Animals
Northern Bornholm have many different habitats. Rocky heath, pastures, woods and wetlands. Together with a careful management this results in a rich selection of animal life.
Game animals
The area houses roe deer, hares, pheasant and partridge. The deer keep to forested areas while the other three live in the open country where they are threatened by intensive farming. The Danish Nature Agency is experimenting with game friendly farming around Hammersholm to alleviate this. In recent years another game animal have come to inhabit Bornholm: the rabbit. The Rabbits have escaped from captivity, so many of them can be seen in domesticated colours like black and white.
Bats
Nine different bat species have been found in Northern Bornholm. Among them is whiskered bat, Natterer's bat and Brandt's bat. All three have a limited occurrence in Denmark. Hammershus and Hammerknuden are home to brown long-eared bat and seratine bat.
Amphibians and reptiles
On the heaths the european adder and sand lizard is common. In forested areas the viviparous lizard and slowworm can be found. In and around the ponds great crested newt, smooth newt, common water frog and European toad can be found.
Insects and arachnids
Denmark's only mygalomorph spider atypus affinis was rediscovered in Ravnedal in the 1990s. The female spends her whole life in a silk tube that she spins underground. When prey passes the tube she drags it down in the tube with her poisinous fangs.
In the cellars at Hammershus and in caves and wells you may find the European cave spider. It lives in dark, damp places and is even active in the winter.
The black-and-red-bug (lygaeus equestris) (pictured on white swallow-wort) is another noteworthy species.
Birds
Hammerknuden and Slotslyngen have Denmark's only two real nesting cliffs. These are home to razorbill and peregrine falcon (pictured) as well as western jackdaw, rock dove and several species of seagull. These locations are best experienced from the sea. In spring Hammerknuden is a great place to watch migrating birds as many species use the northernmost part of Bornholm as a landmark.
Plants
Northern Bornholm is a mix of heath, pastures, rocks, juniper thickets and decidious forest with oak, beech, birch and hornwort. Along the coast you may find small areas with bird's-eye primrose and dragon's teeth. At the waterfall at Pissebækken the blue pennywort is common and you may be lucky to find black spleenwort as well. Near Salomons Kapel on Hammerknuden there is an area of wetland where heath spotted-orchid, greater butterfly-orchid and lesser butterfly-orchid grows together with the carnivorous plant round-leaved sundew. The greater and lesser butterfly-orchids can be found at Ravnedal as well while Langebjerg is home to the elder-flowered orchid (pictured).
Medieval relict plants at Hammershus
Hammershus and the area around the castle is a very interesting botanical site. 50 different plant species can be traced back to the middle age where monks at Hammershus imported and grew them for medical purposes or for consumption. These plants still survive to this day as living relicts and reminders of the past.
Among the medicinal plants is the poisonous black henbane or stinking nightshade (pictured below) which have been used in medicine for more than 5.000 years. It was used as a seditive and in larger doses for assasinations. More peacefully the mullein which can also be found at Hammershus was used to treat cough and in skin balms.
Hammershus is one of the richest botanical sites in Denmark, and the Nature Agency is actively preserving the medieval relict plants as well as the hundreds of other species in the area around the castle.
The botanical site Hammershus
Aside from the medieval relict plants the area around Hammershus Castle is home to an unusually large number of plants. More than 300 species can be found here - that's over 10 percent of every Danish species. Many of them, like the grass pea, wild service tree, black spleenwort and white swallow-wort are rare.