Hazel dormice aren’t picky; they take advantage of whatever food is around
Eating is not only essential to life, but what is eaten and when can have a considerable impact on a species: where it’s found, how many offspring a female gives birth to, how much competitive overlap there is with other animals and even if there are sufficient resources to provide the energy needed to hibernate.
How much food is available in a woodland or hedgerow, at any one time and also seasonally, may impact not just individual dormice but the entire local population. Limited food sources may result in a smaller population, one more vulnerable to threats.
We know that dormice change their diet seasonally but how does the availability of food at individual sites impact our hazel dormice? Are dormice with access to more food plants in autumn heavier because they have access to more food, and therefore more likely to survive hibernation? Is higher food abundance related to more successful breeding, and stable or increasing populations?
Cecily’s study found honeysuckle makes up a large part of their diet. Image by Karen Arnold
SIA provides some answers
Cecily Goodwin, from the University of Exeter, set out to answer these questions. It’s not very easy to work out what an animal eats. It’s possible to look closely at droppings. However, different foods are digested in different ways, so remains are hard to compare. Chewed nuts and seed cases give us some idea but it’s difficult to quantify them. Stable isotope analysis (SIA) provides a way to both quantify and compare what individuals and populations of the same species have been eating. SIA also provides a longer timeframe than the snapshot a dropping provides.
Dormice appear to be adaptable
The good news is that dormice appear to be adaptable. They appear to eat more invertebrates when this food source is more plentiful. When there are fewer plant food sources available, they make good use of honeysuckle. Cecily’s findings also highlight the importance of the flowers and seeds of large trees such as oak and ash in their diets. Dormice have a broader trophic niche in the autumn than the spring. This reflects the wider variety of trees and shrubs they feed on before going into hibernation.
Cecily didn’t find any correlation between food abundance and how well the dormice were doing at any particular site. It may be that food resource availability wasn’t a factor at the sites she studied, compared with climatic or landscape factors. Or it’s possible the effects were too small to be detected. Further studies would be useful, while trying to account for the other impacts caused by varying weather patterns and habitat type and fragmentation.
Cecily Goodwin studied hazel dormice for her PhD at the University of Exeter. Her research, which was part-funded by PTES, looked at what impacts different types of woodland management has on dormice. Cecily radio-tracked dormice in different woods to see which areas they used the most and whether they avoided areas that had recently been felled. This study, looking at dormouse feeding habits, was part of her wider investigation to see whether some types of management provide better habitat for dormice.
Main image credit Hugh Clark