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Of Mutants and New Generations

She's a little monster until she realizes you're not food. Then she's as docile as any animal could possibly be.

She's also this year's featured mother. Meet Carmel:

No sane person can hate that face.

It's been quite a while since I last talked about the Cape house snake, so before going further let's recap and discuss a few things I've also learned in that time. Firstly: the species name for these guys is Boaedon capensis, once placed in the genus Lamprophis but since being separated out due to genetic testing (which also found them, and many of their relatives, to not fit in the Colubridae family where they were once placed but rather in their own separate family, the Lamprophiidae, sister to the Elapidae family -that's the cobras and their kin). There's a fair bit of confusion between this species and B. fuliginosus, as both are often called "brown house snakes" and in captivity many are actually introgressed hybrids, but generally this species is found more to the south in Africa and sports a more heavily spotted pattern rather than the flat colors or lines the "other" Brown house snake typically possess. They also sport the classic nocturnal slit/elliptical pupils most people (incorrectly) associate with venomous snakes, but these guys have no toxins whatsoever to dispense; they're constrictors only.

With males growing to no more than 2-3 feet long and females rarely exceeding 4 feet, Cape housies are a fairly moderately sized snake and also sexually dimorphic, their size telling the two sexes apart. Voracious eaters in most cases (particularly the females), but hard-pressed to bite once they've realized it's not feeding day, they make fantastic but as-yet still rather uncommon pets in captivity.

Both Carmel and Hobbes together, displaying not only the dimorphism they display in size but also the distinct difference in color between the wild-type male and the recessive-mutation female.

Carmel is not a normal house snake however; her bright caramel-yellow/orange coloration comes from a single point mutation within the gene complex that produces melanin pigment. In house snakes (and a few other species) there are two different versions of mutations in this area: tyrosinase-positive amelanism, and tyrosinase-negative. T+ amelanism is what Carmel has, where at some point the process in making melanin has been broken, but the tyrosinase enzyme in the chain still functions to produce a precursor protein, resulting in her no longer displaying blacks or browns in her patterns but instead having a tannish replacement that melds with her light erythrin pigments to make her caramel coloration and pupils that look black, but are really a very, very deep brownish-red

T- amelanism, the version that is most common in reptiles, breaks the process even earlier in the tyrosinase enzyme itself and results in even the melanin precursors not being produced. These animals are brighter creamsicle yellow or tangerine orange (depending on their locality, as some wild animals are more brown/tan and others reddish) and have red pupils, lacking any melanin-like compounds to darken them. In some species (such as Nelson's milksnakes) these two mutations are allelic, occurring at the same place in the genome and so can be inherited together and will express with a copy of each version present (usually with the T+ allele overshadowing the T-). In others, such as the house snakes, they occur in different places. As such, breeding a T- amel or a carrier for that mutation with a T+ results in wild-type animals that carry one copy of each gene instead.

Displaying her caramel colors in full; the blank white bellies they possess is also seen here.

Hobbes is a carrier of the T- gene; Carmel is purely T+, with nothing else hiding underneath. The proof that these two genes don't work together we'll get to shortly, but first, how things work to get to that point:

Cape house snakes can mature fairly early, some animals even sexually mature at 6-8 months old. This is not a recommended age to start breeding them however, as early breedings can greatly reduce the lifespan of an otherwise healthy female. Rather, after preferably at least 1 1/2-2 years, males can be introduced to females...and that's basically all it takes. Living in tropical to subtropical regions this species doesn't really have a particular breeding season, and instead they will pair up at basically any time. Once again, not at all recommended or encouraged, but well-fed females can even ovulate every 2-4 months and so produce several clutches of eggs throughout the year. Males, of course, are ready whenever the female is too. So, at one point I put Hobbes into Carmel's tub and...they immediately got busy, and stayed busy for 14 hours. Males have a pair of reproductive structures housed at the base of their tail (useful for sexing as this causes their tails to be longer and thicker than females; this does not work visually for all snakes but certainly does in these) and when sliding up along either side of the female will try to encourage her to lift her tail to expose her vent, and evert one hemipene to fertilize her.

After breeding, a female will feed heavily for around 2 months to put on weight and feed the growing eggs within her. Toward the end of this period, those eggs start to become quite apparent, and the female will look...uncomfortable, in about any position. Letting her crawl over your hand flat on the floor, you can often count the bumps of the eggs within to determine how many she might lay.

Carmel nearing the end of her gravid period, swollen with eggs.

After this heavy feeding period, females will enter a pre-lay shed cycle, seeking out a moist location to both help them shed as well as use for a deposit spot for the eggs. I keep containers of sphagnum moss in their cages all the time to use for shedding, so Carmel had this accessible already.

Exiting the shed box and just starting on her prenatal shed.

Once shed, the female will often become very active, alternating between hiding in the given box and exploring her entire enclosure to determine if that is, in fact, the best spot to lay her eggs. There is a period averaging between 5-14 days after their shed before the females finally settle into the box, wait a while to get comfortable, and then start laying. House snakes can vary in their clutch sizes depending on age, weight, and mere individual genetics, depositing anywhere from 3-sometimes a dozen or more eggs, and bigger, older females tend to lay more eggs than younger ones (though young females, interestingly, may lay some of the largest eggs at times).

Carmel's first clutch was 6 perfectly formed, fertile eggs, each with soft, leathery shells. These were removed from the nest/shed box and put into a separate container of moss to be incubated at around 82 degrees Fahrenheit. Note that the eggs are all together in one clump; as they are laid they adhere to each other, both ensuring they don't roll while incubating (as snakes don't generally care for their young, their eggs are designed not to be turned; doing so can drown the embryo in the fluid in the egg) as well as some new research suggests contact with other eggs may benefit the behavior of the hatchlings in the long run, as well as act as a trigger to keep them hatching at nearly the same time for safety.

If you're curious whether or not an egg is fertile, the first clue is size and color. Healthy eggs are more or less a smooth off-white color and filled out, dry to the touch once they've set, and clearly very different from the shriveled, wet, infertile slug eggs that failed to be fertilized. Additionally, right from the start most viable eggs will have a ring of red veins around the air bubble inside at the top of the shell, which continue to grow as the embryo develops. This can be seen by shining a flashlight through the opposite side of the egg, known as candling.

Veins signaling fertility are just visible in the side of this egg being candled.

The eggs are left alone more or less for between 60-80 days on average, checked occasionally to make sure they're healthy and that the moss stays moist but otherwise unbothered. In this time, the eggs actually absorb water from their surroundings and can nearly double in size.

At the same time, this does not always happen but a female house snake may either breed again or, as was the case for me, retain sperm from her first mating and develop a second clutch of eggs. While I was waiting for the first ones to hatch, Carmel fattened up again, went through a shed, and produced another perfect set of 5 eggs. When compared to their older siblings nearing the end of their incubation period, the size change is quite clear:

Both sets of eggs in the incubation container. The newer, smaller ones are visible at the bottom.

When eggs near completion of their incubation, candling can sometimes show the shadows of the actual babies within, and just before hatching eggs sometimes begin to dimple and deflate slightly as the neonates absorb their yolk. At hatching, a tiny growth on the end of their nose called an egg tooth is used to slice the shell from within, cutting an exit (or sometimes several) and permitting the baby to stick its head out to take its first breaths and looks around its environment. The egg tooth then usually rather promptly falls off.

The moment of birth; baby snakes will start out sticking only their noses or heads out and venturing no further.

Babies will then stay in their shells for a period, sometimes only a couple hours and sometimes up to 2 days, as they absorb all of their yolk and break the connection to their umbilical cord that connects them to the amniotic sac in the egg before venturing out. Fun fact: when first born, snakes do have belly buttons of a sort! The connection to that cord remains as a slit on their lower bellies and stays visible until a couple sheds remove the scar left over.

Beginning to venture out. As you can see by the fingers they start out TINY.

Cape house snakes hatch out at only around 8-10 inches in length, tiny little creatures. They will almost immediately enter a shed cycle, removing their soft "egg-skin" and finishing using up the resources of their yolks before getting ready to feed. At this stage, it's often difficult to tell one sex from the other, but I have discovered that a strong enough light will often show the silhouette of the hemipenes in the base of a male's tail as the babies are so small they're somewhat translucent. After a few weeks they become hardy enough for more reliable methods however, expert hands being able to probe or "pop" them (a little pressure at the base of the tail can make the hemipenes evert, showing a male; females will have scent glands barely peek out and nothing else) to tell for certain.

Fun fact: in snakes, or at least those studied so far for it, it's the females that determine the sex of the offspring. Unlike mammals that have XY chromosomes and males with one of each, snakes have ZW chromosomes and it's the females with one of each; males are ZZ.

They're tiny and cute at this stage, and very dark; most develop lighter colors as they grow.

Though they look too small to take on almost anything, baby house snakes are more than able to take on newborn pinky mice at this stage, though some insist on eating things that they might more likely encounter in the wild (ie. tiny lizards, or at least things that smell like lizard; I have one baby who insists on the pinkies smelling like gecko before she eats them as of writing this). They grow rapidly, shedding every couple of weeks and slowly developing colors more like the adults. They start out fairly dark, drab or dramatic deep browns, before most being to lighten to softer, warmer earthy and reddish tones (many taking after their father, Hobbes, and sporting a rusty appearance now).

And speaking of color: you'll note in these photos that all the babies shown are brown. Not one hatched out looking like their mother, or anything else. As the two amelanism mutations don't occur at the same spot in the genome, they are incompatible and so all the babies are wild-types, carrying mom's mutation and having a 50% chance each at carrying the hidden mutation their father also has. Breeding to another carrier or a snake showing the mutations already is the only way to make those genes show up.

In the end, this first season has resulted in 2 clutches of 11 eggs total, all 11 hatching into beautiful, healthy little babies who are terrified of everything until they're actually in hand. As they grow they'll calm down, and also get fiercer appetites (many like eating only in hiding right now), and hopefully make great new pets for someone else out there.

And their parents...well, we're going to wait until some time well after these little noodles leave the house, but eventually they'll probably be allowed to get back to continuing the life cycle again :)

And would you look at her; so proud of her accomplishments :D

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