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Keyler, D.E. and B.L. Oldfield. 1992. Timber rattlesnake (Crotalus horridus) field survey on southeastern Minnesota state lands (1990-1991). Final report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. 28 pp.


Minnesota represents the northernmost range for the Timber Rattlesnake (Crotalus horridus) in the Midwest. Although the species was reported along the upper Mississippi river valley as early as 1680 there is virtually no recent documentation of Timber Rattlesnake distribution, population, density, or the biology of the species in Minnesota.

The current distribution of Crotalus horridus was studied on state lands in Houston, Goodhue, Fillmore, Winona, and Wabasha Counties of southeastern Minnesota. Field surveys were conducted during the months of April through October in the years of 1991 and 1992.

A total of 101 specimens of Crotalus horridus were observed in the field at 16 of 33 survey sites with 48 snakes processed for biological information and 43 marked for identification. The majority of the specimens (n = 86) were found in XXXX County. Most specimens were observed in bluff prairie habitat (often in close proximity to hiking trails and observation points) with the exception of 2 snakes at a quarry site, 3 captured on paved roads, and 1 caught on a paved biking trail.

May 4 was the date of earliest snake sightings with the latest observations having been made on September 7. Temperatures were taken in the field of habitat environment and specimens yielding a mean substrate temperature of 26.7 +/- 3.3 C (n = 52), mean air temperature of 24.8 +/- 3.5 C (n = 52), and mean body temperature of 27.7 +/- 3.4 C (n = 49). The largest specimen measured 135 cm from the tip of its snout to the base of its rattle and had a body mass of 1.76 kg. Sex ratio was approximately 1:1.

It is hoped that the collective data in this report will contribute to the biological information on the species in the state of Minnesota and provide for rational land use patterns on state lands which will insure the protection and preservation of the Timber Rattlesnake.

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Please note that all location information has been removed from this document to protect the timber rattlesnake populations