The air in the Cairngorms is noticeably colder, the days are becoming shorter and nature is slowing down. In the past few weeks, I have seen a noticeable difference in the number of insects on the Flowering Ivy and the lovely crisp, crunchy orange leaves have become brown and wet on the woodland floors. The trees are bare and the berries have been blown off from strong winds. With the change in daylight, there is less food available and along with cooler temperatures this has triggered most mammals into a state of hibernation.
Not all truly hibernate and most just slow down, simply choosing to conserve energy by avoiding foraging during harsh conditions, and potentially on less frequently. Our only true hibernators include our little Hedgehogs and bats - still both have different strategies.
Over autumn, Hedgehogs will have built up a large fat store, enough to see them through the whole winter until spring. They will find a cosy spot under a large pile of leaves or brush piles around the start of November - often in our gardens, they seek out shelter under sheds or decking. They slow their heartbeat, their metabolic rate and body temperature so much so, that they can be mistaken to be dead if found. They will stay in this state of hibernation for the duration of the winter.
Bats often hibernate in groups, their state of hibernation, also known as torpor, involves the same slowing of heartbeat, body temperature and metabolic rate, however, they do this in stages. At the end of autumn, they will take longer naps than over the summer, especially when the temperature starts to drop, but only when the temperature and conditions are very harsh, will they go into a prolonged period of torpor. They often seek shelter in tree cavities in old tree’s, caves, or in old buildings. They will gently wake up to get rid of waste throughout the winter, but only once the early weeks of spring arrive, will they venture out for a snack. Again, if the temperatures and food availability aren’t quite right, they will go back to ‘sleep’.
My favourite insect, the bumblebee also hibernates, although, it is only the queens that hibernate. Picking a bank, with well-drained soil, to avoid flooding, usually north facing, to avoid the winter sun from waking them up, bumblebees will burrow into the soil and stay for the duration of winter and wake up in spring to create a new nest. Some insects have the amazing ability to just pause their life cycle. The term for this is diapause. To avoid the frost and freezing, butterflies and moths seek out a warm spot, usually in a crevice of a tree, cave or sometimes even a shed. An interesting part of their life cycle is that they will diapause in any stage, whether egg, larvae, pupa, or adult. This depends on the species. Caterpillars crawl into leaf piles and can almost always be found when doing the end of autumn garden tidy. I always place the found larva into a safe place, deep in my leaf piles in the corners of the garden. Occasionally, an adult butterfly makes an appearance over the winter inside a room that hasn’t had the heating on for a while. In this case, butterflies can be put into a dark cool shed or garage to continue diapause.
Mammals that don’t hibernate are our lovely Red Squirrels, Wood Mice and Badgers. During very bad weather they hunker down and become less active over the winter. However, on a cold morning, I find that the Red Squirrels are ravenous, and their footprints are found in the fresh snow usually going towards a peanut feeder.
Spring is a great time for a Guided Day Out to look for all of our species coming out of hibernation - it feels like seeing old friends again. Although the next month or two, we would be unlikely to spot bats, butterflies and Hedgehogs, we do still manage to seek out all of the birds and mammals keeping their energy up on colder days. If you’d like to join us for a Guided Day Out over winter, please find out more here.