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Elgaria coerulea - Northern Alligator Lizard

Page history last edited by PBworks 16 years, 4 months ago

Elgaria  coerulea - Northern Alligator Lizard

    Tetrapoda:  Amniota:  Reptilia:  Squamata:  Scleroglossa:  Anguidae

 

Northern Alligator Lizard (Elgaria coerulea principis) showing a typical color variation for the only subspecies present in Idaho.

 

Photo by: Gary Nafis of californiaherps.com

 

Identification:  Lizards of the genus Elgaria are characterized by a fold of skin running along each side of the body. The skin fold allows for body expansion after eating and during the development of offspring.   The scales dorsal and ventral to the skin fold are quadrangular while the scales within the skin fold have a granular morphology.  Northern alligator lizards measure just under 100 mm from snout to vent.  The tail is less than twice the body length.  They have 12 rows of dorsal scales above the base of the tail with a keeled morphology and 12 rows of smooth ventral scales.  Each row of ventral scales has a streak of darker pigmentation along its edges.  Eyes are darkly pigmented.  Elgaria coerulea principis, the only subspecies native to Idaho, has dark spots running along the back within a broad dorsal stripe that is typically of a brown or olive pigmentation.  The young are not colored as dark as adults with the dorsal stripe being of a more brassy tone. 

 

Distribution:  There are four subspecies of Elgaria coerulea that range from the bay area of California north along the pacific coast into southern British Colombia.  They also extend east into northern Idaho and western Montana.  Elgaria coerulea principis is the only subspecies native to Idaho and it is constrained to the northern panhandle area of the state.  

 

Habitat:  Northern alligator lizards inhabit areas of relative humidity and at elevations up to 1,800 m.  These lizards are most often sighted along the outskirts or clearings of coniferous forests.  They are often seen using fallen logs or rocks as cover.

 

Behavior:   Northern alligator lizards spend most of their active time under the cover of leaf litter or grass.  Their diet consists of a variety of arthropods.  To increase the effectiveness of their bite they will twist their body.  As a defense mechanism the tail of the lizard is easily broken off.  Tails from northern alligator lizards have even been reported in the stomachs of snakes, showing the value of this mechanism. 

 

Reproduction:  Mating takes place in April or May.  Copulation can last 24 hours or more, during which the male will bite the back of the female's neck.  Northern alligator lizards are viviparous, giving birth to fully formed young.  Normal litter size is four young that measure 25 to 30 mm from snout to vent.  

 

Scientific Study:

 

Tansy ragwort (Senecio jacobaea) is potentially toxic to grazing animals.  In an attempt to control the population of this toxic plant the cinnabar moth ( Tyria jacobaea, Arctiidae) was introduced into the northwest.  The toxins from the ragwort plant accumulate in the body of the cinnibar moth larvae.  Daniel Formanowicz and Edmund Brodie attempted to see what impact the introduction of the cinnabar moth would have on local predators. 

 

Northern alligator lizards along with western fence lizards, deer mice, and short tailed shrews were tested to see if they would accept cinnabar moth larvae as prey items and what the effect would be.  Predator animals were collected and then offered cinnabar moth larvae and then a palatable control prey item (mealworm larvae or sow bugs).  One prey item was introduced into a bare tank holding the predator animals for 5 minutes followed by an introduction to one of the palatebable controls.  Responses of the predators were recorded.  In all three trials involving northern alligator lizards the moth larvae prey item was killed and consumed.  All three lizards lost the ability to stand up and later died within 20 to 60 minutes from consuming the cinnabar larvae.  The other predator animals either consumed the first cinnabar larvae and none of the larvae offered later, or they did not consume the larvae at all.

 

It is uncertain whether the toxicity of the cinnabar larvae is due to the accumulation of toxin from eating the ragwort plants or if it is due to other irritating or toxic secretions from the larvae.  The study determined that the larvae were unpalatable to three of the predator animals and toxic to the northern alligator lizards.  Since the northern alligator lizards were so sensitive to the toxins of the moth larvae they were unable to learn to avoid the larvae.  The researchers made the assumption that the introduction of the cinnabar moth into the northwest may have detrimental effects on the populations of  Elgaria coerulea.

 

References:

 

Formanowicz, Daniel R. , and Edmund D. Brodie. "Unpalatability and Toxicity of an Introduced Species (Cinnabar Moth Larvae) to Native Predators." American Midland Naturalist Vol 113, No. 2(1985): 401-403.

 

Nussbaum, R.A., E.D. Brodie, and R.M. Storm.  1983.  Amphibians and Reptiles of the Pacific Northwest.  University of Idaho Press, Moscow, Idaho, USA.

 

Pough, F. Harvey, Andrews, R.M, Cadle, J.E., Crump, M. L., and Savitzky, A. H.. Herpetology. 3rd ed. Upper Saddle River, NJ: Pearson Education, Inc, 2004.

 

http://www.californiaherps.com/

 

 

Created By:  Orin Ford

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