Joosep Sarapuu, a zoologist at the Estonian Museum of Natural History, said caution is warranted when claiming a population has grown. According to him, people's impressions do not always reflect the actual situation.

"People's observations may not be the most objective. It may simply be that people have started noticing them more," Sarapuu said.

He added that he himself has not observed a significant increase in moles this year and it is difficult to make generalizations without more precise data. At the same time, Sarapuu noted that fluctuations in nature are entirely normal. "Most animals experience some kind of population fluctuations," he said.

Zoologist Uudo Timm confirmed that animal numbers in nature are generally influenced by natural cycles: some years there are more animals, in others fewer. However, the unusually large number of molehills this year may instead be linked to the type of winter Estonia experienced.

"This year the snow fell on unfrozen ground and remained there. The soil did not freeze deeply," Timm explained. Because the ground stayed softer, moles were able to remain active in higher soil layers during the winter. As they dig tunnels underground, excess soil accumulates and has to be pushed somewhere, which is how molehills form on the surface.

In a typical winter, alternating thaws and freezes sometimes harden the snow layer, but this year that largely did not happen. "Moles were able to work calmly in the upper soil layers during the winter and push the excess soil upward," Timm said. When the snow melted in spring, those mounds simply became clearly visible.

More attentive observers have noticed molehills, for example, around new housing developments in Tartu County. According to Sarapuu, one possible explanation here is human activity. When a previously natural area is partially built over, moles may have nowhere to go.

"If they previously had a larger habitat, but part of it is turned into a parking lot or houses, they may end up concentrated in a smaller area," he explained. In that case, molehills may appear especially dense in one location.

Although molehills may give the impression that moles move around a lot on the surface, Timm said this is not actually the case. "Moles do not want to come to the surface," he said. They spend almost their entire lives in underground tunnels. Moles may appear above ground only during certain periods of their lives — for example, when young animals are driven out of the nest and must find a new territory. At that point, they can even move surprisingly quickly across the ground.

Pests or a blessing?

Many gardeners try to drive moles away from their yards, but Timm stressed that moles are actually rather beneficial animals. They feed mainly on earthworms and insect larvae living in the soil, meaning they also help destroy several garden pests.

Problems can arise, however, when a mole digs tunnels beneath garden beds and lifts plants out of the soil. "Then the plants can dry out and gardeners may become upset with the moles," Timm said.

Sometimes the soil mounds in a garden may actually be made by a different animal — the water vole. Unlike the mole, the water vole is herbivorous and can cause considerably greater damage in gardens. "They may gnaw on the roots of fruit trees or eat carrots and beets from below," Timm explained. Often the damage is only discovered in autumn during harvest when the tops appear healthy but the root vegetable has disappeared underground.

The activity of moles and water voles can be distinguished by the shape of the soil mound. In a molehill, the opening is usually located in the center of the mound, whereas with a water vole the opening is typically beside the pile.

Populations fluctuate

The numbers of both moles and other small animals fluctuate naturally in the wild. When animal populations grow too large, diseases begin to spread and stress reduces reproduction. After a few years, numbers decline until the cycle repeats again.

"In our conditions, these cycles are often about four years long," Timm said. Predators and birds of prey also respond to changes in the numbers of small animals: when food is abundant, their numbers increase as well. For this reason, the abundance of molehills is not anything unusual, the zoologist said.

"These are simply environmental conditions. We have to live with them. And it would be a little boring if there were no one to blame for the molehills," Uudo Timm said.

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