|Henry Campa III|
|Professor of Wildlife Ecology, Michigan State University|
|Sistrurus catenatus catenatus Movement and Habitat Use Within a Managed Preserve in Southwestern Lower Michigan.|
|Location: Barry County, Michigan, USA|
|Species: Eastern massasauga rattlesnake (Sistrurus catenatus catenatus)|
|Abstract: Michigan is considered the last stronghold for the eastern massasauga rattlesnake (EMR, Sistrurus catenatus catenatus), where it is a species of Special Concern. Recent research has focused on the movements and habitat use of EMRs in southwestern Michigan. However, the direct effects of habitat management practices (i.e. prairie burning and invasive vegetation removal) on EMR movement, habitat use, and survival have not been thoroughly studied. This project proposes research to quantify the movement and habitat use patterns of EMRs within areas planned for management in 2007 and the change in vegetation structure and composition in those areas at Pierce Cedar Creek Institute (PCCI) in Barry County, Michigan. Results of this study will provide baseline data for research on the effects of habitat management practices in 2007 and will allow researchers to guide management practices at PCCI to minimize negative impacts on EMRs.|
Project Report: August 2007
The purpose of this project was to provide baseline data on habitat use and movement patterns of Eastern Massasauga Rattlesnakes (EMRs, Sistrurus catenatus catenatus) known to frequent vegetation stands planned for management (i.e. prairie burning and invasive vegetation removal) on privately managed property in southwestern lower Michigan in 2007. Specific objectives for the project were to: (1) quantify movement and habitat use patterns of EMRs known to use vegetation stands that will be burned and/or managed for invasive vegetation in 2007, (2) quantify vegetation structure and composition within areas planned for management as well as stands used by EMRs throughout the remaining portion of the active season, (3) quantify survival of EMRs known to use areas planned for management, (4) develop suggestions for carrying out management techniques to minimize negative impacts to EMRs and similar species in the stands planned for management, and (5) distribute project results to the public on the potential influences of habitat management practices on EMRs.
Upon receipt of a small grant from Cleveland Metroparks Zoo, researchers arranged a meeting with the director and staff of the Pierce Cedar Creek Institute for Ecological Education (PCCI) in Hastings, Michigan. Also attending the meeting were representatives of the Michigan Department of Natural Resources (MDNR) Wildlife Division. Meeting attendees reiterated that conservation of the EMR is a priority on PCCI property. Current and proposed vegetation management techniques were discussed for potential EMR habitat at PCCI. The main concern among attendees was the effects of burning on restored prairie vegetation on EMRs using those fields. Therefore, researchers agreed to focus research efforts on upland fields scheduled for burning in spring of 2007.
Researchers began searching the proposed burn areas for EMRs in early July 2006 (Figure 1). EMRs that were going to be included in the study had to have surgeries completed by the first week of August, so researchers had one month to find EMRs to radio-track. Researchers found 2 male EMRs in restored prairie areas surrounding the PCCI Visitor’s and Educations Centers (Figure 2). One of the EMRs (EMR #1) had been radio-tracked in a previous study at PCCI, so background data were available on the previous movement and habitat use patterns of the snake. Unfortunately, no additional EMRs were found in the area during the 2006 activity season.
Researcher hours were limited; however, radio-tracking took place on a weekly basis until mid-September 2006. Home range sizes for EMRs were estimated using the minimum convex polygon (MCP) method, calculated with the animal movement program (Hooge et al. 1999) in ArcView 3.2 GIS (Figure 3). The MCP method was considered to be more appropriate for the data set because limited location points for each snake would have resulted in an exaggerated home range size if the fixed kernel method was used. The home range sizes were 10.1 ha (EMR #1) and 5.3 ha (EMR #2). Site fidelity was evident for the EMR that was previously radio-tracked in 2005, 67% of the 2006 MCP fell within the 2005 MCP.
Several vegetation attributes were measured in the grasslands used by EMRs in 2006; however, only 4 attributes were available within sample plots and transects (Table 1). Plots where EMRs were present had slightly more (i.e., than adjacent paired sampling areas) dead herbaceous material available, which seems to be an important habitat component to EMRs on PCCI property (Bissell 2006). EMR locations also seemed to have slightly less live herbaceous vegetation; structure which possibly allows for more basking opportunity and may be highly suitable for EMRs at PCCI (Bissell 2006). Tree and shrub densities and absolute dominance in the restored prairie areas were so low that they were not encountered in vegetation sampling plots. It is apparent that these early successional areas were providing suitable habitat for the EMRs for at least a large portion (July-September) of the activity season (April-October).
EMRs moved towards the edges of the upland grasslands, closer to bordering wetland vegetation types in early September. EMR #1 was radio-tracked towards a hibernaculum in a mid-late successional vegetation type, where he had previously hibernated. EMR #2 selected a hibernaculum within the grassland complex studied; however, was on the edge (within 10 m) of a wetland area.
Although sample sizes were low, this continued research has some implications for management. It is clear that the restored prairie areas at PCCI are providing suitable habitat for EMRs during at least part of their activity season. The two male EMRs covered fairly large areas and remained within the grass uplands throughout mid-summer; and there may be a large presence of EMRs in these areas that are actively managed (burning as well as mowing). Also, this study and previous research (Bissell 2006) indicates that there is fairly strong site fidelity, so it can be expected that areas heavily used by an EMR in one year will most likely be used the next. Therefore, it is very important to consider the effects of management practices on EMRs in these areas and minimize the negative impacts (i.e., by considering the type and timing of the habitat manipulations). However, it seems that EMRs are hibernating on the transitional zones between these upland areas, or in another vegetation type altogether, so managers may be able to conduct burns while many EMRs are near hibernacula on the upland edge or in a different habitat type (i.e., in early spring). The importance of these early successional uplands to EMRs is evident, so management practices should be implemented to maintain the suitability of these areas. A female EMR previously tracked in 2004 and 2005 was re-captured and tracked in 2006, as well. The female was not found in the area proposed for management; however still within the study area, and ultrasounds and radiographs of the snake confirmed that she was gravid for a third consecutive year. The parturition site was the same site used by the snake in 2004. The parturition site-fidelity of females and the potential for annual reproduction in EMRs in Michigan will have implications for management of the species, as well.
Biologists and land managers in Michigan are concerned that management practices will negatively impact the EMR population by increasing mortality or potentially disrupting habitat use and movement patterns. Continued research on the effects of management practices on EMRs in Michigan is necessary to address these issues and this study has established a baseline to build from in our efforts to research these questions. We hope to continue radio-tracking and monitoring EMR movements, habitat use, and survival at PCCI prior to and after management practices are implemented in 2007. We will continue to work with PCCI, MDNR, and Lansing Potter Park Zoo to design and conduct research projects to improve our understanding of EMR ecology and increase the knowledge base of the species so that we can better conserve their populations through the use of sound management practices and education and outreach.
Although everyone has a different opinion of rattlesnakes, they all want to know more. I recently gave a presentation on the EMR research at PCCI that was 45 minutes long and filled with general, natural history, information, as well as research data and results. I was worried that it would be too boring for the public (too many graphs and numbers). As I was giving the presentation and moving into the "numbers" section of the talk, I was thrilled to see that everyone in the audience was listening intently, following along with the charts and diagrams, interested in every aspect of EMR research. Afterwards, I was pleasantly surprised with over an hour of questions and comments. It is obvious that there are many more unanswered questions among laypeople and researchers alike. Education is integral to the promotion of "living with Massasaugas." The opportunity to be involved in creating awareness of EMRs and their conservation needs by collaborating with invaluable partners from diverse organizations and developing posters, giving seminars, and participating in public workshops has been immensely rewarding. When I first became interested in EMR conservation I posed the question to myself: "how do you conserve a species that everyone hates?" The answer is education. Continued research and communication of the results to the public and fellow professionals in the field of wildlife conservation and management will strengthen the foundation for the conservation EMR populations.
Information from this project will be shared with natural resources researchers and managers at the 2007 Annual Wildlife Society Conference.