title: Assessing translocation outcomes and revealing behavioural insights in two red squirrel populations in the West of Ireland
Creators: name: Reilly, Emily
Publisher: name: University of Galway
Year: 2024
Subjects: subject: Science and Engineering
subject: Natural Sciences
subject: Zoology
subject: FOS: Biological sciences
subject: red squirrel populations

description: The red squirrel (Sciurus vulgaris) population suffered a dramatic decline in Ireland following the introduction of the invasive grey squirrel (Sciurus carolinensis) in 1911. Two red squirrel translocations, the intentional movement of a living organism from one area to another, were undertaken as part of efforts to conserve the species. These translocations took place in 2005 and 2007 at two sites in the west of Ireland, outside the range of grey squirrels: Derryclare in Co. Galway and Belleek woods in Co. Mayo. In the years following the translocations, monitoring efforts were implemented to observe and assess both populations. The most recent survey, conducted in 2012, provided evidence of the sustained presence and growth of both populations. The core aim of the present study was to investigate the current status of the translocated populations. At this stage the translocated populations were expected to have reached the regulation phase, exhibiting a continued presence and stabilised density. Following the introduction of the red squirrel population to Derryclare in 2005, the woodland underwent significant changes. Clear-felling operations, both expected and unexpected occurred frequently, owing to the woodland's commercial nature. This activity, combined with a significant forest fire in 2011, resulted in substantial habitat loss. We investigated the extent of this habitat loss and its effects on the carrying capacity of the woodland. We utilised digitised historical maps to compare past and present habitat, revealing a 53% reduction in habitat since 2005. A feeding survey was conducted, and the results were compared to previous feeding survey data, allowing us to track the changes in the estimated squirrel abundance and carrying capacity of the woodland. Carrying capacity estimates declined by 41–81%, with the lowest estimate at 65 individuals. Deterioration of the quality of the habitat, due to a shift in the proportion of tree species towards the less favourable species, further reduced the suitability of the woodland. Feeding surveys estimated a total of 2-4 individuals in the woods, illustrating the negative effects of habitat loss and deterioration. The Derryclare population was monitored using a combination of non-invasive and invasive techniques from January 2020 to January 2023. Trail camera, hair tube, and feeding survey data indicated a sparse squirrel presence throughout the entire woodland, with squirrel activity concentrated in patches of higher quality. Live trapping data revealed an eighteen fold decline in density compared to previous estimates, averaging at 0.032 squirrels/ha, or 6.5 total individuals. Breeding and recruitment rates were low, and squirrels were underweight compared to other red squirrel populations, including Belleek. Home ranges, estimated using trapping data, averaged 19.61ha. The large size of these ranges indicates a poor quality habitat. A feeding survey in nearby woodlands did not reveal any signs of dispersal, making it likely that carrying capacity was never reached in Derryclare. It was deemed that the translocation will ultimately not be successful, due to the low likelihood of the population’s recovery. The Belleek population were monitored from February 2020 to March 2023. Hairtube and trail camera surveys revealed a uniform population distribution throughout the woods. A live trapping study estimated an average density of 0.41 squirrels/ha, or 24.6 individuals, aligning with other healthy red squirrel populations. Breeding, recruitments rates and squirrel body weight were all indicative of a healthy population. Radiotracking was employed, revealing an average home range of 4.02ha. A citizen science survey conducted from March 2021 to January 2023, revealed a significant expansion of the Belleek population’s range, estimated to span 738.5km2 . The success of this translocation was attributed to the maintenance and persistence of consistent suitable habitat and the abundance of food, bolstered by continuous supplementary feeding. In contrast, ongoing loss and deterioration of habitat in Derryclare was believed to be responsible for this population’s decline. The behaviour of individuals in both populations was analysed during live trapping sessions to gain insights into their behavioural diversity. Additional open field tests and mirror image simulation tests were performed on a subsample of individuals in Belleek. While it was hypothesised that these populations would exhibit multiple differences due to their contrasting habitats, only one significant difference was identified. Belleek squirrels displayed a diminished flight response compared to Derryclare, possibly owing to their habituation to humans. A trade-off between reproduction and longevity was observed in Belleek females. In Belleek males, boldness was found to be associated with smaller individuals and increased longevity, while in Belleek females, boldness was linked to larger individuals and a higher reproductive output. These personality differences impact population dynamics and therefore have implications for conservation management. The recent resurgence of the pine marten has caused a decline in the invasive grey squirrel in Ireland, allowing for a red squirrel population recovery. The coevolutionary history between the red squirrel and pine marten, and the naivety of the grey squirrel to this novel predator are thought to be responsible for the contrasting outcomes of both squirrel species. We used trail cameras to record pine marten and red squirrel visits to feeders, and analysed the behaviour of the red squirrel following recent pine marten presence. We found that red squirrels visiting within 48 hours of a pine marten displayed an enhanced antipredator response involving increased sniffing and vigilance, and decreased feeding. These results support the hypothesis that red squirrels have avoided predation by the pine marten due to their behavioural adaptations. The divergent outcomes at Derryclare and Belleek underscore the intricacies of translocation projects, providing valuable insights into factors influencing their success or failure. In particular, this study has provided insights into the importance of habitat quality as a determinant of translocation success. We recommend that future translocation projects choose stable habitats, and place greater emphasis on habitat quality during the planning phase of the project. Additionally, our findings stress the significance of post-release monitoring, suggesting that monitoring is conducted at least until the regulation phase of the project, in order to reveal the true outcome of the project. Additionally, this study yields insights into red squirrel behaviour and ecology, emphasizing the need for behavioural screening in translocation projects. It also contributes to our understanding of the dynamics between red squirrels and pine martens, shedding light on the red squirrel's recovery in Ireland. We believe the insights gained from this study can provide valuable insights for future translocation projects, aiding in their successful planning and execution.