Reproduction

This species generally matures slowly if fed conservatively; males may breed at 2.5 years of age, but females often will not breed successfully until they are 3.5 or 4.5 years of age. Both males and females tend to grow to their mature length of approximately 1000mm (Orlov et al., 8) before attaining their adult girth; some females do not attain their adult proportions until the hormone shift associated with being paired for breeding. I am not aware of anyone ever successfully double clutching this species in a single breeding season. Fertility is typically best in animals younger than 10 years old, though I have had success with males and females in their mid-teens.

Though some report success breeding this species without subjecting them to deliberate seasonal temperature or light cycle variations (acknowledging intrinsic ambient seasonal pressure and humidity changes), my best results have been achieved utilizing a seasonal cooling period between November and March, where the daily temperatures fluctuate from the mid-50s to low-70s with brief isolated access to temperatures into the 80s should the animals desire it. I have observed this species active, though their movements are exceptionally slow and deliberate, at 38-degrees Fahrenheit. It is generally inadvisable to leave this species at a constant temperature below approximately 52; variation in temperature mimics their natural range and prevents the possibility of neurological damage occasionally observed in Rhynos kept consistently cold throughout the cooling period.

In the wild, gravid females have been observed in May and June (Orlov et al., 8). In captivity, eggs are typically laid between June and early August (Schulz et al., 387), though I have had some females that regularly laid as early as late April. Rhynos generally lay five to fifteen (typically six to eight) elongated eggs (Id.), often stacked together in a packet (Orlov, 180), which is laid either horizontally or vertically inside a cavity or hide. The largest clutch in my collection to date was comprised of seventeen eggs; interestingly, there is greater variation in egg consistency (size and shape) as the number of eggs increases. Most clutches in my collection of six or seven eggs appear as uniform packets, while those over twelve or thirteen tend to produce a variety of egg dimensions including some that are nearly circular.

Fertile eggs are typically deposited ten or eleven days after completion of the post-ovulation shed (Schulz et al., 387). It is common to have unfertilized or non-viable eggs laid inside or accompanying the post-ovulation shed when these are nearest the vent. Such non-viable eggs can be laid throughout the period preceding the anticipated time of egg deposition; generally, eggs laid sooner than seven days after the post-ovulation shed will not be viable. Occasionally, follicles will get so large before ovulation that they will induce a pre-ovulation shed; in such instances it is possible to get two sheds from the same female within a five or six week period, with egg deposition coming approximately ten to fourteen days after the second shed.

As a note of potential distinction relative to most colubrid species, after egg deposition females will regularly encircle and seemingly guard their eggs or lay adjoining them in narrow/ essentially inaccessible places for at least a week; I cannot say how much longer they would remain with them, as I've never left the clutch in situ longer than a week to avoid egg desiccation. Interestingly, even once the eggs have been removed the females seem to have a very strong affinity for the spot of egg deposition.

Anecdotal evidence suggests genetic sex determination may be overridden by incubation temperature in Rhynos, as well as the Oreocryptophis porphyraceus ssp.; novel access to commercial genetic sex determination for colubrid snakes is certainly intriguing to examine and potentially validate this phenomenon previously known in other reptiles but not validated in snakes. Initial herpetoculture of this species utilized higher incubation temperatures of 82.5 to 84-degrees with offspring hatching after 57-61 days (Orlov et al., 6); in my experience this tends to lead to the production of a higher number of males, as well as non-viable or deformed offspring. 78-degrees is a generally-accepted safe incubation temperature that generally produces an approximately even sex ratio. I have incubated a clutch at variable temperatures in the 60s Fahrenheit; the offspring, all of which were female, took twice as long to hatch (117-121 days). I have utilized a variety of egg incubation methods successfully including half-burying eggs in damp vermiculite or perlite or suspending them on light-diffuser panel over either water, saturated particulate substrate, or damp long-fibered sphagnum moss.

There are no identified and proven single gene mutations in Rhynos as of this writing. Since the Russian Academy of Sciences field study there has been a report of a single mature animal that had retained its neonate coloration (Schulz et al., 388). In general, the normal male phenotype presents as a green snake with yellow ventral scales, while females tend to be green or bluish green snakes with white ventrals. Some of the original captive stock descended from Tam Dao animals have a propensity to produce blue, bluish green, or turquoise adults (Id.); this appearance appears to be inherited polygenically. Additionally, like Green Pythons (Morelia viridis complex), a blue phenotype is possible through reductions in the amount of yellow-appearing pigment. Reproductive cycling and egg production in females appears to utilize hormones that either produce or cause yellow pigment to be present in the skin, causing mature females to become continually more ‘hormonal blue’ with each consecutive clutch. Accordingly, determining a truly genetic blue mutation would benefit from the production of phenotypically blue males, which necessarily will not be ‘hormonal blue’ at least pursuant to the same mechanism. Finally, exposure to UV-light has anecdotally been observed to cause green animals to appear bluer or vice versa in some lizard species including those in the genera Abronia and Crotaphytus.

Neonates average 6mm in diameter and are approximately 250mm long (Schulz et al., 387). In light of their thin proportions, newborns are best kept individually in lidded enclosures or tubs; newborn Rhynos can escape from exceptionally small tolerances between tubs and a rack system. Neonates occasionally will eat other neonates when kept in groups. They can be hesitant to start feeding on rodents. Some breeders report success leaving frozen/ thawed pink mice in the enclosure or floating them in the water bowl. Historically, I tease-fed reluctant feeders pink mouse heads offered while holding the snake in my other hand to limit a flight behavior response; this is effectual for snakes that will bite and hold the prey item, but not valuable for ‘runners’ that cannot be provoked into a strike response or those that strike and immediately release. Now, I offer live fish or tadpoles to those that will not voluntarily feed on mice, sequentially reducing the number of alternative feeders offered and replacing them with a floating frozen/ thawed pink. This transition process is typically effectual and avoids unnecessary stress on both the snake and I. Neonates shed between one and two weeks after hatching; the rostral ‘horn’ is typically flattened to the top of the head upon hatching to expose the egg tooth and flattens out after the first shed (Schulz et al., 387). There is variation in horn length and shape, and the angle at which it extends from the face, all of which seem to be inherited polygenically.