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.

Western Painted Turtle Conservation