| Few ecological studies have focused on understanding how reptiles use anthropogenically disturbed habitats. Consequently, this research bias has constrained efforts to conserve the ever-increasing number of reptiles threatened by human-induced landscape changes. One such reptile, the Timber Rattlesnake (Crotalus horridus), is a well-studied North American snake species considered to be imperiled by the loss and fragmentation of closed-canopy forest. Despite the threat posed to the Timber Rattlesnake by anthropogenic changes in habitat structure, most research on this species has been carried-out in large tracts of mature forest. Given the important conservation implications of understanding how this species uses anthropogenic habitat, I studied the ecology (spatial, foraging, and thermal) and life history (individual growth rates) of a Timber Rattlesnake population that uses a fragmented agricultural landscape in west-central Missouri.;Data obtained using temperature sensitive radio-transmitters indicated that median snake body temperature (Tb) did not differ among woodland (median = 28.0°C, range = 16.4--34.2°C, n = 63), edge (median = 28.6°C, range = 16.7--33.9°C, n = 56), or field (median = 28.2°C, range = 20.2--34.4°C, n = 61) habitats. Additionally, operative temperature models were used to quantify thermal constraints on activity in both a woodland and a field. During each two week interval of the sampling period (02 June to 26 August 2006), the overall percentage of thermally available habitat was high in both woodland (range 84.2--99.8%) and field (range 78.1--94.9%) habitats. However, sharp decreases in habitat availability occurred in both the woodland and field during midday. The lowest hourly percentages of thermally available habitat were recorded at 1400 hours in the field (19.7%) and at 1500 hours in the woodland (36.7%) during the two-week interval from 29 July to 11 August. Body temperatures of gravid females gestating within a man-made quarry (median = 32.5°C, range = 25.3--34.7°C, n = 113) were significantly warmer and less variable than T b's of males and non-gravid females using woodlands, edges, and fields (median = 28.3°C, range = 16.4--34.4°C, n = 180).;Finally, mark-recapture data and rattle morphology were used to compare the birth size and early growth rates of timber rattlesnakes in a fragmented habitat of west central Missouri (MO) to those in a closed-canopy forest of northwest Arkansas (AR). Missouri snakes increased in length more rapidly than their AR counterparts through their first eight ecdyses. Furthermore, males and females from MO diverge in size between the fifth and sixth ecdysis event, while growth trajectories of AR males and females remain indistinguishable through eight ecdyses. Despite climatic data suggesting that AR snakes may potentially have an average of 8.5% more time each season to acquire and assimilate prey, MO snakes still exhibited superior growth and early maturation.;Results of this study suggest that Timber Rattlesnakes may not require large tracts of closed-canopy forest as long as their thermal and dietary needs are met. Thus, employing habitat management techniques that enhance small mammal densities may be a more effective strategy for conserving Timber Rattlesnake populations than strictly attempting to preserve closed-canopy forest. Future studies should use habitat manipulation as a tool to better understand how forest-dwelling Timber Rattlesnakes respond to changes in habitat structure.;Despite large differences in habitat structure, the spatial data and movement patterns of individuals in this study monitored with radiotelemetry were similar to those previously reported for individuals in closed-canopy forests. However, 9 of the 27 individuals implanted with radiotransmitters (33.3%) exited the study when they were found dead upon relocation. Sources of mortality were known for 6 of the dead individuals (66.7%), all of which were human-induced. Snakes readily foraged in secondary woodland tracts and corridors, agricultural fields, and habitat edges. Dietary analysis found that snakes fed exclusively on mammals including shrews (Soricidae), mice in the genus Peromyscus, Prairie Voles (Microtus ochrogaster), Cotton Rats (Sigmodon hispidus), Eastern Gray Squirrels (Sciurus carolinensis), and Eastern Cottontails (Sylvilagus floridanus). Although small mammal trapping indicated that fields contained fewer numbers of prey than woodlands and habitat edges, field dwelling Prairie Voles were the most frequently consumed prey item. |
