Seasonal variations in spatial ecology, habitat use and habitat selection by San Cristóbal lava lizards Microlophus bivittatus in Galápagos
Activity of terrestrial ectotherms in seasonal equatorial environments can be challenging due to temporal variations in temperature and water availability. Social interactions among conspecifics, along with predation risks, can also place limitations on activity patterns and spatial ecology. We studied the spatial ecology, habitat use, and habitat selection in the San Cristóbal lava lizard (Microlophus bivittatus) during a hot-wet period (March), and a cool-dry period (August). Overall, lizards used rock faces under canopy more frequently than other microhabitats. Compared to the hot-wet period, lizards increased their use of rock crevices and detritus and were sometimes inactive for several consecutive days during the cool-dry period. Lizards varied in their selection of structural features and thermal characteristics across seasons and throughout the day, relying on open areas for basking (especially during the mornings) during the hot-wet period and shifting to sheltered, cooler microhabitats during the cool-dry season. Within their larger activity areas, each lizard concentrated movements within a single area but occasionally and often repeatedly traveled to peripheral specific areas. While minimum convex polygons and AKDE-95% utility distributions (UDs) overlapped among individuals extensively, AKDE-50% UDs rarely overlapped among individuals that resided adjacent to one another. Lizards showed a reduction in space use metrics by over 50% between the hot-wet and the cool-dry period further indicating seasonal limitations on activity between seasons. Overall, San Cristóbal lava lizards are sensitive to both thermal and structural habitat characteristics and vary their habitat use and activity patterns seasonally.
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