Road Mortality Mitigation

 

Beaver Ponds; K. Ovaska Photo

Fencing & Passages

 

Turtles can be exposed to road kill during migrations to and from wetlands and nesting areas on land or when moving among wetlands. Mortality of adult females, in particular, can be devastating to turtle populations that rely on high adult survival for their persistence (add ref). Situations where a nesting area is located across a busy road from water bodies are particularly hazardous. Several technics exist to mitigate road mortality of turtles. Underpasses with drift fences that direct turtles to the passages are suitable for identified migration corridors and well-defined problem areas. In some cases, permanent fencing along the road together with enhancing or creating a nesting area on the wetland side are appropriate. The problem with this method is that turtles can be persistent in attempting to reach tradional nesting areas, and fences have to be long and completely turtle-proof.

Turtles are wary of passages that are dark and of small diameter. These problems can be overcome by using large-diameter culverts or other structures and adding light for longer tunnels. Turtles are known to use square culverts with dimensions of 180 by 180 cm (6x 6 feet) as passageways to cross roads[1]. CARCNET website (http://www.carcnet.ca/english/tunnels/spotted_turtle_tunnel.php) describes a case where a tunnel equiped with a grate to let in light was used to create a safe passage for the Spotted Turtle. Similar specialized underpasses have been used with success for amphibians, and many designs are available (see http://www.carcnet.ca/english/tunnels/amph_tunnels.php). Any installed structures need to be monitored for their effectiveness for turtles. See http://www.icoet.net/ICOET_2011/documents/posters/CRB-P71-DYorks-Poster-ICOET2011.pdf for experiments testing various tunnel designs for freshwater turtles.

Signage

 

Interpretive signs placed in strategic locations in turtle habitat function to increase the public' awareness of turtles and threats to populations and habitat. These signs are particularly useful in parks, beaches, and other recreational sites where turtles occupy wetlands or nest on swimming beaches, in camp sites, or in picnic areas.

Road signs that alert drivers to the possible presence of turtles on the road can be useful for preventing road mortality, although their effectiveness is largely untested. Signs are expected to function best on small side roads - other measures, such as fencing and underpasses, are more appropriate for busy roads and highways. Turtles are especially vulnerable to road mortality where roads intercept migration routes between water bodies and nesting areas on land. Although signage may reduce road kill of adults, it is probably ineffective in preventing mortality of hatchlings, which are too small for most drivers to detect. Again, consider other other methods to prevent hatchling road mortality. See additional pages for examples for case studies of road signage.

Other Techniques

Trapping and manually moving turtles across roads is a temporary method that can be deployed to alleviate road kill in problem areas. This method is labour-intensive and suitable as an emergency measure until more permanent measures, such as underpasses, can be put in place. It is also suitable for hatchling turtles in areas where turtles nest on gravel road sides and where nest sites have been identified.

- To keep turtles off the road, install low (about 2' high) drift fencing flush to the ground on the side of the road; either visually monitor the fence or add a turtle trap (to be described) at each end and at periodic intervals; monitor the fence frequently and move turtles across the road by hand as they are found.

- If the locations of road side nests are known (e.g., emerging nests have been identified by developing exit holes), place a box frame (about 2' x 2') with hardware cloth top on the nest; be sure to insert a branch or an equivalent object to provide shade for the emerging hatchlings. Inspect the boxes frequently and transport emerged hatchlings across the road to the nearest suitable water body.Be patient and let the hatchling turtles to dig their own way out.

Case Study 1: Mitigating Road Mortality of the Western Painted Turtle in the Municipality of Saanich: Road Sign Installation in 2010.

Prepared by Christian Engelstoft1, MSc, RPBio, Kristiina Ovaska1, MSc, PhD, Adam Taylor1, and Darren Copley2

1Habitat Acquisition Trust, P.O. Box 8552, Victoria, BC, V8W 3S2
2District of Saanich, 770 Vernon Avenue Victoria BC V8X 2W7

This project is part of broader conservation effort aiming to mitigate threats to endangered Pacific Coast populations of Western Painted Turtle (Chrysemys picta bellii) on Vancouver Island. In an attempt to mitigate road mortality, the District of Saanich in collaboration with Habitat Acquisition Trust, erected two “turtle crossing” signs in an area where mortality had been observed in 2008 and 2009 on Beaver Lake Road. Signs were installed in late March and removed in mid-September 2010. One of the signs had to be replaced because it disappeared soon after its installation. The road and road shoulders between the signs were surveyed for turtles 117 times from March to July 2010, when hatchlings emerge from their nests and females lay their eggs. Over a weekend, a traffic counter was installed for a 5-day period both before and after the signs were erected. In the first period, 1584 vehicles passed the site going an average speed of 34 km/h; the speed of 85% of the vehicles was less than 42 km/h. In the second period, 2089 vehicles passed the site going an average speed of 33 km/h; the speed of 85% of the vehicles was less than 40 km/h. More than 69-75% of the traffic occurred between 10:00 to 16:00.

The slightly lower speed after the installation of the signs did not prevent five Western Painted Turtle hatchlings from being run over on 31 March 2010. A desiccated Western Painted Turtle hatchling was found on the side of the road on 26 April. A newly emerged nest on the shoulder of the road adjacent to the road kill site was located on 31 March, and we assumed that all six hatchlings emerged from this nest as it was the only nest found in the area. No adult females were seen laying eggs and no other signs of nesting were observed along the road. We did observe adult turtles crossing adjacent gravel roads in June and July 2010.


Considering the small size of newly hatched Western Painted Turtles, it is not surprising that motorists did not see the juveniles on the road. A more effective measure for protecting hatchling turtles would be to install a low fence around the nest sites. The enclosure should be monitored daily for hatchlings and, if found, they should be carried to the nearest pond.

The intention of the signs was to prevent adult mortality, and we documented that the majority of the traffic occur during the day time. Generally the Western Painted Turtle females lay their eggs at dusk and dawn, so traffic at this time of day is the greatest threat to them. Drivers that regularly pass the signs would have been alerted to the possibility of encountering turtles on the road and hopefully would have been prepared to avoid a collision. The signs also functioned as outreach tools, informing drivers of the presence of turtles in the area and their vulnerability to road mortality.

We recommend that the signs be reinstalled for the March – July hatching and breeding period in 2011, that motorist be surveyed to find out whether they saw the signs and how it affected their behaviour. We also recommend that the road be monitored for mortality, turtle nests, and that, if emerging nests are found, the nests be protected with an enclosure and hatchlings be carried to the nearby pond.

  1. Kaye DR, Walsh KM, Rulison EL and Ross CC. 2006. Spotted turtle use of a culvert under relocated Route 44 in Carver, Massachusetts. IN: Proceedings of the 2005 International Conference on Ecology and Transportation, Eds. Irwin CL, Garrett P, McDermott KP. Center for Transportation and the Environment, North Carolina State University, Raleigh, NC: pp. 426-432.

 

Nesting Habitat Enhancement

Survey Methods

Female Western Painted Turtles on Vancouver Island usually lay their eggs from late May to late June; sometimes the nesting season extends into early July. Unless you see a turtle in the process of digging a nest or egg-laying, it can be very difficult find nests. One tell-tale sign is a wet patch, such as in the photo below, as the female urinates on the ground during nest construction. The wet patches can be detected after the female has returned to the water, but they will dry up rapidly on sunny days, leaving little evidence of the presence of nests. Look for these signs of nesting from the evening before in the following morning. In areas with several species of turltes, it is not possible to tell the different species apart from the sign only.

WPT wet patch CE

 

In the spring, hatchling turtles emerge, after having over-wintered in the nest, and the oblong or round emergence holes can be used as evidence of nests that have successfully produced young; the emergence holes are about the size of a loonie. The photo below shows an emergence hole, as well as an unhatched, dead egg retrieved from the hole. On Vancouver Island, hatchlings usually emerge from February to May, but the exact timing varies from year to year, depending on environmental conditions.

 WPT emerged hole egg

Swan Lake emerged nest close

Nesting Habitat Enhancement:

 

Shortage of suitable nesting habitat may limit the distribution and viability of Western Painted Turtle populations. Creation, restoration, or enhancement of nesting habitat can be an effective tool to conserve populations. Habitat creation refers to the construction of a nesting ground in a suitable new site, whereas restoration and enhancement refer to activities undertaken at sites with known turtle use that have become degraded (restoration) or that would benefit from modification (enhancement). Historic use of particular sites is often unknown, and the three terms are sometimes used interchangeably. Here, nesting habitat enhancement is used as a general term to cover all these activities. Nesting habitat enhancement usually involves removal of vegetation, weeding, tilling, modifying the terrain shape, and addition of substrate materials, or a combination of these activities. The photos below show examples of nesting habitat enhancement at three sites on Vancouver Island as part of Habitat Aquisition Trust's stewardship initiatives.

Nesting area BL DSC 5626

Nesting area PA DSC 5609

Nesting area Swan L IMG 2427

 

Characteristics of nesting habitat

Nesting areas of the Western Painted Turtle have the following characteristics: open canopy, warm exposure, at least some bare soil free of vegetation, sandy or loamy substrates, and proximity to water bodies (usually within 150 m)[1]. Loamy soils, consisting of sand, silt, and clay in about equal proportions are considered optimal in areas with cold winters[2], but optimal turtle nesting substrates along the Pacific Coast of B.C. are largely unknown. Studies have shown that turtles prefer recently tilled soils (Blanding's Turtle in New York[3]; Western Painted Turtle on Vancouver Island: [4])). Blanding's Turtles preferred tilled ground (5 x 7 m plots) to similar-sized weeded or mowed plots. Western Painted Turtles preferred tilled (turned over) plots (1 x 1 m) to similar-sized plots with bare, compact ground that had been used in the previous year for nesting and to unmanipulated, grassy plots. Nesting habitat enhancement attempts to mimic the above conditions. Common causes of nesting habitat degradation include overgrowth of ground vegetation and excessive shading by trees. 

 

Steps to enhancement activities

Suggested procedure for nesting habitat enhancement:

1. Assess whether the site would benefit from nesting habitat creation or enhancement. Considerations include availability of existing nesting areas, safety of these areas (e.g., do turtles have to cross roads or other unsafe areas to reach them), and condition of known current and historical nesting areas.

2. If nesting habitat enhancement is deemed desirable, select a suitable site with a southernly, warm exposure.

3. Prepare a written plan for the site, showing the location of the area to be enhanced on a map or orthophoto and methods to be used. 

4. Consult with landowners/managers to ensure that the plan is acceptable and check permitting requirements by the Ministry of Environment or by other authorities, such as local governments.

5. Implement the plan; this step usually includes the following:

- remove existing vegetation

- turn over soil to about spade-depth

- add sand or sand/soil mixture as required; shape the terrain to form a gentle, south-facing slope

- where needed, fence the area off to prevent trampling and disturbance to nesting turtles and nests; a low snake-fence may be all that is needed, and display interpretive signage.

Timing of activities

If the site has not been recently used by turtles, nesting habitat enhancement can take place at any time of the year when the ground is accessible. However, it is desirable to complete the work by late May (in coastal areas), if turtles are expected to use the site in the same year. If turtles are currently using the site, there is only a narrow time-window to conduct enhancement activities. The activities should take place after hatchlings have emerged from nests but before females start laying eggs. In coastal B.C., this time-window is in late May.

Enhancement as an experiment

Where possible, set up the project as an experiment. For example, you may want to provide turtles with 2 or more different substrates or different slopes to choose from. You can divide the area to be enhanced into smaller sections and assign each section a different treatment. This will help to evaluate which methods are the most successful and should eventually be expanded over the entire site and perhaps used in other areas as well.

Monitoring effectiveness of the activities

It is important to monitor the effectivess of the methods used. Monitor whether turtles use the restored area for nesting and whether hatchlings from these nests emerge successfully. Be patient, as it may take turtles a year or more to find the new area. Where enhanced habitat is near traditional nesting areas, turtles may begin to use the enhanced area almost immediately. However, often more time is needed.

It is also important to maintain the enhanced nesting areas, so that they remain usable for turtles year after year. Schedule at least one inspection per year of the site to ensure that fences are in good repair and that the substrate is not overtaken by weeds. The amount of weeding required depends on the site and the substrate type - sandy substrates tend to require less maintanance than those with a large component of soil.

Nesting habitat maintenanceDSCN1022


For further information on how to construct turtle nesting areas, see Toronto Zoo's website: http://www.torontozoo.com/AdoptAPond/Turtlenests.asp?opx=2

 

  1. Bodie J.R. 2001. Stream and riparian management for freshwater turtles. Journal of Environmental Management 62:443–455.
  2. Costanzo, J.P., Litzgus, J.D., Larson, J.L., Iverson, J.B. and Lee, R.E. Jr. 2000. Characteristics of nest soil, but not geographic origin, influence cold hardiness of hatchling Painted Turtles. J. Therm. Biol. 26:65-73.
  3. Dowling. Z., T. Hartwig, E. Kiviat, and F. Keesing. 2010. Experimental Management of Nesting Habitat for the Blanding’s Turtle (Emydoidea blandingii). Ecological Rest. 28(2):154-159.
  4. Engelstoft, C. and K. Ovaska. 2011. Western Painted Turtle surveys and stewardship activities on Vancouver Island, 2010. Report prepared for Habitat Acquisition Trust (contact Adam Taylor), Victoria, BC. 64 pp.

Enhancement of Basking Sites

The availability of suitable basking sites is important for freshwater turtles. Basking in the sun elevates the turtle's body temperature, so permitting digestion of food. It also provides vitamin D and helps rid the body of ectoparasites. Suitable basking sites must have exposure to the sun, be accessible to turtles, and provide a safe site from predators and disturbance. Turtles are often seen basking on logs that are partially in water and partially on the shore. These slanted logs give turtles a choice to either climb completely out of the water or remain partially submerged. Other natural basking sites include rhizome mats of water lilies and exposed sites on the shoreline.

Water bodies with few natural basking sites may benefit from the addition of basking logs. Turtles readily use different types of installed logs and platforms, and the choice often depends on the availability of materials and resources.

Installation of Basking Logs

Swan Lake, June 2010; K. Ovaska photo

Examples of basking structures for habitat enhancement

1. Fallen logs from the vicinity of the water body or logs brought in to the site from elsewhere (suggested diameter at least 30 cm) are ideal; the larger the better); use machinery or roll the logs into water, then tow them with a boat to desired location and anchor them in place. Two logs can be tied together, side by side, to create a larger surface for turtles and to prevent them from rolling.

2. Mill-end slabs with one side milled and the other side with bark attached (3 - 4 m long; ~30 cm wide) are also suitable. These slabs are the by-product of lumber processing and can be obtained inexpensively or even for free - ask your local saw mills. The slabs are relatively light and can be carried into water by one person and then towed with a boat to desired location. However, they are not as durable as round logs and can become water-logged or sink with the weight of aquatic vegetation after only a few years.

Selecting location for basking logs

- Select a sunny area, such as the north side of the water body.

- Select a secluded site away from people, pets, and areas where trails are close to the shore; turtles are wary of disturbance from land.

- Use locations where the logs will be visible from a vantage point along the shore; this will help with monitoring of their use by turtles.

 Basking log DSCN4706

Basking log DSCN4708

Installing basking logs

- Place the logs perpendicular to the shoreline with one end firmly attached to the shore or shoreline vegetation; in our experience, turtles are reluctant to use floating boards away from the shoreline[1]

- Where feasible, attempt to place the log at an angle with the shore-end raised; this provides a range of distances from the water for turtles and allows for water level fluctuations. This may not be possible at all sites, such as where there is much aquatic vegetation near the shore.

- Anchor the log firmly in place at the shore-end. For mill-end slabs, drill a hole near the end and push a 5' or longer rebar through the hole and into the shore, bottom substrate, or matted vegetation. For larger logs, use rope to secure the end to trees or shrubs (such as willows along the shoreline), or use  an anchor.

Camosun Environmental Technology students Alanna Umphrey, Amanda Kletchko, Danny Desrosiers, & Marie Burgess prepared a report on basking log use at Swan Lake: "Basking Preferences and Interspecies Interactions of the Western Painted Turtle (Chrysemys picta bellii) at Swan Lake, Victoria, BC", Umphrey, Kletchko, Desrosiers, & Burgess, 2012. They designed small basking structures with floats for use in smaller ponds. While turtles readily use these structures, longer-term monitoring has revealed that they are likely to flip over in winter storms and provide only a short-term solution.

  1.  Engelstoft, C. and K. Ovaska. 2011. Western Painted Turtle surveys and stewardship activities on Vancouver Island in 2010. Unpublished report prepared for Habitat Acquisition Trust, Victoria, BC. 67 pp.

Western Painted Turtle Conservation