Temperature and UV preferences for Sceloporus undulatus

    In observing squamate behavior, a study published in 2021 by the British Ecological Society was conducted by Matthew Lattanzio and Dane Conley from the Department of Organismal and Environmental Biology Department at Christopher Newport University, Virginia. A correlation in the exhibited behavior of eastern fence lizards in the preference of ultraviolet light. 

    Conley and Lattanzio found that eastern fence lizards (Sceloporus undulatus) actively regulate UV and temperature to produce behavioral activity in which S. undulatus had a preference for higher UV levels as opposed to high temperatures. The methodology used included 40 adult S. undulatus (15 female and 25 male) caught in Newport News Park, Virginia. Once captured, the individuals were placed in plastic enclosures and were fed mealworms and water (Conley and Lattanzio (2021). Three treatments were done to observe this behavior, the first being temperature, then UV exposure, and then UV and temperature alterations. They were all placed in an equal 12 hour light and dark schedule and in a six-lane arena. Heat emittent bulbs (75-W) were placed in each lane to create a thermal gradient ranging from 23 C to 50 C. A thermocouple was placed on the cloacal of each lizard from which data was collected in an OMEGA 8-channel software. The UV gradient was then created by suspending a fluorescent UV bulb at a 30 degree angle in each of the six lanes. The UV lights were varied while the temperaturesremained constant from which the time each lizard spent near the UV bulb was recorded. The combined observation of UV light exposure and thermal preference was studied in altering the temperatures without UV bulbs present from which the behavior was logged. 

    From the data collected, it was found that the lizards had a preference for UV exposure more so than thermal preferences, in staying longer in the UV light sources.

        Figure 1: Lattanzio and Conley (2021) table showing the differences in all lizards’ bodytemperature and preference for either UV or high thermal temperatures.  

    In the table above, there was no difference in body temperature and UV body temperature preference for either males or females. S. undulatus had regulated UV and thermal temperatures with a UV value of 0.72 overall (shown on Figure 1 under ‘UVI’ baseline treatment). However, in Figure 2 below, all treatments supported that lizards had a high temperature preference in staying longer in high thermal temperatures, but only when there was a UV gradient present. Treatments 1 (temperature gradient) and Treatment 2 (UV gradient) were compared against the results shown from Treatment 3 (temperature and UV gradient). Particularly, for females, there was a high temperature preference shown in Treatment 3 (p = 0.038). 

    Lizards, being ectotherms, exhibit basking behavior as part of regulating their body temperature. The combination of high thermal temperatures and UV light is useful for S. undulatus to regulate body temperature efficiently. From the results showing the preference of high UV and temperature ranges, it can be concluded that lizards would be able to withstand their temperature tolerance range to have UV exposure for body temperature regulation or metabolic processes. 

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REFERENCE CITED

Hutchison, Victor H., and Richard J. Kosh. "Thermoregulatory function of the parietal eye in the lizard Anolis carolinensis." Oecologia 16 (1974): 173-177

ARTICLE: 

Active regulation of ultraviolet light exposure overrides thermal preference behaviour in eastern fence lizards by Conley and Lattanzio (2021)