Gotland grass snake
| Gotland grass snake | ||||||||||||
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| Scientific name | ||||||||||||
| Natrix natrix gotlandica | ||||||||||||
| Nilson & Andrén , 1981 |
The Gotland grass snake ( Natrix natrix gotlandica ) is a subspecies of the common grass snake that is endemic to the Swedish island of Gotland and neighboring islands.
features
With a total length of less than one meter, the subspecies is shorter than the nominate form ( Natrix natrix natrix ). Females are larger than males and an average of 74 cm long, with individual specimens reaching 95 cm. The average length of the males is 55 cm, with a maximum length of 67 cm. Two color variants are known for the Gotland grass snake. The first variant is approximately black ( melanism ), although many specimens have small white or brown spots on the trunk that are arranged in rows. About 40 percent of the total population belong to this dark form. The light variant is mainly gray, olive green or brown in color. Several dark spots or stripes appear on this base color.
The large orange, reddish or white spots on the back of the head typical of the grass snake are always present in the light variant. The dark variant can occasionally have light patches on the neck. The Gotland grass snake has fewer belly and tail scales than the nominate form. Furthermore, the signs on the head have a different shape.
distribution
The Gotland grass snake's range is limited to Gotland, Fårö , Lilla Karlsö and Gotska Sandön . The subspecies mostly lives near water, e.g. B. on ponds, lakes, flowing waters, on the Baltic coast and in swamps and moors.
According to a phylogenetic study from 2014, the Gotland subspecies mainly reached from Central Europe . The first individuals could have drifted north across the Baltic Sea or humans introduced them consciously or unconsciously. A later mixing with imported specimens from southern Sweden is not excluded.
Way of life
The Gotland grass snake lives near its prey, which consists of frogs , toads, and fish , during the warm season . Eggs are usually laid in partially rotted parts of the plant. Before winter, the subspecies migrates to a place with stones or rocks that offers suitable hiding places. The winter quarters are usually left in March.
Specimens that feel threatened primarily try to reach the closest hiding place. Other variants of defensive behavior are straightening the front body, sham attacks, the release of a foul-smelling liquid from the post-anal glands or rigor .
The females lay 11 to 15 eggs in June or July. The offspring hatch after about two months of breeding .
status
The population probably decreased as a result of drainage measures in the 20th century. Furthermore, a smaller number of manure and compost heaps has a negative effect on the stand. Trapping, killing or changing known hiding places of the subspecies is prohibited by law in Sweden. The Gotland grass snake is listed as potentially endangered in Sweden's Red List (corresponding to Near Threatened by IUCN ).
Individual evidence
- ↑ a b c d e f g Claes Andrén: Gotlandssnok ( schw. , PDF) In: Artdatabanken . Swedish University of Agricultural Sciences . 2006. Retrieved June 26, 2017.
- ↑ Kindler et al .: Phylogeography of grass snakes (Natrix natrix) all around the Baltic Sea ( English , PDF) In: Amphibia-Reptilia . Senckenberg Nature Museum . 2014. Retrieved June 26, 2017.
Web links
- Natrix natrix in The Reptile Database (with list of subspecies)
- Gotland grass snake , North Ark