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Graptemys cagleiCagle's Map Turtle

By Lauren Printz

Geographic Range

Calge’s map turtles (Graptemys caglei) are native to the San Antonio River (Texas, United States), which feeds into the Guadalupe River. These turtles are concentrated (60-82% of all individuals) along a 27-km section of the middle Guadalupe River. They are less common in the upper (11% of all individuals) and lower (7%) Gualadupe.

The turtles can also be found in the San Marcos River. Counties in Texas that these turtles inhabit are: DeWitt, Kerr, Kendall, Comal, Guadalupe, Gonzales, DeWitt, Hays, and Victoria counties. Lindeman (2014) states that in the southern extent of Victoria county, this turtle reaches as close as 71 linear river kilometers to the Gulf of Mexico. (Ernst and Lovich, 2009; "Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; Jones, 1996; Lindeman, 2014; Ward, et al., 2013)

Habitat

Calge’s map turtles inhabit relatively large creeks and rivers with a sand, gravel, or mucky substrate. Shallow locales with moderate flow rates are common. Their basking locations include newly fallen trees, rocks, or even cypress (Taxodium) knees (pneumatophores). Cagle’s map turtles are commonly found at depths of 1-3m when submerged. They are equally common in riffles (fast-moving water) or pools (slow-moving water) in these waterways, though males often forage at transitional areas between riffles and pools.

Female Cagle’s map turtles dig nests ca. 1-20 m from the water’s edge, often in sandy soils. The females dig furrows about 1-5 cm deep to test out the potential problems within the substrate. Once situated, a flask-shaped hole about 15cm deep is formed with a lower chamber, with the diameter of about 10cm and the neck diameter of 4cm. (Curie, 2009; "Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; Haynes, 1976; Lindeman, 1999; McAllister, et al., 1991)

  • Aquatic Biomes
  • rivers and streams
  • Range depth
    0 to 3 m
    0.00 to 9.84 ft

Physical Description

Adult Cagle's map turtles have a minimum carapace length (CL) of 45mm, making them one of the smallest map turtle species. Adult females can reach CL measures up to 220 mm and can more than double the size of the adult males (typically 70-120 mm). Males rarely exceed 126 mm. Mass is reported by Hone and O'Gorman (2013) as 1232 g, but sex or age was not reported.

They possess a somewhat flattened carapace. These turtles can be identified by the prominent V-shaped marking on the top of their head leading to their eye area. On the lower jaw they have a longitudinal yellow mark leading up to the transverse bar on the chin. Located on the top of the carapace, the spine is raised into vertebral scutes that almost come to a sharp point. The skin on their arms, legs, head, and tail is dark green, almost black, with yellow to cream-colored stripes throughout. The shell is a dark yellow to brown with brown to black swirl-like markings on each scute of the shell. The yellowish plastron has black flecks and each scute has a black edging to it. On the posterior portion of the body, there are compressed knobs of vertebra numbers 2 and 3. Both sexes have almost flat plastrons. A major difference between the sexes is that males have a longer tail than females.

As hatchlings, the map turtles are about 32 mm CL. They have rounder shells than adults. Additionally, on the plastron, the lines around the scutes are more pronounced, but they lack the dark flecks that adults possess. ("Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; Haynes, 1976; Hone and O'Gorman, 2013; Lindeman, 2008; vanDijk, 2011)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Average mass
    1232 g
    43.42 oz
  • Range length
    45 to 226 cm
    17.72 to 88.98 in

Development

Cagle's map turtle eggs incubate in the nests for 74-79 days, averaging at 76 days. The ideal temperature of the nests ranges from 23 to 31 °C. This species exhibits temperature-dependent sex determination. Incubation at or above 30.0 °C produces all female offspring, and temperatures about 29 °C and below are all males. Wibbels et al. (1991) suggest that there is a very narrow window of 0.5 to 1.0 °C that produces a mix of males and females. Ewert et al. (2004) summarized that the point ("pivotal point") when the bias changes from one sex to the other was 29.9˚C in one study, and 29.6˚C by Wibbels et al. (1991).

Growth rates in this species were studied by Lindeman (1999), but only for juveniles and males. Juveniles exhibited plastron lengths of ca. 35-45 mm PL in their first year and 45 to 60 mm in their second year. Males typically reach sexual maturity late in their second year or early of their third year. After reaching maturity by age 3, their growth curves somewhat leveled off (at maximum PL of ca. 80 mm). Growth curves for females are not available. Like all turtles, these map turtles exhibit indeterminate growth. (Ewert, et al., 2004; Lindeman, 1999; Wibbels, et al., 1991)

Reproduction

Mating in Cagle's map turtles is thought to occur in late spring and early summer months, as ovulation by females begins in late April and continues through late July. They are considered polygynandrous, although females may be receptive to mating just once per season.

Mating behavior is not well described in the wild; in captivity, Bartlett (2011) states that males court females by facing them and vibrating their head against the female's head region. (Bartlett, 2011; Ernst and Lovich, 2009; "Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002)

Cagle's map turtles breed in spring and summer months, with nesting reported from late March until late August. Females dig nests in sandy areas, but when sand is less available, they can also place them in clay loam or sandy-gravel locales.

Females may have one, two, or three clutches per season, and the number of eggs per clutch is 1-6. Clutch size is correlated with female size. Females travel 2-11 m from the edge of the river. They choose nests that are 0.5 m to 1 m above the water level to minimize nest flooding.

The young are fully independent upon hatching, and have been found on the landscape from September through November.

Males are reported to reach sexual maturity, at 2-3 years of age. Females reach maturity at a large size and later age, but age has not been reported. ("Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; Lindeman, 1999; vanDijk, 2011)

  • Breeding interval
    Breeding occurs once yearly
  • Breeding season
    March through August
  • Range number of offspring
    1 to 6
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Males provide no parental investment beyond the act of mating. Females provide no care after laying and covering the eggs. Females use tactile and visual senses to dig nests. They travel 2-11 m from the edge of the river and 0.5 m to 1 m above the water level to minimize nest flooding. ("Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; Lindeman, 1999)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

Cagle's map turtles' life span in the wild is thought to be more than 20 years. One record in captivity stated that an individual lived 14.5 years. (Slavens and Slavens, 2003; vanDijk, 2011)

  • Range lifespan
    Status: captivity
    14.5 (low) years
  • Typical lifespan
    Status: wild
    20 (low) years

Behavior

Cagle's map turtles are diurnal, basking in the sun on large rocks, fallen trees, or stumps along the shoreline. When foraging, males spend most of their time feeding on insects at the point where pools transition to riffles, around gravel bars. Females use pools for about 86.6% of their diurnal activities. Both sexes most commonly use riverine sites with moderate currents. They do no use land except when females dig nests on the water's edge.

Mating behavior is not well described in the wild; in captivity, Bartlett (2011) states that males court females by facing them and vibrating their head against the female's head region. In captivity, Schober and Richter (2014) state that they can be aggressive and should be kept solitarily, only mating once per year, while supervised.

These turtles are thought to hibernate, as they can be induced to do so in captivity. (Bartlett, 2011; Ernst and Lovich, 2009; "Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002)

Home Range

Craig (1992) used radiotelemetry to study movements of these turtles. He reported males had an average home range of 1300m of river length (range 520 - 2700 m), while females averaged 1400m (range 230 - 4100 m). They are not known to defend a territory but are aggressive in captivity. (Craig, 1992; "Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002)

Communication and Perception

Map turtles communicate through visual, tactile, and vibrational efforts. They use vision to feed, and to mate, as males approach females head-to-head. They use tactile efforts to mate, as males vibrate their heads against females' heads. They bask and avoid predation through visual cues.

Females use tactile and vision to dig nests.

Members of the genus Graptemys may use pheromones to begin courtship efforts, but this has not yet been proven for Cagle's map turtles. ("Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; Jenkins, 1979; Schober and Richter, 2014)

Food Habits

Adult Cagle’s map turtle diets vary by sex. Adult females are molluscivores, consuming primarily snails (Order Gastropoda), Asian clams (Corbicula fluminea), and crayfish. Molluscs comprise 88% of their diet.

Adult males are primarily insectivores, consuming aquatic insects and smaller crustaceans. Included aquatic insect larva are from the orders Trichoptera (caddisflies), Ephemeroptera (mayflies), Odonata (dragonflies and damselflies), and Plecoptera (stoneflies). The remaining 15% of their diet is aquatic snails (Gastropoda).

Juveniles' diet varies by sex; young males consume snails and insects equally, while young females consume clams and insects equally.

Plant matter is also consumed by males and juveniles by accident, as they are consuming the invertebrates on the plants. (Ernst and Lovich, 2009; "Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; Haynes, 1976)

  • Animal Foods
  • insects
  • mollusks
  • Plant Foods
  • wood, bark, or stems
  • algae

Predation

Predators of Cagle's map turtles are unknown, although it's suspected that predation of nests is high. Humans (Homo sapiens) have reportedly shot and killed these turtles. (Ernst and Lovich, 2009)

Ecosystem Roles

Cagle's map turtles prey on mollusks and insects, and are likely prey in the egg stage. Parasites of these turtles include coccidians: Eimeria chrysemydis, Eimeria graptemydos, Eimeria lutotestudinis, Eimeria pseudogeographica, and Eimeria trachemydis. (Ernst and Lovich, 2009; "Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics", 2002; McAllister, et al., 1991)

Commensal/Parasitic Species
  • Coccidia Eimeria chrysemydis
  • Coccidia Eimeria graptemydos
  • Coccidia Eimeria lutotestudinis
  • Coccidia Eimeria pseudogeographica
  • Coccidia Eimeria trachemydis

Economic Importance for Humans: Positive

Cagle’s map turtles are often kept as pets and collected locally for conservation efforts. (Bartlett, 2011; Lindeman, 2014; Schober and Richter, 2014)

Economic Importance for Humans: Negative

Cagle’s map turtles just like many captive turtles, can transmit salmonella. (Royal Veterinary College of London, 2016)

Conservation Status

Cagle's map turtles are currently listed as "Endangered" on the IUCN Red List. Like all map turtles in the genus Graptemys, they are listed in CITES under Appendix III, which means that they need regulation in trade on an international scale. Often export permits are granted for these animals. Texas lists Cagle’s map turtles as state-threatened; as result of that the turtles cannot be taken, transported, or sold in the state. Private breeders on the outside of Texas are the reason these turtles are available in the U.S trade of pets. They have no special status on the US Federal list, although they were considered for listing in 2006. The listing was denied because it was deemed that that conservation efforts at the state level were sufficient to protect Cagle's map turtles.

Map turtles are threatened by water pollution, habitat destruction, and recreational power boating. Illegal collection for the pet trade and shooting of these turtles also are significant threats.

Cagle’s map turtles have been listed as threatened in Texas since 2000. The state increased protection of the map turtles against shooting and collecting of their species, and this has been deemed successful to date. Population monitoring and continued status surveys are warranted for this species. (Curie, 2009; vanDijk, 2011)

Contributors

Lauren Printz (author), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

freshwater

mainly lives in water that is not salty.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Killebrew FC, WJ Rogers, and JB Babitzke. Field study on population and habitat of Cagle’s Map Turtle and factors affecting them, including instream flow requirements, water quality, and benthics. Edwards Aquifer Authority Contract #00-52-AS. Canyon, Texas: West Texas A&M University. 2002. Accessed November 27, 2021 at https://www.edwardsaquifer.org/science_docs/assessment-of-instream-flow-and-habitat-requirements-for-cagles-map-turtle-graptemys-caglei/.

Bartlett, D. 2011. Cagle's map turtle. Reptiles Magazine, 3: n/a. Accessed November 27, 2021 at https://reptilesmagazine.com/cagles-map-turtle/.

Bertl, J., F. Killebrew. 1983. An osteological comparison of Graptemys caglei Haynes and McKown and Graptemys versa Stejneger. Herpetologica, 39/4: 375-382.

Bulte, G., M. Leveillee, G. Blouin-Demers, S. Cooke, S. Bertram. 2020. Observations on the short-term effects of motorboat disturbance on the use of basking sites by female northern map turtles. Chelonian Conservation and Biology, 19/2: 302–304.

Craig, M. 1992. Radio-telemetry and Tagging Study of Movement Patterns, Activity Cycles, and Habitat Utilization in Cagle's Map Turtle, Graptemys caglei (Master's Thesis). Canyon, TX: West Texas State University.

Curie, M. 2009. Impact of recreational power boating on two populations of northern map turtles (Graptemys geographica). Aquatic Conservation: Marine And Freshwater Ecosystems, 20: 31-38.

Ernst, C., J. Lovich. 2009. Turtles of the United States and Canada, 2nd edition. Baltimore, Maryland: Johns Hopkins University Press.

Ewert, M., C. Etchberger, C. Nelson. 2004. Turtle sex-determining modes and TSD patterns, and some TSD pattern correlates. Pp. 21-32 in N Valenzuela, V Lance, eds. Temperature-Dependent Sex Determination in Vertebrates. Washington, D.C.: Smithsonian Institution.

Haynes, D. 1976. Graptemys caglei Haynes and McKown Cagle's map turtle. Catalogue of American Amphibians and Reptiles, 184: 1-2.

Hone, D., E. O'Gorman. 2013. Body Size datasets for PLOS ONE paper doi:10.1371. PLoS ONE. Accessed November 27, 2021 at http://dx.doi.org/10.6084/m9.figshare.627530.

Horne, B., R. Brauman, M. Moore, R. Seigel. 2003. Reproductive and nesting ecology of the yellow-blotched map turtle, Graptemys flavimaculata: Implications for conservation and management. Copeia, 2003/4: 729–738.

Jenkins, J. 1979. Notes on the courtship of the map turtle Graptemys pseudogeographica (Gray) (Reptilia, Testudines, Emydidae). Journal of Herpetology, 13/1: 129-131.

Jones, R. 1996. Home range and seasonal movements of the turtle Graptemys flavimaculata. Journal of Herpetology, 30/3: 376-385.

Lindeman, P. 2008. Evolution of body size in the map turtles and sawbacks (Emydidae: Deirochelyinae: Graptemys). Herpetologica, 64/1: 32-46.

Lindeman, P. 1999. Growth curves for Graptemys, with a comparison to other emydid turtles. The American Midland Naturalist, 142: 141-151.

Lindeman, P. 2014. A significant range extension for the Texas map turtle (Graptemys versa) and the inertia of an incomplete literature. Herpetological Conservation and Biology, 9/2: 334−341.

McAllister, C., S. Upton, F. Killebrew. 1991. Coccidian parasites (Apicomplexa: Eimeriidae) of Graptemys caglei and Graptemys versa (Testudines: Emydidae) from Texas. Journal of Parasitology, 77/3: 500-502.

Praschag, P., F. Ihlow, M. Flecks, M. Vamberger, U. Fritz. 2017. Diversity of North American map and sawback turtles (Testudines: Emydidae: Graptemys). Zoologica Scripta, 46/6: 674-682.

Royal Veterinary College of London, 2016. "Map Turtle Care" (On-line). Accessed December 01, 2021 at https://www.rvc.ac.uk/Media/Default/small-animal/documents/Map-turtle-care-sheet%202016-1.pdf.

Schober, L., M. Richter. 2014. "Graptemys studbooks overview" (On-line). Accessed November 27, 2021 at https://www.studbooks.eu/site/assets/files/1466/graptemys_studbooks_overview_082014.pdf.

Selman, W., C. Qualls. 2009. Distribution and abundance of two imperiled Graptemys species of the Pascagoula River system. Herpetological Conservation and Biology, 4/2: 171-184.

Slavens, F., K. Slavens. 2003. "Graptemys caglei" (On-line). Reptiles and Amphibians in Captivity. Accessed November 27, 2021 at http://www.pondturtle.com/lturtle.html.

Ward, R., J. Babitzke, F. Killebrew. 2013. Genetic population structure of Cagle's map turtle (Graptemys caglei) in the Guadalupe and San Marcos Rivers of Texas—A landscape perspective. Copeia, 2013/4: 723–728.

Wibbels, T., F. Killebrew, D. Crews. 1991. Sex determination in Cagle's map turtle: Implications for evolution, development, and conservation. Canadian Journal of Zoology, 69/10: 2693-2696.

vanDijk, P. 2011. "Graptemys caglei (errata version published in 2016)" (On-line). The IUCN Red List of Threatened Species 2011: e.T9497A97417639. Accessed November 27, 2021 at https://dx.doi.org/10.2305/IUCN.UK.2013.RLTS.T9497A12996153.en.

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