ENHS Nature Trails May 2000 Article 3

Lizards of the Willamette Valley
by Tom Titus

May is great time for observing amphibians and reptiles in and around the Willamette Valley. Our cool, wet springs provide sufficient moisture for many amphibians to remain active at or near the surface. Warm, sunny days are prime time for lizards and snakes that have recently emerged from winter hibernation and are actively foraging and searching for mates. Be on the lookout four lizard species in your effort to bust cabin fever with some outdoor activity this spring.

Western Fence Lizard (Sceloporus occidentalis). The western fence lizard is by far the most obvious and frequently encountered of western Oregon's lizards. They are easily recognized by the blue throat and belly patches, which are particularly vibrant in males. These stocky lizards have scales with a pronounced point on the back end, giving them a "prickly" appearance. Western fence lizards are encountered in open areas with plenty of sun and rocks, logs or debris piles for basking. They are territorial and can be spotted during daylight hours basking on their favorite perch, waiting for prey, interlopers, and potential mates. Search for them with binoculars on a rock-strewn hillside on a sunny day. If one moves slowly, they can often be approached closely, especially during the breeding season. Males use a series of "pushup" displays to defend their territories and display to females. These are designed to show off the blue patches on the throat and belly. Notice the basking posture. All lizards are ectothermic (derive their body heat from the surrounding environment) but many, including the western fence lizard, are able to precisely regulate their body temperature within a few degrees of a preferred optimum. To a large extent this is done by adjusting their posture to maximize or minimize heat uptake. For example, a cold lizard on a warm rock will position itself vertically to the sun to maximize exposure to solar radiation, and flatten its body against the rock to absorb as much heat as possible from the substrate.

Western Oregon is home also for two species of alligator lizards, the Northern Alligator Lizard (Elgaria coerulea) and the Southern Alligator Lizard (Elgaria multicarinata). Both species are readily distinguished from other Oregon lizards by a distinct fold in the skin along each side between the front and hind legs. In addition, the head, body, and tail are more elongate than those of the western fence lizard. Northern alligator lizards are typically encountered in open, sunny areas in heavy forest, whereas southern alligator lizards occur on open hillsides of the Willamette Valley foothills and along the valley floor. The two lizards can be distinguished from one another by eye color (yellow in the southern alligator lizard vs. brown in the northern alligator lizard) and a series of dark lines that run between the belly scales of the northern alligator lizard vs. through the belly scales of the southern alligator lizard. In contrast to the perching, "sit and wait" behavior of the western fence lizard, alligator lizards are active foragers, and are constantly on the move in grass or low brush. Therefore, they are not seen as often by casual observers and the only indication of their presence is a rustle in the grass or leaves caused by an escaping lizard. Serious lizard watchers can find them by carefully lifting flat rocks or pieces of bark in good habitat. My favorite southern alligator lizard "hole" was a section of down cedar fence posts in the southern foothills of the McKenzie Valley; in May about every third post had a large adult hiding beneath it. If you choose to pick up an alligator lizard, beware! A captured lizard has the endearing habit of biting the nearest finger, hanging on tenaciously, writhing vigorously, and smearing feces and urine on everything around it. It's okay; you get used to it.

Western Skink (Eumeces skiltonianus). In my opinion, the western skink is the most beautiful of our small collection of lizards in western Oregon. The back and sides exhibit alternating, longitudinal stripes of dark brown and cream and the bright blue tail makes identification unmistakable. Look for skinks along roadcuts and in sunlit glades of forested areas of the Coast Range and Cascades, as well as on open hillsides of the Willamette Valley foothills. Like the alligator lizards, skinks are active foragers and are rarely seen basking motionless on the surface. They are found by looking under flat rocks, pieces of bark, or other debris, and seem to prefer moister soil conditions than alligator lizards. If you decide to catch one for closer examination, take care not to handle it by the tail, as it is easily broken or autotomized. If this should happen, don't panic. Tail autotomy is not fatal to the lizard. The vertebrae and blood vessels of the tail are designed to accomplish this with a minimum of trauma, and the tail will be regrown. Nevertheless, the sight of a violently twitching bright blue tail separated from its original owner can be a bit unnerving.

[ Back ]

Page last modified: 16 May 2000
Location: http://biology.uoregon.edu/enhs/archive/may00/may003.html
E-mail the WebSpinner: aloysius@gladstone.uoregon.edu