De Schauensee's anaconda

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De Schauensee's anaconda
Systematics
Subordination : Snakes (serpentes)
Superfamily : Boa-like (Booidea)
Family : Boas (Boidae)
Subfamily : Boa snakes (Boinae)
Genre : Anacondas ( Eunectes )
Type : De Schauensee's anaconda
Scientific name
Eunectes deschauenseei
Dunn & Conant , 1936

De Look lake anaconda ( Eunectes deschauenseei ) is a species of snake from the family of boas (Boidae), where it is in the subfamily of the constrictor snakes found (Boinae). This up to three meters long anaconda has in tropical South America is a relatively small distribution area of French Guiana to the Amazon - Delta . Practically nothing is known about the biology of this species, which is closely related to water.

description

Physique and length

The species is very strongly built, the body is approximately round in cross section. The head is relatively small and only slightly separated from the neck. The eyes and nostrils are located high on the head in adaptation to the aquatic way of life. Males as well as females with total lengths between 1.3 m and 1.9 m are considered adults . As with all anacondas, De Schauensee's anaconda shows a clear gender dimorphism in terms of body length . Among the 102 specimens examined by Dirksen (2002) there were no males with a total length of over two meters. The largest female was 3.01 m long. The rudimentary hind bones ( dorsal spurs ) are much more prominent and longer in males. The tail length varies relatively strongly within the species and accounts for an average of 13.5% of the total length in females and 15.4% in males.

Scaling

The snout shield ( Scutum rostrale ) is twice as wide as it is high. In the middle of the top of the head it is joined by a large pair of frontonasalia . It is followed by an optional fused forehead shield ( prefrontal ) and a forehead shield ( frontal ). The rest of the top of the head shows large shields, which are quite irregular in number and shape. Each nostril is of three nasal shields ( nasalia surrounded). From the nose to the eyes they are joined by a large, irregular, pentagonal rein shield ( Loreale ). The eyes themselves are framed by a large over-eye shield ( supraoculars ), a fore-eye shield (pre- oculars ), one to three under-eye shields ( subocularia ) and 2 to 4 rear-eye shields ( postocularia ). Upper lip shields ( supralabials ) exist 12 to 16, lower lip shields ( infralabials ) 16 to 20, whereby both the anterior upper and the anterior lower lip shields up to below the eye are significantly higher than wide and become square behind them.

The number of ventral shields ( ventralia ) varies between 214 and 236, the number of dorsal rows of scales in the middle of the body between 43 and 54. From the cloaca to the tip of the tail there are 49 to 62 tail underside shields ( subcaudalia ), which, otherwise rather untypical for boa snakes , can be paired. The anal shield ( anal ) is undivided.

coloring

The upper side of the body of De Schauensee's anaconda is yellowish brown, the underside light yellow to lemon yellow in color. Five black head stripes run from the muzzle towards the neck. One runs in the middle of the top of the head and in some individuals can pull up to the first black crossbar of the neck. To the side of this strip, another one above and one below the eye runs on both sides. On the upper side of the body up to the tip of the tail there are about 115 large oval, black transverse bars, which are fewer in number, but larger than in the yellow anaconda . They are often irregular in size, sometimes only lying on one side of the spine, or they can also form short zigzag patterns. The flank spots consist of one or two rows of black, irregularly shaped spots, which, in contrast to the yellow anaconda, are larger and always completely filled. The belly side is provided with many small black spots that can form more or less clearly recognizable rows.

distribution and habitat

Distribution area of ​​the De Schauensees anaconda

According to current knowledge, the relatively small distribution area of ​​De Schauensee's anaconda extends in South America from the coastal region of French Guiana south to the Brazilian states of Amapá and Pará . In Pará, the species inhabits the lower Amazon between the city of Santarém in the west and the Amazon delta in the east, including the large delta island of Marajó . From a zoogeographical point of view, Dirksen (2002) also considers occurrence in marshland in the coastal area further north in Suriname and further west on the Amazon in the Brazilian state of Amazonas between Santarém and Manaus . The species is so far considered to be very rare. Most of the specimens sighted so far come from the large delta island of Marajo, where they have been observed in open standing water habitats, including seasonally flooded grasslands, and in Lago do Arari, which is only two meters deep, seasonally drying and covered with aquatic plants. In French Guiana their typical habitat is described as a swampy landscape.

behavior

Almost nothing is known about the behavior of De Schauensee's anaconda. Like all anacondas, it is strongly bound to water. The specimens observed so far prefer to hide in cloudy water, with only the nostrils and eyes protruding above the surface of the water. In contrast to the idol snake , which also lives in the same areas , this anaconda has not yet been observed climbing in bushes. In case of danger, the species dives into the water for minutes or tries to escape. If she is cornered, she secretes a foul-smelling anal gland secretion and tries to scare off the opponent with defensive bites. If this is not enough either, she wraps her head in front body loops, as is typical for anacondas, and forms a protective ball around the rest of the body.

food

According to reports from the people of Marajó, the species occasionally eats small domesticated pigs and chickens, which makes it undesirable to see near settlements. Further observations on the food spectrum are not yet available. Dirksen (2002) suspects that their diet consists of fish, birds, bird eggs, turtles, small crocodiles, lizards and mammals of corresponding size, similar to the yellow anaconda. As with all giant snakes, the De Schauensees anaconda bites its prey and suffocates it by entangling it, if possible while drowning it under water.

Reproduction

Practically nothing is known about the reproduction of De Schauensee's anaconda. Like all boa snakes , it is viviparous . Dirksen (2002) uses data on the large anaconda from French Guiana to assume that De Schauensee's anaconda also mates at the beginning of the dry season from June to August and that the young are born between December and February. It is not known whether the species, like other anacondas, forms “mating balls” to mate, with several males wrapping around a female, sometimes for weeks. From captivity and based on museum specimens, litters with three to 26 young animals are known. Newborn individuals have a total length of 30 to 60 cm.

Danger

Information on the risk is currently not available, the species is also not listed by the IUCN . Anacondas are generally cultured refugees. Human influences on their habitat generally lead to the disruption of their way of life or the loss of their livelihood. Presumably this snake is sometimes wrongly declared as yellow anaconda in the form of hides and exported live specimens. However, the demand for this rather rare and unknown species seems to be low, which means that trade seems to play an insignificant role as a risk factor overall.

Systematics

The genus name Eunectes was coined by Wagler in 1830, who separated the anacondas from the genus Boa . Eunectes is Greek and means "good swimmer". In 1936, De Schauensees anaconda ( Eunectes deschauenseei ) was first described by Dunn & Conant based on a live specimen probably caught by Rodolphe Meyer de Schauensee on Marajó in the Brazilian state of Pará and sent to the Philadelphia Zoo in 1924. E. deschauenseei differs only slightly from the yellow anaconda ( E. notaeus ) in terms of coloration, scaling and morphology . Although the distribution areas of the two species are far apart and they live in different climatic conditions, it has not yet been clarified in terms of molecular genetics whether E. deschauenseei and E. notaeus are really separate species, or whether E. deschauenseei should have a subspecies status. These two anacondas are currently considered to be valid, closely related sister species. Among the anacondas, E. deschauenseei , E. notaeus and the similarly closely related Beni anaconda ( E. beniensis ) represent a separate phylogenetic line compared to the great anaconda ( E. murinus ). So far, no hybrids between E. deschauenseei and the E. murinus , some of which live sympathetically , is still described with E. notaueus in captivity.

swell

literature

  • L. Dirksen: Anacondas: monographic revision of the genus Eunectes Wagler, 1830 (Serpentes, Boidae). Natur und Tier Verlag, Münster 2002, ISBN 3-931587-43-6 (also dissertation University of Bonn 2001)

supporting documents

  1. ↑ a b c 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.5 Pholidose , Dirksen 2002, p. 111.
  2. ↑ a b c 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.4 Morphometry , Dirksen 2002, p. 107.
  3. ↑ 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.7 Gender dimorphism , Dirksen 2002, p. 111.
  4. ↑ a b 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.1 Diagnose , Dirksen 2002, p. 104.
  5. ↑ 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.3 Coloring and drawing , Dirksen 2002, p. 105.
  6. ↑ a b 4. Results, 4.1.1 Distribution Eunectes deschaeunseei DUNN & CONANT, 1936 , Dirksen 2002, p. 30.
  7. ↑ a b c 6. Synopsis of the genus Eunectes, 6.2 Zur Systematik , Dirksen 2002, pp. 101, 102.
  8. ↑ a b 5. Discussion, 5.1.1 Eunectes deschauenseei , Dirksen 2002, p. 69.
  9. ↑ a b 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.10 Habitat , Dirksen 2002, pp. 114, 116.
  10. ↑ a b c 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.12 Behavior , Dirksen 2002, p. 116
  11. ↑ 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.11 Food , Dirksen 2002, p. 116.
  12. ↑ 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.9 Fortpflanzung , Dirksen 2002, p. 113.
  13. ↑ 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.14 Handel , Dirksen 2002, p. 116.
  14. ↑ 6. Synopsis of the genus Eunectes, 6.4.1 Eunectes deschaeunseei DUNN & CONANT, 1936, 6.4.1.2 Etymology and common names , Dirksen 2002, pp. 104-105
  15. ↑ ER Dunn, R. Conant: Notes on Anacondas, with Descriptions of Two New Species. Proceedings of the Academy of Natural Sciences of Philadelphia, Vol. 88, 1936, pp. 503-506.

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