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Observations and measurements on the North American Wood Turtle:

Glyptemys (Clemmys) insculpta

with notation of two different phenotypes.



- A 1985 study











Typical dimensions of Glyptemys insculpta







Based on eight live specimens



Research conducted 1985





Carapace length Carapace width Head width Carapace-

plastron length

("Carastron index"



inches / centimeters







Males -Yellowlegs phenotype







7 3/4 19.8 5 9/16 14.2 1 5/16 3.5 11/16 1.6





7 5/16 18.3 5 1/2 13.9 1 7/16 3.6 6/16 1.0







Males -redlegs phenotype







7 1/16 17.8 5 4/16 13.6 1 3/16 2.8 9/16 1.3







7 14/16 19.9 5 12/16 14.4 1 4/16 3.2 1 5/16 2.2





Females -yellowlegs phenotype







6 11/16 17.4 5 9/16 14.3 1 1/16 2.7 -1/16 -0.2





7 3/16 18.3 5 11/16 14.4 1 3/16 2.9 -2/16 -0.3





Females -redlegs phenotype







7 4/16 18.5 5 1/2 13.9 1 2/16 2.8 4/16 0.7





7 4/16 18.5 5 9/16 14.0 1 3/16 2.9 5/16 0.9







Abstract:







Research and observations were conducted in 1985 by Brian L. Schnirel on Glyptemys insculpta.



Live specimens were acquired and it was noted at that time that two distinct phenotypes were in



evidence with this species. The different color aspect of this species has been mentioned by Pope



(1938) and Harding (1997).







Both types of Glyptemys insculpta were measured for carapace and plastron length, head width,



and difference in length between the carapace and plastron ('carastron' index). Two of these



measurements (the head width and the 'carastron index are linked with sexual dimorphism of



Glyptemys insculpta. The two varieties were tested using variations of the Tinklepaugh labyrinth



experiment, Yerkes space reaction experiment, and mirror association experiments. Photographs



were taken at this time on these two phenotypes and were included in this report.





Introduction:







The third suborder of turtles to evolve from the Amphichelydia



are the Cryptodires- which are the most successful group of turtles



today. They possess the ability to pull their heads directly into their



shells without a full sideways motion. The largest family of



Cryptodirians are the Emydidae. Within this family, lies the genus



Glyptemys; which began in the Paleocene Epoch (55 million years



ago). The North American wood turtle (Glyptemys insculpta)- the



sculptured turtle- begins extensively in the Pleistocene



(approximately 1 million years ago). Voorhies (2000) reported a



discovery of a wood turtle shell from the Hemiphillian Miocene (6



million years ago. Pope (1939) mentions the remains of N.A. wood



turtles found in Pennsylvania that were at least ten's of thousands



of years old. As wiil be mentioned in the Geographic Range section,



ice age wood turtles were found in Tennessee and Georgia where



they have never been known from modern times. Since the advent



of Homo sapiens, the population has diminished considerably due to



overcollecting, highway deaths, extensive habitat destruction, etc.



In the past, native americans reduced some of the population for



rituals, shell helmets, rattles, and so on. For the white settler,



Insulptas were a convenient source of food. Indeed, in the early



part of the 20th century, quite a market developed for the 'Redleg'



as Glyptemys insculpta was called in the vernacular. Many



individuals were pulled out of muskrats holes in the winter using



sticks to locate something hard (Pope, 1939). The toughened



individual would then reach into the icy, cold water to claim his



prize.





Relationships:





The wood turtle, as stated belongs to the family Emydidae. The



Genus Clemmys, (as of 1985) consisted of the wood turtle Clemmys



insculpta, the bog turtle Clemmys muhlenbergi, the spotted turtle



Clemmys guttata, and the pacific pond Turtle Clemmys marmorata.



As 0f 2001, Mitochondrial DNA studies have now placed the wood



and bog turtles in the genus: Glyptemys and the pacific pond turtle



in the genus Actinemys. Only the spotted turtle remains in the now



monotypic genus Clemmys. The spotted turtle and the bog turtle



(although widely separated and rare) are also denizens of the



northeast. The pacific pond turtle is the most aquatic member of



this former group and resides along the Pacific coast.





An interesting example of parallel evolution or common ancestral



trait exists between the wood turtle and the semi-box turtle



Emydoidea blandingi , also known as the blanding turtle. The



plastron of both species is amazingly similar. The pattern is a



yellow-white background with black blotches on each of the scutes.



Other studies indicate a close genetic relationship between the two



(See 2003 update in Morphs and Ancestral Relationships). The semi-



box turtle, a cold hardy species, also resides in the northeast;



overlapping the range of the wood turtle. This turtle's range-like so



many others- is slowly shrinking. At one time, it may well indeed



have had the exact same range as the wood turtle.





Behavior and Intelligence:







Tinklepaugh (1932) conducted experiments to



determine the intellegence of the wood turtle. Using a



labyrinth, he concluded Glyptemys (Clemmys) insculpta had



the learning capacity of a rat. In personal experiments



and observations(B. Schnirel,1985,1998) the wood turtle



does indeed show great resourcefulness in problem



solving. One male in particular was quite adroit at



climbing and would systematically probe for weaknesses at



all levels in the outdoor fencing he was kept in. In a



variation to the labyrinth experiment, a three



dimensional approach was conducted in 1985. Ramps were



used to allow choices at 3 different heights. Wood



turtles in the experiment quickly learned the right route



to find food or females placed in a consistent area.





Yerkes (1901) conducted the famous 'space



reaction'experiments. Included on his guest list was



none other than our friend, the wood turtle. The



experiments tested the animal's fear of heights. What



was learned was the more aquatic the species, the more



careless the species is in regards to heights. This is



due to aquatic animals being used to dropping off stones,



logs, or whatever into boyount water. How did the wood



turtle make out? It was found to have less fear of



heights than the more aquatic spotted turtle. In tests



performed (B.Schnirel,1985) at various heights up to 20



feet, great fear and respect of height was demonstrated



by the wood turtle. The turtles would stick their heads



way over to inspect the untouchable surface with a note



of displeasure. More aquatic species would simply walk



straight off the edge. No turtles were hurt in the



experiments and special precautions were taken.







Glyptemys (Clemmys) insculpta appears more cognizant



of it's own reflections when facing mirrors. Experiments



conducted (B. Schnirel, 1985) with wood turtles showed



that individuals would stop, lower their heads and touch



'noses' with their reflections. Other turtles and



tortoises tested (Geocheleone carbonaria, Geocheleone



denticulata,Geochelone chilensis, Testudo horsfieldi,



Kinixys belliana belliana, Gopherus polyphemus, Terrapene



carolina carolina,Terrapene carolina bauri,and



Rhinoclemmys pulcherima showed no interest in their



mirrored image.



Results:





Dimensional Parameters:





The 1985 measurements on the eight insculpta's showed the following pertaining to sexual



dimorphism: Carapace length - males: 7 1/16 - 7 14/16 inches (17.8 - 19.9 centimeters).



Carapace length - females: 6 11/16 - 7 4/16 inches (17.4 - 18.5 centimeters). All test subjects



were mature adults and as such, males showed a larger ultimate size. Carapace width - males:



5 4/16- 5 12/16 inches (13.6 - 14.4 centimeters). Carapace width - females: 5 1/2 - 5 11/16



inches (13.9 - 14.4 centimeters). Again, males were slightly larger. Width of head - males:



1 3/16 - 1 7/16 inches (2.8 - 3.6 centimeters). Width of head - females: 1 1/16 - 1 3/16 inches



(2.7 - 2.9 centimeters). Males show a significant difference. Carapace minus Plastron length



(Carastron index) - Males: 6/16 - 15/16 inches ( 1.0 - 2.2 centimeters). Carapace minus



Plastron length (Carastron index) - females: 5/16 - 2/16 inches ( 0.9- -0.3 centimeters). This



was a sizeable difference with males possessing a large carapace overhang. In subsequent



observations, this is always the case. Female redlegs phenotype insculpta have a narrower



overhang but in the case of the yellowlegs phenotype insculpta, the plastron was actually longer



than the carapace (giving a minus Carastron value). One yellowlegs female that had a Carastron



value of -.06 (not included in parameter table) was unusual in having a completely round



carapace similar to a dinner plate. One thought is that she was a member of a peripheral isolate



population. Another thought was paedomorphism of the carapace. Hatchling



Glyptemys insculpta display a round carapace which develops into a more oval shape during



development towards adulthood.





Results: (Continued)





Tinklepaugh Labyrinth Experiments:





Glyptemys insculpta indeed showed great resourcefulness and speed in problem solving. In



addition to finding escape routes quickly, subjects in variation quickly found correct pathways



to food and male Glyptemys insculpta to females in different sections of the labyrinth. Male



insculpta had been observed in 1985 lying in ambush near pools for females to happen by



looking to soak or a drink. The male would proceed to jump on the back of the female to



mate. A three dimensional approach in the labyrinth experiments did not slow down the



wood turtles in their quest. One male in particular was very adroit in climbing and would



systematically probe for weaknessess. This was done at all levels in the outdoor fencing he



was kept in.







Yerkes Space Reaction Experiments:





At all levels up to twenty feet, great fear and respect of heights was demonstrated by



Geochelone carbonaria. Glyptemys insculpta and Terrapene carolina carolina showed



respect for all distances but did not show fear at the two foot height. Clemmys guttata



showed respect and fear at ten and twenty feet, but did not so at two and five feet. Indeed, at



the latter two heights, the subjects tried to drop off as aquatic species would be expected to



into buoyant water.











Results: (Continued)





Mirror Experiment:





All test species with the exception of Glyptemys insculpta, showed no interest in their reflected



images. Glyptemys insculpta appeared more cognizant of it's own reflections when facing



mirrors. test subjects would stop, lower their heads, and touch 'noses' with their reflections.



This behavior has been noted between encounters between two Glyptemys insculpta. In addition



to the head lowering and nose tipping, individuals will often tip their heads and sniff each other



in the manner of dogs. They seem to treat each other on an individual basis. Knowlton describes



the behavior of insculpta in an encounter in the following manner: "Their heads were slowly



lowered when the turtles were with eight inches of each other. Next, their heads were



swung from side to side for up to an hour without cessation. Mating occurred in a nearby



pool. " Harding also mentions that Glyptemys insculpta conduct a mating dance initiated by



both parties. They position themselves in front of one another and swing their heads in a



sideways swing.





Text (Introduction):







The North American wood turtle belongs to the Family Emydidae. The Genus Clemmys



(as of 1985) consisted of the wood turtle Clemmys insculpta, the bog turtle



Clemmys muhlenbergi, the spotted turtle Clemmys guttata, and the Pacific pond turtle



Clemmys marmorata. As of 2002, mitochrondrial DNA studies have now placed the wood



and bog turtles in the Genus: Glyptemys and the pacific pond turtle in the Genus: Actinemys.



Only the spotted turtle remains in the now monotypic Genus: Clemmys.







In 1985, several live Glyptemys insculpa were acquired for study. Individuals were selected



from extreme ends of their natural range. Some individuals came from Wisconsin



(Oneida county). This represented the western end of the range. Other individuals hailed



from Northern Virginia. This represented the eastern as well as the southern part of their range.



It immediately became apparent that there were consistent differences in coloration between the



geographically separated groups. The eastern group consisted of the standard reddish orange



color phase known in the vernacular as the "redlegs" (Pope, 1939). This standard morph also is



characteristic of having a yellow-ringed iris. The western group of Glyptemys insculpta was



different in that the skin color was yellow instead of reddish-orange and the iris was entirely



black with no yellow ring. This phenotype will be referred to as the "yellowlegs" for the duration



of this paper. Photographs of both phenotypes were taken and accompany this report. In the



early twentieth century, Clifford Pope mentions having specimens of the yellowlegs phenotype



which he describes as follows: " The soft parts lack the normal salmon red color of the adult,



Text (Introduction) - Continued:









the plastron is dark except for a narrow light margin and a little light mottling ".



Harding (1997) also mentions the color variation aspect and geographical distinctiveness of



Glyptemys insculpta.







Measurements were recorded on eight selected individuals (4 males, 4 females- divided by 2



from each region). The data recorded was significant in regards to sexual dimorphism.



Typically, male Glyptemys insculpta are noted for having wider heads, carapace's significantly



longer than the plastron (always), longer claws, concave plastron, and thicker tails with the vent



further out from the shell than the female. Female Glyptemys insculpta posses narrower heads,



a carapace slightly longer than the plastron or in some cases, the plastron is longer than the



carapace, shorter claws, flat plastron, and thinner tails with the vent close to the edge of the



shell.







Tinklepaugh (1932) conducted experiments to determine the intelligence of Glyptemys insculpta.



He concluded that this species had the learning capacity of a rat. The 1985 experiments of the



same were done with a labyrinth constructed of 2 x 4's. The width of the corridors were ten



inches wide with area covering twenty feet by twenty feet. In a variation of the original



experiment, a three dimensional approach was conducted. Ramps were used to allow choices



at three different levels. Incentives included food and females placed at specific locations.







Text (Introduction) - Continued:









Yerkes (1901) conducted the famous 'space' reaction experiments. Included on his guest list was



Glyptemys insculpta. The experiment tested the animal's fear of heights. What was learned was



the more aquatic the species, the more careless the species is in regards to heights. This behavior



has evolved due to aquatic turtles being used to dropping off stones, logs, or whatever into



buoyant water. The following test heights were chosen: two feet, five feet, ten feet, and twenty



feet. In addition to Glyptemys insculpta, other species tested were the spotted turtle:



Clemmys guttata, the redfoot tortoise: Geochelone carbonaria, and the Eastern box turtle,



Terrapene carolina carolina.







The last series of experiments involved reaction to reflections in mirrors. The mirror used was



twenty four inches wide. In addition to the North American wood turtle: Glyptemys insculpta,



the following chelonian species were tested: the redfoot tortoise: Geochelone carbonaria, the



yellowfoot tortoise: Geochelone denticulata, The Chaco tortoise: Geochelone chilensis, the



Afghan tortoise: Testudo horsefieldi, the hingeback tortoise: Kinixys belliana, The Eastern



gopher tortoise: Gopherus polyphemus, the Eastern box turtle: Terrapene carolina carolina,



the Florida box turtle: Terrapene carolina bauri, and the Central American wood turtle:



Rhinoclemmys pulcherima.

Discussion:







The differences between the redlegs and yellowlegs phenotypes of Glyptemys insculpta are suttle



but distinctive. Present evidence suggests the yellowlegs phenotype resides in the western part



of the biozone. The yellowlegs form may exist as peripheral isolates evolving eventually into a



new subspecies if not disturbed by Homo sapiens. However, an alternative view may have the



yellowlegs as ancestral stock. Harding (1999) mentions hybrids between Emydoidea blandingi



and Glyptemys insculpta. The range of these two species overlaps with the greatest core



concentration (as of 1985) remaining in the Great Lakes region. During the 1985 research,



individuals of Emydoidea blandingi were present and studied with similarities noted with



Glyptemys insculpta. The plastron of both species is very similar with the same arrangement



of black spots on the plastral scutes. The skin color is yellowish on blandingii as is with the



yellowlegs insculpta. It might be possible that a common emydid ancestor to both species



resided in the same region and the ancestral color trait being yellow in regards to skin color.



This would be a pre-Miocene event as the earliest known wood turtle (an adult male) found



(Voorhies, 2000) was in the Hemphillian Miocene. If this is the case, the redlegs phenotype



would be a derived apomorphic trait.



Ernest, Lovitch and Barborn in 1994 reported that in the cooler climes of



the ice age, the wood turtle had a more southern distribution. The evidence



suggested that the species could be found as far south as Tennessee and



Georgia.









The noted differences in the phenotypes with dimensional measurements were the females with



the Carastron values. Plastrons seem to be longer than the carapace with the yellowlegs



phenotype. However, more measurements on more yellowlegs and redlegs individuals would



be needed to draw an absolute conclusion.





Discussion: (Continued)









In behavior, both phenotypes acted along similar lines and showed no differences in intelligence.



This was true for the Tinklepaugh labyrinth experiment, the Yerkes space reaction experiment



and the mirror reflection experiment.











References:









Behler/King. 1979. Audubon Society field guide to North American reptiles and amphibians.

Knopf, New York. 744 pp.



Bickman, J. 1996. Molecular systematics of the genus Clemmys and the intergeneric

Lamb, T. Minx, P. relationships of Emydid turtles. Herpetologica. Bainbridge, Ga.

Patton, J. 521 (1) pp.89-97.





Burton, M. 1973. The world of reptiles and amphibians. Bounty Books, London-New

York. 128 pp.



Carr, A.F. 1952. Handbook of turtles. Comstock Publ. Associates, Cornell University

Press. Ithaca, New York. 542 pp.



Conant, R. 1958. A field guide to reptiles and amphibians of Eastern North America.

Houghton Mifflin Co., Boston Massachusetts. 366 pp.



Ernest, C. H./ 1972. Turtles of the United States. University of Kentucky Press. 347 pp.

Barbour, R.W.



Harding, James 2003. Clemmys Insculpta. Animal Diversity Web - Michigan State University

Museum of Zoology 7 pp.



Lanworn, R.A. 1972. The book of reptiles. Hamlin, London. 127 pp.



Pope, C. H. 1939. Turtles of the United States and Canada. Alfred A. Knolpf, New

York. 343 pp.



Pritchard, P. 1979. Encyclopedia of turtles. T.F.H. Publications, Neptune, New

Jersey. 895 pp.



Roberts, M. 1980. Turtles. T.F.H. Publications, Neptune, New Jersey. 93 pp.



Tinklepaugh, 1932. Maze learning of a turtle. Journal Comprehensive Psychology 13:

O. pp. 210-206.



Zim, H. 1953. Reptiles and amphibians (North America). Golden Press, New

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