Radio telemetry

Antenna attachement

There are basically two ways the radio transmitter can be attached to the turtle.

Bolt attachment method

Info needed from people who have done this needed here

Transmitter attached via bolt method

Epoxy glueing method

Info needed from people who have done this needed here

Image:EpoxyTransmitter Burnaby Lake.JPG

Telemetry tracking protocol

The most accurate method to determine the location of a turtle with a transmitter is by using a canoe and going to the vicinity of the turtle or by triangulation from several points at a distance (see below).

Canoe/boat

• Turtles equipped with transmitters are located via homing to their position either by estimating the location from the shore or from water by boat (marking GPS location where the strongest, most consistent signal is received)[1] using a portable receiver (e.g., Wildlife Elements) and 3-element (e.g., YAGI) antenna.

• Visual observations of tagged turtles during the day are also be recorded; a test of transmitter functioning should be conducted with visual observations.

• Observers may estimate the turtle's position from land when the turtle is near the shoreline. Using a boat for these detections may be biased if turtles are disturbed by the researcher's activities or movements. When the turtle is not visible, locations are estimated by moving the antenna back and forth, detecting where the signal drops and where it is the strongest, then picking the direction of the strongest, most consistent signal. Observers should obtain directions from at least two sites until confident that the true location can be estimated and that any inconsistences in signal strength are not due to movements of the turtle (e.g., coming closer to the water surface).

• GPS coordinates from which turtle locations are estimated from the shore are recorded, along with the estimated distance to the turtle and a description of the location. These can then be used to determine the GPS coordinates of the turtle more accurately via plotting on GPS mapping software (e.g., Map Source). In cases when this methoc is not be sufficient to derive an accurate location, a single person can ‘triangulate’ as described below.

• The method of using a boat to acquire locations is appropriate for daily detections far from the shore; an adaptation of the shore method of locating turtles may be used at night due to safety concerns.

Triangulation

An alternative tracking method consists of triangulation to determine the turtle's location; this requires two people simultaneously determining the strongest direction of the radio signal and recording an angle (using a compass) from two different localities on land(A and B in Figure 2), while being in constant radio contact with each other[2]. To minimize error observers need to position themselves so as to create as close to a 90 degree angle as possible with the turtle's location. Locations of turtles can be estimated using GPS software (such as Map Source) by inputing each observers' location (marked via GPS) and the angle of the strongest signal strength. The point of intersection between the two lines of the angles is used to estimate turtle location (Figure 2). However, for this method an additional receiver unit, GPS, and compass are needed.

 

Image:Triangulation.jpg

Figure 2. Triangulation method for determining turtle location using radio-telemetry.

 

Image:Telemetry.JPG

Turtle with a radio-transmitter bolted on to the edge of the carapace.

 

Image:Telemetry 2.JPG

Turtle with a transmitter epoxied onto the carapace.

Overwintering area can be determined after the turtle’s tracked location has been in approximately the same place for three tracking sessions at the appropriate overwintering time (late fall/early winter). 

Habitat-use assessment

To assess habitat use by turtles, habitat is described both at locations of tracked turtles and random sites within movement capabilities of the turtle. Comparisons are then made between multiple variables that are recorded for the habitat plots (see below for examples) to determine if significant differences exist between the areas turtles are using and random locations. Please refer to the Western Painted Turtle Monitoring at Alaksen National Wildlife Area (NWA)- Final Report March 2011 by Vanessa Kilburn and Aimee Mitchell of the South Coast Western Painted Turtle Recovery Project for an example and details on habitat analysis and results (PDF)

Habitat plots

• To compare habitat use daily and seasonally, habitat is described at tracking locations that are >10m apart  (average error of locations). See Datasheets for sample on recording data.

• In addition, habitat plots can be placed within the estimated overwintering area to characterize that habitat.

• The following aquatic habitat charateristics will be measured/recorded as soon as possible to the tracking of each location:

  • Air temperature
  • Surface water temperature
  • Water column temperature (mid-way)
  • Bottom water temperature
  • Nearest basking location temperature (during summer only)
  • pH
  • Conductivity
  • Water depth (using pre-marked rope with weight)
  • General habitat description: habitat type (i.e., edge, open, basking), degree of cover (i.e., shaded, clear of canopy), degree of woody emergents and submergents in 2 m radius, other fish, wildlife, plant species visibly present in immediate area

• General habitat features are identified as follows[3]: Edge Habitat (ED) refers to the area within 10 m of shore which can be shaded by riparian vegetation (including trees) and generally has more woody emergents/submergents because of dead fall from the surrounding areas. This usually means most ED is also basking habitat (BA), but BA can also exist in open water. Open water habitat (OP) is the area outside of the 10 m zone on edges of a water body that is typically clear of vegetation and woody emergent/submergents.

 

Image:Habitat use Edge.JPG

Example of Edge Habitat (ED) (with basking habitat also)

 

Image:Habitat use Open.JPG

Example of Open Water Habitat (OP)


• In addition, an aquatic sediment/vegetation sample to examine the substrate composition can be collected: organic (e.g., leaf litter, woody debris) and inorganic (e.g., silt, sand, clay)[4] , which may be accessed using a paddle dipped at the plot location.

• A selection of random points equal in number to tracked locations (excluding overlapping locations) should also have habitat plots placed throughout the available aquatic habitat for comparisons. Random plot locations were generated by CWS staff while tracking at Alaksen National Wildlife Area in Delta, BC via Hauth’s Analysis Tools for ArcGIS (source: http://www.spatialecology.com/htools/rndpnts.php)

• Any locations on land would be categorized via habitat categories (or landscape composition categories) already described in the Site Management Plans as part of The South Coast Turtle Recovery Project Final Report (Kilburn and Mitchell, 2011) and outlined by Marchand and Litvaitis, 2004 (Reference 16).

Equipment needed

  • Kayak, paddle, and life jacket
  • Binoculars
  • Chest waders
  • Receiver and antenna (x 2 for triangulation)
  • GPS unit (x 2 for triangulation)
  • Notebook and pencil
  • Temp/Cond/pH meter
  • Glass thermometer
  • Weighted rope with depths pre-marked

Examples of Datasheets

Locations form boat

        

Triangulation:

Habitat Use:

          

Reference

  1. Bowne, D.R., M.A. Bowers, and J.E. Hines. 2006. Connectivity in an agricultural landscape as reflected by interpond movements of a freshwater turtle. Conserv. Biol. 20(3):780-791.
  2. Springer, J. T. 1979. Some sources of bias and sampling error in radio triangulation. J.Wildlife Mgmnt 43:926-935.
  3. Rowe, J.W. and S.J. Dalgran. 2009. Effects of Sex and Microhabitat Use on Diel Body Temperature Variation in Midland Painted Turtles (Chrysemys picta marginata). Copeia, 1:85-92
  4. Marchand, M.N and J.A. Litvaitis. 2004. Effects of habitat features and landscape composition on the population structure of a common aquatic turtle in a region undergoing rapid development. Conserv. Biol. 18(3):758-767.

Marking turtles

Notching the shell edge for permanent marking

Marking of turtles for individual recognition may be required under some circumstances, for example when detailed information on demography, survivorship, or movement patterns are needed. Note that permits are required for capturing, handling, and marking of turtles. A common method of marking turtles involves filing notches to the edge of peripheral scutes of the carapace. There are several ways to number the scutes. The scheme outlined in the Resource Inventory Standard Committee's manual for Pond-breeding Amphibians and Painted Turtle[1] has been adopted by the B.C. Western Painted Turtle Working Group.

Notches are filed in the middle edge of the peripheral scutes using a triangular file (e.g., 15 cm long; 0.7 cm wide). Most turtles have 12 scutes (partitions on the edge of their shell) on either side of their carapace , excluding one small central scute (0) at the top of the carapace behind the head. However, for marking purposes scutes 4,5 and 6 are skipped to avoid the thickest part of the shell with the most vascularisation and also to avoid turtles rubbing the notches with their limbs and causing injury. The scutes that are used are numbered right or left 1 through to 9. The first scutes on one side can be designated as a location (water body) identifier, and one of these scutes is notched in all turtles from a specific location. The notches should be disinfected after filing.


Figure1 notichingturtles

Figure 1. Top view of carapace with numbering scheme. In example, marked scute on left side indicates waterbody number: 3 and marked scute on right side indicates individual number: 2.

Notching

Using file to notch turtle carapace

Marking of hatchling turtles is sometimes desirable, for example to evaluate predation rates or effectiveness of head-starting programs. Visible Implant Elastomers have been used with success to mark hatchling Snapping Turtles[2]. A small, fluorescent tag is injected sub-cutaneously on the underside of the hindleg. The marks are permanent and appear to cause no adverse effects. This marking system has been used with success for amphibians (REF).

  1. Resource Inventory Standard Committee. 1998a. Inventory methods for pond-breeding amphibians and painted turtle. Standards for components of British Columbia’s Biodiverslty No. 37. Resource Inventory Branch, Ministry of Environment, Lands and Parks (available at http://www.ilmb.gov.bc.ca/risc/pubs/tebiodiv/pond/assets/pond.pdf). pp 94
  2. Davy, C.M., S.M. Coombes, A.K. whitear, and A.S. MacKenzie. 2010. Visible implant elastomer: a simple non-harmful method for marking hatchling turtles. Herp. Review 41(4): 442-445.

Capture methods

Image:Trapping turtles Ruby Lake.jpg

Setting a hoop trap (Turtle Workshop, May 2010)

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Hoop trap, baited with sardines.

Snorkeling hand-capture.

Snorkeling hand-capture.

Need to briefly describe methods here: hoop traps, basking traps

Measurements

Measurements to take of captured turtles

Once captured, turtles are measured for the following characteristics and photos are taken of the carapace, plastron, head and left/right front feet claws. Please note that permits are required to handle turtles and other wildlife in BC.

  • Weight (kg)
  • Height (cm)
  • Plastron's straight width and length (cm)
  • Carapace's straight width and length (cm)
  • Right and left front middle claws (cm)
  • Total tail length, tail length to cloaca, tail width at cloaca (cm), some takes the tail with at the carapace but it is variable
  • Sex and age are determined based on measurements and overall appearance (e.g., males are generally smaller, have longer claws, and a longer proportional distance of their tail to their cloaca from the plastron)
  • Note any special identifying features, such as scaring, are also noted.
  • When required, blood samples may be collected (up to 20 turtles per location is desirable, but the actual number of samples depends on the objectives of the study).
  • To identify individual turtles for mark-recapture studies, turtles are notched on both sides of their carapace (Figure 1).
  • When required by the study objectives, transmitters can be affixed to adult turtles via bolts to two lower scutes (usually 9 and 10, or scutes number 6 and 7 in the marking scheme below - Figure 1), or via an epoxy glueing method to the very top part of the carapace (further comments in the tagging section below from groups who have done this).

Example of datasheet for capturing morphological data:

WPT Measurement data sheet

Nest surveys

Image:Nesting WPT, Beaver Ponds.jpg

The availability of suitable nesting habitats often constrains the distribution of freshwater turtles, including the Western Painted Turtle. In many areas, nesting sites appear to be in short supply for the Pacific Coast Population because of dense forest cover and paucity of suitable sandy soils. It is important to identify nesting areas in the vicinity of water bodies occupied by the turtles, so that they can be protected from development and disturbance.

To survey for nesting areas, look for sites with the following features:

- open areas close to an occupied water body, usually within 150 m[1]

- warm, southern exposure

- exposed soil with little or no vegetation

- sandy or loamy substrate


On Vancouver Island, natural nesting habitats include patches of deeper soil on rocky bluffs bordering wetlands. Turtle nesting areas have also been found along sides of gravel roads and driveways, in old gravel pits, gravel parking lots, and along abandoned logging roads.

Examine sites deemed suitable for evidence of turtle nesting activity. This evidence may consist of the following: - exit holes through which hatchlings have emerged from nests (in spring) - test holes dug by nesting females (from early spring to mid-summer) - recently completed nests identified by a circular patch of flattened ground and/or a wet spot (from early spring to mid-summer) - adult females digging or laying eggs (from early spring to mid-summer)

  1. Bodie J.R. 2001. Stream and riparian management for freshwater turtles. Journal of Environmental Management 62:443–455.

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