Time to help our hibernating mammals…not just hedgehogs!
We all know that hedgehogs hibernate, but what about the UK’s other hibernating mammals?
Hibernation isn’t just a really deep sleep. It is the technical term that describes a state of extreme inactivity, which an animal chooses to enter in order to preserve energy. During hibernation an animal’s temperature will drop, metabolism will reduce and breathing and heart rate will slow down.
Although many species are less active over winter in the UK, only three groups enter true hibernation: the hedgehog, the hazel dormouse and our native bats. Other mammals, like badgers and red squirrels, instead enter a state called torpor. Unlike hibernation, torpor is involuntary. This means that it is only entered when dictated by the environmental conditions. Another key difference is that torpor tends to last for shorter periods, and is easier for animals to re-enter if woken too early.
Because our hibernating animals sleep for so long, so deeply, it is essential that they store enough fat reserves before they hunker down in their dens. Their survival also hinges on not being disturbed. If they are woken too early they can lose vital energy or fail to return to sleep, entering a cold landscape where very little can be found to eat. As we enter autumn, now is the best time to take action to help these species, helping to build up their fat reserves and find suitable spaces to spend the winter months.
Weighing in a tiny 27g, these pocket sized mammals are classed as vulnerable to extinction in the UK. It’s not just their low numbers that make them a rare sight though, as dormice can spend more than half of the year hibernating.
Dormice use the warmer summer months to build up their fat reserves as much as possible, even doubling their body weight. As the weather turns in October they climb down from the trees where they have been feasting on nuts, berries and insects to build a nest. Roughly the size of a tennis ball, this bed of tightly woven grass will help to keep the dormouse insulated from the worst of the cold.
It is vital for dormice to build up their fat reserves before curling up in the nest. By planting trees and shrubs that provide food for wildlife, you can make a real difference. Over their active period dormice will feed on the pollen and nectar in flowers of species like hawthorn and honeysuckle before switching to bramble and hazel as they fruit in the late summer. For more information about planting trees and shrubs for wildlife head to the Take action tab in the Naturehood platform.
The 17 species of British bat all hibernate during the winter months. This is partly because of the chilly weather, but also due to a lack of insects for them to feed on. Different species prefer different sites to spend the winter - there are some that will roost in their very own bat cave, but most have actually evolved to hibernate in trees.
Because there aren’t as many ancient trees in our landscape as there used to be, suitable roosting sites like a hollow in the trunk or a nook in the bark can be hard to find. This means that many bats will instead settle in buildings like barns and sheds or tailor-made bat boxes. If you’re interested in adding a bat box to your Naturespace, one of the most successful designs is the Kent bat box.
The common months for bat hibernation are between November and April. If they are disturbed in this period, they can wake up and go searching for food. Unfortunately, because there are so few flying insects around and the weather is so severe, it can be a very expensive use of energy. This is why it’s important to respect their roosts and avoid cutting down old trees, renovating old buildings or moving bat boxes in this period if at all possible.
Badgers and squirrels
Unlike hedgehogs, dormice and bats, badgers and squirrels don’t hibernate over winter. They still don’t enjoy being out and about in the cold winter weather though! Instead they enter a lighter (but still deep compared to what you and I experience) sleep state known as torpor. Badgers will nestle down underground in their burrow – called a sett, while squirrels retire to their den, hidden in a tree trunk, or drey in the branches.
Because torpor is easier for animals to enter and leave than hibernation, badgers and squirrels can to use patches of warmer weather to feed and restock their energy supplies. Famously a squirrel will visit a cache of food that it has buried and stored up over the autumn. Meanwhile a badger will go hunting. These adaptable animals mainly eat worms, but with the ground frozen can switch over to vegetables, fruit, nuts, insects or even small vertebrates, like frogs and shrews.
By planting a good mix of trees and shrubs, adding a compost bin and taking other actions for wildlife (for guidance head to the Take action tab) there is plenty you can do to encourage natural food sources for these animals. Topping up the diets of non-hibernators through the winter by providing extra food, is also an option, but there are important factors to keep in mind:
- Feeding by hand should be avoided, these are wild animals that could harm you and it also isn’t good for them to lose their natural fear of people.
- Don’t leave out too much food as this can lead to animal numbers reaching pest levels and raise the risk of disease transmission between species and groups.
- Choose what you feed animals based on what you have visiting. For example, hedgehogs are lactose intolerant, so drinking milk can make them unwell.
- Maybe don’t provide extra feed. If you have both red and grey squirrels nearby then providing food can lead to conflicts. A feeder may also become a favoured ambush site for a neighbour’s cat.
If you have questions about feeding animals I’d encourage you to join our Naturehood community and post your thoughts or concerns on the platform live feed.