Husbandry

Most keepers, even advanced ones, acquire new animals as hatchlings. Purchase hatchling leonis from reputable breeders who are responsive to your questions and support you after the sale. Hatchlings should not be sold or shipped to you until they have voluntarily fed on live or (preferably) frozen-thawed mouse pinkies unless you have experience raising your own newly-hatched mountain kingsnakes. Some hatchlings can be difficult to start feeding and it's important that they are well-established before shipping. 

Leonis hatchlings are small (5 -10 grams), so it is best not to handle them unless absolutely necessary until they gain some size. When they are so small, it is very easy to harm them while handling because they will be squirmy and nervous until they grow bigger and no longer consider their keeper to be such a threat.

Hatchlings can be kept in an enclosure the size of a plastic shoe box tub for their first year. In fact, snakes generally prefer tighter quarters and tend to feed better in a small enclosure with lots of hiding places. Make sure the tub or tank is escape-proof. Hatchling kingsnakes can squeeze through any opening their head can get through, and once they've escaped there is little chance of finding them. No matter what enclosure you select, keep your hatchling individually or you may learn how kingsnakes acquired their common name.

Add hides to the enclosure so the snakes feel comfortable.  The substrate can be as simple as paper towels (which I prefer for hatchlings as it allows me to easily monitor for defecations or regurgitations), but can also include coconut fiber material, wood shavings or chips, or reptile bark. Avoid cedar and other aromatic woods. Their oils are toxic to reptiles. Snakes of all sizes like to burrow in their substrate, so don't skimp on a deep layer.

Always keep a container of fresh water available. The container should be large enough for the animal to soak in when it feels the need. 

The enclosure should allow for a temperature gradient of around 70 F on the cool side and up to 85 F on the warm end. Regulate your heat source - be it a heat mat, heat tape, heat cable, or radiant heater - with a reliable thermostat. Heat sources that get too hot or fail are a leading cause of death for captive reptiles.

The enclosure should also maintain a humidity of around 50%. You can mist the enclosure as needed with a hand-held spray bottle. Alternatively, you could provide hides with dampened sphagnum moss or paper towels to provide humid escapes. This is especially important when the snake is in a shed cycle. A fast-growing hatchling should shed every 1-2 months.

Hatchling leonis should be fed pinky mice and then they can graduate to larger prey items as they grow.  Don't feed your snake prey items that are larger than the widest part of its body. It's better to feed multiple smaller prey items than to feed one larger one. I feed my hatchlings 1 appropriately-sized rodent every week, but some keepers feed hatchlings more often than that. Watch your hatchling - when it has eaten it will move to the warm side of the enclosure to digest. When it is ready for a meal again, it will be on the cool end of the cage or cruising around hunting.

Spot clean your enclosures every time your animal defecates, and deep cleanings and disinfectings are something I do on a monthly basis.

With proper care and feeding, your hatchling will grow quickly.

As they grow, leonis often undergo ontogenetic color changes. This is absolutely normal and one of the great parts of keeping this species. Certain strains, like the VR (Vivid Reptiles) strain, intensify in color saturation as they age. Other strains, like the Earth Tone, hatch out with high coloration that becomes more muted (and I think more interesting) as they grow. They develop varying amounts of dark stippling, change from red to orange, and more. Watching them change is always interesting and with practice an experienced breeder can predict what a hatchling will do. But leonis can always surprise even the most experienced keeper.

I consider subadults to be animals that are more than a year old but less than 3 years old or adult size.

Subadult leonis care differs very little from that of hatchlings.  They should be moving into a larger enclosure after the first year - something along the lines of a 10-gallon aquarium or 18 quart tub is sufficient.

At this point, they should also have moved up to larger prey items.  A yearling leonis should be able to at least take down 2 large pinkies or 1 small fuzzy mouse per week.

Little else differs about their care from that of hatchlings. Subadult animals can tolerate longer handling sessions and this is the time to really train your animal to be comfortable with handling should you want your animal to be more of a pet. Leonis individuals vary in temperment, as all snakes do, but the vast majority of leonis are very easy to handle. The most common complaints about them are musking, where they emit foul-smelling liquid from the cloaca, and flightiness. Both musking and flightiness are usually easily overcome with a few 10-minute handling sessions per week. A very small number of snakes may continue those behaviors despite all the efforts of their keeper, but those animals are the exceptions rather than the rule.

Subadults don't need to be brumated yet, although very occasionally a Nuevo León kingsnake will go off feed in the fall. If the snake refuses to feed in the fall and winter and begins to lose weight, then brumation should be considered. Details about brumation are found in the Adult Care section. Personally, I do not brumate any animals I do not intend to breed the following year because brumation is a dangerous time for snakes. Plus, feeding yearling and 2-year-old animals over the first 2 winters allows them to gain more size than their brumated counterparts.

I consider leonis to be adults when they are capable of breeding safely. For me, the threshold is that the female is over 3 years old and more than 225 grams and a male is over 2 years old and 150 grams. Nuevo León kingsnakes can be bred younger and smaller than that, but the odds of the animal having complications and dying during breeding are magnified. For my animals, safety comes before profit and I stick to the guidelines I just gave. I have had animals in the past, for example, who did not hit 225 grams until they were 4 or 5 years of age. Those animals were not bred until they had met both thresholds.

Normal adult care is the same as care for younger animals, except that their prey items and enclosures should be of appropriately larger size. The main difference for adults is preparation for brumation and breeding, so we'll focus briefly on that here.

Once an animal has reached the fall season at the age and size I consider safe for breeding, it will be brumated for the winter. During brumation, the snake's body prepares for successful breeding the following spring. I feed the snakes their last meals of the year around October 15. Then I monitor their defecations.  Once they have not defecated for 2 weeks, I lower the temperature gradually until it is around 45 - 55 F.  I keep mine at 50 F on the heat source to allow for the small fluctuations that will occur to stay within the 45 - 55 F range. The enclosure is kept dark, and the only disturbance is my once-a-week, 2-minute check of the animal's condition and breathing and replacement of water.  If a snake shows signs of respiratory infection, it is immediately warmed back up to normal temperature and treated. This is the most dangerous time of year for your snake - don't forget to check on it! 

Around March 1, the adults are warmed back up to their normal temperature and fed heavily until the female's first shed. During this time, feed multiple prey items per week - especially to the females.  After that first shed, the female is introduced to the male's enclosure.  Breeding should begin almost immediately if that pair has been properly cycled and is compatible. The pair can be left together or reintroduced a few times per week to ensure success. Separate the animals for feeding and let a couple hours pass before reintroduction. Egg laying should occur 30-50 days later, usually 10-14 days after the female's next shed cycle.  Both of these time frames vary based on the individual female.

Some animals can be induced to lay a second clutch of eggs if the male is reintroduced the week following egg laying, and some females will lay a second clutch using retained sperm from earlier breedings.

After breeding season, feed both sexes heavily until fall.  The female must regain the weight and condition she lost during breeding season, and many males refuse food while there are receptive females they can sense. Beef both sexes back up during late summer and early fall.

Incubation of eggs and the establishment of neonates is beyond the scope of this short page, but there are lots of detailed guides available online or I am always happy to talk snakes.