Progress 10/01/00 to 09/30/06
Outputs
The central goal of this study was to test the hypothesis that snakes select habitat to meet thermoregulatory needs, so that habitat use will vary seasonally, by sex, and by latitude. Understanding this relationship helps understand how snakes are affected by habitat fragmentation in agricultural landscapes, and in turn how their use of habitat affects their broader ecology (e.g., predator-prey relationships). This hypothesis was tested by comparing habitat use by ratsnakes and racers in Illinois. Illinois ratsnakes used upland forest more and forest edges less than ratsnakes at their northern range limit, although female ratsnakes in Illinois used edges less than males, regardless of their reproductive status. As predicted, relative to Illinois ratsnakes, racers preferred forest edges and avoided forest interior. Also, female racers used edge more than males, especially while gravid. Most seasonal differences in habitat use among and between species were consistent
with the thermal ecology hypothesis. Thus, both latitudinal and species differences in habitat use were broadly consistent with differences in thermal ecologies. Forest fragmentation is likely to be detrimental to ratsnakes in Illinois but beneficial to racers. Separate from this work, a collaborative study on the genetic structure of northern ratsnake populations was completed. The thermal ecology study will form the basis for Ph.D. student Gerardo Carfagno's dissertation (currently being written). This work has produced three publications thus far with several more in preparation
Impacts
Agricultural landscapes are characterized by both decreases in the area of original habitat and fragmentation of the original habitat that remains. Preserving biodiversity in natural habitats within agricultural ecosystems requires an understanding of how individual species respond to habitat reduction and fragmentation and how those responses affect their interactions with other species. There is abundant evidence documenting the decline of forest birds in fragmented forests, and increased nest predation is often implicated as a proximate cause of the decline. Snakes are the most important avian nest predators in forests in the Midwest, and the snakes' preference for edge habitats may increase their impact on birds nesting in fragmented forests. By determining how black rat snakes respond to habitat fragmentation and how this affects nest predation of breeding birds, it will be possible to assess the impact of potential habitat management practices on the abundance
and distribution of snakes, and thus on nesting birds.
Publications
- Carfagno, G.L.F., Heske E.J. and Weatherhead P.J. 2006. Does mammalian prey abundance explain forest-edge use by snakes? Ecoscience 13:293-297.
- Gibbs, H.L., Coreyl, S.J., Blouin-Demers, G., Prior, K.A. and Weatherhead, P.J. 2006. Hybridization between mtDNA-defined phylogeographic lineages of ratsnakes (Pantherophis sp.). Mol. Ecol. 15: 3755-3767.
- Carfagno, G.L.F. and Weatherhead, P.J. 2007. Intraspecific and interspecific variation in use of forest-edge habitat by snakes. Can. J. Zool. (In Press).
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Progress 01/01/05 to 12/31/05
Outputs
The fieldwork begun three years ago in the Cache River State Natural Area in southern Illinois is being completed this year, led by Ph.D student Gerardo Carfagno. The goal this year was to complete tracking of black ratsnakes and blue racers that still carried transmitters, with particular emphasis on fine-scale activity patterns. Toward the end of the active season, snakes were captured and brought back to campus so transmitters could be removed. As transmitters were removed, information on the snakes' health was recorded for use in a publication on health effects of transmitters. At present, only 4 of the initial 14 snakes remain to be recaptured for transmitter removal. These snakes will be captured by the end of October. Fine-scale tracking was necessary to assess the frequency with which snakes moved between habitats, and thus encountered different microclimatic conditions. Ratsnakes proved to be very sedentary whereas racers make numerous movements over the
course of a day. These data will be used when quantifying patterns of thermoregulation. With the completion of fieldwork, attention will be focused on data analysis and writing.
Impacts
Agricultural landscapes are characterized by both decreases in the area of original habitat and fragmentation of the original habitat that remains. Preserving biodiversity in natural habitats within agricultural ecosystems requires an understanding of how individual species respond to habitat reduction and fragmentation and how those responses affect their interactions with other species. There is abundant evidence documenting the decline of forest birds in fragmented forests, and increased nest predation is often implicated as a proximate cause of the decline. Snakes are the most important avian nest predators in forests in the Midwest, and the snakes' preference for edge habitats may increase their impact on birds nesting in fragmented forests. By determining how black rat snakes respond to habitat fragmentation and how this affects nest predation of breeding birds, it will be possible to assess the impact of potential habitat management practices on the abundance
and distribution of snakes, and thus on nesting birds.
Publications
- Carfagno, G.L.F., Heske E.J. and Weatherhead P.J. 2006. Does mammalian prey abundance explain forest-edge use by snakes? Ecoscience (In Press).
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Progress 01/01/04 to 12/30/04
Outputs
The fieldwork begun two years ago in the Cache River State Natural Area in southern Illinois was continued this year, led by the Ph.D student Gerardo Carfagno. The field work will be completed this fall. The goals this year were to continue tracking black ratsnakes and blue racers beginning when they emerged from hibernation to obtain data on snake body temperatures and to continue quantifying the habitat used by the snakes. Substantial progress toward meeting all these goals was realized. We captured 26 new racers and 32 new ratsnakes. Transmitters were implanted into 6 ratsnakes and 4 racers (in addition to the 14 individuals implanted in 2003). Snakes were located every 48 hours through the spring and summer, and twice a week beginning at the end of September. Six snakes were lost during the summer, two due to transmitter failure and the rest to predation. The remaining snakes will be tracked until they go underground, which occurs between October and mid-November.
Tracking in 2004 yielded approximately 700 new snake locations and approximately 60,000 body temperature measurements. Habitat variables were quantified at every second new snake location (approximately 300 thus far), and at randomly selected locations (approximately 150 thus far). Two female ratsnakes and two female racers were captured while gravid and laid eggs in the lab. Those eggs were incubated and blood samples collected before releasing the hatchlings. Overall, therefore, substantial progress was made on all major objectives.
Impacts
Agricultural landscapes are characterized by both decreases in the area of original habitat and fragmentation of the original habitat that remains. Preserving biodiversity in natural habitats within agricultural ecosystems requires an understanding of how individual species respond to habitat reduction and fragmentation and how those responses affect their interactions with other species. There is abundant evidence documenting the decline of forest birds in fragmented forests, and increased nest predation is often implicated as a proximate cause of the decline. Snakes are the most important avian nest predators in forests in the Midwest, and the snakes' preference for edge habitats may increase their impact on birds nesting in fragmented forests. By determining how black rat snakes respond to habitat fragmentation and how this affects nest predation of breeding birds, it will be possible to assess the impact of potential habitat management practices on the abundance
and distribution of snakes, and thus on nesting birds.
Publications
- Weatherhead, P.J. and Blouin-Demers, G. 2004. Understanding avian nest predation: Why ornithologists should study snakes. J. Avian Biol. 35:1-6.
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Progress 01/01/03 to 12/31/03
Outputs
The fieldwork begun last year in the Cache River State Natural Area in southern Illinois was continued this year, led by the Ph.D student Gerardo Carfagno. The goals this year were to capture black ratsnakes and blue racers as they emerged from hibernation sites located last fall, implant a subset of these with radio transmitters, radio track the snakes through the active season, obtain data on snake body temperatures, and to continue quantifying the habitat used by the snakes. Substantial progress toward meeting all these goals was realized. We captured 99 racers and 54 ratsnakes. Transmitters were implanted into 7 ratsnakes (in addition to the 11 individuals implanted in 2002) and 12 racers. Snakes were located every 48 hours through the spring and summer, and twice a week beginning at the end of September. Eight snakes were lost during the summer, two due to transmitter failure and the rest to predation. The remaining snakes were tracked until they went
underground, which occurred between October and mid-November. Tracking in 2003 yielded approximately 950 snake locations and approximately 75,000 body temperature measurements. Habitat variables were quantified at every second new snake location (approximately 420 thus far), and at randomly selected locations (approximately 200 thus far). Two female ratsnakes and three female racers were captured while gravid and laid eggs in the lab. Those eggs were incubated and blood samples collected before releasing the hatchlings. Overall, therefore, substantial progress was made on all major objectives.
Impacts
Agricultural landscapes are characterized by both decreases in the area of original habitat and fragmentation of the original habitat that remains. Preserving biodiversity in natural habitats within agricultural ecosystems requires an understanding of how individual species respond to habitat reduction and fragmentation and how those responses affect their interactions with other species. There is abundant evidence documenting the decline of forest birds in fragmented forests, and increased nest predation is often implicated as a proximate cause of the decline. Snakes are the most important avian nest predators in forests in the Midwest, and the snakes' preference for edge habitats may increase their impact on birds nesting in fragmented forests. By determining how black rat snakes respond to habitat fragmentation and how this affects nest predation of breeding birds, it will be possible to assess the impact of potential habitat management practices on the abundance
and distribution of snakes, and thus on nesting birds.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Last year the Cache River Natural Area in southern Illinois was selected as the study site for this work, and Gerardo Carfagno was recruited as the Ph.D. student to lead the field work. Data collection for this project was initiated in 2002. The goals this year were to capture black rat snakes and implant radio transmitters in them, radio track the snakes through the active season, and to begin quantifying the habitat used by the snakes. Substantial progress toward meeting all these goals was realized. Eleven snakes were captured that were large enough to carry a transmitter. Transmitters were surgically implanted in each of these snakes between May 15th and September 2nd. Snakes were located every 48 hours through the summer, and twice a week beginning in September. Two snakes were lost during the summer, either due to transmitter failure or because the snakes were taken by predators and removed from the study area. A third snake suffered from a chronic infection
following surgery, which eventually required that the transmitter be removed. The remaining 8 individuals will be tracked until they go underground to hibernate, which should occur in October. Tracking has yielded approximately 350 snake locations thus far. Habitat variables have been quantified at every second new snake location (approximately 80 thus far), and at randomly selected locations (approximately 40 thus far). Four females were captured while gravid and laid eggs in the lab. Those eggs were incubated and blood samples collected before releasing the hatchlings.
Impacts
Agricultural landscapes are characterized by both decreases in the area of original habitat and fragmentation of the original habitat that remains. Preserving biodiversity in natural habitats within agricultural ecosystems requires an understanding of how individual species respond to habitat reduction and fragmentation and how those responses affect their interactions with other species. There is abundant evidence documenting the decline of forest birds in fragmented forests, and increased nest predation is often implicated as a proximate cause of the decline. Black rat snakes may be the most important species of avian nest predator in forests in the Midwest, and the snakes' preference for edge habitats may increase their impact on birds nesting in fragmented forests. By determining how black rat snakes respond to habitat fragmentation and how this affects nest predation of breeding birds, it will be possible to assess the impact of potential habitat management
practices on the abundance and distribution of black rat snakes, and thus on nesting birds.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
The study site for this project has been selected. After visiting a number of potential sites in southern Illinois, the Cache River drainage was chosen. Past research on nesting birds at this site confirms that rat snakes are abundant and an important nest predator. In addition, the habitat at the site is a mixture of mature upland and bottomland forest, interspersed with both natural and man-made edges. The man-made edges are the boundaries between agricultural fields and forest. Forest restoration is underway in some of those fields. As a consequence, the study site contains a rich variety of the habitat types required for this study. A potential field station at the site has been identified and steps are being taken to make that facility available to support this research. A PhD student (Geraldo Carfagno) has been recruited to undertake this research. He is currently in his first semester at U of I. However, he was given the opportunity to participate in an ongoing
snake study last summer, which provided him with valuable experience relevant to the work he will be undertaking. Beginning in March 2002, snakes will be captured at the study site and transmitters will be implanted. At that point data collection will begin.
Impacts
The results from this study will be used to develop guidelines for the management of forests that exist in agricultural landscapes. By knowing how the structure of the boundary between forests and agricultural fields affects the ecological relationship between birds that nest in the forest and their snake predators, potential ways of influencing that relationship can be identified.
Publications
- No publications reported this period
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