By Abigail Fay Case
Initially, it was surprising to see the amount of people who were shocked to know that domestic cats were actually considered as predators of bats. However, cats are undoubtedly the most prevalent species of urban predators, as they are the most abundant carnivores within the British Isles with an estimated total population of 8 million. Therefore, the impact that domestic cats have upon British wildlife is staggering; annually it is predicted cats kill 100 million animals, with small mammals making up 70% of this total.
Bats are considered a keystone species which provide many economical and ecological benefits to ecosystems, and therefore their conservation is paramount. However, there has been a severe global decline in bat populations and declines of the 17 resident breeding species within the UK have also been witnessed.
It is estimated that annually 250,000 bats are killed as a result of domestic cat predation, but as previously mentioned research into this subject area is limited, and therefore it s believed that this figure is a severe underestimation. However, bat carers agree that cats have a serious impact upon British bats, since 30% of all casualties they receive are directly resulted from cat attacks. Out of this total 56% are fatalities where either the individual does not survive or needs to be euthanized. Typically, evidence of cat attack is in the form of punctures/tears to the wing membrane.
The aim of my research was to develop a method, which was fully optimised to ensure maximum results, which could test swab samples from injured and perished bats in order to detect if domestic cat DNA was present. This in turn could potentially assist with the more accurate quantification of instances of cat predation on British bat species. Additionally, the research could be used to develop methods for the management and control of the predation, for example educating cat owners about the threat to British wildlife and advising them on what time of day to avoid letting their pet out the house.
To ensure I gained a maximum possible sample yield, across locations throughout the UK, I took to social media to enlist the help of bat groups and carers to ask for their assistance in swabbing the wings of any casualties they received. I created a webpage (http://thebatcatproject.weebly.com/ ) with details about the project and a form to fill in where people could register their interest and get involved. With thanks to Bat Conservation Trust, Manchester Metropolitan University and bat groups nationwide I received an overwhelming number of people who wished to participate!
To all registered volunteers, I dispatched a swabbing kit which contained: instructions on how to optimally swab bat wings, gloves to minimise contamination risk, swabs, and a prepaid envelope addressed to the University for sending back samples. These kits were posted out during March/April so they were with bat carers for the bat season.
Once the basic procedures of the method had been established, I optimised each of the stages to ensure the process was efficient as possible. For example: testing two different swabbing techniques to see which had a higher DNA recovery, and testing different annealing temperatures during Polymerase Chain Reaction (PCR) to see which gave a greater yield of target DNA.
When analysing the returned samples from bat carers, the DNA extraction and amplification on all samples was successful- this showed that the method worked and was reliable! Through a process called melt curve analysis it is possible to look at results and distinguish which species are present within a sample. Species can be differentiated between by looking at melting temperature as different species have different melting temperatures of DNA fragments. The average melting temperature of domestic cat DNA was calculated from results of the study, and it was therefore assumed that samples which had a temperature of equal to or greater than this figure, contained cat DNA.
The final results of my study indicated the possible presence of domestic cat DNA within some samples, and therefore it could be assumed that the developed method had worked! I had such an amazing time working on the project and I hope that as research into this area continues more samples can be analysed, leading to the better quantification and understanding of cat predation upon British bat species.