Breeding Uromastyx

The short version

• Uromastyx are one of the slowest, hardest commonly kept lizards to breed. Females mature at 3 to 4 years and lay one clutch a year [9][15].
• Sexing is easy late and hard early. Many animals cannot be sexed reliably until around 3 years old [9].
• A winter cool-down with short days is what sets up spring breeding. Only cool mature, healthy, well-fleshed animals [9][3][12].
• Pairings are rough. Watch closely and pull the male at the first bite that draws blood [9][15].
• Give a deep, damp lay box: 8–10 in (20–25 cm) of substrate is the safe target [15].
• Incubate at 90–93°F (32–34°C). Most eggs hatch in about 60–90 days [3][12].

Who this chapter is for

This chapter is for keepers who want to understand what it really takes to produce captive-bred uromastyx, and why they are scarce. It focuses on the ornate (Uromastyx ornata) and the Saharan (U. geyri), with notes where the Mali (U. dispar maliensis) or others differ. Never mix species in one enclosure or one breeding group [12][13].

Sexing

Uromastyx are hard to sex young and easy to sex late. Several breeders say sex is often not visible until around 3 years of age [9], and ornate males take years to reach full color [12].

When color appears. In one ornate colony, all males had full adult color by about 13 months [10]. Another long-time ornate breeder says males take three to six years to reach full color and are brightest in breeding season [12]. Sources disagree, and the spread is real: a 13-month-old with no color might be a female or a slow male. Call young ornates "unsexed" unless the tail check is clear.

Maturity and breeding size

• Most references put sexual maturity at 3 to 4 years, with some animals taking up to 5 [9]. An ornate breeding guide gives 2–3 years, with some pairs needing about 4 [15]. A CITES review says smaller species like the Saharan "may reach sexual maturity in two or three years" [18].
• One captive ornate colony recorded a female laying her first clutch at about 11 months old with no brumation; she weighed about 150 grams when gravid and dropped to about 80 grams after laying [10]. Treat this as what is possible under heavy feeding, not what is wise. Breeding an undersized female risks egg binding and small, poorly fertile clutches [15].
• Size rule of thumb (Mali): over 10 in (25 cm) total length and over 5¼ oz (about 150 grams) before breeding, which takes about three years in captivity [13]. Ornate breeders also use 10 in (25 cm) as a minimum [15].
• We recommend not pairing a female under 3 years old or under about 150 grams. A rested, healthy 4-year-old gives better eggs than a pushed 2-year-old.
• Do a pre-season check: weight, body condition, a fecal parasite test, and ideally a vet exam. The female should pass normal stool and should not have been bred the season before [15].

Brumation: the breeding trigger

Almost every breeder who produces uromastyx reliably cools them. One ornate colony did breed without brumation [10], and some keepers skip it [15], but the consensus is that a winter cool-down with short days sets up spring breeding [9][3][12][13][15][4]. Only cool animals that are mature, healthy and well-fleshed [9].

A typical indoor schedule, compiled from several breeders [9][3][12][13][15]:

• One breeder notes that his outdoor animals in Arizona naturally stayed inactive three to four months, and that cooling temperature and length should be judged species by species on health and egg results [3].
• Weigh every two weeks during cooling. Weight loss should stay within 5–10% of the starting weight. If it goes past that, warm the animal up and stop [15].
• Males usually show breeding interest within 1–2 weeks of reaching full temperature [15]. Mating in the wild and in many collections falls in March and April, with eggs in April to June [14].

Pairing and male aggression

• House singly most of the year. One experienced ornate breeder keeps about 90% of his animals alone and puts a few pairs together for roughly six months a year; another suggests keeping animals solo "99% of the year" [12][4]. Malis are the exception some breeders keep as year-round pairs [13]. Never house two males together [15].
• Courtship is rough. The male circles, head-bobs, does push-ups, flattens his body sideways, then bites and grips the female's neck fold and may drag her [9][12][15]. Mating lasts a few minutes to half an hour; one account says 2–10 minutes, another 5–30 [12][15].
• Refusal signals. The female flips onto her back, runs, whips her tail, puffs up, gapes or bites [12][15]. If she keeps refusing, separate them and try again after several days [15].
• When to pull the male. Any bite that draws blood, a female who stops eating or keeps trying to escape, or a female who turns aggressive, which is common once she is carrying eggs [9][15]. In one documented colony, the female turned on the male within days of mating and he had to be removed [10].
• How long to pair. Some breeders leave pairs together for only a few days in a very large enclosure, at least 60 in (152 cm) long [9]; others run 2–4 weeks of pairing and then separate [15]. Several matings over days to weeks improve fertility [11].
• Same species only. Keep bloodlines pure. Do not cross ornates with Saharans, or U. dispar subspecies with each other [9][12].

Gravid signs, calcium and the lay box

Gestation (mating to laying) is about 4–6 weeks [9][11][12][13]. Wikipedia gives about 30 days [17].

Signs she is carrying eggs:

• Her girth increases, first mid-body, and eggs may show as lumps along her sides [9][11][15].
• Appetite may rise early, then drop in the last 1–2 weeks [11][15].
• She digs restlessly in corners and goes in and out of the lay box. Right before laying, her girth seems to decrease as the eggs drop into the pelvis [10][11][15].
• An X-ray confirms eggs if you are unsure [10].

Calcium. Dust with plain calcium at every feeding while she is gravid [15]. One hobby source also uses a calcium with D3 3–4 times a week [15]; under a strong UVB tube, most keepers use D3 far less often, and too much D3 can build up to toxic levels, so agree on a D3 schedule with your vet. A free-access calcium dish is a common extra (keeper experience, not proven). In one colony, gravid females were given calcium injections or oral calcium drops in the weeks before laying [10]. Injections are a vet's call, not a home treatment.

The lay box: deep and damp.

• Depth matters. Use at least 6–10 in (15–25 cm) of substrate. One ornate laid in 4–5 in (10–13 cm) of damp play sand [10], but 8–10 in (20–25 cm) is the safer target [15]. A 10-gallon tub filled two-thirds full works [13].
• Substrate: half washed play sand and half peat or organic soil; some breeders add 10% caliche [13]. It should be moist enough to hold a tunnel when squeezed, never dripping [11][15]. One starting point is 4 parts substrate to 1 part water by volume [9].
• Box: a covered tub with a 3–4 in (8–10 cm) side hole, optionally with flexible drainpipe as an entry tunnel [3][13]. She must be able to turn around inside [9].
• Placement: put it in the cool end early. One breeder adds it in January or by February 1 so she gets used to it, and moves it to the warm end if she ignores it [12]. Provide it by the third week of gravidity at the latest [15].

After laying. Females look noticeably thinner [12]. Offer an unflavored electrolyte drink or a supervised lukewarm soak of 15–20 minutes in water no deeper than her elbows, and calcium at every feeding for 2–3 weeks. Expect weight to come back in 1–2 weeks and full condition in 4–8 weeks [12][15].

Clutch size by species

• First-time and small females lay at the low end [11][15]. Infertile eggs are normal; in the documented ornate clutches, roughly a third were infertile [10].
• One clutch a year is the norm. Double clutching has been recorded in ornates, with one female laying in June and again the next April [10], but do not plan on it.
• Eggs are leathery, oval and white. One hobby source gives a length of about 0.4–0.6 in (1–1.5 cm) [15], which is smaller than most breeders describe for ornate and Mali eggs. Treat egg size as unconfirmed.

Egg handling

• Let her finish burying the eggs, then remove them promptly [13].
• Wear gloves [12]. Mark the top of each egg with a soft pencil and keep that side up. Do not rotate eggs after the first 24 hours [11][12].
• Space eggs about 1 in (2.5 cm) apart [12]; one guide suggests 2–3 in (5–8 cm) [9]. Bury each egg half to two-thirds, with the top exposed [9][13].
• Medium: perlite, vermiculite or a commercial incubation medium. One breeder squeezes perlite until it is just damp enough to clump [12]. Another uses slightly damp vermiculite or a commercial medium with activated charcoal and 10% dry perlite [13]. Quoted ratios run from 1 part water to 1 part medium by weight [11], down to 1 part water to 3–4 parts vermiculite [9]. Err on the dry side: uromastyx eggs tolerate dry better than wet.
• Weigh egg boxes weekly. Condensation should appear on the sides within a day or two; add a little water if it does not [12]. Throw out eggs that are more than 25% caved in, leaking, or growing mold or bacteria [13]. Candle after 2–3 weeks to look for veins [15].
• Never use millet or seed as an egg medium. It sprouts on the eggs [12].

Incubation

• A night drop of 5–10°F (3–6°C) is tolerated; one breeder has hatched eggs incubated in the mid-80s°F (about 29°C) [3].
• Warmer incubation shortens the time. No published study shows that incubation temperature sets the sex of uromastyx babies. In one colony, two clutches incubated together at 90°F (32°C) gave 10 males and 2 females, and 2 males and 10 females [10], so temperature alone did not decide sex there.
• Open the lid briefly once or twice a week for fresh air [9][13].

Hatchlings and first meals

• Hatchlings may take a day or two to leave the egg. Do not pull them out [9]. Babies weigh about 4–8 grams and are roughly 2 in (5 cm) snout-to-vent [10][17].
• First food: the adult greens, stems removed and finely chopped. Breeders report ornates eating within 1–2 days and Malis looking for food within 24 hours; most are eating within a few days [12][13]. Feed daily; twice a day is fine [13].
• No dry seed or bean mix for hatchlings. One breeder holds off on seed and bean mixes until 6 months [12]. Another warns that dry food can kill small U. thomasi and U. princeps hatchlings and should not be fed to young babies at all [4].
• Water: a shallow dish, about ½ in (1 cm) deep, for the first two months [13], or none at all, with water coming from greens [12]. If a baby looks dehydrated, give a brief, supervised soak in lukewarm water about ½ in (1 cm) deep, so its head stays well clear.
• Substrate: paper towel, tile or a bare floor until at least 4–5 months, ideally a year [9][12][13]. Give many small hides [9].
• Housing: hatchlings can be grouped because they lack adult territorial behavior [3]. One breeder raises 8–10 in a 4 x 2 ft (120 x 60 cm) tub and pulls two out every 2–3 months as they grow [13]; another prefers individual tubs from the start [12]. Watch for bullies and competition at the food dish.
• Give hatchlings the same heat gradient as adults [12] and the same UVB. Calcium is critical for growing babies [3].
• Wash your hands after handling any baby or its tub. Young children should not handle reptiles (see chapter 5).

Slow maturity and realistic expectations

As a rough estimate (ours, not from a study), a good year might give 8–12 hatchlings from a proven ornate female and somewhat fewer from a Saharan, and none in a bad year. Compare a leopard gecko, which lays several small clutches a season and can start in its first or second year.

Why captive-bred uromastyx are scarce:

1. Slow maturity. A breeder who buys hatchlings waits 3–4 years to learn their sex and whether they will breed [9][15].
2. Low output. One clutch a year, often a third infertile [10].
3. Cooling is risky. Brumating a lizard that needs 120°F (49°C) or more to digest means a thin or sick animal can die. Only animals in top condition should be cooled [9][15].
4. Low success across the hobby. The CITES review says the Saharan is "not known to be particularly easy to breed" [18]. One breeder writes that US demand has grown steadily for 20 years but captive breeding has "a generally low success rate" [4]; another calls it a challenge, with sporadic imports and high demand [3].
5. Imports filled the gap. Large numbers of wild-caught Saharans and Malis were exported for years: more than 14,000 Saharans from Mali in 1994–2003, about 16,000 from Niger in 2001–2003, and a Mali export quota of 30,000 for U. dispar [18]. Mali exports have since closed, which makes captive breeding more important [13], but output has stayed small.
6. Hatchlings are a lot of work. A clutch of 10 or more needs individual or carefully managed group housing, daily feeding, and months of care before the babies go to new homes [15].

Season calendar (indoor, Northern Hemisphere)