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Phrynosoma douglasii, Short-horned lizard

Page history last edited by PBworks 12 years, 2 months ago

 Phrynosoma douglasii - Pygmy Short Horned Lizard

 

 

 www.californiaherps.com

 

 www.wildherps.com

 

www.californiaherps.com  

Taxonomy

Kingdom Animalia
Phylum Chordata
Class Reptilia
Order Squamata
Sub Order Sauria
Family Phrynosomatidae
Genus Phrynosoma
Species Phrynosoma douglassii

 

 

Identification: 

The Pygmy Short Horned Lizard can easily be confused with its close relative, the Greater Horned Lizard.  Pygmy Short Horned Lizards are genreally much smaller around 1 1/4 - 2/1/2 inches or 3.2 - 6.3 centimeters long.  The horns on the back of the head are very small and blunted projecting off the back of the head.  They have spiked scales running down the sides of their body in a single line pointing outward.  Their coloration usually matches the substrate and can range from whitish grey to red, brown, and nearly black. There are dark brown to black blotches on the back usually with white edging.  The belly ranges from white to a pale yellow (Stebbins 2003).  

 

Distribution:

The Pygmy Short Horned Lizard is found throughout much of southern Idaho.  It is very wide spread throughout North America from Mexico all the way into Canada.  In the U.S. it found in many states including Oregon, Utah, Arizona, Wyoming, Colorado, and Montana.

 

 Stephen Burton, and Mike Legler © 1999

Habitat:

Flat open plains with shrub step habitats are the preferred terrain of the Pygmy Short Horned lizard.  They are also found in open woodlands with terrain varying from sandy loose soil, rocky and hardpan, usually between the elevations of 1000-6000 ft.(Stebbins 2003).

 

 

 www.californiaherps.com

 

 

Behavior:

When seeking refuge in a terrain consisting of loosely compacted soil or sand, they use a technique called shimmy burial. Sliding it's body side to side in loose soil it can partly submerse itself to escape predators or the hotter hours of the day. They are dirunal and are most active during the middle of the day.  When compared to it's close relatives the pygmy short horned lizard is much more adapted to colder weather and therefore is found much farther north than many other species.  Their diet consists mostly of insects with ants making up most of their day to day diet (www.californiaherps.com).

 

Reproduction:

Mating occurs in ealry spring and young are born between July and September, they are viviparous, giving birth to live young, usually 3-15 are born at a time (Stebbins 2003).  There is obvious sexual dimorphisim in the Pygmy Short Horned Lizard, females are a great deal larger than males on average.  Males generally become sexually mature during their first year while females are not able to breed until their second year on average.  Breeding occurs in early spring usually in May (McGill 2000). 

 

Scientific Study:

Blood-Squirting Varaibility in Horned Lizards (Phrynosoma)

Sherbrooke and Middendorf did a study on the ability of the horned lizards to squirt blood out of there eyes when threatend by a predator.  Dogs were used as a test predator in the study. Five species were tested and of those five only one squirted blood out of its eyes when threatened by the dog.  That species was Phrynosoma hernandesi.  Phrynosoma douglasii may have independently evolved an autopomorphic condition to squirt blood but it is not known for certain and is in need of futher study.  Sherbrooke and Middendorf also looked at the frequency of blood squirting and the potential physiological cost it poses for the lizards' survival.  They also looked at the amount of blood squirted based on sex, body weight, and age. 40 Phrynosoma hernandesi were used and after 153 tests, 85% of lizards squirted in at least one trial, and 82% squirted in more than one. They did find that body mass positively correlated with the total number of squirts per individual.  

 

References:

 

http://www.californiaherps.com

 

McGill, Annick CROS. Canadian Biodiversity Project.  http://biology.mcgill.ca/undergra/c465a/biodriver/index.htm.  December 2000.  Veiwed October 2008 

 

Robert C. Stebbins (2003). Western Reptiles and Amphibians. 3rd ed. Singapore: Houghton Mifflin. 303-304, 488

 

Sherbrooke C. Wade, Middendorf III A. George (2000). Blood-Squirting Varaibility in Horned Lizards (Phrynosoma).  Copeia. Vol. 2001(4). pp. 1114-1122

 

www.wildherps.com

 

 

Created By:

Jonathan Lipke, University of Idaho

 

 

 

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