Western fence lizards are a very common sight for hikers in the Silicon Valley. Found across many habitats in California, these replies are also native to Arizona, Idaho, Nevada, New Mexico, Oregon, Utah, Washington.
What do western fence lizards look like?
Western fence lizards (Sceloporus occidentalis), also called “blue-bellies,” are medium-sized lizards with a rough, spiny appearance. Both males and females have pale bellies, but adult males have bright blue patches on the sides of their belly and throat. These lizards are generally gray, brown, or black along the back.
Most commonly seen species in California
Western fence lizards are highly adaptable reptiles. These lizards are found in both open space areas and in urban environments. Except for harsh deserts, western fence lizards can be seen in the state’s grasslands, woodlands, forests, and chaparral environments.
Being so widespread, western fence lizards are the most commonly logged reptile in the United States in iNaturalist, the crowdsourced database of species sightings. Within California, an analysis of species sightings found that the western fence lizard is the most frequently listed observation. The same LA Times analysis also found that 90% of all western fence lizard observations are based in California.
Why is it so easy to see western fence lizards?
While western fence lizards will scurry away if you get too close, these reptiles are diurnal which means they are most active during the day. Western fence lizards can often be spotted by hikers basking for warmth on rocks, tree branches, and fences.
Lizard Push-ups
Male western fence lizards often engage in a display that looks like they are doing push-ups. The lizard pushup involves the lizard raising and lowering his body using his front legs. Push-ups are used to defend territory, attract females for mating, and ward off rivals by showing off the bright blue patches on their bellies and throats.
Western fence lizards and ticks
Western fence lizards are one of the preferred hosts for ticks. Ticks can often be found feeding behind the ears of western fence lizards.
One study looked at the correlation between western fence lizards and western black-legged ticks (Ixodes pacificus) populations. After experimentally removing western fence lizards from the study area, most larval ticks did not switch to different hosts and died. The following year, the abundance of nymphal ticks was less dense in the plots that had western fence removed compared to the plots where western fence lizards were present. The authors of the study concluded that western fence lizards help to maintain a higher population of ticks.
On the flip side, studies have also shown that western fence lizards help to lower the prevalence of Lyme disease, caused by Borrelia burgdorferi. When ticks carrying B. burgdorferi feed on western fence lizards, a protein in the reptile’s blood kill the bacteria, clearing the disease from the tick.
Hotter urban areas are changing the bodies of western fence lizards
Western fence lizards have been the subject of an interesting study on the effects of urban surfaces and a changing climate. A study in Los Angeles County by UCLA researchers found that lizards living in cities have shorter limbs and toes, likely helping them move better on smooth surfaces like concrete. They also tend to have fewer and larger back scales, which researchers hypothesize is a possible adaptation to deal with hotter city temperatures.
References
Lane, R. S., & Quistad, G. B. (1998). Borreliacidal factor in the blood of the western fence lizard (Sceloporus occidentalis). The Journal of parasitology, 29-34. DOI: 10.2307/3284524
Putman, B. J., Gasca, M., Blumstein, D. T., & Pauly, G. B. (2019). Downsizing for downtown: limb lengths, toe lengths, and scale counts decrease with urbanization in western fence lizards (Sceloporus occidentalis). Urban Ecosystems, 22(6), 1071-1081. DOI: 10.1007/s11252-019-00889-z
Swei, A., Ostfeld, R. S., Lane, R. S., & Briggs, C. J. (2011). Impact of the experimental removal of lizards on Lyme disease risk. Proceedings of the Royal Society B: Biological Sciences, 278(1720), 2970-2978. DOI: /10.1098/rspb.2010.2402
