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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Northern Alligator Lizard
Elgaria coerulea
Family: Anguidae
The subspecies of the Northern Alligator Lizard that occurs in Canada is the Northwestern Alligator Lizard (Elgaria coerulea principis).
COSEWIC status:- Not at Risk
- Not at Risk
- Least Concern
Description
The Northern Alligator Lizard is a small lizard that resembles a miniature alligator, from which the species derives its common name. Adult females can reach a total length of ~20 cm with males being slightly smaller. The back and sides are grey or tan and marked by dark blotches, and the belly is white to gray. Males become more colourful along their flanks during the mating season. The young are uniformly copper or bronze above, broken only by the eyeline, and have a broad, bronze stripe on their back. Males have relatively wider heads than females, likely for gripping females in their jaws during mating. Adults have a distinctive fold of skin that runs along their sides, which helps the body to expand when the lizard inflates itself with air (in defense against predators) or is distended by eggs or food.
Similar Species
On Vancouver Island, the Gulf Islands and parts of the Lower Mainland, Alligator Lizards may be confused with the similarly sized and rapidly spreading introduced European Common Wall Lizard (Podarcis muralis). Northern Alligator Lizards have shorter toes, a skin fold along the lower sides of the body, larger plate-like scales and a browner background colour than Common Wall Lizards.
Distribution
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In Canada, the Northern Alligator Lizard occurs in southern British Columbia, including eastern Vancouver Island and several Gulf Islands. It ranges north to Stuie in the Bella Coola Valley, Clearwater in the Interior, and as far east as Creston in the Columbia River Valley. In the United States, the subspecies Elgaria coerulea principis is found along the coasts of Washington and Oregon, and east of the Cascades to the north tip of Idaho and northwestern Montana. Three other subspecies extend further south in California to Little Sur River in Monterrey County and in the Sierra Nevada past Sequoia National Forest, Kern County.
Habitat
The Northern Alligator Lizard can be found in a broad range of habitats: dry woodland, grassland, northern and montane coniferous forests, riparian areas, and ocean beaches. Within these, it is often associated with rocky outcroppings and talus slopes. This species also thrives in disturbed areas where there is an abundance of surface debris such as around logging mills, clearcuts, and rail and hydro right-of-ways. Rocks and surrounding vegetation are important for providing shelter, and basking typically occurs in sheltered areas such as crevices or under rocks. Though it is often found within or along forest edges, the association with forests is unclear. Individuals require access to rock crevices that extend below the frost line for hibernation. There is no seasonal migration; hibernation sites are located in the same areas as summer habitat, although movement away from hibernation sites has been reported for some U.S. populations. Northern Alligator Lizards display high site fidelity and individuals are typically recaptured within 10 metres of a previous capture, both within a season and from year to year; movements of greater than 100 metres are rare.
Biology
Northern Alligator Lizards emerge from hibernation in mid-April. Mating takes place shortly thereafter, from mid-April to late-May, and 2–8 young are live-born from mid-August to mid-September. Depending on elevation, most males and females will be ready to breed the third spring after birth. Females may reproduce until seven years of age; males as old as eight years have been captured. Males actively pursue females and hold their head in their jaws during mating. Mating can be a risky undertaking if it takes place in the open as it can continue for up to 12 hours. Reproductive females tend to use the same sites from year to year when gravid; these sites provide protection from predators and the necessary thermal conditions to complete gestation. Northern Alligator Lizards are diurnal foragers that are typically active in late afternoon. Adults eat larger insects (beetles, caterpillars, and grasshoppers), spiders, snails, scorpions, and millipedes. Stinging and biting animals are consumed, although invertebrates having offensive secretions seem to be avoided. Known predators include racers, rattlesnakes, gartersnakes, rubber boas, shrikes, red-tailed hawks, and cats. Lizards will use their tail as a decoy and are likely to drop it (autotomize) if captured. Although the tail will eventually grow back, this is energetically costly and may negatively affect growth and survival. Northern Alligator Lizards spend much of their time in retreat or cryptic basking sites and are uncommon in the open. Although it is a reasonably cold-tolerant species, individuals enter hibernation in late-September.
Threats
Site-fidelity and dependency on rock and vegetative cover make Northern Alligator Lizards vulnerable to modification of localized habitat, and habitat loss is likely the most significant threat to this species in Canada. Human activity near basking sites can disturb basking individuals; frequent disturbances may be detrimental to gravid females, particularly in cooler years when reproductive output is already limited by thermoregulatory constraints. There is likely little road mortality, although roads may act as barriers. Illegal collecting appears minimal and not detrimental at a population level. Predation by domestic and feral pets, especially cats, is a growing threat in many areas.