Due in part to its secretive nature, the bog turtle was not discovered in Maryland until 1941 (McCauley and Mansueti, 1943). Presently, Maryland contains roughly one-third of all recorded bog turtle sites, but nearly half of these have been lost in the last twenty years (Lee and Norden, 1996).
Habitat restoration efforts to date have consisted almost exclusively of fencing sites to control grazing and of removing undesirable invasive vegetation. Prior to the completion of The Baltimore Zoo’s bog exhibit (Wisnieski and Poole, 1999), no attempts had been made to restore sites that were excavated to create ponds (Scott Smith, personal communication).
Therefore this exhibit serves as a blueprint for restoration efforts in situ. It also enables us to educate over 600,000 visitors, most of whom reside within the bog turtle’s range, about the plight of this disappearing species, the importance of its habitat, and the actions that can be taken to make a difference (Fig. 1).
Figure 1. A young girl rides a human-sized bog turtle at the Baltimore Zoo.
A spring-fed pond, which was the first exhibit in the Lyn P. Meyerhoff Maryland Wilderness section of the zoo, was the site of the restoration. The theme of the Maryland Wilderness area is “a walk across Maryland,” with a series of immersion exhibits depicting various Maryland habitats and displaying associated wildlife and plant species. Educational signage emphasizes the importance of protecting the Chesapeake Bay watershed.
The restoration of the site began in October 1997. The adjacent woodland was cleared to provide an open, sunny area, critical to the bog turtle and the plant species in a wet sedge meadow habitat. A Grade-All machine was brought in to reshape the topography, with the goal of creating the largest possible wetland footprint. The difference in elevation between the upper section where the pond was located and the lower extremes of the wetland area necessitated the creation of two distinct wet sedge meadows with a connecting stream corridor. Dams, consisting of smooth, flat river stones, were placed at the bottom of each separate wetland and provided a means of adjusting the water levels.
The pond was drained and the pump was left running in the deepest section (Fig. 2). Invasive parrot feather (Myriophyllum aquaticum) and saturated soil were removed by the Grade-All. Once excavation to the natural clay layer was completed, PVC pipes were driven into the locations with the greatest spring flow. The purpose of the pipes was to ensure a path for the spring water to reach the surface. The former pond area was then filled to the desired elevation with pea gravel and covered with filter cloth (Fig.3). Suitable wetland soil donated by the Maryland State Highway Administration and the previously removed saturated soil were used to fill in the remainder of the pond site. The pipes were then filled with large pieces of crushed rock which allowed water to flow, but eliminated potential death traps for the turtles.
Figure 2. The spring-fed pond is drained.
Figure 3. Pea gravel being added.
The lower section of the wetland had previously consisted of a small stream approximately 0.6 m (2 ft) wide that drained the pond and of an additional spring seep. A shallow basin was excavated using the Grade-All and then wetland soil was added (Fig. 4).
Figure 4. An overview of the two wetland sections and the interconnecting stream.
Though both sections now held water, we still had not managed to achieve the proper consistency in the saturated soil, or muck layer, which defines these wet sedge meadow habitats. Michigan peat was pumped into the two sites until they had the correct “feel” of wading through a wetlands.
Planting the Bog
Selecting the appropriate plant species in the proper proportions was critical to the restoration. A plant list was generated utilizing data collected on plant communities in Maryland bog turtle habitats. The most numerous species planted included tussock sedge (Carex stricta), arrowhead (Saggitaria latifolia), marsh fern (Thelypteris palustris), monkey flower (Mimulus rungens), turtlehead (Chelone glabra), and swamp milkweed (Asclepias incarnata). All plants were purchased from a nursery that specializes in cultivating native plant species.
Staff from the zoo, Maryland Department of Natural Resources (DNR), Maryland Department of the Environment (MDE), Sylva Native Nursery, middle school students and teachers participated in planting the wetland in May of 1998. Equal proportions of Michigan peat and topsoil were deposited in the deeper sections to create surface level mounds for the plants. Tussock sedge, the most abundant species, was the first to be planted (Fig.5). These were used to break-up the sheet flow into the rivulets of water typical of these habitats. Color-coded signs with the names of specific plants indicated where they should be planted.
Figure 5. Tussock sedge being planted.
A bog turtle was maintained on-site and impromptu presentations and question and answer sessions were provided for the crowds of inquisitive visitors that would stop along the boardwalk.
Presentations were also provided for the students during lunch and informal teaching was on going throughout the planting phase. Through their hands-on participation in this project, the students gained an appreciation for the importance of these wetland habitats that would be difficult to instill in a traditional classroom setting (Fig.6).
Figure 6. A middle school student takes a break after helping plant the restored bog for this little bog turtle.
The plant community is continuously monitored and any undesirable invasives are eliminated.
To contain the turtles, a plastic-coated hardware cloth fence buried to a depth of 30 cm (1 ft) encloses the exhibit. The installation of the final fence sections did not occur until July of 1999, which allowed time for native wildlife species to colonize the area. Faunal components of in situ sites, such as meadow voles (Microtus pennsylvanticus), green frogs (Rana clamitans melanota), Southern leopard frogs (Rana utricularia), American toads (Bufo americanus), Eastern garter snakes (Thamnophis s. sirtalis), Northern water snakes (Nerodia s. sipedon), as well as numerous species of birds and invertebrates, have all been observed in our restored wetland.
Potential bog turtle predators, such as raccoons (Procyon lotor) are kept out of the area through the use of hot wires which surround the site.
The bog exhibit also serves as an on-grounds study site. A primary goal of this project is to gather data that will benefit in situ restoration efforts. In collaboration with Towson University, a habitat utilization study is being conducted. Transmitters attached to three male and six female bog turtles and the same number of spotted turtles (Clemmys guttata) which share the exhibit, enable us to track the turtles’ movements and also to monitor their temperatures remotely. This data will be compared to data from ongoing studies in situ being conducted by biologists from Frostburg State University, as well as to previous studies (Chase, et al., 1989; Lovich, J.E., et al., 1992; Carter, et al., 1999; Morrow, et al., 2001; Behler, unpub. data; Stine, unpub. data).
DNA fingerprinting will provide a means of determining (and comparing) the degree of inter-relatedness in both the zoo’s captive bog turtle population and the population from which they were collected, as well as the parentage of any offspring produced. This is part of a larger study conducted in conjunction with the DNR and Frostburg State University, which involves DNA fingerprinting and disease screening of a minimum of ten bog turtles from each Maryland watershed from which they are known. Zoo staff also continue their involvement in DNR’s long-term bog turtle population and habitat assessment surveys.
Other species of reptiles, amphibians, mammals, birds, and invertebrates that have colonized or frequented our bog are also being monitored through periodic trapping and direct field observation, and these data will be compared to data on wild populations. Since the number of plant species and their locations within the site are known, data will be gathered on their survivability and on the presence of opportunistic invasives.
One of the greatest challenges presented by this exhibit was its interpretation. How does one capture the public’s interest when they cannot see the bog turtles?
All educational elements were designed to ensure that the exhibit’s conservation message appeals to all age groups. While some of the graphics are written for adults, parallel signs mounted directly below target children, with the help of an illustrated character named “Billy Bog Turtle.” Each sign station, therefore, provides a family-oriented educational experience which begins on the lower observation deck and continues along the boardwalk. The lower deck is also used for Keeper Encounter presentations where staff demonstrate the use of telemetry equipment.
On each deck children are greeted by a realistic fiberglass model bog turtle measuring 1.65 m (5.5 ft) in length upon which they can climb. The model turtles are surrounded with planters containing maiden grass (Miscanthus sinensis) which resembles giant tussock sedges. Together with the giant models, these create an environment where children are the same size as the turtles.
Both decks and an adjacent swinging bridge are coated with spongy rubber (Vitriturf ®) to simulate the sensation of walking in a bog.
Additionally, the Baltimore Zoo has collaborated with other organizations on the following bog turtle conservation education projects: 1) Producing an educational brochure on Maryland’s bog turtles [DNR/MDE/National Aquarium in Baltimore (NAIB)/USFWS]; 2) Organizing a land-owners forum at a local community college to explain the importance of these disappearing wetlands to the people who own the majority of them and to disseminate information on state and federal tax incentive/conservation easement programs and funding sources for habitat restoration (DNR/MDE/NAIB/USFWS); 3) Conducting a workshop on bog turtle conservation targeting local, state, and federal planning and regulatory agencies, conservation/education organizations, and private consultants that may be effected by the bog turtle’s recent classification as a federally threatened species. Field trips to pristine and impacted bog turtle habitats and a comprehensive resource guide were provided (DNR/Maryland Herpetological Society/MARS Preservation Fund/NAIB).
DNR and MDE allocated wetland mitigation funds for this project. Additional funding, materials, and services were provided by the Maryland Conservation Corps, the Maryland State Highway Administration, Defenders of Wildlife, Concrete General, Inc., the Mid-Atlantic Turtle and Tortoise Society, Daniel G. Schuster, Inc., students and teachers from Parkville Middle School, and private donors. The total value of these contributions is approximately $75,000.
The Baltimore Zoo was also awarded a $30,000 grant for educational graphics by the Chesapeake Bay Trust, as well as a $1,000 award from The Tortoise Reserve, Inc. (TTR) for its innovative chelonian educational program. For the exhibit, TTR also provided the nine bog turtles, which were legally collected from a known Maryland locality in the early 1990s.
Through the commitment of all of the partner organizations involved, the wetland restoration project at the Baltimore Zoo has accomplished all of its initial objectives. We now have a beautiful wet sedge meadow exhibit for our turtles and other wildlife, complete with immersive and interactive elements and educational messages consistent with our other Maryland Wilderness exhibits. Most importantly, we also have an on-grounds study site, which provides data that will be extremely valuable to in situ restoration efforts.
In considering everything we have learned from this project, the one fact that stands out above the rest is that restoring a wetland is much more difficult and expensive than protecting one.
The authors would like to express their appreciation to the following individuals for their help in making this project a reality: George Beston, Don Forester, Alexis Grant, Dave Lee, Kevin Smith, Scott Smith, and Herman Twining. Additional thanks go out to all Baltimore Zoo staff who have been involved in this project and to all of the organizations previously mentioned in this paper who have provided funding, materials, and services. Thanks to Heather Kalb for assistance with this article. Finally, we would thank our Executive Director, Roger Birkel, for supporting an exhibit for nine tiny turtles that few visitors will ever see!
Carter, S.H., C.A. Haas and J.C. Mitchell. 1999. Home range and habitat selection of the bog turtles in southwestern Virginia. Journal of Wildlife Management 63(3):853-860.
Chase, J.D., K.R. Dixon, J.E. Gates, D. Jacobs and G.J. Taylor. 1989. Habitat characteristics, population size, and home range of the bog turtle, Clemmys muhlenbergii, in Maryland. Journal of Herpetology. 23:356-362.
Ernst, C.H., J.E. Lovich and R.W. Barbour. 1994. Turtles of the United States and Canada. Smithsonian Institution Press, Washington, D.C. 578 pp.
Lee, D.S. and A.W. Norden. 1996. The distribution, ecology, and conservation needs of bog turtles, with special emphasis on Maryland. Maryland Naturalist 40:1-46.
Lovich, J.E., D.W. Herman and K.M. Fahey. 1992. Seasonal activity and movements of turtles (Clemmys muhlenbergii) in North Carolina. Copeia 1992:1107-1111.
McCauley, R. and R. Mansueti. 1943. Clemmys muhlenbergii in Maryland. Copeia 3:197.
Morrow, J.L., J.H. Howard, S.A. Smith and D.K. Poppel. 2001. Home range and movements of the bog turtle (Clemmys muhlenbergii) in Maryland. Journal of Herp 35 (1):68-73.
Wisnieski, A. and V.A. Poole. 1999. Creating a bog: An on-site wetland restoration project at The Baltimore Zoo. In: Proc. of AZA 1999 Annual Conference, Minneapolis, Minnesota. Pp. 171-176.