Macroclemys temminckii

The taxonomy of M. temmincki has been reviewed by King and Burke (1989), Pritchard (1989), Lovich (1993), and Iverson et al. (2000).  Although Pritchard (1989) has argued in favor of using the name Macroclemys temmincki, Iverson et al. (2000) follow the more current research of Webb (1995) and use the name Macrochelys temminckii based upon priority.

The Alligator Snapping Turtle has been illustrated by numerous authorities (Pope, 1939; Carr, 1952; Ernst and Barbour, 1972, 1989; Mount, 1975; Behler and King, 1979; Pritchard, 1979,1989, 1992; Caldwell and Collins, 1981; Smith and Brodie, 1982; Obst, 1986,1998; Alderton, 1988; [Sievert] and Sievert, [1988]; Dundee and Rossman, 1989; Ashton and Ashton, 1991; Carmichael and Williams, 1991; Ernst et al., 1994; Lamar, 1997; Conant and Collins, 1998; Powell et al., 1998; Bartlett and Bartlett, 1999a, b; Behler, 1999; Phillips et al., 1999; Johnson, 2000; Pough et al., 2001; Zug et al., 2001).

The Alligator Snapping Turtle is a massive, highly aquatic turtle that inhabits deep waters, primarily deep rivers with steep banks, but also lakes and swamps (Pritchard, 1989, 1992).

For the most part, M. temminckii is a carnivore that feeds primarily on fish, smaller turtles (especially kinosternids), crayfish, and mollusks (mussels and snails), but occasionally eats juvenile alligators, small mammals, ducks, amphibians, carrion, fruit, and acorns (Dundee and Rossman, 1989; Ernst and Barbour, 1989; Pritchard, 1989; Ernst et al. 1994; Conant and Collins, 1998). Although they actively forage for food along the bottom, they hunt for fish by lying still in ambush, with open mouth while wriggling the lure appendage on the tongue (Obst, 1986, 1998; Pritchard, 1989, 1992; Zug et al. 2001). Fish are trapped in their mouths in this fashion more commonly by smaller, younger turtles than by larger adults that spend more time actively foraging (Pritchard, 1989).  Females typically lay their eggs in loose, moist soil in or near river banks (Pritchard, 1989).

Potential pathway(s) of introduction: Unauthorized intentional release

This species has been reported in the St. Joseph’s River, MI (Brazo, 1999; personal communication).  The northernmost extent of its range is just below Davenport, Illinois; however, overland movement in this species is extremely rare (Ewert et al., 2006).

The Alligator Snapping Turtle is a popular pet in many countries and is widely available online (Jones, 2005; Koo et al., 2021). Like other turtles, this species is long-lived (>70 years) and grows to a substantial size; naive pet owners of this species may not be aware of the financial investment and time required to care for it (Ewert et al., 2006). Subsequently, a lack of responsibility and education among pet owners may lead to unauthorized releases into nearby water bodies. Escape from captivity is unlikely as overland movement in this species is extremely rare and is only known to occur in hatchlings seeking aquatic habitats shortly after hatching (Ewert et al., 2006).

Macrochelys temminckii has a low probability of establishment if introduced to the Great Lakes (Confidence level: High).

There is no evidence that Macrochelys temminckii will be able to successfully reproduce and overwinter in the Great Lakes basin due to cooler temperatures under the present climate. Although its northernmost distribution is in western Illinois, which would have similar seasonality to the basin, ecological niche models suggest that low soil temperatures in the Great Lakes are likely to inhibit successful embryonic development during the incubation period which generally occurs in May or June (Thompson et al., 2017). In a study in the Apalachicola River, Ewert and Jackson (1994) found that Alligator Snapping Turtle embryos can develop and hatch at a constant temperature of 22.5^oC but struggle at lower temperatures than the formerly mentioned. Higher temperatures equal to or more than 30^oC also preclude the full development of embryos. Finally, in response to cooler temperatures, captive Alligator Snapping Turtles refuse to eat food at 18^oC and become dormant at 10^oC (Grimpe, 1987; Riedle, 2001).

Nonetheless, warmer temperatures, shorter duration of ice cover, and increased salinization due to climate change are likely to benefit the success of this species in the Great Lakes in the future. M. temminckii is a habitat generalist and, if given the right abiotic conditions, it can be found in rivers, floodplains, turbid water, impoundments, river mouths, and bays. Barnacles have been found on the carapace of an Alligator Snapping Turtle in Alabama, suggesting that it can spend a significant amount of time in brackish water (Jackson and Ross, 1971; Ewert et al., 2006). This species is also an opportunistic forager and consumes a variety of food types including fruit, roots, tree nuts (acorns), tubers, fish, bivalves, gastropods, large salamanders, small mammals, snakes, small alligators, and other turtles (Riedle, 2001; Ewert et al., 2006). Most of these habitats and food items are available in the Great Lakes basin.

The fecundity of this species is relatively high compared to other turtles native to the Great Lakes. A study on Alligator Snapping Turtles in the Apalachicola River found an average clutch size of 31.5 eggs and a range of 17-52 eggs per clutch (Ewert and Jackson, 1994). Both sexes mature at 11-13 years (Ewert et al., 2006). Though M. temminckii has a relatively high reproductive output, it is unlikely that this will aid in its establishment unless limiting abiotic factors are removed, such as low soil temperatures. In addition, there are no records of M. temminckii successfully establishing itself (overwintering and reproducing) in areas outside of its native distribution. It is also possible that the successful establishment of this species (even within projected climate change scenarios) could be precluded by depredation by nest predators such as the common racoon (Procyon lotor), which is ubiquitously distributed in the Great Lakes basin. Fire ants have also been known to kill hatchlings and the Great Lakes is currently being invaded by the European Fire Ant (Myrmica rubra) which has the potential to provide the same function. In the Apalachicola River, for example, about 87% of all M. temminckii nests were depredated by natural predators (mainly racoons) and only about three eggs successfully hatched per female in a year (Ewert et al., 2006).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic

Due to the lack of research on this species, it is not clear whether M. temminckii has the ability to impact, outcompete, or displace native species in the Great Lakes. However, the Alligator Snapping Turtle is an apex predator and could potentially have severe impacts on native food webs, though no realized effects of this have been recorded in the literature. It is also not clear whether or not M. temminckii would affect the overall health of native species, though it has been reported that Alligator Snapping Turtles are capable of carrying polystomes (Neopolystoma cf. orbiculare), ranavirus, herpesvirus, nematodes (Brevimulticaecum tenuicolle, Falcaustra chelydrae, F. wardi, and Serpinema trispinosus), and acanthocephalans (Neoechinorhynchus chrysemydis, N. emydis, and N. pseudemydis; Chaffin et al., 2008; Yu et al., 2015). Hybridization is not known to occur or significantly impact other species.

There is little or no evidence to support that Macrochelys temminckii has the potential for significant socio-economic impacts if introduced to the Great Lakes.

M. temminckii has the potential to cause some harm to human health but no widespread impacts have been recorded in the literature. For instance, a single adolescent boy lost an index finger from picking up an Alligator Snapping Turtle in Oklahoma but this is one of the few reported incidents (Johnson et al., 2016). In addition, reptile pets are often kept in unsanitary conditions and act as a reservoir for bacteria (Back et al., 2016). In turn, pet Alligator Snapping Turtles can carry or spread zoonotic bacteria that could potentially cause disease in humans but widespread effects from this have not been observed for this species. Those recorded in the literature include Salmonella spp. and Citrobacter freundii (Hossain et al., 2016).

Macrochelys temminckii has the potential for high beneficial impact if introduced to the Great Lakes.

Historically, M. temminckii was a large source of income for commercial industries across its native distribution due to its popularity as a soup ingredient and as a pet (Folt et al. 2016). It was heavily exploited for its meat in the 1960s and 1970s, especially in the southeastern United States. However, the commercial harvest of this species has closed (December 2004) as stable native populations have declined or have been extirpated (Ewert et al., 2006; Dreslik et al., 2017). Because the Alligator Snapping Turtle was heavily targeted for commercial harvesting and has declined, it is now protected across its native distribution (Folt et al., 2016). The recreational harvest of M. temminckii is still available in some states (e.g. Louisiana) but is regulated (Huntzinger et al., 2019). If introduced to or established in the Great Lakes, the Alligator Snapping Turtle could be of some recreational or commercial value.

Internationally, M. temminckii is listed in CITES (Appendix III), limiting international trade and exploitation. The species is also currently under review by the U. S. Fish and Wildlife Service for protection under the Endangered Species Act at the federal level.

In 1975, the U. S. banned the sale and public distribution of live turtles and viable turtle eggs measuring less than 4 inches in carapace length to mitigate the spread of salmonellosis in humans, particularly in young children (40 Fed. Reg. 22543). This regulation does not apply to the distribution of turtles for educational, scientific, or exhibitional purposes and does not impact business related exports internationally.In some states, the purchase, acquisition, and possession of Macroclemys temminckii is illegal due to its status as a threatened species across its native range. M. temminckii is protected by the Endangered Species Protection Act in the State of Illinois (510 ILCS 68/5-30) and by the Nongame and Endangered Species Conservation Act in the State of Indiana (IN Code § 14-22-34-1).

In Illinois (Ill. Admin. Code tit. 8, § 25.110(c)), it is illegal to sell or possess turtles and turtle eggs that violate the Public Health Service Act (42 USCA 264; 21 CFR 1240.62; 2005) and Section 3372 of the Lacey Act (16 USCA 3372). The Alligator Snapping Turtle is protected under the Illinois Endangered Species Protection Act and the Herptiles-Herp Act; it is illegal to harvest or collect through any method, including sport fishing (510 ILCS 68/5-30). It is not an approved species on the Aquatic Life Approved Species List for aquaculture, transportation, stocking, importation and/or possession in the State of Illinois (515 ILCS 5/20-90). In Indiana (312 Ind. Admin. Code 9-5- 7.5), it is illegal to sell turtles of any species or origin that are less than 4 inches in carapace length unless it is associated with scientific research, an accredited museum, educational institution, college, university, or government agency. The Alligator Snapping Turtle is protected under the Nongame and Endangered Species Conservation Act by the State of Indiana (IN Code § 14-22-34-1) and its possession, acquisition, transport, export, or sale is illegal. In Minnesota, the Alligator Snapping Turtle is subject to regulation (it is not listed as an unregulated nonnative species) and its introduction is prohibited by the State (MN Admin. Rules 6216.0270, MN Statute 84D.06). In Michigan (Mich. Comp. Laws § 287.312), it is legal to sell turtles and viable eggs under 4 inches if the distributor provides a health advisory sheet with the purchase. In New York (N.Y. Comp. Codes R. & Regs. tit. 10 § 2.58(a)), it remains illegal to sell small turtles and health advisory warnings must be posted near every commercial or educational display where turtles may be handled by the public. In addition, turtles in NY may be tested for salmonellosis at any time and ordered humanely euthanized if they test positive for bacterial infections by health officials. Pennsylvania (35 PA. Code § 1071) maintains federal law and reinforces the ban on the sale of small turtles.

Refer to the CDC website for all regulations related to salmonellosis (https://www.cdc.gov/phlp/docs/turtle-menu.pdf).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Physical

Historically, baited hoop net traps and set lines were effective for capturing M. temminckii for commercial purposes (Folt et al., 2016). Professional trappers often use large hoop net traps that consist of three to seven hoops, allotted with liberal amounts of bait. Other methods include using trotlines (lengthy lines of baited hooks submerged underwater), baited bush lines (single hooks hanging from surrounding foliage), and setting bait in the water at night to lure turtles for seizure or gaffing (Ewert et al., 2006). Alligator Snapping Turtles are relatively more active at night and Ewert et al. (2006) found that setting baited traps during crepuscular or night hours and collecting trapped individuals in the morning was highly effective.

Alligator snapping turtles are exploited for their meat in parts of the rural South, and to a lesser extent by the pet trade (Dundee and Rossman, 1989; Pritchard, 1989; Sloan and Lovich, 1995); they are becoming scarce in parts of their indigenous range (Pritchard, 1989, 1992; Dixon, 2000). Macrochelys temminckii does not receive federal protection but does receive some kind of legal protection in various states (Pritchard, 1992; Levell, 1997).

The identity of M. temminckii found out of their indigenous range should be carefully verified as many untrained people mistake C. serpentina, the common snapping turtle, for this species (personal observation). The nonindigenous M. temminckii in Washington, D.C. (see above), which was scheduled for relocation in another part of D.C. by park rangers, is particularly suspicious.