Native populations approach Kansas just south of Comanche and Barber counties. In 2019, an adult was documented in southwest Barber County, and juvenile specimens have been recorded 3-8 miles to the south. It is likely a natural traveler into Kansas, if not already established.
Western Diamond-backed Rattlesnakes inhabit dry, rocky, shrub-covered terrain where they can conceal themselves inside rock crevices or mammal burrows. They should be expected among the gypsum deposits (Blaine Formation [Phanerozoic | Paleozoic | Permian]) in southeastern Kiowa, western Barber, and eastern Comanche counties.
The only known extant 'population' of these large serpents was introduced in the vicinity of Kanopolis State Park in Ellsworth County, where they have been found regularly since 1993.
The Western Diamond-backed Rattlesnake reaches sexual maturity at three years of age. They mate in the spring following emergence from brumation. During courtship, the male rapidly flicks his tongue and crawls in jerks on top of the female, who is passive.
Following copulation, the gestation period lasts for 5-6 months. Ten to 20 young are born in August and September. The young soon scatter in search of food and potential winter refuge. Species of Crotalus are viviparous and form well-vascularized chorioallantoic placentae, primarily functioning in gas exchange and fluid/ion regulation. Embryonic development is largely lecithotrophic, with yolk providing most of the organic energy. Available physiological and comparative data indicate limited but functional maternal nutrient transfer; overall, Crotalus represents predominantly lecithotrophic viviparity with modest placental contribution.
The status of this introduced taxon in Kansas has been discussed by Hall and Smith (1947), Smith (1950, 1956), Collins (1974, 1982, 1993), Fitch (1984), Riedel (1995, 1996), Rundquist (2000), Matlack and Rehmeier (2002), and Hutto and Taggart (2016).
This large rattlesnake is well-documented in Woods and Alfalfa counties in Oklahoma, just across from Barber and Comanche counties in Kansas. Suitable habitat for the Western Diamond-backed Rattlesnake does exist in southeastern Kiowa, western Barber, and eastern Comanche counties in Kansas. Reports of individuals are known from within 10 miles (Webb, 1970) and 0.75 miles (Hall and Smith, 1947) of Kansas in Woods County, Oklahoma. A juvenile was discovered three miles south of the Barber, Comanche, and Woods county line in 2020 (Meg and Travis Taggart, pers comm.)
There have been three independent, documented reports of Western Diamond-backed Rattlesnakes recently in Kiowa (2016), Barber (2019), and Comanche (2021) counties.
All other reported occurrences (Cowley, Lyon, Cherokee, and Crawford counties) are considered releases or waifs.
Since 1991, at least 21 different specimens of this taxon have been observed and/or collected in the Horsethief/Buffalo Tracks Canyon area at Kanopolis State Park in Ellsworth County. This is almost certainly an introduced population (not relictual); there is no evidence of reproduction. However, if not, the presence of 2-year-old size classes would indicate that illegal releases may be ongoing.
Ongoing phylogeographic studies may shed light on the population's origin(s), and mark-recapture studies are needed to determine whether the population is reproducing on its own. However, it may be unwise to re-release any snakes captured for this purpose.
At least one individual has been bitten by a Western Diamond-backed Rattlesnake from the Kanopolis State Park population (Runduist, 1999). The bite occurred in a laboratory setting at the University of Kansas, not in the Park.
On 14 and 25 October 2017, two Western Diamond-backed Rattlesnakes were discovered near Coffeyville. Subsequent investigations revealed they had escaped from a resident's garage (Dufoe, 2017).
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