Venom, burns and paralysis: Denmark’s most dangerous wildlife

Newcomers often expect Danish flora and fauna to be mild-mannered – especially those of us who move to the Nordic countries from more tropical climes. We’ve rounded up a list of creatures (and one plant) to keep an eye out for.

Common horse fly
Female horse and cleg flies need a blood meal to lay their eggs. Photo: Botaurus, Wikimedia Commons.
European hornet, Vespa crabro.
The European hornet, which can reach sizes up to 35 mm or 1.4 inches, is known to drift through open windows at night. Photo: Judy Gallagher/Flickr.

European hornet

One of the most alarming Danish creatures makes house calls.  The European hornet, Denmark’s largest wasp at 2.5-3.5 cm or 1-1.4 inches in length, is known to drift through open windows on a warm summer night with all the stealth and grace of a rogue apache helicopter. You’ll likely hear it before you see it.

Despite its distressing size, no, it’s not a murder hornet. And unlike its semi-demonic cousin the yellowjacket, the European hornet isn’t aggressive unless its nest is disturbed (get professional help to remove a nest), though it will sting if handled. The European hornet’s sting is more painful than a bee sting, and since hornets don’t lose their stingers a single individual can jab repeatedly.

Common horse fly

Female horse and cleg flies need a blood meal to lay their eggs. Photo: Botaurus, Wikimedia.

Horse and cleg flies

Horse and cleg flies look like beefy houseflies – but like mosquitos, the females suck blood in order to lay their eggs. If a mosquitos’ proboscis is a hypodermic needle, the horse fly breaks the skin with dull serrated scissors, leaving a painful red welt behind. Horse and cleg fly bites are usually no cause for concern. 

Common European adder

This common European adder, with its distinctive zig-zag pattern, is basking in the sun and minding its own business. Photo: Peter von Bagh/Flickr.

Common European adder (or viper)

Denmark’s only venomous snake, the common European adder, typically avoids humans but will bite if handled. It’s important to seek treatment immediately. About 200 Danes a year are bitten, but only 10 percent require hospitalization after initial treatment, according to the Statens Serum Institut. The European viper is protected by Danish law, so if you find one living too close for comfort reach out to the Danish Nature Agency for help with removal.  

Greater weever fish

The greater weever fish delivers a potent toxin through spines in its back. Photo: Guy Paz/Public Domain.

Weever fish

The greater weever fish is the scourge of the Danish coast. It’s an invasive species that lurks on the bottom of shallow waters in the summer. Sharp spines on the weever’s back deliver an extraordinarily painful toxin, and most encounters with humans occur when a weever is unintentionally stepped on (though even a dead weaver can land a sting). According to the Bispebjerg Hospital, weever stings are rarely serious but are characterized by discoloration, radiating pain, dizziness, headaches and for up to 24 hours. Swelling can persist for several months.

Call the Danish poison line at 82 12 12 12 for advice if stung by a weever fish.

Ticks are “the most dangerous animal in Denmark,” according to health officials. Photo: Bartłomiej Bulicz, Wikimedia Commons.

Wood tick

According to the Danish Nature Agency, the wood tick is the most dangerous animal in Denmark. Ticks can carry the borrelia bacteria, which can cause Lyme disease if left untreated. The Statens Serum Institut, Denmark’s infectious disease agency, says that about 180 Danes a year are diagnosed with neuroborreliosis, an infection of the brain by the borrelia bacteria. Symptoms include headache, stiffness of the back and neck, and nerve pain or muscle paralysis, typically in the face. Borrelia infections identified early can be treated easily with a course of antibiotics.

Check yourself and loved ones for ticks after time spent outside, and be certain to remove any ticks you find properly.


Contact with giant hogweed can cause severe burns and a long-term sensitivity to sunlight. Photo: Rob Hille, Wikimedia Commons.

 Giant bear claw, or giant hogweed

Kæmpebjørneklo, or ‘giant bear claw,’ is an invasive plant that secretes a sap that makes skin extremely sensitive to sunlight and can cause severe burns, according to the Danish Environmental Protection Agency (Miljøstyrelsen). While the sap doesn’t hurt when it touches the skin initially, it can make the affected area sensitive to sunlight for years.

Giant bear claw is a tall plant topped with white flowers, growing 2-5 meters high. Its stalk is green with red-brown spots and white hairs.

The Danish EPA recommends washing skin that might have had contact with sap using soap and water within 20 minutes. Avoid sunlight for at least 48 hours and ask a doctor about additional measures.

Member comments

Log in here to leave a comment.
Become a Member to leave a comment.


How and where is Denmark celebrating Sankt Hans Aften in 2021?

After last year's subdued celebrations, this year's Sankt Hans Aften promises to be somewhat closer to normal, although many events are cancelled. Here are some of the ones going ahead.

How and where is Denmark celebrating Sankt Hans Aften in 2021?
A fire is lit in the Engen woods outside Odense in 2020. Photo: Sophia Juliane Lydolph/Ritzau Scanpix

Sankt Hans Aften, with its giant fires, raucous group singing and drunken jubilance, is one of the highlights of the Danish calendar, bringing in the summer in style.

But despite the lifting of many of Denmark’s most thoroughgoing coronavirus restrictions, this year’s events will still be somewhat constrained. 

What are the restrictions in place for Sankt Hans? 

The remaining restrictions still impose a limit of 500 people for private outdoor events, although up to 2,000 people can attend formal cultural events, so long as the organisers divide the crowd into groups of 500. 

But organisers of public events still need to check participants’ coronavirus passes. There is also a recommendation that people be seated when engaged in group singing, something that conflicts fairly strongly with the traditional Sankt Hans Aften celebrations. 

Which of the big events have cancelled? 

As a result, several of the bigger events have in the past few weeks decided to cancel. 

The event at Frederiksberg Gardens in Copenhagen, a city centre favourite, announced last week that it was cancelling, as did the Bakken amusement park, a favourite for kids’ events. 

The municipality in Gentofte, where some of Copenhagen’s big Sankt Hans events are held, has put out a press release explaining that at least seven of the big ones have been cancelled. 

The Herfølge citizens association, which puts on a big event across the Køge bay from Copenhagen, announced it was cancelling last week, citing the need to check coronavirus passes and also its judgement that the ground is too soft and muddy for participants to be expected to sit. 

Other recent cancellations include the celebrations at Cirkuspladsen in Rudersdal Municipality, the Kirkehalvøen outside Horshølm, at the Rådhusplænen square in Rødovre, the celebrations at Søvang in Dragør, and at the northern tip of Jutland, the popular celebrations at Skagen. 

So where are events happening? 


Tivoli The capital’s iconic amusement park and gardens will have a bonfire by the lake, and cool jazz played by the Tivoli ensemble. 

Reffen. The streetfood market on the Refshaleøn peninsular is holding a party with a bonfire, tasty food, and live music. 

Rebæk Søpark. This event by the pond in a park in Hvidovre is going ahead, albeit with the crowd limited to 1,000 people. The event is already sold out but you can get on the waiting list here. The crowd is being divided into five sections of 200 people. The band Rocazino will perform and Helle Adelborg, the mayor of the Copenhagen suburb, will make a traditional Sankt Hans speech. 

Nordhavn. There’s a event organised from 4pm to 9pm at Nordhavn in Copenhagen, with concerts, a market and speeches. 

Amager Strandpark. There doesn’t seem to be an organised public event happening, but you can be sure that individual groups will light bonfires on the beach and do the traditional singing and drinking. 


Tivoli Friheden. Aarhus’ fairground near the Marselis forest is offering up live music and a speech by the city’s lord mayor Jacob Bundsgaard. 

Braband Lake. The local scouts are putting on a child-friendly Sankt Hans celebration in Braband, outside Aarhus. 

St Johannes Churchyard. This is one of the most “hygglig” of the city’s celebrations, at a churchyard right in the city centre, although it has already sold out

Langenæs Church. A longstanding and family-friendly event at the Langenæs church south of the city centre.


Engen. Natural soundings and a rather sizeable bonfire are two reasons to follow the decades-long Odense tradition of attending Sankt Hans at Engen in the Fruens Bøge forest. Until Monday it looked like the event would have to be cancelled due to the risk of wildfires, but has now confirmed it is going ahead. 

A previous version of this article linked to a Facebook event page for Sankt Hans at Islands Brygge, which actually took place in 2019. Apologies.