Light pollution threatens the brown bear

By choosing the beautiful moth butterfly of the year, conservationists want to draw attention to the consequences of artificial lighting. (Image: creativenaturemedia / iStock)

Brown and white patterned wings and a shining orange undergarment with iridescent dots: the brown bear is one of the most magnificent representatives of our native nocturnal insects. But unfortunately you can admire the beautiful moth less and less – the artificial light of our cultural landscape makes it difficult. In order to draw attention to the topic, the nature conservation organization BUND has now chosen the brown bear as the butterfly of the year 2021.

The Mohrenfalter started in 2003 and in 2020 the green hairstreak was in the spotlight: every year the Association for the Environment and Nature Conservation Germany (BUND) makes a native butterfly butterfly of the year. With this, the conservationists want to draw attention to the threat to specific species and the entire group of insects, as well as to clarify ecological relationships. For the year 2021, the choice is now on the Brown Bear (Arctia caja) like. As the BUND reports, the populations of this species are declining nationwide, which is why the once common brown bear is now on the warning list of endangered animals.

Lamps with a fatal attraction

But what causes these insects problems? In addition to the intensification of agriculture and the elimination of hedges in the landscape, light pollution in particular threatens the moths, say the conservationists. Like most nocturnal insects, the brown bear can orient itself well in weak moon or starlight. But the bright blue light from the high-pressure mercury vapor lamps in the street and industrial lighting is particularly annoying to the night insects.

“The brown bears are attracted by nocturnal light sources and then flutter around them without orientation until exhaustion,” says Jochen Behrmann from BUND. “In addition to the direct losses, the insects lose valuable energy and time for finding partners and for reproduction, and predators such as bats have an easy time of it.” Like other nature conservation organizations, the BUND advocates that lamps are temporarily switched off and replaced by better ones . Because there are alternatives with less seductive light frequencies: Sodium vapor lamps and modern, economical LEDs emit little or no blue light and thus irritate the Brown Bear and its relatives comparatively little.

The caterpillars have thick brown hair that is reminiscent of a bear’s skin. (Image: Tree4Two / iStock)

Furry caterpillars and chilling wings show

When looking at the butterfly, one may wonder how it got the name Brown Bear. As the BUND explains, this designation does not refer to the adult animals, but to their caterpillars. They have thick brown hair that is reminiscent of a bear’s skin. They can feed on a variety of plants – from herbs to deciduous trees. The moths then develop from the caterpillars in midsummer. With a wingspan of up to 65 millimeters, they are among the largest in Germany.

The appearance of the butterflies, which we find beautiful, has interesting functions: the brown-white pattern of the normally closed front wings camouflages them in the tangle of branches with light and shadow when they sit on tree trunks during the day. They cover the underlying orange-red hind wings with the dark “eyes”. The moth only presents them when it feels threatened: by opening the front wings at lightning speed, they come to the fore. This way they can frighten predators and the insect can escape. In addition, they convey the message: “Don’t eat me, because that will be bad for you”. Because the moths produce toxic body fluids.

As far as the causes of the endangerment are concerned, the BUND emphasizes that, in addition to light pollution, a mixture of other problems is also bothering the brown bear: the cleaning up of the landscape, species-poor industrial forests, urban sprawl and traffic pollution are to be mentioned. As the BUND concludes, the butterfly of the year 2021 can be seen as a bio-indicator for near-natural communities: where it flutters in large numbers, the habitat quality is still good – but when sources of interference spread, its populations dwindle.

Source: FEDERATION

Recent Articles

Related Stories

Stay on op - Ge the daily news in your inbox