Chapter 8 of 13 · Ball Python Breeding Guide

Ovulation to laying

Disclaimer: I'm not a veterinarian and I don't hold a degree in animal science or animal care. This is a guide I compiled and use for my own ball pythons. For a sick or egg-bound snake, a reptile vet is the authority.

The short version

  • Ovulation looks like a big swelling in the middle to lower part of her body, as if she ate a huge meal. It lasts about a day. After it, stop introductions.
  • About 2 to 3 weeks later she sheds. This is the "pre-lay shed."
  • Eggs usually come about 30 days after the pre-lay shed.
  • Give her a warm side, fresh water, and a laying box with damp moss. Handle her only when you must. She will likely not eat.
  • If laying starts and stops, she strains with no eggs, or she is well past her date, call a reptile vet. Never try to push eggs out yourself.

Ovulation

Ovulation shows as a swelling in the middle to lower third of the body, as if the female had swallowed a large meal, that lasts about a day [1][2]. It's easy to miss; even ultrasound couldn't reliably catch the exact moment in the 129-female study [2]. Once she ovulates, introductions stop.

The timeline

StepTypical timingSource
Ovulation to pre-lay shedabout 2 to 3 weeksbreeders [1][3]
Pre-lay shed to laying28.8 ± 4.4 days[2]
Ovulation to laying47.3 ± 6.1 days; a vet review gives 45 to 60[5][4]
Embryos visible by ultrasoundabout 12 days before laying[6]
A timeline with four points: ovulation, pre-lay shed, laying and hatching. Ovulation to the pre-lay shed takes about 2 to 3 weeks, according to breeders. The pre-lay shed to laying takes about 29 days (28.8 plus or minus 4.4 days in one study). Laying to hatching takes about 59 days in the egg (59.4 plus or minus 3.7 days in one study; breeders commonly see 55 to 60, and 65 isn't unusual). A bracket over the first two steps shows ovulation to laying is about 47 days (47.3 plus or minus 6.1 in one study; a vet review gives 45 to 60). Three notes follow: the pre-lay shed is the best marker, so count about 30 days from it to find the laying window; after a baby pips, or slits its shell, it crawls out 24 to 48 hours later; and a red warning that eggs still inside more than 45 to 60 days after ovulation count as egg-binding, so call a reptile vet.
From ovulation, expect a pre-lay shed in about 2 to 3 weeks, laying about 29 days after the shed, and hatching about 59 days after laying. Diagram: Amnesia Oddities. Tap the diagram to open it full size.

The pre-lay shed is the most reliable marker most keepers have: count about 30 days from it to find the laying window [1].

A large ball python resting in a plastic tub on paper towel, its body thick through the middle.
A gravid female about a week before she laid her eggs; her lower body is swollen with eggs. Photo: WingedWolfPsion, CC BY-SA 3.0 via Wikimedia Commons.

The gravid female

  • Heat. Gravid pythons seek warmer temperatures. In Children's pythons, females carrying eggs chose about 31.5 °C (89 °F). When not breeding, they chose about 28.7 °C (84 °F). They stayed warmer in the last weeks before laying. With less heat, carrying the eggs took longer and the babies were weaker [7][8]. Give her a reliable warm side at the top of the normal range (see Heat).
  • Food. Gravid females typically refuse food until after they lay [9]. Offering is fine; forcing isn't.
  • Water. Always available; she may soak.
  • Handling. Keep it to essential checks.

The laying box

Give her a private, slightly humid place to lay: a hide or tub with an entrance hole, lined with slightly damp sphagnum moss. No study tests laying-box designs; this is keeper practice. A female without a suitable site can hold her eggs, which is one of the causes of egg-binding [10].

Our plan: a laying box goes in after the pre-lay shed, and we check daily, quietly, from about day 24 after the shed.

Step by step

From ovulation to eggs:

  1. Watch for ovulation: a swelling in the middle to lower third of her body that lasts about a day. Write down the date.
  2. Stop introductions.
  3. Give her a reliable warm side at the top of the normal range (see Heat), and water at all times.
  4. Keep handling to essential checks. You can offer food, but never force it.
  5. Wait for the pre-lay shed, about 2 to 3 weeks after ovulation. Write down the date.
  6. After the shed, put in a laying box: a hide or tub with an entrance hole, lined with slightly damp sphagnum moss.
  7. Count about 30 days from the shed. From about day 24, check on her quietly every day (our plan).
  8. When she lays, make sure the whole clutch came out. Most females finish within a day. If not, read the next section.

Egg-binding (dystocia)

Most females lay their whole clutch within a day. Problems to watch for [4][10][11]:

  • laying that starts and then stops, or eggs still inside after the rest are laid;
  • straining without producing eggs, prolapse, lethargy, a swollen lower body;
  • a female well past her expected date. Most lay about 41 to 53 days after ovulation, or about 24 to 33 days after the pre-lay shed [2][5]. If 60 days have passed since ovulation, or about 6 weeks since the pre-lay shed, and there are no eggs, see a reptile vet. An X-ray shows whether eggs are stuck [4].

What to do. Call a reptile vet as soon as laying stalls or she strains without passing eggs. Don't wait to see what happens. Egg-binding needs treatment within 48 to 72 hours of the first laying attempts, and the longer it waits, the harder it is to fix [4][10]. The vet may give calcium, or a hormone called oxytocin (it works in fewer than half of snakes). Draining the eggs with a needle is a last resort with real risks. Surgery is another option [4][10]. Don't try to massage eggs out at home; a ruptured oviduct is a far worse problem than a vet visit.

Sources for this chapter

  1. Northwest Reptiles (breeder), So you wanna be a ball python breeder
  2. Bertocchi, M. et al. (2018), PLOS ONE 13(6): e0199377, doi:10.1371/journal.pone.0199377
  3. ball-pythons.net breeder thread, ovulation, pre-lay shed and laying dates (keeper forum)
  4. Morel, M. et al. (2025), causes and management of egg-binding (dystocia) in reptiles, a review, Veterinary Sciences 13(1): 30, PMC12846459
  5. University of Pisa veterinary thesis (2024), 48 females (abstract), etd.adm.unipi.it
  6. Bertocchi et al. (2018), embryonic vesicles 12.1 ± 2.3 days before laying, repository PDF
  7. Lorioux, S. et al. (2012), maternal thermoregulation in Children's pythons, Journal of Experimental Biology 215: 1346, PDF
  8. Lourdais, O., DeNardo, D. F. and Heulin, B., gravid Children's pythons keep higher body temperatures (abstract), SICB
  9. Ellis, T. M. and Chappell, M. A. (1987), Journal of Comparative Physiology B 157: 393–402, PDF
  10. Vet Times (2009), Reproductive diseases in reptiles
  11. Merck Veterinary Manual, Reproductive diseases of reptiles

Last revised October 31, 2026.