Thread Trailing

"Very little is known about the daily travels of any animal, except that they are usually limited to a definite home range. It is not surprising that this subject has been studied so little, for most animals are difficult to observe. Many are nocturnal, and almost all are wary. In contrast to other animals, the box turtle is almost ideally suited for studies of travel and range relationships, for it can be made to map its own travel routes.'

'In the present study the use of a trailing device has been the principal technique in determining movement patterns of the box turtles. The trailer, a small light structure that is attached to the turtle's carapace, is described in detail and illustrated in the section on methods. As the turtle moves, a spool of thread unwinds, and makes an exact and detailed record of the turtle's travels.  Routes can be followed for days or weeks. The behavior of a turtle carrying a trailer appears absolutely normal.  Its method of walking, speed, and other actions are the same as for turtles without trailers. The distances traveled are entirely comparable.

'The principal difficulty of the method is that only a few turtles can be studied this way at any one time.  Locating the turtles each day and supplying new thread occupies about two hours per day for five turtles if they all live in the same vicinity. When their paths are divergent, or they live at distances from each other, the time required is greatly increased. More prohibitive is the problem of mapping the travel routes.  In the study area markers at regular intervals simplified the mapping but it was nevertheless very time consuming.

'The distance a turtle travels in a day usually has very little relationship to the distance measured in a straight line. People occasionally report finding the same turtle in nearly the same spot several different times, and conclude that the turtle is extremely sedentary. There are times when turtles travel very short distances, or none at all for some days, but if a day is favorably warm and moist the actual distance may be great in relation to the straight-line distance, or even to the total diameter of the home range. One of the trailer turtles covered 456 feet in a day without leaving its home range, which was less than 300 feet in diameter. The straight-line distance between the form the turtle left in the morning and the form where he spent the night was only 170 feet. This much travel on a favorable day is not exceptional.'

In her research paper:   " POPULATIONS AND HOME RANGE RELATIONSHIPS OF THE BOX TURTLE, TERRAPENE C. CAROLINA" ,  Lucille F. Stickel explains how she used thread trailing in her study of  a local population of Box turtles at the Patuxent Research Refuge, Maryland, during the years 1944-1947.   She didn't have the luxury of GPS or even telemetry but used thread trailing to follow the movements of a number of Box turtles, and drew the routes traveled on graph paper.
Thead trailing is MUCH more accurate and provides MUCH more information than radio-tracking and GPS'ing a location because it shows EXACTLY where the turtle has walked.  Unfortunately,  it is a lot of work, especially if more than a few turtles are being thread trailed.  You have to find each turtle and put on new thread BEFORE it runs out, or risk loosing that turtle.   It's really that simple, and it's a great way for school kids to get involved with box turtle research.

To be clear, there is no tension on the thread at all.  It rides in a plastic carrier that has a hole in the back, and unspools as the turtle moves.  The thread bobbin is changed every day or 2,  hopefully before it runs out.  The old bobbin is taken out of the carrier, the new one is threaded though the hole from the inside and the new bobbin dropped in and the top put on.  The loose thread is then simply tied to a twig or some grass and left. (mark the starting location). Since the thread pulls out as the turtle walks around it just feeds the thread behind.

Thread doesn't get caught on things because it is not moving once it leaves the plastic carrier.  The thread just lays there.  Sometimes a turtle will backtrack or go in circles and get into it's own thread but that's rare.  Otherwise the thread is on the ground where the turtle walked.   I often leave the threads where they are in the woods, because I am finding that the exact same routes are followed year to year, and by different turtles.  That would be hard to prove without thread trailing. 

The bobbin of thread is inserted into a plastic "carrier" that is attached to the turtle's rear, lower carapace with 5-minute epoxy.

The holes in the bottom allow epoxy to squeeze through forming small rivets.  The hole in the side is where the thread feeds through.
Devcon 5-minute epoxy works best.  It will soften after about 2 months allowing for easy removal without harming the turtle's scute, but will keep a transmitter attached up to 18 months.  Use the 1500psi type.  It doesn't get as hot during setting as the 2500psi.

It takes a very small amount of mixed epoxy to attach a thread carrier......much less than expected.  Only use enough to cover the plastic carrier's bottom and "clamp" with finger pressure until set.
Bobbins come in different thicknesses indicated by a letter, and different thread sizes and lengths.  The paper sides must be pulled off prior to use, because any moisture will cause them to jam.  There are also coreless bobbins.  Bobbin diameters are standard, because they must fit in a sewing machine the exact same place the metal ones do.

Nearly all bobbin thread now-a-days is polyester, or cotton-poly mix.  In either case the thread biodegrades quickly in the sun or even in the woods if not taken up.  Ebay is a good source to watch for cheap bobbins, especially if you don't care too much about color or age.  Bobbins are usually sold in boxes of 144.    They are used up faster than expected.
The 5 gram sized COSMETIC MAKEUP SAMPLE JAR is the right size. 
This turtle is a male, but the carrier is mounted about the same on females.  So far I have observed no behavior changes......not even in mating.    I have never seen a turtle get stuck with these carriers or with a transmitter.   Occassionally, the thread will get wet inside the carrier, and jam solid, but so far every time this occurred, the turtle was able to break the tread and go on it's way.  Box turtles are VERY strong and are able to handle most situations that would stop their movements.
This "5ml Cosmetic Cream Snap On Cap Jar" is almost perfect dimension.  An "M" size bobbin, holding 275 yards of thread, works well as long as you don't use too much epoxy when attaching the plastic container.
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When not thread trailing, the plastic carriers are usually left on the turtle.  They can be used to carry a small transmitter to serve as a backup. This is what they look like. Info on the transmitters are found elsewhere on this site.
Lucille Stickel used a much different and larger thead spool, but this photo shows the plastic container and bobbin used in this study.

The bobbin has 225 yards of thread that needs to be checked and replaced avery couple days.
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