Student Spotlight – Rachel Findlay-Robinson
PhD student at the University of Cumbria
They spend most of their time sleeping, aren’t fans of social situations and can be difficult to track down when you want to find them; these are just a few similarities between PhD students and my study species, the hazel dormouse (Muscardinus avellanarius). Although hazel dormice are native to the UK and are the subject of a national monitoring programme (the National Dormouse Monitoring Programme (NDMP), run by the People’s Trust for Endangered Species), there is still much that we don’t know about this endearing little creature. I have spent the last 3 years attempting to unravel a few of the mysteries surrounding their habits, and how these habits might shift in the face of future climatic and environmental change.
During my PhD at the University of Cumbria, I have focused on three key routes by which climate change could affect the habits and population success of hazel dormice: (1) through effects on patterns of arousal (i.e. waking up from hibernation) during the winter months; (2) by causing changes in the timing of food availability at different times of the year; and (3) by influencing aspects of the hazel dormouse’s lifecycle that might affect its reproductive success, such as reproductive timing.
Hazel dormice are particularly special and interesting due to their sleepy nature. They hibernate for approximately six to seven months of the year in the UK (and longer in other places in their range). Even during the active season, they will go into daily torpor (a state of low metabolism and body temperature, which looks like sleeping) fairly regularly to save energy. Patterns of hibernation and daily torpor have been related to climatic conditions in other hibernating species, prompting the idea that climate change might lead to shifts in these patterns. This could then have subsequent effects on other aspects of a hibernator’s lifecycle. The hazel dormouse’s habit of hibernating in a nest on the forest floor, where it is exposed to changing weather conditions throughout the winter, rather than in a more climatically-stable underground burrow or cave, makes it even more likely that our changing climate is going to have an effect on them.
With funding and support from the People’s Trust for Endangered Species, Suffolk Wildlife Trust and Chester Zoo, I have spent many long hours (though not as many as I would have liked, due to the COVID-19 pandemic) painstakingly searching woodland floors for hibernating hazel dormice. At my fieldwork sites, hazel dormice are microchipped during the active season when they are found in nest-boxes. This allowed me to make use of a long-range PIT-tag scanner to help in the search for hibernation nests, as they are often buried under leaf litter or clumps of moss. I am using a combination of camera traps, temperature/humidity recorders and computer modelling to determine if weather conditions during hibernation influence when hazel dormice leave their hibernation nests, which they are known to do during the winter, but which uses up lots of their limited energy supplies.
Hazel dormice are reasonably picky eaters, as they can’t eat leaves or grass due to not having a caecum in their gut, which is needed to digest cellulose. During the active season, their diet follows a sequence of buds, flowers, insects and fruit as each become available at different times. Changes in the timing of budding and flowering in association with warming spring temperatures have been documented in a range of plant species, but very little research has been done on the timing of autumn events, such as fruiting. Fruit, nuts and berries are a very important food source for hazel dormice, as their autumn production coincides both with the majority of juveniles becoming weaned, and with the important pre-hibernation fattening period. Changes in the timing of production and/or abundance of fruits could have big impacts on the amount of weight that hazel dormice are able to gain before the hibernation season. Insufficient fat stores may negatively affect survival probability during hibernation, as hazel dormice don’t cache food, or may cause hazel dormice to come out of hibernation in poor body condition in the spring. The Woodland Trust Nature’s Calendar dataset is a real treasure trove of observations on the timing of natural events across the UK, including budding, flowering and fruiting, that spans decades. I am using this dataset to examine changes in the timing of hazel dormouse food plant events relative to hazel dormouse life events, and to look for potential mismatches that may be occurring over time.
Previous research has found that body condition of females emerging from hibernation in the spring may affect when in the year they are able to reproduce. Reproducing early in the year gives babies more time to grow and put on weight before their first hibernation. It might even allow them to mate and reproduce themselves in their first year of life. Litters born late in the year have a shorter period to gain weight, although there are more high-calorie foods around at this point. For seasonally-reproducing animals, including hazel dormice, early reproduction has generally been found to be the more successful strategy in terms of lifetime reproductive success (i.e. the number of offspring that survive to reproduction over a parent’s lifetime). This means that any climatic influences that could affect spring body mass also have the potential to indirectly affect reproductive timing. If climate change is somehow causing hazel dormice to reproduce later in the year, this could be a factor in their decline. I am using hazel dormouse litter data from the NDMP’s long-term dataset in conjunction with weather data from the Met Office’s HADUK Grid dataset to test for associations between long and short-term weather conditions and mean birthdates at different sites across the UK.
Piecing it together
As I approach the final few months before thesis hand-in, I am piecing all these bits of information together into what I hope will be the foundations of future research on the effects of climate change for both hazel dormice and other British mammals. Understanding the routes by which climate change may affect British mammals will help us to produce future-proof conservation plans for them, and hopefully mean that hazel dormice will continue to flourish in British woodlands for years to come.
With huge thanks to my supervisors, Dr. Davina Hill (University of Glasgow), Dr. Volker Deecke and Dr. Andrew Weatherall (University of Cumbria), the People’s Trust for Endangered Species for funding and access to the NDMP dataset, the Woodland Trust for access to the Nature’s Calendar dataset, Suffolk Wildlife Trust and Chester Zoo for support and access to sites (in particular Dr. Simone Bullion and Alison Looser), the University of Cumbria for funding and to Ellen and Gary for fieldwork assistance.