Managing deer: attractants, repellents, invasion modelling and impact assessment

  • Erfan Fadaei

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Deer play an important role in many ecosystem processes and have been recognised as keystone species, but increasing numbers and expanding ranges of both native and introduced deer worldwide, including the British Isles, is contributing to negative ecological impacts on natural systems, economic losses in forestry, agriculture and transportation, and the transmission of several animal and human diseases. Culling of growing populations is viewed as a necessity in order to protect human and ecological interests, but such deer management may be aided by the development and use of additional approaches, including attractants and repellents. These remain largely untested on deer in the British Isles, therefore this thesis aims to develop knowledge of the efficacy of each of these. In addition, with the continuing invasion of introduced deer species, predicting their impacts and future distributions will be key to management and control.

A favourable attractant should draw deer from the surrounding landscape and keep animals interested such that culling efficiency is improved. Using wildlife camera traps to remotely record sika and fallow deer, the efficacy of several attractants in modifying behaviour was assessed using multiple analyses. Only one of the attractants – apples – was effective in altering behaviour, demonstrating its potential as a tool to aid deer management. Further research is needed to test these attractants on other deer species and in different habitats, and to investigate if attractants would indeed improve culling success. A potential deer repellent – wolf faeces – was likewise tested for its efficacy in modifying deer behaviour. The faeces did not alter the rate, duration, or latency of deer visits to plots, indicating poor repellency, and while it did cause deer to increase their investigation of odours, a trade-off between vigilance and foraging was not observed as has been demonstrated by deer populations where wolves are sympatric. Deer have likely lost sensitivity to wolf odours given the absence of wolves from the landscape for two centuries.

The potential distribution and dispersal of the invasive muntjac deer in Ireland was predicted using an invasive Species Distribution Model (iSDM) combined with Least Cost Path Analysis. The findings indicated that 94% of Ireland is vulnerable to invasion, and deer numbers could reach almost 100,000 when the island is fully colonised in potentially just over a century’s time. Immediate action is urged in order to control and eradicate muntjac in Ireland, while they are still at an early stage of colonisation.

The Relative Impact Potential (RIP), a novel means for quantitatively assessing and predicting invasive species impact, was for the first time, applied to both native and invasive deer in the British Isles, in order to predict the impacts of present and growing populations of invasive species on vegetation communities. As the impacts of invasive species may change over the course of an invasion, a new metric, the Relative Total Impact Potential (RTIP) was developed, providing insight into the effects of invasive species over time by comparing the impacts of introduced species at any time point against a baseline of impact arising from trophically analogous native species before the introduction of non-native species. A case study focussing on muntjac and roe deer in Thetford forest, where the two species have been sympatric for some time, found that invasive muntjac likely exert a much greater negative influence on vegetation than the native roe deer.
Date of Award2019
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorJaimie Thomas Allan Dick (Supervisor) & Neil Reid (Supervisor)

Cite this

Managing deer: attractants, repellents, invasion modelling and impact assessment
Fadaei, E. (Author). 2019

Student thesis: Doctoral ThesisDoctor of Philosophy