Species Account: Northwest Alligator Lizard (Elgaria coerulea)

Description of Species

The Northern Alligator Lizard is a medium sized, short legged lizard with a triangular head. On average, adult lizards can grow up to 254 mm in length and their tail makes up more than half of its total length. Northern Alligator lizards are distinguished from other lizards by their square and folded dorsolateral folds scales on the sides of their body. The smooth ventral scales on the underside of their body are divided from the keeled scales on top of their body by this fold of skin. These folded scales expand and contract as they breathe, well up with blood to regulate temperature, or when females bear offspring. The square scales are darkly pigmented and found in a blotchy pattern. Their body color ranges from brown, white, to yellow-green, but the underside is almost always light grey. This allows them to blend in with the natural landscape of the pacific northwest effectively. Their eyes are darkly pigmented black and brown, which distinguishes them from their southern relative Alligator lizard that has yellow eyes. Another key indicator is the bronze-black streak on their back which distinguishes it from other subspecies of alligator lizard (Rockney, 2016).

Conservation Status 

As of 2007, the IUCN Red List Assessment categorized the Northern Alligator Lizard as a least concern (LC) species due to their resiliency to habitat destruction and their stable population distribution (Lavin 2018). The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has designated the Northern Alligator Lizard as “not at risk” in May 1, 2002. The distribution of this lizard throughout western Washington and southern British Columbia is relatively even and no recent accounts have indicated recent declines in lizard populations. This may be due the lack of research, funding, or interest, but it may also be due to their secretive nature that makes research challenging.  

Genetic Research

Molecular dating was conducted to determine genetic lineage of (Elgaria coerulea) throughout time (Lavin 2018). Data suggests that the major diversification events that gave rise to the Northern Alligator subspecies (Elgaria coerulea) occurred during the Pleistocene period approximately 2.6 to 12 million years ago (Lavin 2018).

Abundance

While there is not a lot known about the population distribution of Northern Alligator Lizards, the few studies conducted have shown no significant decline in population. The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) reports them as yellow listed (COSEWIC, 2002). This means that the Northern Alligator Lizard’s populations are not at immediate risk of extinction and that their populations are stable. In Washington state specifically, there have been no reports showing a decline in the population or distribution of this species (Hallock 2009). The population of this lizard seems to be stable in the pacific northwest.

Behavior

Northern Alligator lizards spend much of their lifetime alone within hidden areas amongst rocks and vegetation. They are unlikely to be sited in the winter during hibernation because they are sheltered under rocks and leaf cover. When they emerge to mate and to bask in the spring time, the become active and the chances of spotting them increases. Northern Alligator Lizards are ectothermic so they depend on sunlight heat for regulating body temperature. The availability of warm basking sites during the gestation period is critical for allocating energy for offspring development (Rutherford and Gregory 2003). In autumn as temperatures begin to drop, they search for overwintering sites where they can stay warm and protected until spring. In the fall, they have been noticed entering houses presumably in search of overwintering sites. In the wintertime, they may hibernate up to 7 months between the months of September and April.

Habitat Use

The Northern Alligator Lizard’s habitat expands from southern British Columbia south to the Sierra Nevada range in California. They are also present eastwardly in northern Idaho and northeastern Montana. These states have a wide range and variety of habitats. These lizards are terrestrial reptiles that survive well in dry woodlands, grasslands, stream, and beach habitats. They do exceptionally well in rocky environments as well as coniferous forests like Douglas Fir and Hemlock (Rutherford and Gregory 2003). They primarily use rocks for shelter but also rely on vegetative cover and fallen logs for shelter during the spring and summer time. They also use this shelter to avoid predation (Rutherford and Gregory 2003).

Reproduction

Soon after the Northern Alligator lizard emerges from hibernation between the months of April and May, the mating season begins. The mating patterns of Northern Alligator Lizards are unlike other species because males do not forgo any displays of attraction. When male lizards are ready to mate, they chase down a female lizard and grabs onto her head using its jaw. Once they are bonded, he holds on tightly to initiate the ritual and to deter other males from mating with her. When she is ready, they engage in the mating process. This mating process can go on for hours.On average, female lizards will give birth to 4-6 young in the months of August and September, but this range varies based on locality. These lizards are unique because they do not lay eggs, they give live birth to their offspring. In the region near Seattle, Washington females may produce (3-8) offspring but along the Oregon coast they produce 2-6 offspring. Females reach sexual maturity around 32—44 months of age and mate every two years due to energetic limitations (Rutherford and Gregory 2003).

Feeding Habits

 Mature Northern Alligator lizards are primarily insectivores and feed on large insects like spiders, crickets, grasshoppers, centipedes, millipedes, but also on snails, ticks, moths, baby mice, slugs, and scorpions (Rutherford and Gregory 2003). Juvenile Northern Alligator lizards prefer to prey on smaller insects. They are diurnal feeders and only feed at mid to late evening.

These lizards hibernate through the cold months of winter during mid-September. They hibernate underground and emerge in early spring to feed on these insects. In the wintertime, these lizards slow down their metabolic rate and body temperature. They do this to conserve the stored energy in their tails over the winter (Hallock 2009).

Mortality

Northern Alligator lizards are predators to some but prey for many animals such as garter snakes, red-tailed hawks and feral cats. These lizards use a unique defensive strategy to avoid predators. When these lizards are in stressful conditions, they will detach their tail to distract their predator and give them time to escape. The nerves within its tail can tremor up to minutes after it becomes detached as to distract its predator. This escape strategy is not a favorable method because without its tail, it does not have as much stored energy to survive through the winter (Rutherford and Gregory 2003). Lizards without tails may have decreased fitness, reproduction, and can affect energy allocation during gestation. These lizards can live between 10-15 years depending on its region (Hallock 2009).

 Conservation and Management

Habitat fragmentation is widespread in the Pacific Northwest due to logging, urbanization, and agriculture. it has not shown to have significant impacts on the population density of this species (COSEWIC, 2002) In some cases, they thrive in disturbed habitats. Northern Alligator lizards may benefit from land- use alteration like deforestation. Openings in the forest canopy cover increases sunlight availability for basking sites. This is especially important for gravid lizards during their gestation period. Conversely, road construction and rock quarrying results in direct habitat removal and fragmentation which can affect their migratory patterns between winter hibernation and summer habitat (Rutherford and Gregory 2003). Additionally, the removal of rocks and logs can have a negative impact by reducing the amount of shelter for overwintering and basking sites.

Climate Change

Northern Alligators are a resilient species to the pacific northwest. Dating back to the Pleistocene period, these lizards have survived through various climate conditions. They are an ectothermic species that thrives in mild, wet, and temperate areas. Climate change will certainly alter their wintertime hibernation cycles as warmer seasons extend later into the fall. Warming global temperatures may shift their habitat range northwards into cooler climates in British Columbia. In addition, habitat fragmentation poses a serious threat to their summer migratory patterns as climate migrations increase. Northern Alligator lizards may be more resilient to climate change than other species due to their overall resiliency to environmental disturbances, but studies have not been done to analyze the potential impact. The future of this species as well as other reptiles in the pacific northwest will endure dramatic changes this century unless humans reduce greenhouse gas emissions significantly and soon.

Works Cited

COSEWIC. 2002. COSEWIC Status Report on the Northern Alligator Lizard  Elgaria in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 32 pp.

Cossel, J., Jr. (n.d.). Elgaria coerulea. Retrieved 1997, from https://imnh.iri.isu.edu/digitalatlas/bio/reptile/lacer/elco/elcofram.htm

Hallock, L.A. and McAllister, K.R. 2009. Northern Alligator Lizard. Washington Herp Atlas. http://wdfw.wa.gov/conservation/herp_atlas/

Northern Alligator Lizard — Elgaria coerulea.  Montana Field Guide.  Montana Natural Heritage Program and Montana Fish, Wildlife and Parks.  Retrieved on October 23, 2018, from http://FieldGuide.mt.gov/speciesDetail.aspx?elcode=ARACB01010 

Lavin, B. R., Wogan, G. O., Mcguire, J. A., & Feldman, C. R. (2018). Phylogeography of the Northern Alligator Lizard (Squamata, Anguidae): Hidden diversity in a western endemic. Zoologica Scripta, 47(4), 462-476. doi:10.1111/zsc.12294

Rockney, H., & Wu, K. (2016, May 06). Northern Alligator Lizard. Retrieved from https://www.burkemuseum.org/blog/northern-alligator-lizard

Rutherford, P.L. and Gregory, P.T. 2003. Habitat use and movement patterns of northern alligator lizards (Elgaria coerulea) and western skinks (Eumeces skiltonianus) in southeastern British Columbia.Journal of Herpetology 37 (1): 98-106.