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First North American Captive Breeding of the Giant Horned Lizard

Texas horned LizardHorned Lizards of various species, usually sold as “Horned Toads”, were US pet trade staples in the 1950’s and 60’s.  Looking much like minute dinosaurs, they needed more heat and UVB than most could provide, along with an ant-dominated diet, and fared poorly.  As a boy, I was able to keep them going in the summer, thanks to natural sunlight and plentiful ants, but they declined in winter (I discovered they did not like the “house ants” I collected in local stores!).  As I moved into zoo work, the key to keeping most species remained elusive.  So I was very happy to hear that the Los Angeles Zoo had recently (January, 2011) succeeded in breeding the largest species, the Giant Horned Lizard, Phrynosoma asio.

Natural History

The 6 ¼-inch-long Giant Horned Lizard inhabits tropical scrub, rocky hillsides and forest edges along the Pacific Coast of southern Mexico.  Unlike the more familiar desert-adapted species, it experiences prolonged rainy and dry seasons, and seems less dependent upon an ant-based diet.

The Giant Horned Lizard is one of the eight species in the genus Phrynosoma known to squirt blood from its eyes when disturbed (please see photo).

Captive Breeding

Partly because they accept food other than ants, Giant Horned Lizards have done rather well, and have even bred, in European collections.  The 9 eggs that hatched at the LA Zoo represent the first North American success.  The parents are part of a group imported from Mexico and shared with the San Diego Zoo.

European reports indicate that Giant Horned Lizards mate in April-June, with gravid females laying 10-30 eggs after a gestation period of 60-70 days.  The eggs hatch in 10-12 weeks when incubated at 85 F.

Horned Lizard Care

Horned Lizards are hard to resist, but it is a mistake to attempt keeping them unless you are well-experienced and able to provide for their very specific needs.

Those that accept a variety of insects, such as the Short-Horned Lizard, Phrynosoma douglassii, are better choices than the ant specialists.  The Short-Horned Lizard, I learned to my surprise and delight many years ago, also gives birth to live young.

Please write in for details on proper care before acquiring a Horned Lizard.

Lizard Oddities

As if their appearance, diet, and blood-squirting abilities were not enough to distinguish Horned Lizards, several species are now known to guard their nests, attacking snakes and other predators…others inflate themselves with air and flip over as if dead when attacked (please see video below).

And there’s more – both the Giant Horned Lizard and the Coast Horned Lizard, Phrynosoma coronatum, have been observed mating in a most un-reptilian manner…belly-to-belly!

Further Reading

Great BBC video of a Horned Lizard defending her nest and feigning death.

Natural History of the Giant Horned Lizard

Excellent natural history and husbandry information can be found on this website.


Horned Lizard defense image referenced from wikipedia and originally posted by Zylorian


  1. avatar


    I can only emphasize…put Namibia on your “still to do list”!
    One time in Winter for the big five that visit waterholes and one time in summer when all kind of reptiles thrive on our doorsteps.

    • avatar

      Hello Gert, Frank Indiviglio here.

      Well, if that’s not inspiration….! Thanks, I’ll be sure to as for advice beforehand,

      Best regards, Frank Indiviglio.

  2. avatar

    Great article and wonderful news. I love to hear about en situ and ex situ breeding success stories.

    Woot Woot !


    • avatar

      Hello Scott, Frank Indiviglio here.

      Thanks for the feedback; I’ll post other updates from time to time. Please let me know if you have any specific interests, as I may have similar articles online already.

      Please let me know if you need any further information. Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

  3. avatar

    It’s great to hear of new captive breeding programmes. I live in the UK and have kept horned lizards in the past with much difficulty. There seems to be very little information about their care, yet they are still available for sale to anyone who wants them. I hope that captive programmes like this will provide more care information for the pet trade.

    • avatar

      Hello, Frank Indiviglio here.

      Thanks…very interesting to learn that horned lizards are being shipped to the UK; I wasn’t aware. They are protected in some but not all of their range here. When I was younger, millions flooded the market here; it was a bad situation. Staten Island Zoo here in NY had success with the short-horned lizard while I was doing some work there…seemed to thrive on other insects other than ants. Other than that species, most seem not suitable for private collections; however, harvester ants are now being offered for sale b at least 1 co here; perhaps that will make allow some others to fare well in captivity. Do you know which species are available in the UK?

      Please let me know if you need any further information. Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

  4. avatar

    We had Phrynosoma platyrhinos – Desert horned lizards. I think they are also known as Short-horn lizards? Ours were not fed on ants, we just couldn’t source them (and the pet shop didn’t realise that was what they needed). Ours were fed micro black crickets and seemed to do well for a while, we had them for a year and then they died. They were adult size and may well have just reached the end of their lives.

    Brown crickets didn’t work as a food source because they jumped too much and the lizards couldn’t catch them 🙂

    I haven’t seen any for sale since we had ours (2yrs ago now) so maybe they are not coming over any more. I would never have bought them had I known that they were not captive bred. I’m very careful to check now as for many species, there is no population data in the wild, so who knows what damage we could be doing.

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for the feedback. The Desert Horned Lizard is likely an ant specialist; they typically die after a year or so on other diets, as you describe. The Short-Horned Lizard’s Latin name is P. douglassi.

      Please let me know if you need any further information. Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

  5. avatar

    Thanks for clarifying the name. One thing that was suggested was that it was the formic acid in the ants which was important. So to feed the crickets on stinging nettles which contain formic acid, gut loading them to make them more similar feed to the ants. I didn’t get chance to try, but it was an interesting idea. I’m not sure if the formic acid would be broken down by the crickets, or if it wasn’t, if it would be in high enough levels to make a difference.

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for the most interesting idea.

      I worked with Giant Anteaters years ago, and had to concoct a soup flavored with vinegar and other things to make it “taste like” ants. At that time there wasn’t much being done re actual nutritional value of different foods. Some of the prof journals, i.e. Herpetological Review are adding captive research sections (finally!). I’ll try to do a search and see if anything has turned up on Horned Lizards…much needed, but research $ scarce these days. I do know that various horned lizards accept and reject different ant species…maybe nature/taste of their acidic defenses?
      Please keep in touch…whether or not the formic acid theory works out, it represents the type of thinking we need to engage in.

      Please let me know if you need any further information. Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

  6. avatar

    Hi Frank, my son has a Phrynosoma cornatum and I’m having a hard time to provide him with a daily diet. Currently I’m feeding him flies and moths (what ever insect I can get my hands on), but I wanted to ask you, any idea on how I can make this easy on my self?

    • avatar

      Hi Daniel,

      One of my favorites, but unfortunately very difficult to provide for in captivity. Ants should make up the bulk of the diet, no less than 50% but more if possible. Trapping them works in many places, but not all species will be accepted. Harvester ants are available commercially, and taken by most horned lizards; see supplier here.

      This article and those linked there provide some info on collecting. Termite traps are also an option, as is the ZooMed Bug napper and similar traps.

      Appropriate heat and high levels of UVB are critical to success…please let me know if you need any info.

      Best, Frank

  7. avatar

    Hey Frank,

    I found a young short horned lizard in my backyard and have been keeping it for about a week. I know I can provide proper heat and light for it, but I only have access to crickets year-round. I kept it because I haven’t seen one in a few years even though there have been tons of them in the past.

    I wonder if it would be best to let it go back where I found it, but I don’t want to if it has a better chance of survival in captivity. I just don’t know why they keep disappearing.

    What do you think? Should I look for an ant supplier and do what I can to keep it, or will it have a better chance if I let it go?

    • avatar

      Hi Erin,

      Short Horned Lizards are considered to be one of the more difficult species to keep (not that any of its relatives are easy); even zoos have difficulties and rarely exhibit them. Not all ant species are accepted, and their UVB requirements are difficult to meet with available bulbs; they are protected along much of their range as well. Although they are declining in places, and the reasons are not always clear, I believe it would be best to release the animal.

      Thanks for checking, and for your concern, Best, Frank

  8. avatar

    I have a pair of Asio’s at the moment. They seem to be doing very well and we are seeing lots of head-bobbing and tail-wagging, so we’re hopeful for breeding season.

    We’re also working in conjunction with our vet to get blood samples for baselines and research.

    These little guys have a ton of character and it’s been a real joy to watch our daughter watching them and learning about them.

    • avatar

      Wonderful idea, Mark…thanks for letting me know. I look forward to hearing how all goes. I and readers would be interested to hear some details as to care..diet, UVB etc., when you have a chance, Best, Frank

  9. avatar

    Hi Frank,

    They are in a custom built oak enclosure measuring 36 x 36 x 24″ high. Substrate is washed playsand. The temps are thermostatically controlled. A 100W basking spot bulb (ZooMed incandescent) and a ReptiSun 5.0 18″ UVB strip handle the lighting. Temps run around 112 in the basking area and 80 in the cool zone. They have some grapewood to climb on (they do climb) and some half logs when they want to hide.

    Diet consists of Harvester Ants (they need the formic acid to aid digestion), Phoenix Worms and the occasional waxworm. Unlike many Horned Lizards the Asios don’t need as many ants in their diet. For me, I give them about 70% ants, which seems to work. Feeding is best at early morning or late afternoon/early evening, which is when they seem to be most active. Harvester Ants pack a very painful sting, so should be handled with care and kept away from children or those with allergies to insect bites.

    The regions they come from experience a broad variety of climates. Water is important for them, so once a week I give them a bath in shallow water and drip it on their heads/noses so that they drink.

    Hope this helps,

    • avatar

      Hi mark,

      Thanks very much; I was interested in how the harvester ants worked out, have used them for other species at zoos but need to have them shipped in. I tend to go with the Zoo Med 10.0 for similar species, keep it within 6-12″ of basking site per earlier research, but they likely alter their basking time as needed (please see here re research concerning chameleons; no info as to whether this applies to others, but interesting possibilities…)

      Best, Frank

  10. avatar

    Hi Frank,

    I usually order about 1,000 Harvester Ants at a time. This will last them a couple of weeks. I give them about 100 at each feeding but I put them in a little at a time because I don’t want them swarming or biting the lizards. I put them in the fridge for about 30 minutes before giving them to the lizards. This slows them down and makes them less aggressive.

    The ReptiSun 5.0 has served me well over the years. I use it for my Beardies, Rankins Dragons, Uromastyx and Skinks. Their output is higher than many 8.0 bulbs and even some 10.0 bulbs but I try to keep mine a little further from the basking spot, especially when the bulb is new and going through burn-in. You may have seen this site. I came across it a few years back when I was talking to my vet regarding an increase she had seen in eye damage in young Bearded Dragons http://www.uvguide.co.uk/phototherapyphosphor-tests.htmhttp://www.uvguide.co.uk/phototherapyphosphor-tests.htm

    It surprised me to see how much UVB and other solar radiation gets put out by some of these bulbs. Granted, some of the data is old now but there’s some food for thought here.

    Best regards,

    • avatar

      Thanks, mark. I’ve used the fridge for houseflies, back before flightless cultures were available, good idea for ants. The UK site you mention is the best out there, I hope they keep looking into new models, etc. I’ve had eye problems with a variety of amphibs in zoo exhibits, esp. US native treefrogs that tended to stay at top of exhibits; likely related to over-exposure. Our vets linked reptile eye problems to fat deposits; esp common where largely insectivorous species were fed pinky-rich diets (occured in tiger salamanders, White’s treefrogs as well), but worth looking at it from UVB angle as well, I believe.

      Best, Frank

  11. avatar

    I recently uploaded some video of Lucy and Louis, the GHLs, after a quick snack. It’s a cell phone video, so not the best quality in the world.


  12. avatar

    Thiis is both for Frank and Mark. I am thinking of obtaining a pair of GHLs and need to know the proper husbandry for them to thrive. I have a 48″L x 32″W x 15″H PVC cage for them and plan on using a substrate of playsand to a depth of 3″. I have read and that GHLs can be fed a diet without ant without any ill effects. Is this true? Please e-mail me with info @ the above eimail address

    Thanks in advance


    • avatar

      Hi Sherrie,

      While some success has been reported using a varied diet, ants should be included. They take a wider variety of prey than related species, but I don;t believe they do well long term if ants are not a regular part of the diet. Fortunately, they accept the 2-3 ant species that are available commercially. The few field studies that have been done indicate that ants comprise at least 1/3 of the diet. Termites are also taken, and some feel that these may provide some of the same dietary benefits as do ants; in any case, they are a healthful food item. If conditions near you permit, termites can be trapped as described in this article.

      Please keep me posted, Best, Frank

  13. avatar

    Hi Sherrie,

    My experience with the GHLs has been that there’s no substitute for Harvester Ants in their diet. The formic acid plays a big part in aiding digestion and on the days when I have given them Phoenix Worms dusted with Repashy formic acid powder I have noticed undigested food in the feces.

    Personally speaking, the ants make up about 90% of their diet and they seem very happy with that. They get a bath once a week in warm, shallow water and they love to drink the water.

    Your enclosure sounds fine. I have something similar but slightly smaller. They like to climb, so I have some grapewood in there for them. My male also likes to bury himself in the sand in the afternoons.

    They seem to be most active in the late afternoon, early evening and that’s when I feed them.

    Hope this helps,

  14. avatar


    What are the 3 different ant species available for food for the GHL and can you name reliable suppliers. Can they be raised for a continuous food supply?



  15. avatar

    I only use Harvester Ants with mine. I have ordered from both the sources Frank lists above and don’t have any complaints with either, although Ants Alive tends to provide more order feedback and ships very quickly.

    Hope this helps.

  16. avatar

    Frank My family and I have been the sole providers of horned toads for the Coaalinga Ca. Horned Toad Derby for the last 30 years. We usually try to catch about 20 toads and keep them in captivity for about a month. because we have an abundance of harvester ants in our area its pretty easy to keep them happy. Istore the ones we catch in an ice chest with a little bit of ice covered with a towel. To catch the ants I take grass that surrounds the ant colony and pile it over the entrance the ans come out of the hole to clear the debris and when the pile of grass is full of ants into a Tupperware container they go. they also seem to like pill bugs, those little bugs that roll up into s tight circle.

    • avatar

      hI mARK,

      tHANKS FOR THE INTERESTING NOTE..i CATCH OTHER ANT SPECIES HERE IN THE NE WITH BAIT, BUT YOUR METHOD SOUNDS MUCH MORE EFFECTIVE. Pill bugs are a great food source for many lizards, due to the high Calcium content; (breeding info here ) Interesting to hear that the horned toads you keep will accept them; do you know the species? Best, Frank

  17. avatar

    They only eat ants or they eat other insects as well? I have only heard about breeding mealworms and superworms for reptiles. I feel like breeding ants will get out of hand. I have heard of them only eat fire ants too (ones that bite). Could you imagine a colony of those ants getting loose in a home?

    Last question…Do you ever think these will be available to the public?

    • avatar

      Hell0 Chris,

      Thus species seems less dependent upon ants than others, but will not likely be available in the trade. No practical way to breed ants…collected ants can be held dormant in frig; harvesters are sold on the net, but adult lizards consume hundreds weekly. Certain ant species are rejected by variuos horned lizard species, accepted by others..no general rules re fire ants, etc. All will take other insects, but ants needed as a basis of the diet, best, Frank

About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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