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The Captive Breeding of Colubrid Snakes:

This document, written by Steven T. Osborne, was originally published as a 4 part series in the 1982 edition
( Volume 4: Number 3,4,7, & 9 ) of the San Diego Herpetological Society Newsletter.

Part II. Annual Cycles and Breeding Techniques

This article is the second in a series pertaining to the genera Elaphe, Pituophis, and Lampropeltis, although these techniques can probably be applied to other colubrid snakes as well. Until recently, little had been published on the actual implementation of captive-breeding theories and techniques. This article is intended to present in specific terms some of what is required to be successful in captive breeding. Let me point out that there can be many exceptions, but these methods have worked well for the mainstream of captive breeders.

First, the following assumptions must be made:

  1. The sexes of breeding stock are known by the keeper and are of adult breeding size.
  2. All breeding stock are of reasonably good health and have little or no parasites.
  3. The keeper has a well-established rodent-breeding colony or a ready source of feeder rodents.

Let's use an arbitrary date of August 1st as the starting point. Between August 1st and December 1st the main concern is feeding. This time period is extremely important and may determine your success later. Females need to put on an excessive amount of body weight during this period before being cooled for the winter. Basically, you offer as much food to the females as they will take during this time. An every-seven-day feeding schedule is quite adequate. Adult specimens usually will eat several food items per feeding on this schedule and have adequate time for digestion before the next feeding. To get an idea of typical food requirements, it takes about 8-12 adult mice per month for an adult female albino corn snake (Elaphe guttata) or 12-15 fuzzy (10-day-old) mice per month for an adult female Greer's kingsnake (Lampropeltis mexicana greeri). It is very important to maintain a cage or substrate temperature of 75-83F throughout this 4-month period to allow for adequate digestion. Females store fat in the posterior portion of their body that is later critical when forming eggs. Male specimens generally desire less food than an equivalent-size female and do not store as much fat. It is important to get body weight on the males as well, as they may not eat at all during the breeding season. Hopefully, by December 1st, the females will have enough body weight to later produce a maximum number of fertile eggs for their size.

click to enlarge
Between December 1st and March 1st a cooling period seems necessary to initiate physiological changes in both sexes. This sets the groundwork for development of eggs and maturation of sperm when warming begins. The cooling temperature should remain between 55-65F throughout this 3-month period. Males and females should be in separate cages starting on December 1st. NO feeding is done during this 3-month period but water must be provided.

There has been a great deal of argument as to whether light cycles affect reproductive success in snakes. I believe the only essential criteria to initiate reproductive activity is a cooling followed by a warming period. For the purposes of not excluding anything, however, the following is a list of light-cycle methods that have been successful:

  1. On March 1st, 13 hours of cage or room light per day increasing 20 minutes per week thereafter ending at 16 hours of cage or room light per day on April 30th. No sunlight is allowed into the room.
  2. Natural sunlight allowed into the room on a year-round basis with incandescent light or heat tape used when heat is required to maintain correct temperatures.
  3. Twenty-four hours of light per day all year round even during the cooling period.

However, it has yet to be proven conclusively that light cycles influence reproduction in these genera although breeders still use artificial light cycles.

Aside from lighting, between March 1st and August 1st is the time to concentrate on captive breeding. The best feeding response of the entire year usually takes place throughout March and into early April. This is again an extremely important time for fattening of the breeding colony. The snakes can begin feeding within 24 hours of their initial warming on March 1st. It is important to raise the cage temperature to about 83F at some point each day but also allow it to drop to 75F each day. This allows for adequate food digestion and also the ability to get away from prolonged heat. A constant, 24-hour per day cage temperature of 83F or above may cause sterility of males in certain species. A good behavioral cue that the snakes are TOO warm TOO long is if most of the males continually stay as far away from the heat source as possible (i.e., right up against the glass). Providing a cage thermal gradient is the best way of insuring adequate, but not excessive, heating. In this way the snakes can select their own temperature preference.

Specimens that respond well to feeding will usually shed soon after March 1st. For Elaphe and Lampropeltis species, the first shed usually occurs between March 20th-31st. For Pituophis, the first shed normally occurs between March 23rd-April 4th.

Although these shed dates don't apply to every specimen, there seems to be a trend toward this occurrence. The first shed gives the keeper an idea as to how close the females are to full follicle (unfertilized egg) development. Females appear to reach maximum reproductive receptivity from 3-14 days after this first shed. The easiest way to determine if a female is reproductively active is to introduce her into the male's cage. If, upon body contact with the male, the female violently flips her tail, bunches up her body, or constantly tries to stay away from the male, she probably is not ready. Under these circumstances, the male may try to overpower the female or rapidly lose interest. However, if the female responds by slowly crawling around the cage stretched out, allowing the male to crawl on her back, and lifting her tail to expose the cloaca, she is ready. To insure a viable mating to a female that responds positively, it is best to reintroduce a male at least 2 more times, several days apart. At some point in early egg development, the gravid female will begin to show the negative response to the presence of the courting male.

Females will continue to feed for several weeks into pregnancy but generally stop eating during the last 3 weeks before egg laying. Internal development of the eggs after mating normally takes between 28 and 45 days, depending on the individual and the mean cage temperature during this period. Another shedding occurs toward the end of pregnancy. Females will shed approximately 7-12 days prior to egg laying. This is an important cue in preparing a suitable egg-laying location and also for knowing approximately when the eggs will be laid.

Most of the egg laying will take place in the month of May with some species ( i.e. L. t. sinaloae )laying slightly later. I will discuss-preparing for egg laying and incubation of eggs in a future article. As soon as egg laying takes place, most females will feed heavily to regain body weight. It is possible to perform a second mating at this time. If a female has good body weight after the first egg laying, she may rapidly develop new follicles. It is apparently important to keep the male and female together constantly immediately after the first egg laying to ensure a second reproductive success. This is in contrast to the male-female introduction-separation method for the first mating. If a female does produce a second clutch, she will follow the same incubation-shed pattern as for her first clutch. Most second clutches are smaller than the first, and laid in middle to late July.

In summary, the following is recommended:

  1. Heavy feeding of females and males at all times of year except in the cooling period and the latter part of pregnancy.
  2. A cooling period of approximately 3 months at temperatures between 55-65F.
  3. Separation of the males and females during the cooling period.
  4. At all times except during the cooling period, maintain a cage or substrate temperature of 75-83F, allowing the temperature to rise and fall within this range each day.
  5. Introduction of females into the male's cage when full follicle development is suspected-watch for positive female reaction.
  6. Observation of shed dates in relation to follicle development or egg-laying date.
I hope that this information offers a basic understanding of most techniques now being used in captive breeding circles around the country. I look forward to the answers that will be derived by studying these concepts on the physiological level.

Click Here for Part III

All photos and text courtesy Steven T. Osborne - Professional Breeders

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