Literaturdatenbank
Literaturdatenbank |
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Vogt, R. C. , Why not notch more turtle shells? Paper presented at Turtle Survival Alliance 2007 Annual Meeting.
Added by: Sarina Wunderlich (01 Jan 2009 23:10:48 UTC) |
| Resource type: Proceedings Article BibTeX citation key: Vogt2007 View all bibliographic details  |
Categories: General Keywords: Habitat = habitat, Mittelamerika = Central America, Podocnemididae, Podocnemis, Podocnemis unifilis, Schildkröten = turtles + tortoises, Südamerika = South America Creators: Vogt Collection: Turtle Survival Alliance 2007 Annual Meeting |
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| Abstract |
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In 1939 a Fred Cagle published a paper on notching turtle shells for individual recognition of turtles when recaptured. This was a novel idea then, filing notches in turtle shells, kind of like the lost art of whittling. This idea with different themes on how to number the exact same notches differently is still used today by most unimaginative turtle biologists. 68 years later Cagles 1939 paper is still cited. When I began marking turtles in 1968, I followed Kathy Ream and notched shells without blinking an eye. I tried the Harvey Pough technique and marked 100´s of turtles with different colors of plastic buttons, following his Dennison Buttoneer technique, it was fine for a few weeks, some even lasted for 2 years in the field, but the colors faded and the holes grew in diameter and the plastic plugs fell out. At least the holes remained so that you knew the turtle was a recapture, just was not any good for growth data. In Neotropical Mexico, in Veracruz I wanted to do an experimental transplant of hatchling Kinosternon leucostomum, from one laguna to another, to test the hypothesis that the size of the adults was food related and not genetic. But the difficulty of identifying the marks on the carapace of 30 g hatchlings 10 years later when they would be at least 20 times this size seemed impossible. Why didn´t turtle biologists clip toes like other people working with frogs and lizards? Perhaps only because it had never been done before? Perhaps because they thought it would hurt? Well in 1990 I toeclipped 20 hatchling K. leucostomum, being careful to clip only 1 toe per foot, and only the 2nd or 3rd toe, so that an attempted predation would unlikely to have made a similar bite. One toe was severed after the 2nd joint on two different appendages. Also Avid pit tags were inserted in the musculature dorsal to the base of the tail. Twelve years later during the course of another study four of these hatchlings, now adults, were recaptured with both the distinct toe clips and pit tags functioning to identify the turtle. Toe clipping hatchling turtles perhaps causes no more stress than it does to lizards, frogs, mice, or salamanders. It is inexpensive and perhaps less confusing, there are a maximum of five toes to count on each foot, while there are at least 11 marginal scutes to count on each side of the turtle shell this increases the error factor two fold. In areas where there are high populations of piranhas or other predators, and the adult turtles have many foot injuries, toe clipping may not be advantageous, however, in many regions it will work. Pit tags do work in all situations the only problem is cost, but they are effective and I do get recaptures. I marked 2000 hatchling Podocnemis unifilis in December 1995 and released those 2 days later in Lago Erepicu in the Trombetas Reserve, in Amazônia, Brazil. During the first census of this lake since that time, September- December 2006, 11 years later I captured 3 of the pit tagged hatchlings. The turtles were 2 adult females and 1 adult male. An astounding 0.015% minimum survivorship rate was recorded in this large, 65k long, lake. I believe these two small short term studies are sufficient to convince the world that pit tagging for long term projects works and it is not only cost efficient but the only way to mark these hatchling turtles in areas of high predator activity and expect to get identifiable recaptures 10 or more years later. Toe clipping should be used for hatchling turtles and may be a good way to mark trionychids as well!
Added by: Sarina Wunderlich |