The recent dusting of snow, followed by Storm Bert, got me thinking about how our local wildlife endures such variable and often harsh winter conditions.
Despite freezing temperatures, limited food supplies, and shorter daylight hours, our flora and fauna find remarkable ways to survive. Reflecting on their strategies and adaptations to winter reinforces just how truly incredible nature is.
BY ANN HAIGH
Layering up
Wild animals can’t retreat indoors to light the fire or turn on central heating. Some animals, such as bats and hedgehogs, build up fat and energy reserves in autumn and hibernate through winter. Others, like foxes, Irish hares, stoats, and pine martens, grow thicker and denser fur, and spend more time in sheltered areas to stay warm. Out at sea, grey and harbour seals rely on a thick layer of insulating blubber to survive icy waters of the Atlantic.
Starlings roost together in winter in large flocks to conserve heat. (Photo: Nick Haigh)
Self-made shelters
While fur and blubber are familiar adaptations, some creatures take less obvious approaches to protection. In the gravelly beds of nearby streams, caddisfly larvae craft small cocoons, or cases, from tiny pebbles, grains of sand or suitable pieces of vegetation. These ingenious structures shield them from fast-flowing, icy waters, allowing them to develop safely and emerge as flying insects in spring.
Slowing down
Few Irish species truly hibernate, bats and hedgehogs are the only mammals that do. However, many animals, adopt different forms of inactivity to survive until spring. Common frogs enter brumation, slowing their metabolism while sheltering in pond mud, soft earth, or under logs, where they are safe from frost. Many invertebrates burrow into leaf litter, soil, trees, or buildings, entering diapause, a state that halts their development until conditions improve. Badgers and red squirrels reduce activity during the coldest days, entering a state of torpor to conserve energy.
Relocation
When we think of birds relocating in winter, migration from Ireland of species such as swifts, swallows, and house martins come to mind. However, some birds relocate within Ireland to find more suitable microclimates, like meadow pipits and our rare breeding curlew, which breed in uplands in spring and summer, move to lower altitudes and coastal regions in winter to avoid freezing and exposed conditions.
Shrinking
The pygmy shrew, one of Ireland’s smallest mammals, has an extraordinary survival strategy. In summer, they can weigh up to six grams, but in winter, some individuals shrink to as little as three grams. This process, known as Dehnel’s Phenomenon, involves a reduction in body mass, organs, skull, and brain, to conserve energy during the colder months. Remarkably, they regrow these features in spring. Pygmy shrews also eat constantly to fuel their high metabolism, feeding hourly, even in snow.
Food matters
When food is scarce, many species have evolved ways of finding it. Redpolls will perform gymnastics to extract seeds, turning upside down to reach seeds from trees such as alder and birch. They may even shake out seeds from vegetation and drop to the ground to collect them.
Others, such as the treecreeper, change diet from invertebrates to seeds when their usual prey becomes hard to find. Animals may also store and hoard food when there is surplus, in anticipation of frosts and freezes. Squirrels and corvids, such as ravens, rooks, and jays, hoard food during abundance to ensure survival through leaner times.
The pygmy shrew reduces body mass, organs, skull, and brain, in order to conserve energy during the colder months. (Photo: Shutterstock)
Nature’s invention
Necessity drives innovation and nature provides many examples. Some butterflies overwinter as caterpillars or pupae, while others, like the brimstone, small tortoiseshell, and peacock, withstand the winter as adults. To avoid becoming frozen, they store glycerol in their bodily fluids, which acts as an antifreeze to prevent ice crystals.
Mallards showcase counter-current exchange, a system where warm blood flowing to their feet warms cooler blood returning to the heart. This minimises heat loss and reduces energy expenditure, even when their feet are submerged in icy water.
Even slugs show remarkable survival tactics. Large black slugs, often found in gardens, shelter in soil pockets, under logs, or in wall crevices in winter. If caught in sudden freezing conditions, they can survive partial freezing, so long as it is not prolonged.
Grouping together
Huddling together is another effective strategy. Many bird species roost communally in winter and examples include rooks, starlings, pied wagtails, wrens, and even our beautiful long-tailed tits. These birds have learnt that clustering in large groups conserves heat. Rodents, like the wood mouse, often come together in groups to nestle into winter nests, but will disperse in spring to mate and breed.
Lessons in resilience
Much remains to be learned about how plants and animals adapt to changing conditions, ever-more relevant in the age of accelerating climate change. For animals that hibernate fully, or slow down during the colder months, mild winter periods can be particularly challenging. Warmer days may prompt premature activity, but this false signal often leads to trouble, as food remains scarce. Such disruptions risk depleting energy reserves and reducing survival chances.
That said, I sometimes feel I could borrow a few of nature’s winter survival strategies myself. Nature truly offers invaluable lessons in resilience.
