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Some snakes have instant appeal, though why it is not always easy to explain. For most snake keepers there is something about brightly coloured snakes such as the tricoloured milksnakes, also bright green snakes, and the same can be said for glossy jet black snakes such as the Indigo snake Drymachon corais couperi, and its more affordable counterpart the Mexican Black Kingsnake L. g. nigritus.
In terms of keeping and breeding, the Mexican Black Kingsnake is a breeze compared to the Indigo snake. Only recently Paul F.O'Connor stated in the Vivarium magazine (Vol.3, No.3) that Eastern Indigo snakes require a high level of maintenance in captivity. So, if you don’t fancy the expense and challenge of such demanding snakes but still like and want to keep glossy black snakes of a moderate adult size, you can opt for a cheaper and easier to keep and breed alternative in the Mexican Black Kingsnake.
You don’t see many adult Mexican Black Kingsnakes for sale, but like the rest of the getulus group, hatchlings are fairly common and not expensive, now they retail at around £30 to £50 each. With this particular subspecies the young are generally robust (as are the adults) and feed readily on defrosted pink mice once the neonate slough has taken place a week or so after hatching. They grow quickly and maturity may be reached in two years, although three years is probably the norm. Being terrestrial snakes they don’t require elaborate vivarium's and can be maintained in plastic boxes either on a heated shelf system or within a heated vivarium until they require a larger fauna box or vivarium by their second or third year. A substrate of newspaper or paper towelling is adequate, and a small plastic tube will provide a suitable hide. To complete the set-up a bowl of drinking water is all that is required. The temperature range for this subspecies in captivity is 26°C to 28°C during the day, falling to 22°C and 24°C overnight. In line with modern reptile husbandry heating needs only to be applied to one end of the plastic box or vivarium so that a thermal gradient is achieved and the snake can find its own ideal level of temperature within its environment. Like all kingsnakes and milksnakes they should be housed individually to avoid any accidents of a cannibalistic nature, and I doubt that I need to stress this as the feeding habits and dietary preferences of the Lampropeltis group are well documented.
The natural range of the Mexican Black Kingsnake is Western Sonora and Northwestern Sinaloa (Markel, 1990). Like other members of this group they are known to integrate with other subspecies where ranges overlap. As the Mexican Black Kingsnake is typically black all over, save for a few small cream markings ventrally, hybrids should be easily picked out from any markings they might display. They should not be confused with the Black Kingsnake, L. g. niger, (which has a very faint pattern of speckles similar to L. g. holbrooki) or the Black Milksnake, L. triangulum gaigeae, whose young are tricoloured (red with black-edged narrow yellowish bands) and turn black with maturity. Adult Black Milksnakes also have golden-coloured skin between the scales which distinguish them from Mexican Black Kingsnakes.
For breeding purposes, adults will need a period during which they are cooled down. Two to three months at temperature of between 12°C and 15°C should suffice, but the induction of this cool period should be gradual so that the temperature falls by a few degrees C per day over a course of one to two weeks, and prior to this food should not have been consumed by the snakes for at least two weeks. After the cooling down period the temperature can gradually be raised, and once the snakes have been warm for a few days (with a minimum overnight temperature of 20°C) feeding can recommence.
Initial breeding responses vary; some pairs may be introduced and mating takes place almost immediately following a brief courtship, the male crawling over the female’s back after first seizing her head or neck in his mouth. If the female is ready to mate, she will lie quite still while the male’s body rubs against hers until their cloacae are aligned and one of his two hemipenes inserted. Once ejaculation has occurred, the pair will part. Non-receptive females behave differently, they will flee from the male and coil up their body and attempt to hide their tail end (often while ‘rattling’ the tail) to prevent copulation. If the male succeeds in getting among the female’s coils, she may exude a cream coloured fluid from glands within the cloaca and the odour from this fluid is usually sufficient to deter the male from pursuing her. If this is the case it may take a number of introductions before copulation takes place. It is advisable to separate the pair after each introduction whether mating takes place or not. Once the female considers that she has mated sufficient times she may again exhibit the non-receptive behaviour described above. It is usually better to wait until the female has sloughed for the first time following the cooling down period, the scent of a freshly sloughed female often arouses the male and mating will almost certainly take place at some stage after this.
The gestation period given by Mattison (1988) for the getulus group of kingsnakes is 31 - 49 days. Unless only a single mating takes place, it is impossible to accurately determine the length of the gestation period, though the minimum number of days could be calculated from the date of the first mating. Three to four weeks after mating the female enters a prelaying slough, and a week or two later she should lay her eggs. An indication that egg-laying is imminent is the restless nature of the female, by which stage a laying site should have been made available. Most female snakes choose a warm damp place to lay their eggs, if one is not provided they may be laid in the water bowl and effectively drown or they may simply be laid in the vivarium and will desiccate if the keeper is not on hand to remove them. A plastic container large enough to house the snake, half filled with damp sphagnum moss, peat or peat/sand, or vermiculite should suffice, and then the eggs can be removed to an incubator in the container they were laid in or placed in another container using whatever incubation medium you prefer to use.
I incubate my colubrid snake eggs on (not in) damp peat and usually have a two to 4 Kg container half-filled with damp peat for laying and another one ready for incubation. If the eggs are freshly laid separate from each other, they can be placed in depressions made in the peat by a thumb, which prevents them from rolling around when they are inspected. It is important not to turn the eggs during incubation, and the top of each egg can be marked with a pencil to ensure that they remain in the right position. If the eggs have been laid for some time and have become adherent, do not attempt to separate them but incubate them as they are. The peat should be damp enough to squeeze in the hand without forcing out any moisture, yet retain the shape it has been squeezed into and not crumble. If it crumbles, add a little more water, and if moisture can be squeezed out of it mix it with drier material. Some keepers prefer to use vermiculite which has been mixed with an equal weight of water.
It is widely accepted that 28°C is an ideal temperature for the incubation of snake eggs, though fluctuations of a few degrees C +/- wont make a great deal of difference to the length of the incubation period. Generally speaking it takes seven to ten weeks (on average around 55 days). Inspect the eggs daily during the incubation period as mould may form on them or the incubation medium if the atmosphere within the container is too damp. Replace all or part of the medium with drier material if necessary and wipe the mould off the eggs with a damp cloth.
If the mould returns, a diluted solution of gentian violet can be lightly sprayed on the affected eggs and this should cure the problem. If the eggs become too dry, they will indent (which they will also do near to the time of hatching so first check how long they have been incubating) but this can be rectified by light spraying with warm water or placing damp tissues over them until they have filled out again. It may also be necessary to add a little more water to the incubation medium. Any apparently infertile eggs (dark colour and waxy appearance) can be left to incubate in a separate container if they are not attached to the other eggs in the clutch and the keeper is unsure that they are infertile. If they are part of an adherent clutch, the bond between them and fertile eggs usually breaks down sometime during the incubation period and they can be carefully removed at this stage, otherwise leave them in place and check regularly for mould.
The point of hatching is shown by the eggs indenting slightly and small slits in the pliable shell with amniotic fluid seeping out. The baby snakes heads will protrude through the slits in the eggs, but they usually retreat when disturbed. It may take a day or two for the first hatchlings to emerge fully and then they can be transferred to separate boxes placed on a heated shelf or in a larger heated vivarium. It typically takes five to seven days before all the hatchlings have emerged so don’t worry because a couple have hatched and there are no signs of the other eggs doing so.
It is not necessary to offer food immediately, though some hatchlings may accept it. Normally they will begin to feed one or two weeks after hatching once the neonate slough has occurred and once all their reserves of yolk have been absorbed. Mexican Black Kingsnake hatchlings will take newborn pink mice and can be fed on two or three ‘pinkies’ per week. Some may eat more than this and others may eat less; individual appetites can vary so don’t be alarmed. I personally don’t see much point in handling hatchlings other than to clean their cages or to attempt to sex them, and they do better when left alone until they are larger and can be handled more easily.

Markel, R.G. 1990. Kingsnakes and Milksnakes. T.F.H. Publications Inc.
Mattison, C. 1988. Keeping and Breeding Snakes. Blandford Press, London.

Reprinted with permission from The Reptillian Magazine
This site has information on the following genera of Ratsnakes ... Spilotes, Spalerosophis, Ptyas, Zamenis, Elaphe, Rhinechis, Senticolis, Pseudelaphe, Pantherophis, Bogertophis, Orthriophis, Gonyosoma, Oreocryptophis, Oocatochus, Euprepiophis, Coelognathus, Archelaphe