Deer, biodiversity management and ecotourism in the Hebrides: conflict or mutual benefit

Abstract

A new management scheme is planned for an island estate in the Inner Hebrides, and aims to promote short-sward biodiverse grassland habitats through controlled grazing pressures and distribution of red deer, whilst avoiding the negative impacts of deer overabundance. These habitats are biodiverse, and act as important refugia for Zygaenidae, a group of day-flying moths with strongly restricted distributions elsewhere in the UK. Traditionally, sheep grazing is used in the region to maintain grasslands, however, this results in an intensively grazed grassland that is not suitable for Zygaenid moths. Red deer may create preferable habitat conditions for the moth species, as human-linked disturbance will cause the deer to balance foraging with anti-predatory behaviours. Whilst the nature and impacts of red deer grazing upon various vegetation communities has been thoroughly investigated, the applicability of red deer as a viable conservation grazer has not been studied. Furthermore, the impacts of human presence upon ecosystems via the alteration of the behaviour and patterns of habitat use of a key grazer have not been linked in disturbance ecology.
Therefore, the main aim of this thesis was to examine the behavioural and habitat use patterns of red deer in response to human-linked disturbances that vary spatially and temporally. Utilizing the red deer as a primary grazing species, it was imperative to understand the impacts that increasing levels of tourism may have had on the behaviour and consequently grazing intensity and habitat use of the red deer. In appropriating the path systems on the island as an index for human-linked disturbance, key red deer behaviours and patterns in habitat use were mapped temporally (diurnal and seasonal) in relation to the proximity, traffic and visibility of path systems, at both fine and coarse scales. Consequently, the impacts of tourist activities on red deer throughout the south-side of the island were quantified. Additionally, these impacts were linked to the abundance of a day-flying moth, Zygaena purpuralis, which acted as a bioindicator for the short-sward grasslands. Moreover, the vegetative requirements of the moth were identified at varying spatial scales.
In areas of frequent and high human activity, deer exhibited a reduction in anti-predator behaviours by occupying areas associated with human presence. However, in areas with relatively low amounts of human activity, deer routinely disrupted foraging bouts by engaging in anti-predatory behaviours and avoided areas close to paths. These latter patterns were exhibited in the short-sward grassland areas. Z. purpuralis abundances were higher in areas of high deer presence, and both deer and Z. purpuralis favoured areas with high vegetation diversity. Additionally, Z. purpuralis abundances were higher in areas that featured deer trails, and bracken had a strong negative influence on abundance at a variety of spatial scales.
By controlling these patterns of habitat use and foraging behaviours of a wild ungulate, human presence can indirectly dictate the grazing regime experienced in certain habitats. In the case of the island estate, the population of Z. purpuralis in the grassland habitats benefited from the behavioural patterns of deer adopted in response to the levels of tourist activity in the area. Additionally, red deer provided bare soil, an important habitat requirement of Z. purpuralis through the creation of deer trails. Aside from proving that red deer are a viable grazing tool for land management schemes, this thesis has also provided the first evidence of human activity impacting upon the ecological landscape by altering the behaviour and patterns in a grazer through disturbance.