Saturday, 21 December 2013

Bristol snakes 5: Savu Python

Moving on from the boas, we come to the, in many ways similar, pythons. Except for the introduced Burmese pythons in Florida, pythons are restricted to the warmer parts of the Old World, with various species ranging from Africa across into Australia. Here at the zoo there are two species on show in the Reptile House, the Savu Island and Amethystine pythons, plus Royal pythons that are used in education talks, but it is the Savu Python that I will begin with.

Found only on the small island of Savu in Indonesia, this species was originally described in 1993 as a subspecies of the widespread Macklot’s Python Liasis mackloti. It is now generally classed as a full species L.savuensis, as it is quite distinct, not least in size, from its larger relative.

Savu is situated midway between Timor to the east and Sumba to the west, and is exposed for most of the year to dry winds from Australia to the south. Most of the habitat not used for crops is covered with grassland and palms, but the islands have been long inhabited so what the original habitat of the snakes was like is unclear. They seem to be quite adaptable however, and can be found in farmland as well as less obviously modified areas. They are mainly terrestrial, but can climb reasonably well. Savu pythons reach a maximum of around 1.5m, while Macklot’s are around twice the size. This probably reflects the lack of larger prey animals on Savu compared to other areas, and possibly also the rather extreme climate, with long dry seasons. One very unusual feature is the extreme colour change they undergo as they mature – hatchlings are orange, matching the soil of the island, but adults become darker as they mature and develop distinct white eyes. Whether this colour change reflects a change in lifestyle or preferred habitat between neonates and adults is unclear.

The main prey in the wild is probably various rodents, but they will undoubtedly take whatever they can get, including birds and reptiles if available. In captivity they are fed on mice, the size of the prey depending on the size of the snake of course. They have proved rather difficult to breed in captivity, and possibly this is due to a lack of replication of the environmental triggers required to bring on breeding condition in females especially.

Although snakes are usually not thought of as doing much more for their offspring than selecting an egg laying site, pythons put more parental investment into their young. When the eggs are laid, they quickly adhere to each other to form a single egg mass, which the female then coils around to defend against potential threats. She may also “shiver” to raise her body temperature if required, helping to keep the eggs at optimum temperature. Incubation is recoded as around 60 days, and the neonates are around 40cm long at hatching.

The typical clutch size is around 5 or 6 eggs, although as many as 10 have been recorded in captivity. With this amount of energy expenditure, females probably only lay eggs every other year in the wild, as it will take that long to restore their resources and body weight after a breeding cycle.

(images from Wikipedia)

No comments:

Post a Comment