Arizona-Sonora Desert Museum

Spinytail Iguanas stalk the Arizona-Sonora Desert Museum

Among the may animals you may encounter during a visit to Tucson’s Arizona-Sonora Desert Museum are some big lizards, the Spinytail Iguanas.

Spinytail Iguana adult

There are several species of spinytail iguanas (genus Ctenosaura) native to Mexico and Central America that are found in desert scrub and forest. The lizards range from 10 inches to over 39 inches long (some sources claim five feet long). Several species have been introduced into the U.S. in Arizona, Texas, Florida and perhaps other places.

These lizards were introduced into the Arizona-Sonora Desert Museum(ASDM) in the 1970s. They are reproducing but apparently have not expanded beyond Museum grounds, at least none have been reported off the grounds. Maybe, if any leave the Museum they quickly fall prey to coyotes, bobcats, and hawks. The adult lizards at ASDM can get up to about two feet long.

Thomas C. Brennan, proprietor of says that the “lizards that exist at the Arizona-Sonora Desert Museum are a genetic cross between Ctenosaura conspicuosa (San Esteban Island Spiny-tailed Iguana) and C. hemilopha macrolopha (Sonoran Spiny-tailed Iguana).”

While these lizards have the run of the Museum, the easiest place to see them is in the Mountain Habitat and the Bighorn Sheep habitat. These lizards are territorial and usually don’t run away from you. They are rather feisty. While they usually stand their ground, they can run at up to 20 mph. Adults can inflict a painful bite.

The lizards are omnivorous and eat a variety of plant material, bugs, other lizards, small mice, birds and eggs. They take shelter in crevices and tree hollows.

“Mating generally occurs in the spring. Males show dominance and interest by head bobbing, eventually chasing the female until he can catch her and subdue her. Within eight to ten weeks, the female will dig a nest and lay clutches of up to 30 eggs. The eggs hatch in 90 days with the hatchlings digging their way out of the sand. These juveniles are typically green with brown markings, although all brown hatchlings have been recorded as well.” [source]

Newly hatched spinytails at ASDM are bright green, about six inches long. They prefer to climb in trees and bushes. The green gradually disappears as it blends into the grays and browns of the adult lizards.

Spinytail Iguarna juvenile

The young adult in the third photo, just a foot off the path, posed as many people took his photograph. He did watch us warily. This one is about 18 inches long.

Spinytail iguana young adult

According to Wikipedia: “In some parts of Central America, the black spiny-tailed iguana is farmed alongside the green iguana as a food source and for export for the pet trade. Although it is heavily hunted it does not appear to be endangered in any of its native territory.

According to the World Association of Zoos and Aquariums (WAZA): “These iguanas live in colonies, ruled by a pecking order: One male in the colony is dominant, and although the other males hold territories, they will only defend them against one another and not against the dominant individual. Territorial displays involve color changes, body inflation, jaw-gaping, ‘push-ups’ or rapid nodding of the head, and sometimes, biting and tail thrashing battles. Larger males usually hold bigger and better territories and they mate more often. Combat often occurs when iguanas are attaining or defending a territory or a mate. The males always court, but they can only progress if the partner provides them with the right stimuli. The female must respond by species specific sexual stimuli. She must also signal that she is receptive-with mature ova ready for fertilization. The males often bite, scratch, or lick females that have signaled their receptivity.”

Head out to the Arizona-Sonora Desert Museum to see if you can spot the big guys and the babies.

In recent years, there was some concern among Museum staff about having a non-native species on the grounds. The Museum considered removing them from the grounds. I asked Craig Ivanyi, executive director of ASDM about this. Here is what he said:

These lizards “naturally occur in the Sonoran Desert, but not in Arizona. Transplants from Sonora (& Isla San Esteban), Mexico, were apparently released in the 1970’s. We’ve done studies to better understand population demographics and species behavior on the Museum grounds, as well as to see if there’s any evidence of them leaving our property and establishing themselves elsewhere. In spite of not seeing any evidence of them establishing themselves elsewhere, the decision was made several years ago to reduce their numbers on grounds and, over time, to create a sterilized population so that it naturally dies out some day. To this end, we have been opportunistically sterilizing individuals, as well as collecting and sending them to other zoos for exhibit elsewhere.” I am told by another ASDM scientist that this program is essentially defunct.

See also:

Kingsnakes versus Rattlesnakes

Gopher snakes

Clever Horned Lizard

Metachromatic spiny lizards


Speckled Rattlesnakes

Venomous Lizards

Preview of new aquarium exhibit at Arizona-Sonora Desert Museum

The Arizona-Sonora Desert Museum will officially open its new Warden Aquarium “Rivers to the sea” exhibit on January 5, 2013. The aquarium features and interprets aquatic life from the Colorado River and from the Sea of Cortez (Gulf of California). To learn the details of the exhibit go here:

Today, there was a special preview for staff and volunteers at the museum. Since I am a Docent at ASDM, I was able to visit the new exhibit and get some photographs which I share below. One fish seemed fascinated by the people. The photos are uncaptioned, you will just have to visit the exhibit yourself to find out about its inhabitants.




Arizona-Sonora Desert Museum celebrates its 60th anniversary this weekend, Join the celebration

The Arizona-Sonora Desert Museum (ASDM) first opened for business on Labor Day, 1952. Since then, ASDM has been providing education and enjoyment to thousands of visitors with its zoo, botanical gardens, Docent tours and interpretations. It also has a thriving Art Institute.

Since its founding in 1952, the Desert Museum’s mission has been to instill in visitors a deeper understanding, appreciation, and concern for stewardship of the remarkable ecosystem of Sonoran Desert region.



Some new exhibits/programs:

There is a new Great Blue Heron exhibit down in the grasslands habitat.

You can see some behind the scenes activity with the new Keepers Interaction Program. Watch the Museum’s professional keepers working with individual animals in training exercises, feedings or enrichment activities. Upon arrival, check the Plan Your Day board at the Entrance Patio for a daily list of animals, times & locations!

Come join the celebration.

Event: “Mineral Madness” at Arizona-Sonora Desert Museum

On Saturday, January 21, and Sunday, January 22, the Arizona-Sonora Desert Museum will hold its annual mineral sale and a series of events involving minerals. Minerals from all over the world will be on sale from 9 am to 4 pm at the Baldwin Education Building. Prices range from 50 cents to hundreds of dollars.

There will be family oriented educational stations at which children can collect free mineral specimens. Children are encouraged to bring an empty egg carton in which to put their specimens. These events will be held from 10 am to 3 pm both days. The events include: Find Fossils, Seeing Double, Crystal Origami, Ride through the rock cycle, Discover micro-minerals, Minerals in my chocolate? matching game, Mineral Wheel of Fortune, Meteorites and more.

There are also other attractions such as the raptor free flights at 10 am and 2 pm. Come on out and help the museum celebrate its 60th anniversary year.

 See also my ARTICLE INDEX page for more on the natural history of the Sonoran Desert.

Festival of Flight at Arizona-Sonora Desert Museum

Birds, bats, bugs, and butterflies all have one thing in common: flight. These animals will be featured during the Festival of Flight at the Arizona-Sonora Desert Museum on October 14, 15, and 16, from 8:30am to 5:00pm each day.

 ASDM invites you to: “Spend the day enjoying raptor programs, live bat encounters and lectures, tequila tasting, hummingbirds, live bugs, special presentations, hands-on science exploration and much more! Families of all ages can enjoy fun winged-themed arts and crafts projects. There will be a special menu at the Ironwood Restaurant that will give you the opportunity to enjoy a meal that is directly connected to biodiversity while you enjoy live music throughout the Museum grounds.”

Take a free photography class October 15 & 16 at 10:00 a.m. (Pre-registration required).

Did you know that the bumblebee bat is the smallest mammal or that butterflies taste with their feet? You may be wondering what tequila tasting has to do with flight. Tequila and similar spirits come from agave plants which are pollinated by bats, hummingbirds, moths, bees, and other insects.

Come to ASDM and learn many surprising facts.

See the Desert Museum Festival of Flight page which includes some natural history and a schedule of events here.

See description and schedules for other daily events here.

The normal daily Raptor Free Flight program will resume after its summer hiatus on October 14th, and continue through April 15th, 2012 (10:00 a.m. and 2:00 p.m. daily, weather permitting).

 See you there.


Arizona-Sonora Desert Museum digital library adds new features

The Arizona-Sonora Desert Museum has long maintained a public online digital library featuring photographs of plants and animals: click here.

If you click on the photos, that will bring up a short explanation of the natural history for many of the subjects.

There is now a new feature: digital zoom, where you can zoom in and out on photos of selected plants, animals, minerals, and biotic communities: click here. With this feature you can see some awesome close-ups.

 Give it a try. Then come out to the museum to see the real thing.

For more information on the natural history of the Sonoran Desert, see the natural history section of my ARTICLE INDEXpage.

Raptor Free-Flight Returns to Desert Museum

With cooler weather, the raptor free-flight program has returned to the Arizona-Sonora Desert Museum. There are two shows each day at 10 am and 2 pm.

The morning flight features three to five birds which may include Chihuahuan Ravens, Barn Owls, Great Horned Owls, Ferruginous Hawks, Gray Hawks, Prairie Falcons, or Greater Roadrunners. The afternoon flight features a family of Harris’ Hawks.

The shows demonstrate the different behaviors of the birds and their hunting strategies. During the flights, some of the birds fly just inches over your head. After the flights, museum staff usually have the birds on their fist which provides another opportunity to get very close to the birds.

Raptors are birds that eat live prey and also have excellent vision, sharp talons or toenails, and hooked or curved beaks. The ravens and roadrunners are not considered raptors, but they do scavenge and hunt. The raven is an omnivore, and feeds on grains, cactus fruit as well as insects, other invertebrates, reptiles, and carrion. The roadrunner, a member of the cuckoo family, hunts snakes, large insects, lizards, rodents, and various small birds.

The free-flights will be presented each day, weather permitting, through April 11, 2011.

Western Screech Owl, a feisty little raptor

The Western Screech Owl (Otus kennicotti) breeds throughout the western U.S., from southern Canada to Baja California, and other parts of Mexico. This little owl is the fourth and smallest of the raptors I handle and interpret at the Arizona-Sonora Desert Museum. I’ve written previously about the Harris’ Hawk, the Barn Owl, and the American Kestrel. (I also handle snakes.)

Western screech owl

The Western Screech Owl has a body length of 8- to 10 inches, and a wingspan of 20- to 24 inches. (The infamous Cactus Ferruginous Pygmy Owl is slightly smaller.) The yellow eyes are very penetrating. When alert or excited, it raises some feathers on its head – “ear” tufts. The owl is usually gray and streaked with black and white (there is a red race). The only other owl in this region it may be confused with is the Elf Owl, which is much smaller (5 inches in length) and lacks the ear tufts. The screech owl’s toes are zygodactylous (two pointed forward, two pointing backwards). There’s a word for Scrabble fans.

Screech owls generally do not migrate. They are cavity nesters, so you might see one peeking out of a hole in a saguaro cactus. (They will also nest in boxes.) The female lays 4- to 6 eggs, each about 2- to 3 days apart. The chicks hatch after about 26 days and open their eyes after about a week. The female broods the chicks for two weeks while the male brings food. The chicks stay in the nest for about five weeks, all the time being fed by their parents. Life expectancy in the wild is 4- to 6 years, but captive birds are known to have reached an age of 18 years.

The Screech owl is a fierce predator and will attack prey much larger, relative to its size, in comparison with other owls. The screech owl will attack large Norway rats, mice, lizards, insects, smaller birds, scorpions, spiders, ground squirrels, and fish. Its normal habitat in the desert is the wooded areas near mountains, or along tree-lined rivers. In wooded areas, the owl’s dull color makes good camouflage.

Despite its name, the owl doesn’t screech. Instead, it has a series of trilling calls. Screech owls have keen hearing which help in capturing prey, but their hearing is not as specialized as that of the Barn Owl.

Speckled Rattlesnakes at ASDM

The Arizona-Sonora Desert Museum has a new exhibit on Speckled rattlesnakes. The exhibit will run through November.


Speckled rattlesnakes most commonly inhabit dry, rocky, granite-filled canyons and their speckles resemble rock pattern and color, giving the snakes camouflage. Speckled rattlesnakes come in several colors including white, orange, pink, blue, tan, silver, black, and gray. They are generally small, 2- to 3 feet, but one subspecies can be up to 5 feet long.

Their range includes Central and Western Arizona, Southeast California, Northwest Sonora, Baja California, and several islands in the Gulf of California.

The exhibit focuses on the characteristics of skin color and pattern.

For more information on rattlesnakes in general see my article:RATTLESNAKES.

New Prairie Dogs at Desert Museum

Three old bachelor prairie dogs were joined by 24 new, younger animals from the Sedgwick County Zoo in Wichita, Kansas. The new animals (six males, 15 females and three of indeterminate sex) are out of quarantine, and now on display at the Arizona-Sonora Desert Museum in Tucson. They are already renovating the network of tunnels in the exhibit.


Black-tailed prairie dogs (Cynomys ludovicianus, one-to three pounds, 14-to 17 inches long) are the most abundant and widely distributed of the five species of prairie dogs in North America. They are distributed across the great plains from northern Mexico to southern Canada, and they once inhabited southern Arizona.

Mexican prairie dogs also have a black-tipped tail, but are smaller than the black-tailed of the U.S. White-tailed, Gunnison’s, and Utah prairie dogs all have white-tipped tails and are limited in range.

PDrangemap-140x150The estimated prairie dog population in the late 1800s is put at 5 billion. The largest single colony, in Texas, measured 100 miles wide and 250 miles long and was estimated to contain 400 million prairie dogs. Prairie dog populations declined when the bison herds were thinned. Apparently the bison ate the long grasses, leaving the short grass prairie dogs eat. But prairie dogs will not colonize areas of high grass because they cannot see predators in that situation.

It was once thought that prairie dogs competed with cattle for forage. About 80% of prairie dog diet is grass (about two pounds per week). They also eat broad-leafed, non-woody plants. They sometimes eat insects, seeds, and plant roots. Government programs of poisoning prairie dogs, beginning in the early 1900s, have reduced the population to about 1% to 2% of what it was in the mid-1800s. However, newer research indicates that although their diets overlap, prairie dogs do not limit cattle forage because cattle prefer the more protein-rich plants that grow within the prairie dog colonies, as did the bison. The research shows that drought and overgrazing by cattle actually encourage prairie dog colony expansion.

Prairie dogs communicate with each other with at least 11 distinct vocalizations and with various postures. Members of a coterie (family) will appear to kiss; they are touching teeth. This behavior allows them to distinguish coterie members from strangers.

Black-tailed prairie dogs breed once a year, usually in January or February. The female is in estrous for only 3-to 4 hours on one day each year. One to six pups are born after a gestation period of only about 35 days. The pups are naked, blind, and helpless and stay underground for about six weeks. The pups reach maturity by fall and the males tend to disperse. Normal life span is up to eight years for females (who stay in their original coterie) and about five years for males, who face the dangers of travel. The normal coterie consists of one male, four or five females, and up to 30 young less than two years old.

Predators include badgers, weasels, ferrets, coyotes, bobcats, foxes, hawks, and eagles. Snakes may take the young, but usually do not threaten adults.

Prairie dogs carry fleas which contain bubonic plague. This disease may wipe out prairie dog colonies and is a danger to humans. It is the “black plague” that caused the death of one-third of Europe’s population in the 1300s. Rattlesnakes and black widow spiders are common residents of prairie dog towns.

Because prairie dogs dig holes and otherwise scratch the soil, their presence, in short-grass prairies, tends to increase the diversity of plant species, particularly perennial species. Besides predators, prairie dog colonies attract other animals, particularly birds, including the burrowing owl.

Prairie dogs are cute critters, but you wouldn’t want them in your front lawn.

The Desert Museum’s summer hours are 7 a.m. to 2:30 p.m. Sundays through Fridays, and 7 a.m. to 10 p.m. on Saturdays. The prairie dogs are more likely to be out early in the morning when it is cool.