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Habitat Varition Within Sympatric Snake Populations
Author(s) -
Reinert Howard K.
Publication year - 1984
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1939146
Subject(s) - habitat , ecology , biology , intraspecific competition , plant litter , sympatric speciation , discriminant function analysis , vegetation (pathology) , litter , ecosystem , medicine , pathology , machine learning , computer science
Radiotelemetry was used to monitor the habitat use of 21 timber rattlesnakes (Crotalus horridus) and 20 northern copperheads (Agkistrodon contortrix mokeson) during a 3—yr period beginning in 1979. Habitat was quantitatively defined on the basis of 14 structural environmental factors. To examine intraspecific habitat variations, species groups were subdivided by sex and the female subgroup was further separated into gravid and Nodulated segments. The nongravid female A. c. mokeson subgroup was deleted from the analysis because of its small sample size. A random series of habitat samples was obtained from the study site for comparison with the remaining five subgroups. A Muesebeck analysis of variance of six groups with 14 variables indicated that group centroids differed significantly (P < .01). The first three discriminant functions accounted for 94% of the total variance and represented the following respective habitat gradients: (1) rocky, open sites to heavily forested sites with few rocks, (2) sites predominantly covered with leaf litter to sites with dense forest—floor vegetation, and (3) sites with large—diameter overstory trees to sites with small—diameter trees. Gravid specimens of both species were most closely associated in discriminant space and clearly separated from other segments of their respective species groups. The utilization of rocky, sparsely forested sites and decreased variation in site selection were associated with gravidity. A two—group discriminant—function analysis using melanistic and nonmelanistic male C. horridus indicated a gradient in habitat utilization from mature forest sites with numerous fallen logs to young forest sites with predominant leaf litter cover. Melanistic specimens preferred the former and nonmelanistic specimens the latter. The results suggested that A. c mokeson was poorly adapted to the study site due to the preference of all population segments for open sites and young forest stands. In contrast, C. horridus was better adapted, utilizing a broad range of the available habitat. The analyses serve to emphasize the importance of physiological factors in determining the spatial relationships of snakes in temperate environments.