For the most part, contracting diseases from wildlife is not something we need to think about in the UK particularly often. However, Lyme disease, or Lyme borreliosis, is one that any visitors to our stunning countryside must be aware of. This bacterial infection, spread by the bite of blood sucking ticks, can lead to severe and long-lasting symptoms, though if caught early can usually be treated effectively. In this month’s Behind the SCENE, masters student Eleanor Dickinson talks about her research looking at the relationship between deer and tick numbers, and why the habitat around Loch Lomond is an ideal place to study this important relationship.
Deer, ticks and Scottish sunshine
On the banks of Loch Lomond, SCENE hosts a huge diversity of research projects, each of which utilises the natural habitat surrounding the centre. The majority of research at the centre focuses on freshwater or avian systems, however the area of research that I am involved in lies within the field of disease ecology. More specifically, I’m interested in the effect of deer density on the presence of Lyme disease, which is transmitted by ticks.
My project is looking at what factors influence the prevalence of Lyme disease in natural woodland in Scotland. It will contribute to on-going research led by my supervisor, Dr Roman Biek, who is interested in understanding the dynamics of vector-borne infectious diseases. Lyme disease is spread by ticks and is maintained by host species, particularly rodents, which act as reservoirs and transmit the bacteria responsible to uninfected ticks during feeding. While deer do not directly transmit the infection to ticks, they do still have a large impact on the prevalence of Lyme disease as the number of deer in an area can directly affect the number of ticks. However, the resulting impact on the prevalence of the disease is contested. An increased population of ticks may lead to a higher prevalence of disease as there are more ticks that can get infected; or if the amount of infected ticks stay the same there will be a smaller proportion of infected ticks resulting in reduced risk of disease transmission.
Loch Lomond offers the perfect place to base a project like this; variation among the islands and woodland sites around the loch means that there will be different populations of host species, numbers of ticks and levels of disease. We hope that by comparing the density of deer on the islands of the loch we can find a relationship between deer, ticks and the prevalence of Lyme disease. By comparing this variation, we can try to understand what might cause higher incidences of disease.
To work out what is happening in this complex relationship, my task has been to measure the density of deer. However, it’s not as easy as it sounds; deer are well camouflaged and easily spooked, making it tricky to count them—especially in the woodlands. A more effective way of measuring their density is, in fact, through recording their droppings. If you know how much dung there is in a certain area, how much of it a single deer produces and how long it takes the dung to decay, you can measure how many deer there are in that area. My task was simple: record the presence of deer dung along predetermined transects. There are twelve island sites and seven mainland sites, each with a certain number of transects determined by the size of the site. I walked along each transect recording the position of every dung pile that I spotted within a meter of the transect, any further and the dung is too difficult to consistently find. With such a large area to survey and working alone, it seemed a fairly daunting task!
I’ve heard wonderful things about the Loch Lomond islands and I love this area; despite this—perhaps because of the task before me—I wasn’t completely optimistic about how enjoyable nearly eight weeks of fieldwork was going to be. Scotland is well known for its unfortunate weather and I was fully expecting to receive the brunt of it while marooned on an island or lost in the woodland. When the time came and I had to dive into fieldwork full-time, I was pleasantly surprised. I experienced day after day of glorious sunshine, though occasionally some slightly overcast weather hung overhead. In the end I was only rained on a few times, which came as quite a pleasant surprise. With no annoying ticks or midges (very annoying small biting flies that swarm around you) and the warm sun above me, I could thoroughly enjoy being outside doing fieldwork.
The islands of Loch Lomond are truly magical: each one has something different to offer, making it totally unique from the others. There are beautiful beaches, surrounded by woodland with moss blanketed floors or thick blaeberry bushes. They are teeming with wildlife such as woodcocks, kestrels, buzzards, woodpeckers and many other birds. Deer were also plentiful on the islands: I recorded over 2000 observations of deer dung during my survey and even spied the actual animals numerous times, including a beautiful white stag. Despite the abundant wildlife, the most exciting find for me was actually the domestic animals on an island called Inchtavannach. This island is inhabited by a lovely couple, along with their six horses and five highland cattle. It was completely blissful and I had to drag myself away from patting the horses and swooning at the “coos” (a Scottish twist on “cows”) to continue with my survey.
At the end of the survey, I was very tired but pleased to have collected so much data. But it’s not over yet! I am going to repeat the deer survey to see if their density on each island changes depending on the season. This will show how often the deer move between the islands as they can easily swim between them—something that many people, do not expect. I’m also going to measure how many small mammals there are at each site; as important hosts, they could have a large effect on the presence of Lyme disease depending on how many individuals there are. My last bit of fieldwork will also involve determining the number of ticks in the environment. This will also provide me with a measure of disease prevalence. Recording and analysing all of these data will give us a clearer idea of what influences higher levels of disease. Armed with this knowledge, we will then be able to implement better disease control by understanding what areas pose higher risks and why.
With lots of fieldwork still to come, I can only hope that my luck with the weather continues and I get to enjoy the scenery of Loch Lomond and the wildlife some more. Hopefully, all without ticks and midges ruining the fun too much!