Snapping Turtle Monitoring Program Guide

Transcription

1 Snapping Turtle Monitoring Program Guide

2 Table of Contents 1.0 The Snapping Turtle Description Distribution and Habitat Status and Threats Reproduction and Nesting Niagara-on-the-Lake Nesting Site Site Preparation Test Holes Identification of a Nest Site Construction Site Preparation for Artificial Nesting Area Simple Wire Cage Set Up Wire Cage Construction Electric Fence Set Up Testing of Electric Fence Monitoring Maintenance and Requirements Health and Safety References Appendices Appendix A: Maps Appendix B: Example photographs of nest cages Appendix C: Monitoring Form Template... 16

3 1.0 The Snapping Turtle 1.1 Description The common snapping turtle (Chelydra serpentina) is a large freshwater species of turtle that is found across North America. Snapping turtles typically possess a long tail with triangular scales. On top is a ridged carapace or upper shell with three keels. Snapping turtles are commonly brown or olive in colour. On average, they can reach a length of cm and weight of kg (Government of Ontario, 2015). They have large heads, with a hooked upper jaw, and relatively long necks. Skin colour ranges from tan to grey to black to reddish-brown (Government of Canada, 2017). Snapping turtles tend to be aggressive as a defense mechanism, as they lack the ability to retract into their shells and are not very good swimmers. They use their capability to snap if they feel threatened, as an attempt to scare off their predator. Their diet consists primarily of plants, molluscs, insects, small fish, and frogs (Government of Canada, 2017). 1.2 Distribution and Habitat The natural distribution of the species extends between the Rocky Mountains and Nova Scotia; however, the population density is highest in Southern Ontario as seen in Figure 1 of Appendix A. The Canadian population size is estimated to be in the thousands, though the exact figures are unknown. Snapping turtles spend the majority of their lifespan inhabiting shallow freshwaters, where they have the ability to camouflage from potential predators under soft sediment and vegetation. Populations are commonly established in ponds, shallow bays, lagoons and slow streams (Government of Canada, 2017). They can also be found in urbanized waterways, but the population would not be able to persist long term without proper nesting sites. 1.3 Status and Threats As of 2017, the snapping turtle is listed with a status of special concern in Ontario. This indicates that the species is not currently endangered, but has the potential to become endangered given existing threats. Illegal harvesting and road mortality are the primary causes of premature adult death, which is devastating to the population as female turtles shells (carapace) must be at least 8 inches before they can mate (Department of Energy & Environmental Protection, 2013). This typically takes 15 to 20 years (Government of Canada, 2017). Adult snapping turtles are not as vulnerable to predation as those in eggs and hatchling stages (Government of Canada, 2017). Long-term threats to species endangerment include ongoing destruction of habitat and decreased reproductive success due to environmental contamination (Government of Canada, 2017). Predation from coyotes, racoons, foxes, skunks and opossums, are a common threat to turtle nests and these predators are all present in the Niagara Region, and have known to cause decreases in the success rate of yearly reproductive events.

4 1.4 Reproduction and Nesting In Canada, mating occurs in early spring, and nesting occurs late May to late June. Female snapping turtles nesting locations are generally along the banks of waterways. The females will lay a clutch of approximately 40 eggs in a nest. The nests are excavated into the sediment, preferably loose sands, prior to laying the eggs. Incubation period lasts for approximately 75 to 95 days, although external environmental conditions, such as temperature, may cause variations (Department of Energy & Environmental Protection, 2013). Incubation temperature determines the sex of turtle hatchlings, as eggs incubated at 68 F produce female hatchlings; eggs maintained at F produce both male and female turtle hatchlings; and those incubated at F produce only male hatchlings (Department of Energy & Environmental Protection, 2013). Once hatched, snapping turtles move towards the water where they can better protect themselves from predators by burying themselves under vegetation and debris. 2.0 Niagara-on-the-Lake Nesting Site The Niagara College Niagara-on-the-Lake campus includes two large lagoons, connected to the 6-mile creek system. The wetland is located at the bottom of the Niagara Escarpment, and the land is classified as a UNESCO-designed World Biosphere Reserve. The lagoons were constructed in 1965 with the purpose of wastewater treatment, but have been neutralized since 1997 (Smith, 2008). Throughout the years, Ecosystem Restoration students have remediated the land to create an ideal habitat for species such as turtles, frogs and other aquatic species. In 2007, an Artificial Nesting Area (ANA), more commonly called the turtle nesting beaches, was constructed between the North and South Lagoons as seen in Figure 2 of Appendix A. Snapping turtle females lay their eggs into shallow pits along the lagoons. Female snapping turtles have been known to travel great distances to lay their eggs, so it is critical to monitor all suitable areas located across the property as well as the turtle beaches. A noticeable decline in survival rate of the snapping turtle hatchlings over subsequent years resulted in the decision to create a monitoring protocol that could be used in order to protect eggs from predation. A monitoring study conducted by Environmental Restoration students of Niagara College discovered that the principal predator responsible for causing declining populations was the coyote. It has been determined through several studies that the ANA in combination with an electric fence and daily daytime monitoring is the most effective and feasible method to ensure the protection the eggs from predation. 2.1 Site Preparation In order to create an appealing nesting area for the snapping turtles, clearing of the ANA (i.e. site between North and South Lagoons) is crucial. Phragmites and other pond plants overtake the nesting beaches and make the sand difficult to dig in so clearing the area creates an open space for the turtles to lay their eggs, and also increases the probability that they will nest in an area easily accessible for protection protocols to be executed. The steps required for site preparation are described in section 3.1 of the protocol.

5 2.2 Test Holes Test holes are small pits that are dug up by snapping turtles seeking a nesting area. They can be identified by looking for disturbed soil which may have some shallow excavation. Once these areas are identified, it is critical to continually monitor as there is always potential for actual laying of the eggs to occur. 2.3 Identification of a Nest If a nest is located, action should be taken immediately to protect the eggs as they are extremely susceptible to predation. The eggs should not be touched or handled as disturbance or reorientation of the eggs can easily result in mortality or cease development. 3.0 Site Construction There are two main options for courses of action to be taken, depending on available resources. The electric cage has been quite successful in the past, but a standard wire cage may also be effective and constructed in a shorter amount of time, requiring significantly less materials. The electric fence may be more suitable for protection of a larger nesting area, where as a metal cage set up, is more efficient for a single nest that requires immediate protection and is located in a more isolated area. 3.1 Site Preparation for Artificial Nesting Area Equipment: Gloves Shovel Hoe Metal rake Hedge Clippers Foliage is to be cleared in order to increase chances of nesting in the ANA between the North and South lagoons. The following method describes site preparation guidelines: 1. Cut down large branches and tall vegetation impeding on the site using the hedge clippers. 2. Use the hoe and shovel to turn over sediment, and uproot any small vegetation in the area. 3. Using the shovel, dig deeper to turn over and loosen the sediment. 4. The rake can then be used to level out the area, and additionally remove any debris that is resting on top of the sediment. 5. The removed vegetation can be distributed into areas along the lagoon to decompose.

6 3.2 Simple Wire Cage Set Up This strategy is best suited for when immediate protection of a small nesting site is required as it uses the least amount of materials and can be set up relatively quickly. It should not be used as a long-term protection solution. See Figure 3 in Appendix B. Equipment: Gloves Eye protection Chicken wire Wooden Stakes Zip ties Methodology: 1. Wear gloves and protective safety glasses prior to commencing the installation process. 2. Secure chicken wire into a dome shape cage (see Figure 3 in Appendix B) 3. Dig a trench around the nest and place the cage in the trench 4. Secure the cage to wooden stakes using zip ties and hammer the stakes into the ground 5. Fill in the trench to secure the wire cage underground 3.3 Wire Cage Construction This structure is effective for long term protection of smaller or individual nests. Equipment: Gloves Eye protection Chicken wire Pounder/hammer Wood/Lumber Nails Zip ties Cement bricks Methodology: 1. Wear gloves and protective safety glasses prior to commencing the installation process.

7 2. Take longer pieces of lumber and attach them with nails in a rectangular shape large enough to cover the area of the nest (see Figure 4 in Appendix B). 3. Attach additional pieces of wood to the square in a perpendicular fashion (to look like table legs). 4. Cover the wood structure with chicken wire, and secure it to the frame with zip ties (see Figure 5 in Appendix B). 5. Dig a trench where the wire will go into the ground 6. Place the structure over the nest, and hammer it into the soil until it is sturdy, filling in the trench to secure the wire cage underground 7. Place cement bricks along the bottom of circumference of the cage as to prevent anything from the ability to crawl under the wiring (see Figure 6 in Appendix B). 3.4 Electric Fence Set Up This strategy is best suited to protect larger nesting areas, specifically the ANA between the North and South Lagoon, but may be tailored to other sites. Equipment: Eye protection Gloves T-bars Protective case Electric fence wire Zip ties Hammer/mallet Safety sign Snow fencing Hip waders Insulation clips Gallagher Manual, V Gallagher battery Wire cutters Lock Methodology (Kalenuik & Mckillop, 2016): 1. Wear gloves and safety glasses prior to commencing the installation process. 2. Place the T-bars at uniform lengths, then stand the T-bars straight up and use the mallet or hammer to drive the T-bars into the ground. Check to ensure that they are securely imbedded within the sediment. If installing T-bars in the water, then hip waders may be necessary. *Save 2 T- bars for later use.

8 3. Place 3 insulator clips on every T-bar using a zip tie under the clips to fasten the hold if necessary. 4. Thread the electric fence wire through the insulator clips going back and forth in order to essentially create a barrier. Once the stringing of the wire is completed, cut the excess wire off, and tie the end of the wire to the last insulator clip. 5. Install the 2 T-bars at the entrance of the path on either side. Zip tie the snow fencing against the 2 T-bars. 6. Place a safety sign at the entrance to secure the habitat from tampering and safety of others. 7. When connecting the battery, connect the green alligator clip to the ground, and the red clip to the wire. Lock the casing to protect the battery. *Refer to the Gallagher manual for more detailed instructions on how to set up the battery. 8. Remove any visible signs of human disturbance (i.e. footprints) from the area with a rake. 3.5 Testing of Electric Fence Equipment: Activated electric fence Rake Chicken eggs Methodology (Kalenuik & Mckillop, 2016): *Note: The electric fence should be turned off prior to the commencement of the subsequent procedure! 1. Using a rake, level out the sediment in order to later identify predator footprints. 2. Excavate shallow hole to place chicken eggs. 3. Turn on the electric fence and leave the site overnight. 4. The following day, come and inspect the eggs. Record any observations and make the necessary adjustments. The testing period should take approximately 3 days to a week, or until the nesting area is deemed sufficient for protection of the eggs from predators. 4.0 Monitoring Maintenance and Requirements Monitoring potential nesting areas should be continuous and conducted on a daily basis prior to the installation of the ANA in order to locate potential nesting areas. The key identifier to the presence of nesting turtles are test holes. Test holes generally appear as small pits dug into loosened soil, additionally

9 disturbed soil may also be an indication that turtles have been present on the site looking for a location to nest. After the preparation of the ANA, daily monitoring is required so that the nests can be located and permanently protected with a cage and continuously monitored. A monitoring schedule should be established, and students/faculty should be assigned to specific shifts. Monitoring should be ongoing throughout the nesting period (mid-may to mid-june) and this includes weekdays and weekends in order to maximize survival rate of eggs and hatchlings. Daytime Monitoring: 30 minutes at 8 am 30 minutes at 4 pm The cages remain on-site until the eggs hatch which occurs after approximately days from the time of laying (August or September). Attached, in Appendix C, is a template nesting habitat maintenance and monitoring form, which can be utilized by volunteers in order to track and record progress over the course of the nesting season. 5.0 Health and Safety When interacting with species such as the snapping turtle, it is important not to attempt to handle the species, as they can be aggressive, especially since they may perceive you as a threat. Keeping your distance also avoids disturbing the species. If they do not consider the nesting area to be safe, then they will not lay their eggs, resulting in potential off site nesting, where they will not undergo continual monitoring.

10 6.0 References Department of Energy & Environmental Protection. (2013). Common snapping turtle: Chelydra s. serpentina. Retrieved , from Google Maps. (2017). Google Maps. Retrieved 2017, from Google Maps: Government of Canada. (2017). Species Profile (Snapping Turtle). Retrieved 05 22, 2017, from Species at Risk Public Registry: Government of Ontario. (2015). Snapping turtle. Retrieved 05 22, 2017, from Kalenuik, V., & Mckillop, A. (2016). Electric enclosure for the common Snapping Turtle nesting habitat at Niagara College NOTL Campus Lagoons. Smith, M. (2008). Design, construction and monitoring of a successful snapping turtle (Chelydra serpentine) nesting habitat site in Niagara College s on-campus wetland, Niagara-On-The-Lake, Ontario. Retrieved , from Toronto Zoo:

11 7.0 Appendices Appendix A: Maps Figure 1. Population density of snapping turtles in Southern Ontario (Government of Ontario, 2015).

12 Figure 2. Map of NOTL campus, including the North and South Lagoons, along which the snapping turtles nest (Google Maps, 2017).

13 Appendix B: Example photographs of nest cages Figure 3. Simple wire fence cage for immediate protection of an individual nest. Figure 4. Wooden frame for nest.

14 Figure 5. The metal wiring secured by zip ties to the wooden frame.

15 Figure 6. Final cage as seen, protected along the bottom circumference by cement bricks.

16 Appendix C: Monitoring Form Template