Lizards

You may find a collared lizard (or really any lizard) darting from shady spot to shady spot in the heat of a summer day. These lizards balance their time basking, seeking shade, and foraging.

NPS photo

 

Lizards make their way through their environments in many ways. Some are sluggish like the Gila monster, while others you may only see in a flash, like the zebra-tailed lizard. Some lizards will climb walls, while others are ground-bound. Some are distinguished by their color, while others are nearly invisible on the desert backdrop. Evenings and mornings in the summer, and days in the winter are good times to look for lizards in the Monument, when they may be sunning themselves on rocks, or prowling for food. Look out for males making territorial displays of prowess through "push-up" like motions from on top of rocks.

 

 

NPS photo/Andrew Cattoir

Chuckwalla (Sauromalus ater)

Common chuckwallas are in the iguana family and are herbivores. Most of their diet comes from leafy desert vegetation, though they particularly enjoy cactus fruits such as that of the fishhook barrel cactus and various types of cholla. Many common desert plants like the ocotillo and agave do not have enough leafy vegetation to be a food source for the common chuckwalla, but they are handy places to get out of the heat of the sun around midday.

Chuckwallas are social, and visitors may occasionally see several sharing the same rock pile. They do not necessarily breed every year, as they naturally prioritize individual survival during drought years. Chuckwallas prefer areas with heavy boulders and creosote bush as they are great places to quickly hide from threats, and may dart into rock spaces when alarmed. When the chuckwalla climbs in between rocks it will pump up its body, pressing into the rock as an anchor to prevent whatever disturbed the chuckwalla from dragging it out from its hiding space.

Identify this Lizard

Chuckwallas are generally large lizards, growing to be about the size of a small baguette (20 inches or 50 cm long), with a thick, blunt tail. Adult males have dark gray legs and head, an orangish midsection, and a yellow tail. Females are dusty brown or gray with orange flecks. Along roadways in the Monument, you may notice male chuckwallas standing atop rockpiles, performing “pushups” to mark their territories.

 

The collared lizard has beautiful vibrant coloring.

NPS Photo

Collared Lizard (Crotaphytus collaris)

This lizard is known by many names, including the eastern collared lizard, yellow-headed collared lizard, and common collared lizard among others. There are 5 known subspecies of this lizard, which are named for the black band of stripes around their neck. Their diet consists mainly of insects and sometimes other lizards!

Collared lizards are known for their ability of bipedal locomotion, capable of running on their hind legs, and can sprint at incredible speeds of up to 16 miles (24 km) per hour! It's believed they'll do this to run from predators but it may allow them to see distant prey as well. Their tails help maintain their balance and do not break away as easily as some other lizards.

Identify this Lizard

These vibrant lizards grow from 3-4.5 inches (7.5-11.5 cm) from head to vent, and up to 15 inches to the end of its tail. Males have beautiful teal bodies, a yellow-brown head with yellow stripes on the tail and back, yellow-orange throats with two black "collar" stripes, and a white belly. Females have more subdued coloring of greys and browns with a white bellow, but have the distinctive "collar" stripes, as seen at the top of this page.

 

Gila monsters spend over 90% of their time underground in rodent burrows but are quite active during the warmer months of the year.

NPS photo

Gila monster (Heloderma suspectum)

Revered in several Native cultures as a killer or a medicinal animal, the Gila monster is perhaps the only venomous lizard in the United States. This creature has a nasty bite if cornered, and combined with folk lore, the Gila monster developed a bad reputation with early miners who would kill the lizard out of irrational fear. Despite its fearsome name and toxic nature, Gila monsters are not considered particularly dangerous. They will not perceive you as prey and will prefer to avoid you rather than engage in a confrontation. However, they will bite when threatened and can move surprisingly fast.

Gila monsters are sluggish creatures that prowl the creosote shrubland, eating insects and eggs from unattended bird nests. The eggs and young of Gambel’s quail account for most of the Gila monster’s diet, especially in the late spring. A Gila monster will often visit several nests over the course of a day, taking only a couple of eggs or young from each nest before moving on to the next.Although this lizard’s population is stable, it is a protected species in all states it is found.

Identify this Lizard

The Gila Monster is the largest living lizard native to the United States, adults growing to 20 inches long (50 cm) and weighing as much as a brick. Their stout body, powerful head, and swollen tail are distinguishing features. Bright orange to salmon-pink bands over black skin lets predators know that the Gila monster packs a punch. Gila monsters do not possess fangs like snakes, but instead have serrated teeth like steak knives. The venomous saliva wicks into the wound from the edges of the teeth.

 

An orange male showing off for the ladies.

NPS Photo

Side-Blotched Lizard (Uta stansburiana)

The side-blotched lizard can be found on rocks, around structures, and near bushes throughout Organ Pipe Cactus National Monument. They are very common and are most active during the day, making them one of the most often spotted reptiles in the monument. Researchers in the early 2000s revealed this lizard has some of the most complex mating behaviors in the Sonoran Desert. Males fall into three categories defined by the breeding colors they develop on their throats and engage in a mating version of “Paper-Rock-Scissors.”

oirst, Orange-throated males are the typical “dominant males” most folks are familiar with. They are extremely territorial, chasing off other males that enter their zone of control, and they mate with many different females over the course of the season. Second, there are the yellow-throated males, which look very much like females, meaning they can sneak past orange-throated males to mate with females in their territories undetected by the more dominant males; evolutionary biologists call this strategy “cryptic males.” Third, there are the blue-throated males, which typically mate with only one female over the course of a season and hold down a very small territory. Because they are very careful in mate choice and guard one female over the course of the season, they are typically able to spot and avoid the yellow-throated males. In addition, blue-throated males are known to cooperate with other blue-throated males and do not attempt to mate with other blue-throated males’ mates. Thus, each type of male side-blotched lizard has an advantage over one other type.

Because each type has an advantage over one type but not both, side-blotched lizards have developed what is called an "Evolutionarily Stable Strategy". If one component were removed, there would be a dominant type of male that would quickly outcompete the other, but, because all three have their own advantages, the population exists in a state of stability.

Identify this Lizard

These small lizards grow to 1.5-2.5 inches ( 3.5-6.5 cm) long from head to vent (where the tail meets it's backside). Look for a beautiful brown and pale yellow "spotted" pattern along these lizards' backs and for vibrant orange, blue, or yellow patches under its chin, along its belly, and its tail.

 

A whiptail's tail may be more than twice then length of its body!

NPS Photo

Whiptails (Cnemidophorus burti and tigris)

You may see midsize lizards scurry across the road or trail with tails as long as their bodies. These are the two species of aptly named whiptail found in Organ Pipe Cactus National Monument: the canyon whiptail (Cnemidophorus burti) and the western whiptail (Cnemidophorus tigris).Whiptails are insectivores, meaning they eat insects and other small invertebrates. They help control insect populations and provide food for larger reptiles and birds.

Whiptails are some of the few vertebrates that are known to employ a life strategy called parthenogenesis. This means that females can lay eggs and have young without needing to mate with males. The female’s eggs undergo a little bit of genetic recombination before she lays them with only her genetics. While most species of whiptails typically have males and reproduce by parthenogenesis only when necessary, there are other species that only produce males when populations are under stress. There are still other species with no males at all, where every new whiptail is born through parthenogenesis! Often these are hybrids of other whiptail species that would not be viable without this unique reproductive ability.

Identify this Lizard

Canyon whiptails are 3.5 - 5.5 inches (9 - 14 cm) and western whiptails are about 4 inches (10 cm) in length from head to vent, and both may measure more than 12 inches (30.5 cm) if measuring from head to the end of its tail. Both species are brownish with beautiful spots. Western whiptails have brown/black spots while canyon whiptails have yellow/orange spots.

 

NPS photo

Zebra-tailed lizard (Callisaurus draconoides)

Zebra-tailed Lizards are named after the bold black and white stripes on the underside of their tails. When resting, the Zebra-tailed Lizard will curl its tail up, exposing the stipes, and will wag its tail side to side. This may be to distract predators or draw attention away from their face and body and towards their tail, which can break off and regenerate later, in case it is grabbed by a hungry predator.

Identify this Lizard

Zebra-tailed lizards are small, slender ground dwelling reptiles. They grow to a length of about 4-7 inches long (10-18 cm). These lizards have sandy-beige backs with dark brown bars and splotches, and bright white bellies. Males may have blue patches on their sides. Females lack any blue patches, and the name-sake bands on the tail are usually light or absent. If you see one dart past you, try to keep an eye on it until it stops and make note of any dark stripes on the lizard.