Albert Bonet Bigata, PhD Student, University of Aberdeen, August 2023
Hello! I am Albert, an ecology enthusiast who, since October 2022, has been doing a PhD at the University of Aberdeen. My interests and current research revolve around understanding invasive non-native species and how they affect the Scottish environment and biodiversity. In this blog I want to introduce you to my research, the work carried out by the Scottish Invasive Species Initiative and the different ways you could be a part of this project!
My PhD, in collaboration with NatureScot and the Scottish Invasive Species Initiative, aims to understand the effectiveness of long-term control of invasive species and how this control positively impacts native biodiversity – using the American mink control programme as a case study. During my research, I plan to show how the efforts of the extensive volunteer network (which might already include you) together with project and partner staff at the Scottish Invasive Species Initiative help to protect Scottish biodiversity.
The Scottish Invasive Species Initiative’s American mink control project is a large-scale coordinated effort across an immense region of Scotland: over 23,000 km2! Because of the area to be covered, the project goals are only possible thanks to everyone who has volunteered with the scheme. I hope to help in these efforts by providing a detailed understanding of current and past American mink control in Scotland.
However, do to this – I will need help. To start us off, I will summarise my project goals, which will, hopefully, interest you in helping both my research, and the Scottish Invasive Species Initiative mink control project – and ultimately help protect native Scottish wildlife. Let me know if I succeed!
The PhD Project: How many mink is too many mink?
How many is too many? This question is the backbone of any invasive animal species control project when eradication in the near-future might not be possible, as time, money and resources are limited, meaning that a residual number of the invader remain. This is especially the case with highly mobile and widespread invasive species such as the American mink. Because of that, control programmes such as the Scottish Invasive Species Initiative aim to run continuously and cover as much ground as possible, since stopping control could lead to the reinvasion of the species.
I know that might sound pessimistic, but what if we did not have to remove every single individual to succeed in protecting native biodiversity? It could be that, if we keep the invader population at a low enough number, their damage to affected species could become negligible and allow native species to recover. That number is the “too many mink” threshold and we do not currently know where it lies nor what would be needed to reach and maintain it. The main goal of my research is to solve this mystery.
Photo credit: Liam Skinner photography.
But how do we find that threshold? First, we need to go back to the goal of the control project: protect the endemic species from the impact of the invasive American mink. Impact usually means a change in native populations, such as reducing their abundance. Thus, to find the threshold we need to describe and understand the relationship between the number of mink and their impact on native species.
One of the many species affected by the American mink is the water vole. These semi-aquatic rodents experienced an over 98% reduction of their range across the UK during the 20th century. This drastic decline has been attributed to the impact of mink predation (amongst other factors like habitat loss) and made them one of the fastest declining mammals in the UK.
However, water vole populations and ranges have seemed to recover in regions with mink control over the last 15+ years. The extent to which the mink control has influenced water vole recovery is unclear and something I aim to shed light upon so we can find the “too many mink” threshold. To be able to find this threshold we first need to know the answer to two questions.
Question 1: how were the water voles doing before, during and after the mink invasion and control?
Obviously, we cannot go back in time to search for water voles, or at least not physically. Instead, I am collating all known past water vole surveys and records in Scotland (some go all the way back to the 1970s) into one big database to see how their distribution in Scotland has changed over time. To find out their present ranges, I am surveying many waterways in northern Scotland looking for signs that indicate their presence. These signs consist of active burrows on the riverbanks, latrines and droppings, and fresh vegetation clippings or, if lucky, sighting the mighty beasts themselves.
As I only have two legs and one pair of waders, this is where I would be grateful for the help of other nature enthusiasts. If you know where I could find more water vole records or signs, that you, your friends or neighbours might be aware of, I would love to hear from you. Or better still, if you wanted to join me on surveys or undertake your own mini-surveys please get in touch and we can talk about voling!
Question 2: what numbers of mink would be needed to cause the declines and recoveries seen?
Now that we know about the vole side of the equation, to find the now infamous threshold we need to know how many mink there are/were and how these could have impacted the distribution of water voles. How do we know how many mink are/were really present or how many there could be?In reality, it is impossible to know for certain as some areas might not have been under control and, even if controlled, some mink might never be trapped or detected!
Nonetheless, this can be attempted thanks to all the information gathered when operating mink rafts or/traps over the years by all volunteers and project and partner staff from the Scottish Invasive Species Initiative – as well as the efforts from previous American mink control projects. With such data, I will use statistical models to estimate mink numbers over time and different control intensity levels in an area. With the mink numbers and the water vole data, I will aim to uncover the relationship between American mink numbers and their impact on water voles so we can finally know how many mink is too many and what we need to do to get there.
Would you like to help with research on water voles and mink?
If you would be interested in contributing to the project, you can do so by becoming a volunteer and operating a mink raft or trap, and for those that are extra-motivated – you could become a super-volunteer! This is where I need some extra help for my research, beyond the work volunteers already do for the mink control project.
Super-volunteers would operate a raft/trap as usual but also gather some extra information to support my study e.g. recording the signs of other species that are found on rafts as well as reporting when one finds nothing (remember no mink news is good news!). The more information and the more people involved the better, as then we will better understand the impacts of mink and how to manage them. If you want to know more about how you could get involved do not hesitate to get in touch with me or your local Scottish Invasive Species Initiative partner or officer.
Lastly, thanks for having dedicated your time to read this blog – I hope it was at least an interesting read! If you want to participate and lend a hand, know where to find water voles or just have some questions I will be more than happy to get in touch. Let’s work together to protect Scotland’s ecosystems!
Albert Bonet Bigata
Would you like to help Albert with his research and become a ‘super-volunteer’? We will be releasing more details on these opportunities shortly but for now you can email Albert (a.bonetbigata.22@abdn.ac.uk) or Jane at the Scottish Invasive Species Initiative (sisi.janehamilton@gmail.com) to be put on our waiting list. We will be in touch shortly!
For more information on water voles:
The Wildlife Trust’s guide to water voles
Guide to European water voles: Identification, diet and habits
