Climate change is waking bats up from hibernation too early

Imagine waking up from a winter nap to find that it’s already spring. This has become the reality for many bats thanks to rising temperatures and climate change. 

A study from the University of Barcelona shows how bats are adjusting to shorter winters. This affects their sleep patterns, where they travel, and their job as nature’s pest control.

Climate change and bat hibernation

Many bat species living in areas with moderate climates use hibernation as a way to survive the winter. This is a difficult time for bats because their usual food source, insects, are not readily available. To deal with this, bats enter a state called torpor. 

In the state of torpor, the bats’ body functions slow down significantly. Their body temperature drops, and they use much less energy than usual. This allows the bats to live off the fat they stored up before winter and survive the cold months without needing to find food.

Schreiber’s bent-winged bats

The Barcelona team studied Schreiber’s bent-winged bats for 20 years to see how they cope with rising temperatures. They tracked the bats’ weight and fat content throughout their hibernation cycle. 

The researchers observed that these bats entered and exited hibernation weighing less over time, even though winter temperatures became warmer during the study period. Interestingly, despite this weight loss, the bats didn’t lose a significant amount of fat reserves. 

Earlier spring activity

As the Earth’s temperature rises, winters are becoming milder and springs are starting earlier. This has led bats to wake up from their winter sleep sooner than usual. While this change might seem like a good thing at first, allowing them to be active for a longer period, it also comes with risks.

“The fat reserves they accumulate should be large enough to survive the whole winter without eating. However, due to shorter winters and higher temperatures, bats are not fattening up in autumn as they used to do years ago, because they do not need that much fat to get through the winter,” explained Professor Jordi Serra-Cobo.

Bats are hibernating in warmer caves

In the past, bats preferred the cooler, deeper parts of caves to hibernate during winter. However, due to rising global temperatures, these areas are losing their coolness. As a result, bats are being forced to find cooler spots closer to cave entrances for their hibernation.

The shift in location exposes them to greater danger from predators, like genets, who can more easily access these areas near the cave opening. This new challenge makes it even harder for bats to survive the winter.

Potential impact on pest control

As previously mentioned, bats are very important for keeping insect populations, including harmful pests and insects that spread diseases, under control. 

Waking up early in spring could have a big impact on the life cycle of the insects they eat. If both the bats and the insects wake up earlier at the same time due to warmer weather, it might not affect how well the bats control pest populations. 

This suggests that there is a complex balance in nature where changes in one animal’s behavior due to climate change can affect other things in the environment, like pest control. However, unpredictable weather – especially an unexpected cold snap in the spring – could be dangerous for bats that wake up early because they won’t have enough stored fat to survive. 

Varying impacts across all bat species

The experts found that different bat species are affected by climate change in different ways. Bats that live in areas like the Mediterranean, which are already warm, seem to be better able to handle climate change than bats in colder regions. This shows that climate change can have complicated effects on wildlife, with some animals being able to adapt to new conditions more easily than others. 

The study serves as a stark reminder of the far-reaching effects of climate change, even on resilient creatures like bats. As the world warms, understanding and addressing the complex challenges they face will be crucial to ensure their survival in a rapidly changing environment.

The study is published in the journal Scientific Reports.

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