Rabu, 11 Juli 2012

Prairie Racerunners

Closely related to the six-lined racerunner of the Mid-Atlantic and Southeastern U.S., the prairie racerunner is found from northwestern Indiana and southern Wisconsin, westward to southern Wyoming and southward to Arkansas, West Texas and New Mexico.  Favoring dry, sandy soil and hot weather, these lizards inhabit prairie grasslands, abandoned farms, glades and rocky hillsides; attracted to disturbed areas, they are known to spread along power line swaths and railroad lines.  Here in Colorado, prairie racerunners are abundant from the High Plains to the shrub zone of the lower Front Range foothills.

Emerging from hibernation in late April or May, prairie racerunners are best observed during the morning and early afternoon hours of June and July, dashing across trails or clearings and disappearing into clumps of vegetation to snare prey or to avoid predators.  Their long tail, twice the length of their body, is thought to serve as a counter-balance as they zig-zag at speeds up to 18 miles per hour.  Mating occurs by late spring and five eggs are generally produced; as with most lizards, the hatchlings are miniature replicas of the adults and must fend for themselves.  While a second brood may be produced within a few weeks, adult prairie racerunners begin to hibernate by late August or early September; the young, needing more time to generate fat stores, wait until late September or October to settle in their winter burrows (depending on their home latitude).

Feasting on a wide variety of insects and other invertebrates during their brief season of activity, prairie racerunners may fall victim to grassland hawks, prairie falcons, burrowing owls, fox, coyotes, roadrunners, magpies and a variety of snakes.  Using shallow burrows during the warmer months, they dig a deeper channel with a terminal chamber for their prolonged hibernation; during that time, in sharp contrast to their frenzied life above ground, their metabolic rate falls dramatically and they rely on fat deposits to fuel their survival.  If they make it through their first winter, adult prairie racerunners are thought to have a natural life span of 4-5 years.

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