The ecology of a recovering native predator

: The European pine marten (Martes martes)

Abstract

Predators have undergone severe historical decline due to human persecution and habitat loss. Predator populations are starting to recover in parts of Europe for the first time in response to protective legislation and conservation efforts. The landscapes native predators are recovering in are greatly impacted by human presence and settlement. Habitats predators would have existed in, and species predators would have existed alongside are typically highly degraded or entirely absent. Contemporary available habitats are human-modified, and often shared with humans, as well as numerous novel, human introduced species. Although early evidence suggests predators may be able to adapt to these modified landscapes, and ecological theory suggests that the return of predators may have profound impacts in structuring and regulating the systems they inhabit through top-down effects, limited examples of either exist. This thesis therefore investigates the ecology of a recovering predator: the European pine marten in Ireland. The pine marten is a semi-arboreal opportunist, but in the fauna depauperate landscapes of Ireland and Britain, it appears to fill the niche as a key predator species. The natural recovery of the pine marten may provide us with insights into possibilities of the recovery of other predator species. The observed recovery of the pine marten in Ireland and Britain so far is of particular interest, as it is recovering despite a lack of suitable habitat, and it is recovering in the presence of invasive species which have occupied areas since the predators absence. This thesis investigated three key aspects of predator recovery which required address: 1) the most effective non-invasive method to monitor a carnivore population at a large scale; 2) how a recovering predator can fulfil its life requirements in a degraded landscapes lacking preferred habitat and prey and 3) if and how a generalist native predator in recovery can provide control of invasive alien species, and benefit a native species of conservation concern, both of which are prey species of the predator. I demonstrate that camera trapping is likely to be the most efficient and cost-effective method of monitoring carnivores in the future. I highlight that species recovery in human-modified landscapes is likely to be strongly linked to species adaptability. Generalists will hold an advantage here, both in terms of diet as observed through the likely requirement of pronounced prey switching in response to seasonal and environmental fluctuations, and in denning as observed through behavioural plasticity in response to scarcity of natural above ground sites. Finally, I provide robust evidence of a three-way interaction between a recovering native predator, the pine marten, an invasive alien species, they grey squirrel, and a native species of conservation concern, the red squirrel. I demonstrate differential predation rates of the prey species, and differences in behavioural response to the shared native predator. I demonstrate the spatial relationship between the three-species over a regional scale (Northern Ireland) using quantitative techniques allowing for imperfect detection. I elucidate the potential of a recovering native predator to cause declines in an invasive prey species and have positive effects on the occurrence of a competing native prey species. I hypothesise the mechanism driving this relationship to be direct predation, which is facilitated by a lack of anti-predator behaviours in the invasive prey species. Overall, this work demonstrates the substantial impacts a small recovering predator can have on the ecosystems it inhabits, while revealing the incredible propensity of the pine marten to adapt to human modified landscapes. It provides evidence of the European pine marten as a keystone species of Irish and British woodlands and highlights potential benefits of recovering predators to shaping and regulating their environments.

Date of Award	Dec 2020
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Nikki Marks (Supervisor), Michael Scantlebury (Supervisor) & William Montgomery (Supervisor)