Dormice Help to Answer Climate Questions
This year has been a tough time for some wild species and Fingle’s dormice have highlighted how climatic events can cause additional challenges for the wood-wide-web. After emerging from hibernation, the results from the dormouse footprint survey in Halls Cleave showed a steady increase in activity from April to May, as we may usually expect. Then, during a warm May, there were signs that breeding was going well but, as the rain stayed away this year and the dry spells in June turned into prolonged drought through the summer, their behaviour became more unpredictable.
Though there were peak temperature records around parts of the UK, the southwest wasn’t the hottest place, but it was exceptionally dry as the relief from passing showers passed us by. The Met Office stated that 2022 was the “driest July in England since 1935” and “Southern England’s driest July on record”. For a region that is known for, and adapted to, higher than average rainfall, this may be having a long-term effect on our woodlands. By July, there were signs of drought stress in some foliage and the woodland soil was unusually dry as the ground level plants were turning quite crispy.
August continued with the Mediterranean feel and, on the higher ground above the valleys of eastern Dartmoor, signs of stress among the ancient oak canopies were becoming evident.
Patches of browning oak woods stood over parts of the Teign, Wray and Bovey valleys, prompting tree-people to ask the question, “What is going on?”. Visiting some of the worst hit areas, it became clear that this browning foliage was worst where shallow soil on high rocky ridges was most at risk. Conversely, the ancient valley woodlands that were closer to water courses and wet ground may provide greater long-term resilience to changing weather patterns and drought. Is this a new pattern emerging, or will our precious woodlands withstand these climatic changes?
As the summer progressed, many in the world of ecology were having similar discussions about which species might be doing well and which were struggling. It appeared that the dry weather might be impacting dormice as their main source of summer food, insects and their larvae, were in short supply. Even the usual sap-sucking aphids seemed to be less abundant as trees struggled to maintain moisture. This theory was backed up by Charlotte Armitage, one of the University of Exeter researchers who was carrying out field work at Fingle. She was collecting samples of invertebrates and noted that they were proving difficult to find in suitably high numbers to study. Would this lead to a difficulty for dormice in foraging and possibly breeding? Other similarly concerning fluctuations of invertebrate numbers were being noted in data across the country. As many noted a lack of insects, some people reported seeing high numbers of specific species of butterflies, with the gatekeeper doing really well over the summer. This pattern was reflected in the Big Butterfly Count, one of the great citizen science efforts that will help to track the effects of changing climate, but the final report headlined that the overall picture was not good. Butterfly numbers are still in serious decline.
Another University of Exeter researcher, Ellie Scopes, has been using footprint tunnels around the wider Fingle landscape to see how dormice use the different connected habitats between Castle Drogo, Clifford Bridge and Mardon Down. Through the hottest part of the summer, she struggled to collect much information on the presence of dormice but found they returned as the wetter, cooler weather returned in September. This may also have been an issue connected to food supply as, from my own observations when working around several Dartmoor woodlands, I noted that vital food sources have been more available where activity has been seen, for example, rowan berries and flowering gorse. There also appears to be a connection between the areas of higher moisture and greater dormouse success. The arrival of rain showers in September and October have seen dormouse activity return to a more normal level and there are lots of young around. It seems as if they are making up for lost breeding time so we hope the juveniles can gain sufficient weight before the return of hibernation season.
Fingle’s dormice have been contributing to some other surprising research as well. Ellie and Nida (from Peoples’ Trust for Endangered Species) visited one day in October to run a few tests on whether dormice could be encouraged to run through footprint tunnels and leave a set of prints for AI (artificial intelligence) to analyse if it is possible to differentiate between individual dormice. This may be helpful and less intrusive than current methods of tracking individuals that involve fitting micro chips and radio tracking collars.
After an online discussion with dormouse researchers and project leaders from around the country we have set up some i-button temperature sensors in some of the best dormouse habitat at Fingle Woods. These small temperature recorders are set to take a temperature every hour. Here, the temperature inside a nest box and outside the box can be compared with temperatures from boxes where nests don’t get built. This will provide some micro-climate data from individual nest sites. Dormice choose nest sites carefully and these minor fluctuations can be crucial, particularly when extreme temperatures are becoming more likely. It is expected that their chosen nest sites are in locations where temperatures stay more stable so the results will be interesting.
As with all these studies, the results are not fully collated and concluded yet, but when they are, look out for more news on this blog, or you can hear directly form the researchers if you attend the Devon Mammal Group meeting on 29th November at the Kenn Centre.
This kind of research is really useful to understand the behaviour of a protected species, particularly in times of stress due to climate change and habitat destruction, and the increased knowledge supports the work to restore habitats, thanks to the support of the Woodland Trust and People’s Trust for Endangered Species.
by Matt Parkins
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