Mild winter, then heavy snow: what consequences for Swiss animals?
After an exceptionally mild winter, heavy snow is expected in the mid-mountains this week. Is this return of the cold a double-edged sword? There will be winners and losers on the wildlife side.
Blossoming hazel trees, waking bees, birdsong… The winter of 2023 is taking on the air of spring. Heavy snow is expected this week after record high temperatures over a green Christmas and New Year. What are the consequences for wildlife when some species are already waking up from their winter torpor?
Winners and losers. If winter and its white coat is a fairy tale for snow sports enthusiasts, it is a time of tremendous survival for wildlife in general.
For non-hibernating animals such as deer, mountain goats or chamois, the mildness of December and January provides a temporary respite. Lunar animals use less of their fat reserves and are better equipped to survive until the end of winter, including the return of the cold.
Kurt Bollmann, wildlife biologist at the WSL Federal Research Institute:
“They use less energy to maintain their body temperature at 37-38°C and get more food.”
But the success of some in an ecosystem can be the misfortune of others, the naturalist adds:
“Some scavengers, such as foxes, eagles or golden eagles, depend on the high mortality of ungulates in winter. This year there will be less carcasses in the Alps for them to feed on.”
Turbulent hibernation? Hibernation is one of the main strategies developed by mammals to survive the horrors of winter. As the cold season approaches, marmots, hedgehogs and even bats become sluggish, their heart rate and body temperature decrease (3-6°C).
- Couldn’t the high temperatures of the last few months break this cycle? For Kurt Bollmann, there is no need to worry at this level:
“This hibernation is hormonal and depends more on the seasonal rhythm of day and night than the external temperature. Groundhog nests are relatively well insulated by snow and conditions should remain stable. Winters without snow, when the ground freezes, would be more problematic.
- If mild temperatures continue into February, the situation could become more dangerous.
“Bats that spend the winter in poorly insulated shelters, such as under the roofs of churches, may wake up later.”
Bats that come out of hibernation too early have difficulty meeting their energy needs, and the insects they feed on during this season are rare.
Bees in January? The mildness of January already awakens other species such as wild bees, mosquitoes or flies, and in Switzerland the hazel trees are already blooming. “It is important to distinguish between hibernation and hibernation,” reminds Kurt Bollmann. Insects, frogs and even reptiles don’t hibernate, they do hibernation:
“They spend the winter in a shelter, inactive. Their body temperature drops to adjust to the ambient temperature. Therefore, they are more likely to wake up in a warm winter.”
When awake, these insects are active in search of food. Some cherry trees are already blooming, but most of the flowers, and therefore the nectar that pollinating insects depend on, are not there, notes Pro Natura spokesman Nicolas Wuthrich.
What will happen if the cold suddenly returns? “The insects that have found shelter must return to the tired state,” he adds.
“Every time they wake up, they use energy reserves that are important for winter storage. Finally, this high variability between hot and cold can be problematic.
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