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Habitat utilization by Eastern yellowbelly racers (Coluber constrictor flaviventris) in southwest Dallas County Texas.

Abstract.--A population of Coluber constrictor flaviventris was surveyed in both relic and disturbed Blackland Prairie habitats during the spring, summer and fall of 1999 and 2000 at Cedar Hill State Park in Dallas County, Texas. Drift fences with funnel traps and coverboards were used to live-trap snakes. During the two years, 69 specimens were recorded. The study demonstrated that the disturbed Blackland Prairie had significantly more specimens then the relic Blackland Prairie.

There are several publications discussing reptiles and amphibians utilizing and adapting to disturbed habitats (Dyrkacz 1977; Enge 1998; Fitch 1999; Kaufmann 1992.). Bury (1983) reported that the amphibian populations in an old growth forest (both species richness and abundance) were drastically altered after logging had occurred. However, comparisons of reptiles or amphibians utilizing both relic and disturbed habitats of the same habitat type are uncommon.

Coluber constrictor is found in a variety of habitats throughout the United States including grasslands, prairies and forested areas (Conant & Collins 1998). In Cedar Hill State Park, where C. constictor flaviventris occurs, they are abundant in these habitats but were noted to exhibit a strong tendency towards grasslands. Coluber constrictor are strictly diurnal with a relatively high body temperature preference (Fitch 1999). Their diet consists of a large variety of food items including insects, reptiles, amphibians and rodents in adult specimens (Fitch 1999). This study compares habitat usage by Coluber constrictor flaviventris in both relic and disturbed prairie habitats.

STUDY SITE

Cedar Hill State Park is located in southwest Dallas County and encompasses 1826 acres of disturbed prairie, relic prairie, oak forest and disturbed hillside forest. Adjacent to the park is Joe Pool Lake, which was created in 1981 for water consumption by the Dallas/Fort Worth metroplex residents. The topography is gently rolling hills except for steep west-facing bluffs associated with a chalk outcrop of the White Rock Escarpment (Carr 1993). Elevation varies from 115 m in the prairies to 250 m on the escarpment. The two habitats studied were relic Blackland Prairie (RBP) and disturbed Blackland Prairie (DBP).

The RBP (32[degrees] 37'N, 96[degrees] 60'W) is characterized by nearly level to gently rolling hills with extremely fertile soil. The soil of the Blackland Prairie within the park is considered deep, moderately well drained, moderately alkaline and contains black calcareous clay (Coffee et al. 1980). The blackland habitat is true tallgrass prairie, with the little blue-stem (Schizachyrium scopariurn) as the climax dominant vegetation (Simpson 1998). This relatively undisturbed habitat has never been plowed or grazed by livestock and is maintained with controlled burns every three to five years.

DBP (32[degrees] 36'N, 96[degrees] 60'W) is similar to RBP in that the soil content and elevation are comparable. However, DBP has been grazed by livestock and the soil was once extensively farmed. The year of the last disturbance on this habitat was Ca. 1980. At present, the habitat consists of mostly introduced grasses or non-woody native and introduced weeds. No dominant weed species could be discerned. There are no controlled burns in the disturbed prairie. Because of this the vegetation is much thicker and higher than that of the relic prairie.

METHODS AND MATERIALS

Within both habitat types, four 50 [m.sup.2] plots were established. These plots were approximately 20 m from the edge of any other plots. All plots were no less than 50 m from an adjacent habitat edge to avoid sampling species utilizing edge habitat. In the DBP, an unpaved park road measuring four meters wide divides a portion of the habitat sampled. One drift fence made of aluminum flashing measuring 15.5 m long and 0.5 m high was erected in the center of each of the four plots within each habitat type. A funnel trap measuring 60 cm by 25 cm was used at both ends of each drift fence. Due to the lack of shade and the heightened chances of a snake exceeding its thermal limit while confined in a funnel trap, boards (approximately the same size as the traps) were placed on top to provide shade. In addition to the plots, four-one [m.sup.2] cover boards were placed on the prairie ground. These cover boards were placed 10 m from the drift fences. While checking traps, visual searches were conducted on the way to a nd from the traps. If specimens were observed within these plots, they were recorded from that habitat type.

All traps were checked three times per week in the spring (April -- mid June), once a week during the hotter summer months (Mid June -- 1 September) and twice a week in autunm (September -- 1 December), for both years. The traps were checked a total of 134 days during the two years. Specimens were tagged with passive integrated transponders (pit-tags) to record recaptures. Recaptures were not included in the data presented in this study.

RESULTS AND DISCUSSION

In 1999, five specimens were captured in the RBP, compared to 27 specimens in the DBP for a total of 32 specimens. The number of captures between the two habitats were significantly different ([chi square] = 15.2, P<0.O1). In year 2000, seven specimens were captured in the RBP, compared to 30 specimens in the DBP for a total of 37 specimens. Captures between the two habitats was again significantly different ([chi square] 14.3, P < 0.0 1). For the two years sampled, a considerably higher number of C. constictor fiaviventris were captured in the disturbed habitat compared to the relic habitat (Table 1).

Fitch (1999) reported that formerly cultivated fields, woodlands and open pastures that were heavily grazed by livestock had very few C. constrictor. However, when the grazing ended and the grasses returned the C. constrictor population size increased for several years (Fitch 1999). The disturbed habitat in this study was observed as being considerably more dense with meter high vegetation, which created more ground cover than that of the relic habitat. In addition, there was manmade debris in the form of lumber and old car tires in the disturbed habitat only. This debris was approximately 100 m from any of the four plots sampled. Two different species of rodents were observed in the DBP and three different species were found in the RBP. However, much larger numbers of rodents were observed in the DBP compared to the RBP. Insects appeared in be more common in the DBP as well. Further studies on the prevalence of food items and/or vegetative cover within these two habitats needs to be undertaken in order to de termine the importance of these factors in contributing to the differences in the number snakes observed.

ACKNOWLEDGEMENTS

We would like to thank Ruston W. Hartdegen, Winston Card, Cynthia Bennett, the Staff of the Dallas Zoo Department of Herpetology, the staff of the Cedar Hill State Park and Texas Parks and Wildlife Department (Permit # 51-98).
Table 1

Numbers of individual specimens of Coluber constrictor flaviventris
collected in relic Blackland Prairie and disturbed Blackland Prairie
habitats during the spring, summer and fall of 1999 and 2000 in Dallas
County, Texas.

 Spring Summer Fall Totals

Relic Blackland Prairie 1999 (3) 1999 (1) 1999 (1) 5
 2000 (4) 2000 (2) 2000 (1) 7

Disturbed Blackland Prairie 1999 (18) 1999 (2) 1999 (7) 27
 2000 (17) 2000 (4) 2000 (9) 30


LITERATURE CITED

Bury, R. B. 1983. Differences in amphibian population in logged and old growth redwood forest. Amer. Midi. Natur., 103(2):412-416.

Coffee, D. R., R. H. Hill & D. S. Ressel. 1980. Soil survey of Dallas County, Texas. United States Department of Agriculture, Soil Conservation Service, 153 pp.

Conant, R. & J. T. Collins. 1998. A field guild to reptiles and amphibians. Houghton Muffin Company, Boston, Massachusetts, 616 pp.

Dyrkacz, S. 1977. The natural history of the eastern milk snake in a disturbed environment. J. Herpetol., 11(2): 155-159.

Enge, K. M. 1998. Herpetofaunal survey of an upland hardwood forest in Gadsden County, Florida. Florida Scient., 61(3/4): 141-159.

Fitch, H. S. 1999. A Kansas snake community: Composition and changes over 50 years. Krieger Publishing Company, Malabar, Florida, 165 pp.

Kaufmann, J. H. 1992. Habitat use by wood turtles in central Pennsylvania. J. Herpetol., 26(3)315-321.

Lewis, S. D., R. R. Fleet & F. L. Rainwater. 2000. Herpetofaunal assemblages of four forest types in the Big Sandy Creek Unit of the Big Thicket National Preserve. Texas I. Sci., 52(4) Supplement: 139-150.

Simpson, B. J. 1988. A field guild to Texas trees. Gulf Publishing Company, Houston, Texas, 372 pp.

RDR at: hylareams@aol.com
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Article Details
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Author:Reams, Richard D.; Gehrmann, Williams H.
Publication:The Texas Journal of Science
Geographic Code:1U7TX
Date:Feb 1, 2002
Words:1418
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