Breeding

Before you breed

Is the female ready? A vet-reviewed guide puts the floor at 1,500 g and maturity at about 27 to 31 months [1]. In a study of 129 females, the breeders were 2 years old and weighed 1,800 ± 200 g [2].

Is the male ready? Around 700 g and 16 to 18 months old [1]. One large facility paired males over 500 g [3], and some breeders wait for about 800 g [9], so sources differ.

Why the female's weight matters. In one study, a female went from 1,863 g in November to 1,492 g before laying and 1,085 g after laying. Gravid females in that study refused food until the eggs hatched [4]. A clutch costs her about a third of her body weight, and she doesn't eat while she makes it. Start with a heavy, well-fed female, or don't start.

Is there a home for the babies? ReptiFiles calls ball pythons a saturated market where it's hard to do more than break even [20]. Hatchlings stay with you for at least a couple of months before they're ready to go, eating every week. Know where every baby is going before you introduce the adults.

Keep records from day one. Write down every introduction, every lock, follicle sizes, the ovulation date, the pre-lay shed, the lay date, egg count, incubator temperature and every hatch. The dates below only help if you write them down.

The season

Cooling is optional. One study lowered the warm side from 31 °C to 25 °C (88 to 77 °F), 1 °C a day, and held it October to December on a 12:12 light cycle [2]. Other breeders keep the same heat all year: one large facility ran a 32 °C (89.6 °F) day and 29.5 °C (85.1 °F) night hot spot year-round [3], and a commercial breeder doesn't cool at all [9]. Cooling is one method, not a requirement.

Timing. North of the equator, most breeding runs from late fall into spring. In one captive group, females carried eggs December to April and laid in April [4].

Introductions and locks. The male goes in with the female. A lock (the two tails joined) can last up to 24 hours [9]. A male works one female at a time, so a breeder with several females rotates him with a few days' rest between. Without an ultrasound, one male typically covers 4 to 6 females a season [9].

Following the follicles. An ultrasound shows what's happening inside the female:

• Resting follicles never exceeded 10 mm in a study that scanned females through the cycle [5].
• Follicles past 20 mm were called dominant; growth that stalls below 20 mm for 50 days or more usually means they're being reabsorbed (atresia) [5].
• Follicles keep growing from 10 mm to 30–35 mm before ovulation [2]. Breeders often step up introductions as follicles pass 15 mm and again at 25–30 mm [9].
• Palpation (feeling the lower body) caught growing follicles 75% of the time in one study, with 90% specificity. An ultrasound is far better [6].

Ovulation. A mid-body swelling that lasts about a day and is easy to miss. The ultrasound study couldn't reliably pin the exact moment [2], so don't stake everything on seeing it.

From ovulation to eggs.

The gravid female. Stop introductions once she has ovulated. Expect her to refuse food until she lays [4]. Give her a warm, quiet enclosure, a laying box (a hide with damp sphagnum moss) and as little handling as possible.

Eggs

How many. About 6 to 7 good eggs is typical. One study counted 6.3 ± 2.3 fertile eggs plus a few slugs (infertile eggs) per clutch [2], and a facility that logged 5,344 eggs averaged 7 per clutch [3]. Slugs are smaller, yellowish and often don't stick to the rest.

How big. Eggs averaged 85.5 g each, and the whole clutch was about 32% of the female's weight before laying [4].

Don't turn them. Snake embryos attach to the top of the shell early. In a study of another snake species, turned eggs hatched about as well as unturned ones, but 37.5% of hatchlings from turned eggs died afterward against 4.5% from unturned eggs. The authors' advice: incubate eggs in the position you found them [11].

Leave them with mom, or incubate? Both work. In one study, eggs left with the female hatched at 58 to 59 days and incubator eggs at 71 to 76 days, both at about 29–30 °C (84–86 °F), with no difference in losses [4]. A female coiled on her eggs mainly stops them drying out, and her hatchlings came out bigger and more active [12]. Most breeders use an incubator so the female can start eating again.

Incubation

Temperature. A facility that hatched 81% of its eggs on average incubated at 30.9 to 31.7 °C (87.6 to 89.1 °F) [3].

Humidity. The same facility used perlite and vermiculite at 1:2 by volume, moistened with water [3]. Breeders keep the air in the egg box close to saturated, but that figure comes from keepers, not a study.

How long. 59.4 ± 3.7 days from laying to hatching in one study [6]; 63 days at about 30 °C in an older one [13]. Cooler incubation takes longer.

Hatching. The babies slit the shell (pipping) and usually crawl out 24 to 48 hours later [4]. Some breeders cut the eggs open themselves; a careless cut can hit blood vessels or the yolk.

Hatchlings weighed about 50 g in one study [4]. Each one gets its own tub. The first shed usually comes 7 to 14 days after hatching, and the first meal goes in after that (see Feeding).

After laying

A female comes out of a clutch light. Offer a modest meal once she's settled and build back up. Many females skip the next year, and that's fine; recovery comes before the next season.

Retained eggs (dystocia). Causes include a drawn-out follicle phase, poorly timed introductions and low temperatures [7]. The signs are vague: not eating, lethargy, a swollen belly, restlessness, sometimes straining [7]. Treat it as urgent. A female who is straining, or who is clearly past her lay date with eggs still inside, should see a reptile vet within 48 to 72 hours [7]. Retained eggs can be medical or surgical cases, and the longer they sit the fewer options the vet has [7][8]. Don't try to massage eggs out at home.

Genetics in one page

Recessive genes (Clown, Axanthic, Desert Ghost, Hypo and many more) only show when a snake gets a copy from both parents. A snake with one hidden copy is a het [14].

Incomplete dominant genes (Pastel, Enchi, Fire, Butter, Lesser and others) show with one copy. Two copies make a different-looking "super" form, such as Super Pastel [14][19].

Dominant genes look the same with one copy or two [14].

DNA tests. A shed skin can be tested for many recessive hets and gene complexes; Rare Genetics Inc. (RGI) offers single-morph and panel tests [15]. A tested het is worth more than a "possible het," and it stops a breeder from spending three years on a snake that was never carrying the gene.

Genes we won't work with

Some morph genes come with health problems. These are the ones we keep out of our rooms:

• Spider and its complex. Spider ball pythons wobble: the head tilts, corkscrews or loses aim. Researchers have linked it to malformations of the inner ear's balance organs [16][17][18]. Morphpedia lists Champagne, Hidden Gene Woma and Woma with wobble too, and lethal or wobbling super forms [19]. We also skip Spotnose.
• Super Cinnamon and Super Black Pastel. Commonly a deformed face ("duckbill") and some kinking [19]. A single copy is fine; two copies are the problem.
• Two BEL-complex genes together (Lesser, Butter, Mojave and their allelic partners). Super Lesser is the documented one, prone to bulging "bug eyes" [19]. We don't put two of these genes in one baby.
• Caramel Albino: kinking and fertility issues. Desert (a different gene from Desert Ghost): known fertility problems in females [19].

These aren't rare edge cases: a 2026 study of UK ads found morphs with known welfare problems still widely for sale [21].

Sources for this chapter

1. The Vet Desk (Luqman Javed, DVM), When is the best age to breed ball pythons?
2. Bertocchi, M. et al. (2018), reproductive ultrasound in 129 ball pythons, PLOS ONE 13(6): e0199377, doi:10.1371/journal.pone.0199377
3. Morrill, B. H. et al. (2011), Herpetological Review 42: 226–231, 783 clutches at one facility, summary at Conservation Evidence
4. Ellis, T. M. and Chappell, M. A. (1987), metabolism and incubation in ball pythons, Journal of Comparative Physiology B 157: 393–402, PDF
5. Journal of Herpetological Medicine and Surgery 26(3–4): 108–116 (2016), Evaluation of the follicular cycle in ball pythons
6. University of Pisa veterinary thesis (2024), 48 females (abstract), etd.adm.unipi.it
7. Morel, M. et al. (2025), dystocia in reptiles, Veterinary Sciences 13(1): 30, PMC12846459
8. Merck Veterinary Manual, Reproductive diseases of reptiles
9. AME Exotics (breeder), Pairing ball pythons
10. ball-pythons.net breeder thread, ovulation, pre-lay shed and laying dates
11. Egg turning in the viperine snake Natrix maura, PMC4543940
12. Aubret, F. et al. (2005), why female ball pythons coil tightly around their eggs, summary
13. van Mierop, L. H. S. and Bessette, S. M. (1981), incubation of ball python eggs, summary at Conservation Evidence
14. MorphMarket Support, Understanding genetics
15. Rare Genetics Inc. via MorphMarket, DNA testing
16. Rose, M. P. and Williams, D. L. (2014), neurological dysfunction in a ball python colour morph, Journal of Exotic Pet Medicine 23(3): 234–239, doi:10.1053/j.jepm.2014.06.002
17. Starck, J. M. et al. (2022), inner-ear malformations in spider morph pythons, PLOS ONE 17: e0262788, doi:10.1371/journal.pone.0262788
18. Schrenk, F. et al. (2022), CT and MRI of the inner ear in spider ball pythons, Journal of Comparative Pathology 196: 26–40, LMU repository
19. MorphMarket, Morphpedia: ball pythons (gene pages list known issues; not peer-reviewed)
20. ReptiFiles, Responsible reptile breeding
21. Bielby, J. et al. (2026), ball python adverts in the UK, Royal Society Open Science 13: 251216, doi:10.1098/rsos.251216