Friday, 10 January 2014

Bristol snakes 8: Corn Snake

Corn Snake

Almost certainly the most commonly kept pet snake in the world, and tying with the Leopard Gecko and Inland Bearded Dragon as the default reptile pet, at least here in the UK, the Corn Snake Pantherophis guttatusis native to the south eastern United States, where it prefers fairly dry areas with plentiful rodent burrows.

Aesculapian Snake hatchling
The Corn Snake belongs to a fairly well defined group of constricting snakes usually referred to as rat snakes after their diet of rodents, although some species actually prefer to target reptiles or even birds. Formerly they were grouped into a giant genus Elaphe, with species all over the northern hemisphere, but today this has been broken down into several smaller genera, with true Elaphe confined to Asia. The American forms are now placed in Pantherophis (8 species), with a few in smaller genera such as Bogertophis (2 species), Senticolis, Pseudelaphe or Spilotes (1 each). The Old World species have their greatest diversity in India and south east Asia, but one genus, Zamenis, is mostly found in Europe, where its most famous member is the Aesculapian Snake Z.longissimus, which figures in legends of the Roman god Asclepius, god of healing. Indeed, the snake twined around the staff of Asclepius is still used as a symbol of human medicine.
The Caduceus - symbol of Aesculapius
In the US, the Corn Snake is a fairly familiar animal, but occasionally suffers through being confused with the venomous Copperhead Agkistrodon contortrix, which it slightly resembles in colour and pattering. Corn Snakes are easily told apart by their more slender appearance and different shape saddle markings, and they are also much longer, reaching over 1.8m in the largest individuals. Typically they are ground snakes, but can climb well and will raid bird nests when these are accessible. Adults mainly feed on rodents however, from field mice and voles up to chipmunk size for the most part. Hatchlings feed heavily on lizards and frogs until they grow large enough to tackle mammalian prey.
Copperhead - note head shape
In the northern parts of their range, Corn Snakes hibernate over the winter months, but in the south they only retreat to warmer spots, emerging to bask on warm days. Mating takes place in the spring, and the eggs, usually around 12 in a clutch, are laid in sandy soil where the humidity is suitable for incubation. This takes around 70 days, and the hatchlings are around 25cm long on hatching. The life span in captivity at least is quite long – 22 years has been recorded although around 15 years is more usual.

When Corn Snakes were first kept and bred as pets is not clear, probably in the 1970’s, but today a wide variety of colour varieties is kept. Here at the zoo, the Volunteer Department has an erythrystic morph called Sundance who we use in talks to the public. Sundance was actually found wandering around in the open as a hatchling, and has been with us many years. Unfortunately, although Corn Snakes are very common as pets, people who have not kept snakes before often underestimate how good they are at escaping, and they either wind up loose in peoples houses or, as with Sundance, wandering around exposed to predators. In the British climate I doubt that a Corn Snake could survive a winter outside unaided, but if they had access to a suitable source of warmth, say a compost heap or a greenhouse, it is not impossible. In warmer countries they might well fare better, and as it is a very adaptable species, in view of its being widely kept there is some concern with it becoming an invasive species if it manages to establish itself outside its natural range.

Brown Headed Nuthatch
On the Bahamas it has dispersed into pine forests, potentially putting the native Brown Headed Nuthatch Sitta pusilla(currently listed as Least Concern) at risk from nest predation. On Grand Cayman it is known to prey on Anolis conspersus and could potentially prey on hatchlings of the Critically Endangered Grand Cayman Iguana Cyclura lewisi.
Grand Cayman Blue Iguana
Next week, I will wrap up this series on our snakes with one of the most impressive of our education animals, the Northern Pine Snake.

(Images from wikipedia)

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