Depending on your situation, the instructor might previously set the traps or learners may be involved in the trap setting process. We typically bait traps with canned sardines in water. After creating a bait bucket for each trap and hanging it in the trap, place the partially opened can of sardines in the bait bucket. Each trap also needs to have empty sealed containers to make sure there is no danger of the trap sinking. We cut pieces of PVC pipe to hold the traps open and tie the end of the trap to a solid object such as a tree trunk or dock post. Traps are typically placed near areas where turtles bask, but learners may suggest other placements for experimental purposes. It is important to indicate on a map or sketch of the area where traps are located and how they are numbered.
In the picture to the left, the bait bucket is the half-gallon milk jug on the bottom and the trap mouth can also be seen to the right of the trap.In this trap the PVC pipes have been disengaged to allow the trap to collapse so that a turtle could be removed. The picture to the right shows the trap being placed in the water, it is important to tie the trap to a tree or solid structure around the bank. In this trap the PVC pipes are set correctly to hold the trap open.
Learners select and put on waders based on shoe size. Two or three learners can work together to remove traps from their resting location. Two learners should walk to either side of the trap and lift the trap BY THE METAL HOOPS (not by the PVC pipes). Care should be taken not to allow the trap to collapse and the PVC pipes to fall out and sink. The learners carefully walk with the trap back to the shoreline. The third learner can pull in the rope that is tied to the trap. In the picture below there is a different set of PVC pipes. Because this trap was larger, we used larger PVC pipes with capped ends (so that they would float). We permanently affixed these pipes to the trap with cable ties. This kept the trap open and floating but it also made the trap more difficult to move around and store.
Above: These students are checking the trap correctly.
The group should survey the animals that are in the trap before removing anything from the trap. Smaller turtles can be removed by reaching into the throat of the trap and pulling them out, posterior end first. Disengaging the PVC pipe from the trap and allowing the trap to collapse a little will make it easier to retrieve turtles from the trap. Care should be taken to keep hands away from turtle mouths and claws. Other learners should be prepared to take the turtles that are being removed from the trap. If a large collection container is available, turtles can be placed in this. For large turtles (such as snapping turtles in our area) it may be necessary to untie the end of the trap that was previously tied to the stationary object. Once this end is open, fold back the net and place the trap near the water’s edge so that the turtle can walk out on its own. This is safer for people and for the turtle. In our project, we DO NOT handle larger animals.
Sometimes traps will catch other animals such as fish. Reach into the throat of the trap and remove fish and return them to the water.
A fish caught in the Hoop Trap.
Retrieving turtles from the Hoop Trap.
Video Trapping Turtles in a Hoop Trap:
If there are multiple turtles in the trap, learners can work in pairs to identify their assigned turtle. You may create a dichotomous key for turtles in your area or learners can use their field guide, looking at pictures and reading the text and then comparing the information to the turtle in their possession. We ask learners to provide a minimum of three field characteristics to identify a turtle. For example, learners may say that their turtle is a yellow belly slider because it has yellow on its belly. This could actually describe multiple turtles in our area so we push them for a second distinguishing characteristic. They may then say that the turtle has yellow stripes on its leg. Again, this would describe multiple turtles in our area so we ask them for a third characteristic. They may finally refer to a yellow blotch or bar behind the eye linking a pair of yellow stripes on each side of the neck. Only after giving three field characteristics do we allow a learner group to arrive at an identification: Yellowbelly Slider (Trachemys scripta). Typically, we might also ask for a 4th characteristic (pair of dark spots on the gular scutes- just to be sure).
Some of the more common turtles for our project are:
- Eastern Mud turtle (Kinosternon subrubrum) – no distinct head stripes, double hinged plastron, pectoral scutes meet only narrowly on the midline of the plastron forming a triangle.
- Eastern Musk turtle (Sternotherus odoratus) – 2 pair of barbels on the chin and throat, single weakly hinged plastron, pectoral scutes are rectangular in shape, light yellowish line above and below the eye.
- Common Snapping turtle (Chelydra serpentine) – large head, long and tapering tail armed above with large scales, small cross-shaped plastron, carapace with 3 longitudinal keels (more prominent in young turtles). [If large snapping turtles are caught in a trap they should never be handled or removed by students. See suggestions above for how to safely release these large animals.]
- Painted turtle (Chrysemys picta) – pale transverse seams between the dorsal scutes, 2 yellow spots in line behind the eye, conspicuous red markings around the edges of the shell, legs with red and yellow stripes.
Video of Parts of the Turtle Shell:
If you begin in the classroom you can also have learners research the types of semi-aquatic turtles that are common in their area. Field guides or internet sites will be useful. When the guides or websites include range maps, learners could generate their own list of species that might likely be found in the area of the study.
Once learners have identified the turtle to species, I ask them to attempt to identify whether the turtle is male, female or too young to tell. Again, learners will need to go back to their field guides to be able to do this. Depending on the number of different species caught, student groups can share with other student groups the identification of their turtle, the distinguishing features, the sex and selected other information (for example, how many eggs female of the species might lay or what kind of food it prefers).
If you plan to submit data to The HERP Project you should take the following measurements for each turtle:
- Carapace length (notch to notch)
- Width at widest point
- Shell height at tallest point (carapace to plastron)
- Plastron length
Information for submitting data to The HERP Project can be found at http://theherpproject.uncg.edu/research/herpetology-studies/aquatic-turtles/. Please contact us at email@example.com to make us aware of your interest in project participation. A sample of our data sheet can be found in Appendix 2. Another option is to download the free HERP Project data collection app for android devices from http://theherpproject.uncg.edu/apps-collecting-data/ .
The size of the caliper used depends on the size of the turtle. The smallest caliper possible is generally best. We typically measure in millimeters.
To measure carapace length, put one end of the caliper at the most anterior position of the cervical scute and the other end at the farthest position on the posterior end of the carapace (notch to notch).
Using A Digital Caliper to Measure the Carapace Length of a Painted Turtle
- To measure width at widest point, determine the widest point on the shell and measure from one side to the other. Make sure the caliper is perpendicular to an imaginary line drawn from the middle of the head of the turtle to the middle of the tail.
- To measure shell height, determine the tallest point of the shell from plastron to carapace. This measurement is important to describe the size of the dome on the turtle shell. Slide one end of the caliper under the turtle next to the plastron and bring down the other end at the tallest point on the carapace. For some turtles, dome shape may give an indication of the gender of the turtle.
- To measure plastron length, put one end of the caliper at the most anterior position of the plastron and the other end at the farthest position on the posterior end of the plastron.
Using A Digital Caliper to Measure the Plastron Length of a Yellow Belly Slider
If using a pan scale, place container on the scale, tare the scale and then add the turtle. We typically measure mass in grams.
If using a spring scale, the size of the spring scale depends on the mass of the turtle. The smallest scale possible is generally best. Make sure that the spring scale begins at zero.
- Make a “saddle” for weighing turtles by tying loops at both ends of a small piece of rope. The length and thickness of the rope depends on the size of the turtles.
- Holding the turtle low to the ground, wrap the saddle around the shell of the turtle (width). Insert one loop into another and tighten so that the animal is secure in the saddle. Attach the other loop to the spring scale and read the mass. Remove the turtle from the saddle and determine the mass of the saddle to subtract from the first measurement.
Testing out the saddle to mass the turtle.
Massing the turtle.
Other Information Needed if Completing The HERP Project Data Sheets
If you are completing HERP Project data sheets, you will also need to record the following information.
- GPS Site location
- 1= road,
- 2= field/forest edge (within 6m of edge),
- 3= field,
- 4= pine forest,
- 5= hardwood forest,
- 6= stream or stream bank,
- 7= open wetland,
- 8= forested wetland,
- 9= lake,
- Weather conditions at time of capture
- 1 = no precipitation;
- 2 = light drizzle/mist;
- 3 = rain
- Water Temperature in either degrees Fahrenheit or Celsius
- Air Temperature in either degrees Fahrenheit or Celsius
- Number of days since last rain
- Sky Index
- 0 = 0 – 24% clouds;
- 1 = 25 – 49% clouds;
- 2 = 50 – 74% clouds;
- 3 = 75 – 100% clouds)
In some cases, The HERP Project is conducting mark/recapture studies. This is indicated on the data sheets by “turtle code” and “new or recapture”. Descriptions of mark/recapture population studies are beyond the scope of this curriculum. See Resources for suggestions to learn about mark/recapture studies.
Marking a painted turtle and recording data for mark/recapture study.
Marking a Yellow Belly Slider for our Mark/Recapture Study.
If you are conducting a biological inventory or population study, you will want to document your site location, trap location(s), and the day and time of each capture event. You should also record total trap captures. For example, “On June 15, 2014 we set 5 baited (sardines) traps in the lake at 2 PM. The location of each trap is marked on our lake diagram (not provided here). We retrieved the traps on June 16, 2014 at 10AM. We found the following in each trap:
Trap 1 – nothing was found
Trap 2 – 3 yellow belly sliders (data collected on all)
Trap 3 – 1 yellow belly slider (data collected) and 1 large snapping turtle (released-no
Trap 4 – 2 musk turtles and 5 fish (data collected on both turtles, fish released)
Trap 5 – 1 painted turtle (data collected) “
A Non-trapping Option – Observing basking turtles
Select a pond, lake, or river to monitor. Basking turtles are most active in warm weather in the middle of the day. Upon arrival at your site, find a good position from which to observe. If some learners have binoculars, the search range can be wider. As learners observe turtles, have them describe to the rest of the group the distinguishing characteristics that identify this turtle species. Record the GPS location of your site.