Friday, 3 January 2014

Bristol snakes 7: Royal Python

Royal Python
As well as the various snakes on show in the Reptile House, the volunteers have several snakes that are used in the Animal Encounters talks. One of the most popular of these is the Royal Python, Python regius, of which we have three so that we can spread the workload between them. As I am sure most people are aware, Royals are one of the most popular pet snakes, owing to their small size (even large females seldom reach 1.5m) and usually placid demeanour, which makes them very good for handling.

Unfortunately, Royals are also one of the snakes that are often misunderstood in captivity, and as a result many experience much shorter life spans than they should. A typical healthy lifespan for a captive Royal should be well over 20 years, and there is one record of one living to no less than 48, although this last is exceptional. Nonetheless, if a Royal dies before the age of 15, there must have been some error in its care. One of the points I make when giving talks is that although snakes or lizards are often desired by children, it will undoubtedly be the parents who wind up caring for them when the kids grow up, so if the parent is not interested it is best to avoid them as children’s pets.
Striped Grass Mouse
In the wild, Royals are found over a wide area of the drier parts of West and Central Africa as far east as the Sudan, and are often associated with farmland, as this provides a large supply of their favourite prey – various rodents such as grass mice (Lemniscomys), Shaggy Rats (Dasymys) or Gambian Pouched Rats (Cricetomys), although these last are probably too large as adults to be prey. Across their range, they can be found at often quite high densities – one study in Ghana measured a population of 2.34 adults per hectare. Most of the time they hide away in disused rodent burrows, hollow trees, and other areas with a fairly high humidity, emerging when hungry to track down their prey. Although there are few if any studies of their behaviour in the wild, some pythons move around to locate rodent trails in daylight, only feeding however after dark when their prey emerge. In this connection, it is interesting that their eyes apparently contain a small percentage (under 10%) of UV-sensitive cone cells in the retina, the rest being rod cells which operate in low light conditions. Many rodents leave urine trails which reflect ultraviolet light, and apparently some snakes leave scent trails during the breeding season which are composed of compounds visible under UV light. How far they range in search of food probably depends on prey density, but even in areas where there is a high prey population, they probably travel tens of metres each night when hungry or in search of mates.
Gambian Pouched Rat - a trained mine-clearance specialist!

In the areas studied, Royals breed during the cooler months of the year, for the 2-month breeding season they cease feeding and instead embark, especially males, on journeys in search of potential mates. I have not been able to locate any reports of mating behaviour in the wild, but most snakes engage in male combat over suitable females, and this may be important in female mate choice. After mating the female will lay up to 11 eggs, coiling around them in her retreat to protect them until they hatch, which takes around 70-80 days depending on the temperature. Neonates are around 40cm long on hatching and are independent from birth.
Black or Forest Cobra
What predators they have has not been specifically studied, but Black Cobras Naja melanoleuca have been reported as one natural predator, and mongooses, birds of prey, and any medium sized mammalian or reptilian carnivore such as jackals or monitor lizards would undoubtedly take them. It certainly appears from the age structure of the population that recruitment of adults is low and mortality in the early years is high. The only defense they appear to have is to roll themselves into a tight ball with their heads in the centre, from which they get their alternative name of Ball Python.

In captivity, Royals are fairly easy to care for so long as their specific requirements are met. The most important of these are a choice of hides where they can experience body contact on all surfaces, and which provide a choice of humidity’s and temperatures. In the wild they would move between various refuges around their home range depending on the season and local conditions. They will also climb into bushes and bask in the sunshine or at the mouth of their retreats, at which time they would experience at least some ultraviolet exposure. Although it is widely believed that nocturnal snakes, and indeed other nocturnal animals, have no need for UV lighting, this is almost certainly incorrect and is not what they would experience in the wild. For further details of python care there is a vast supply of information on line.

One feature though that I would like to highlight is feeding. As they are fairly secretive, nocturnal snakes they are often kept in small vivaria with limited opportunities for exercise, and in addition a diet of captive raised rodents is one with a much higher fat content than wild rodents would have. A combination of these means that one of the commonest causes of disease in Royals, and also other snakes such as boas and the larger pythons, is obesity. Snakes do not deposit surplus fat reserves under the skin as in mammals, instead storing fat in fat bodies attached to the gut, and unexpected death in a pet snake often reveals a body cavity almost obstructed by fat globules. Owners often panic if their pet refuses food for even a few weeks and resort to force feeding or other invasive methods, and this is particularly the case with Royals. With a combination of the two month breeding season, an often long dry season, and prey shortages I personally doubt that Royal pythons in the wild have food available for more than 8 months of the year, and as a result are adapted to going without for long periods. Obviously, if a pet refuses food the cause must be investigated, but in an adult which is maintaining its weight a month or two without food is no cause for alarm.

Next week, I will move on to the colbrids we also use in our talks, starting with the commonest pet snake in the world, the Corn Snake.

(images from wikipedia)

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