to 200 years. As such, the deer management element of this plan is one of the most important aspects of the proposed woodland management strategy.
5.4 Deer management strategy
It is recommended that significant action be taken at Glenveagh to implement a new deer management regime. The first step in such a regime would be to develop a comprehensive deer management strategy to inform all aspects of management of the deer herd to allow the development of self-sustaining, naturally functioning and expanding woodland. The strategy should address a diverse suite of elements. Below are given some of the main issues to be considered, but other issues would likely be identified in the course of preparing such a strategy.
– A dedicated deer management team should be established within the Park with the sole purpose of implementing deer management, and having duties such as culling, monitoring, and maintaining fences. This should be made up of a minimum of 4 x full-time professional staff or Full-Time Equivalents (FTEs) which may include a combination of a greater number of staff with other duties.
– Deer densities require significant reduction to a point where impacts from grazing are considered low. As such, the target should not be to achieve a specific deer density but rather to achieve a level of impact from grazers that is acceptable and allows woodland recovery and, ultimately, expansion. Once this is achieved, deer densities then require maintenance at that level through continued culling and monitoring. A certain level of grazing in woodlands has been shown to be beneficial (Newman et al., 2014b) and prevents homogenisation of vegetation.
– Deer management staff time and resources should be dedicated to reducing deer densities.
In this regard it should not be a requirement to remove all carcasses from the hill. This decision should be part of a wider long-term objective to operate as closed an ecological cycle within Glenveagh as possible. This concept is in keeping with the IUCN class of National Park that Ireland aims to manage Glenveagh as (CAT II), whereby there are no removals of natural materials from the Park’s natural ecological system (Emmett Johnston, pers. comm.); this would also include other materials such as dead wood, felled timber and fish. To facilitate this, a Deer Protocol should be developed to allow for carcasses to be left on the hill to provide carrion as a food source for invertebrates and fungi, as well as larger scavengers such as golden eagles, ravens, foxes and badgers. This will also save staff significant time otherwise spent carrying / dragging animals off the mountain. The protocol will be clear as to when and where it is acceptable (or not) to leave a carcass for natural decomposition; for example, not to do so next to a stream or lake. It is recommended that a PhD study be initiated that would build on the existing body of international evidence (e.g., Flueck, 2009; Wolf et al., 2013; van Klink et al., 2020) and gather local scientific data to support this policy development and allow it to be implemented on a phased basis over time. This would include a system of labelling carcasses left on the hill and analysing, for example, decomposition time-frames, scavenger populations, changes in nutrient flow between trophic layers and the distribution patterns of seed as a result of the policy.
– Some of the existing deer exclosures should be repaired and some new, small-scale ones erected (see woodland conservation measures in Chapter 6).
– Monitoring of progress is important and should be conducted and documented.
Monitoring protocols should be developed through the deer management strategy, and in association with the monitoring team at Glenveagh (see Chapter 9). A series of permanent deer impact assessment plots (suggested size of 20 m x 20 m) should be introduced across the property in areas inside and outside of deer fences, within or adjacent to woodland or areas of tree cover. The areas should have current regenerating trees present (albeit browsed) or should be areas suitable for woodland. Data recorded in these plots should include:
o Number of seedlings, saplings and poles1 present
o Diversity of seedlings, saplings and poles present
o Presence or absence of recent browsing
o Presence or absence of other stem damage
o Height and stem diameter records of selected (tagged) trees in each plot
o Other condition indicators (to be determined by the deer management strategy)
Many of the above data are recorded as part of the Annex I woodland monitoring surveys periodically carried out in Mullangore (see Appendix 5). As such, both sets of monitoring data are complementary.
– A public information project should be initiated which explains the importance of creating and maintaining a balance between the deer population and woodland ecology, and outlining the rationale behind the treatment of deer carcasses. The data from the deer impact assessment plots will be an important component of this project, including the visual evidence that will come from the Woodland and Tree Regeneration Management proposals set out below in Chapter 6. This function should be fulfilled by the education team at Glenveagh. In addition to this, any research roles that are filled to support this Strategy should also have a communication function whereby their work and findings are clearly accessible and communicated to the public and conservation sectors.
– Deer management is best practised at a landscape scale and agreements should be reached with neighbouring landowners to extend the deer management area outside the Park boundaries. This is in the interest of similar deer management objectives and practices being followed on neighbouring properties, whether farmed, under forestry or another land-use category.
– Linkages with other projects and other National Parks with similar issues should be sought whereby information and experiences can be shared. Some suggested projects include:
o Baronscourt Estate, Co. Tyrone
o Trees for Life (NGO) in Scotland
o Wicklow Mountains National Park
o Killarney National Park
o Mar Lodge Estate, Cairngorms National Park, Scotland (see Rao, 2017)
o Carrifran Wildwood Project, Scotland (see Ashmole & Ashmole, 2009)