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PREDATION ON ALLIGATOR SNAPPING TURTLES(MACROCHELYS TEMMINCKII) BY NORTHERN RIVEROTTERS (LONTRA CANADENSIS)Author(s) Day B Ligon and Jona ReasorSource The Southwestern Naturalist 52(4)608-610 2007Published By Southwestern Association of NaturalistsDOI httpdxdoiorg1018940038-4909(2007)52[608POASTM]20CO2URL httpwwwbiooneorgdoifull1018940038-490928200729525B6083APOASTM5D20CO3B2

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PREDATION ON ALLIGATOR SNAPPING TURTLES (MACROCHELYSTEMMINCKII) BY NORTHERN RIVER OTTERS (LONTRA CANADENSIS)

DAY B LIGON AND JONA REASOR

Department of Zoology 430 Life Sciences West Oklahoma State University Stillwater OK 74078 (DBL)

Tishomingo National Wildlife Refuge 12000 South Refuge Road Tishomingo OK 73460 (JR)

Correspondent dayligonokstateedu

ABSTRACTmdashWe found alligator snapping turtle (Macrochelys temminckii) carcasses in association withnorthern river otters (Lontra canadensis) at two sites in Oklahoma in summer 2006 Both specimens ofturtles were juveniles and at least one had been hatched and head-started in captivity prior to beingreleased This specimen was part of a radiotelemetry study at Sequoyah National Wildlife Refuge in east-central Oklahoma The second carcass was found while investigating recent sightings of northern riverotters at Tishomingo National Wildlife Refuge in southern Oklahoma With the exception ofcannibalism observed in a study of diet of adult alligator snapping turtles these are the first reports ofspecific incidences of likely postembryonic predation of alligator snapping turtles

RESUMENmdashEncontramos caparazones de la tortuga caiman (Macrochelys temminckii) en asociacion connutrias de rıo (Lontra canadensis) en dos sitios en Oklahoma en el verano del ano 2006 Ambas tortugasfueron juveniles y por lo menos una habıa nacido y habıa sido criada en cautiverio antes de ser puestaen libertad Este especimen fue parte de un estudio radiotelemetrico en el Sequoyah National WildlifeRefuge en Oklahoma este-central La segunda caparazon de tortuga fue encontrada durante lainvestigacion de avistamientos recientes de nutrias de rıo en el Tishomingo National Wildlife Refuge alsur de Oklahoma Con la excepcion de canibalismo observado en un estudio de la dieta de adultos de latortuga caiman estos dos incidentes son los primeros informes de la probable depredacionpostembrionica de las tortugas caiman

Survival rates of aquatic turtles vary dramaticallyamong age classes Eggs are targeted by many avianand mammalian predators (MacDonald et al1994 Brown and MacDonald 1995 Horne et al2003 Lanszki et al 2006) and hatchlings areexposed to high rates of predation during terres-trial migration from nest to water (Gyuris 1994Janzen et al 2000) However rates of predationtend to decrease with growth as predators becomegape limited and shells ossify (Swingland and Coe1979) Mature age classes of species of turtles thatbecome especially large as adults generally havefew non-anthropic predators

The alligator snapping turtle (Macrochelystemminckii) is the largest freshwater species of

turtle in North America (Ernst and Barbour1989) Its size combined with a highly aquaticlifestyle is expected to limit exposure to pre-dators Specific occurrences of predation ofpostembryonic alligator snapping turtles havebeen only by adult conspecifics (Sloan et al1996) Therefore potential predators and therelationship between size and predation risk ispoorly known for this species

We report two incidents of apparent predationon juvenile alligator snapping turtles that oc-curred in Oklahoma during summer 2006 Thefirst was a captive-reared female that was one of15 head-started turtles equipped with radio-transmitters and released in Big Vian Creek at

608 The Southwestern Naturalist vol 52 no 4

Sequoyah National Wildlife Refuge on 5 June2006 Its carcass was recovered on 10 July 2006At time of release mass 5 602 g midline lengthof carapace 5 140 mm and length of plastron 5

103 mm The carcass was found 45 m inlandfrom the edge of the creek and about 15 m fromits last known location in the water Circumstan-tial evidence strongly suggested that predationwas by a northern river otter (Lontra canadensis)a species that has experienced a recent re-surgence in numbers in the state (Hatcher1984 Shackelford and Whitaker 1997) Firstscat of the northern river otter was observed ontop of the partially submerged log under whichthe turtle was located for much of the time afterits release Second a northern river otter wasobserved standing upright on the same log6 days prior to finding the carcass Third a denof the northern river otter was on the bank of thecreek between the points where the live turtle waslast located and where its carcass was discoveredAt the time the carcass was found the radio-transmitter was still tightly bonded to the scutesbut no muscle tissue remained in the shell andbones were scattered in about a 1-m radiusaround it Although signals of other radiotrans-mitters disappeared in subsequent months thisturtle was the only confirmed fatality

We observed evidence of a second predationevent at Tishomingo National Wildlife Refuge insouthern Oklahoma where the carcass of a juve-nile alligator snapping turtle was found on 7September 2006 during a search for evidence ofnorthern river otters The intact shell of analligator snapping turtle measuring 88 by82 mm (length and width of carapace respec-tively) was found on top of a midden of theNorth American beaver (Castor canadensis)at LostLake a small oxbow lake located at the refugeTwo northern river otters were observed nearbyduring a spotlight survey the night prior tofinding the turtle carcass and lone otters wereseen on 31 August and 11 September Alligatorsnapping turtles were believed to be rare atTishomingo National Wildlife Refuge becauseonly one specimen incidentally caught ina slough by a local fisherman had been reportedin recent years Formal sampling of the area aspart of a statewide survey of the species in 1998failed to document any alligator snapping turtles(Riedle 2001) A private turtle breeder releasedhatchling alligator snapping turtles at Tisho-mingo National Wildlife Refuge annually from

2001 to 2006 and 25 hatchlings were released inLost Lake in September 2004 These hatchlingswere not marked before release prior to 2006 sopositively identifying the carcass that we found asthat of a captive-bred juvenile is impossibleHowever scute annuli corroborate that the turtlehatched in 2004 and if the carcass was that ofa captive-bred turtle as seems likely then growthwas much greater in the head-started turtlecompared to the turtle released at hatching

Although our observations offer evidenceimplicating northern river otters we cannot ruleout the possibility that one or both alligatorsnapping turtles died of causes unrelated topredation and were subsequently scavengedHowever predation of a wide variety of aquaticvertebrates and invertebrates by northern riverotters is well documented (Lanszki et al 2006)Furthermore the radiotransmittered turtle wasknown to be in good health at the time of itsrelease and was therefore unlikely to die35 days later of causes unrelated to predationThe turtle found at Tishomingo National Wild-life Refuge had apparently survived since au-tumn 2004 and in that time exhibited modestgrowth Therefore we suggest direct predation isa more parsimonious conclusion than a combi-nation of death and subsequent scavenging

Previous descriptions of foraging by Europeanriver otters (Lutra lutra) suggest that turtles areof secondary importance consumed only duringwinter when preferred prey such as fish andamphibians are unavailable (Kotenko 2000Lanszki et al 2006) In contrast the predationevents we observed occurred during summerwhen availability of food presumably was highAdditionally our observations were made indifferent river basins suggesting that consump-tion of turtles by L canadensis might be morecommon than in its European counterpart

It remains unclear to what extent predation bynorthern river otters affects populations ofalligator snapping turtles or to what extentnorthern river otters consume other species ofturtles The larger of the two predated turtlesoverlapped in size with adults of most sympatricspecies of turtles including species of GraptemysTrachemys Apalone Kinosternon Sternotherus andTerrepene (Ernst et al 1994) Furthermore it isunknown whether this specimen was at theupper size limit of turtles that otters willconsume Northern river otters were absent fromOklahoma for many decades and have only

December 2007 Notes 609

recently become reestablished Therefore aspopulations of northern river otters increasedue to reintroduction and other managementpractices their effect on communities of turtlesshould be closely monitored

We thank B Harding S Kasson D Moore and JSanchez for field assistance K Graves B Fillmore andothers at Tishomingo National Fish Hatchery providedthe captive-reared turtles released at Sequoyah Nation-al Wildlife Refuge We also thank K Backues and theTulsa City Zoo for volunteering time and resources tosurgically determine sex of turtles prior to release SFox M Lovern and D Riedle provided valuablecomments on the manuscript and A Cheville providedtranslation of the resumen Work was conducted underan Oklahoma Department of Wildlife Conservationpermit and Oklahoma State University InstitutionalAnimal Care and Use Protocol AS023

LITERATURE CITED

BROWN L AND D W MACDONALD 1995 Predation ongreen turtle Chelonia mydas nests by wild canids atAkyatan Beach Turkey Biological Conservation7155ndash60

ERNST C H AND R W BARBOUR 1989 Turtles of the worldSmithsonian Institution Press Washington DC

ERNST C H J E LOVICH AND R W BARBOUR 1994Turtles of the United States and Canada Smithso-nian Institution Press Washington DC

GYURIS E 1994 The rate of predation by fishes onhatchlings of the green turtle (Chelonia mydas)Coral Reefs 13137ndash144

HATCHER R T 1984 River otters in Oklahoma Proceed-ings of the Oklahoma Academy of Science 6417ndash19

HORNE B D R J BRAUMAN M J C MOORE AND R ASEIGEL 2003 Reproductive and nesting ecology of

the yellow-blotched map turtle Graptemys flavimacu-lata implications for conservation and manage-ment Copeia 2003729ndash738

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageselection on size of hatchling turtles Ecology812290ndash2304

KOTENKO T I 2000 The European pond turtle (Emys

orbicularis) in the Steppe Zone of the UkraineStapfia 6987ndash106

LANSZKI J M MOLNAR AND T MOLNAR 2006 Factorsaffecting the predation of otter (Lutra lutra) onEuropean pond turtle (Emys orbicularis) Journal ofZoology (London) 270219ndash226

MACDONALD D W L BROWN S YERLI AND A FCANBOLAT 1994 Behavior of red foxes Vulpes vulpescaching eggs of loggerhead turtles Caretta carettaJournal of Mammalogy 75985ndash988

RIEDLE J D 2001 The ecology of the alligator snappingturtle Macrochelys temminckii in Oklahoma MSthesis Oklahoma State University Stillwater

SHACKELFORD J AND J WHITAKER 1997 Relative abun-dance of the northern river otter Lutra canadensisin three drainage basins of southeastern OklahomaProceedings of the Oklahoma Academy of Science7793ndash98

SLOAN K N K A BUHLMANN AND J E LOVICH 1996Stomach contents of commercially harvested adultsnapping turtles Macrochelys temminckii ChelonianConservation and Biology 296ndash99

SWINGLAND I R AND M J COE 1979 The naturalregulation of giant tortoise populations on AldabraAtoll recruitment Philosophical Transactions ofthe Royal Society of London 286B177ndash188

Submitted 21 December 2006 Accepted 31 March 2007Editor was Mark Eberle

610 The Southwestern Naturalist vol 52 no 4

Sequoyah National Wildlife Refuge on 5 June2006 Its carcass was recovered on 10 July 2006At time of release mass 5 602 g midline lengthof carapace 5 140 mm and length of plastron 5

103 mm The carcass was found 45 m inlandfrom the edge of the creek and about 15 m fromits last known location in the water Circumstan-tial evidence strongly suggested that predationwas by a northern river otter (Lontra canadensis)a species that has experienced a recent re-surgence in numbers in the state (Hatcher1984 Shackelford and Whitaker 1997) Firstscat of the northern river otter was observed ontop of the partially submerged log under whichthe turtle was located for much of the time afterits release Second a northern river otter wasobserved standing upright on the same log6 days prior to finding the carcass Third a denof the northern river otter was on the bank of thecreek between the points where the live turtle waslast located and where its carcass was discoveredAt the time the carcass was found the radio-transmitter was still tightly bonded to the scutesbut no muscle tissue remained in the shell andbones were scattered in about a 1-m radiusaround it Although signals of other radiotrans-mitters disappeared in subsequent months thisturtle was the only confirmed fatality

We observed evidence of a second predationevent at Tishomingo National Wildlife Refuge insouthern Oklahoma where the carcass of a juve-nile alligator snapping turtle was found on 7September 2006 during a search for evidence ofnorthern river otters The intact shell of analligator snapping turtle measuring 88 by82 mm (length and width of carapace respec-tively) was found on top of a midden of theNorth American beaver (Castor canadensis)at LostLake a small oxbow lake located at the refugeTwo northern river otters were observed nearbyduring a spotlight survey the night prior tofinding the turtle carcass and lone otters wereseen on 31 August and 11 September Alligatorsnapping turtles were believed to be rare atTishomingo National Wildlife Refuge becauseonly one specimen incidentally caught ina slough by a local fisherman had been reportedin recent years Formal sampling of the area aspart of a statewide survey of the species in 1998failed to document any alligator snapping turtles(Riedle 2001) A private turtle breeder releasedhatchling alligator snapping turtles at Tisho-mingo National Wildlife Refuge annually from

2001 to 2006 and 25 hatchlings were released inLost Lake in September 2004 These hatchlingswere not marked before release prior to 2006 sopositively identifying the carcass that we found asthat of a captive-bred juvenile is impossibleHowever scute annuli corroborate that the turtlehatched in 2004 and if the carcass was that ofa captive-bred turtle as seems likely then growthwas much greater in the head-started turtlecompared to the turtle released at hatching

Although our observations offer evidenceimplicating northern river otters we cannot ruleout the possibility that one or both alligatorsnapping turtles died of causes unrelated topredation and were subsequently scavengedHowever predation of a wide variety of aquaticvertebrates and invertebrates by northern riverotters is well documented (Lanszki et al 2006)Furthermore the radiotransmittered turtle wasknown to be in good health at the time of itsrelease and was therefore unlikely to die35 days later of causes unrelated to predationThe turtle found at Tishomingo National Wild-life Refuge had apparently survived since au-tumn 2004 and in that time exhibited modestgrowth Therefore we suggest direct predation isa more parsimonious conclusion than a combi-nation of death and subsequent scavenging

Previous descriptions of foraging by Europeanriver otters (Lutra lutra) suggest that turtles areof secondary importance consumed only duringwinter when preferred prey such as fish andamphibians are unavailable (Kotenko 2000Lanszki et al 2006) In contrast the predationevents we observed occurred during summerwhen availability of food presumably was highAdditionally our observations were made indifferent river basins suggesting that consump-tion of turtles by L canadensis might be morecommon than in its European counterpart

It remains unclear to what extent predation bynorthern river otters affects populations ofalligator snapping turtles or to what extentnorthern river otters consume other species ofturtles The larger of the two predated turtlesoverlapped in size with adults of most sympatricspecies of turtles including species of GraptemysTrachemys Apalone Kinosternon Sternotherus andTerrepene (Ernst et al 1994) Furthermore it isunknown whether this specimen was at theupper size limit of turtles that otters willconsume Northern river otters were absent fromOklahoma for many decades and have only

December 2007 Notes 609

recently become reestablished Therefore aspopulations of northern river otters increasedue to reintroduction and other managementpractices their effect on communities of turtlesshould be closely monitored

We thank B Harding S Kasson D Moore and JSanchez for field assistance K Graves B Fillmore andothers at Tishomingo National Fish Hatchery providedthe captive-reared turtles released at Sequoyah Nation-al Wildlife Refuge We also thank K Backues and theTulsa City Zoo for volunteering time and resources tosurgically determine sex of turtles prior to release SFox M Lovern and D Riedle provided valuablecomments on the manuscript and A Cheville providedtranslation of the resumen Work was conducted underan Oklahoma Department of Wildlife Conservationpermit and Oklahoma State University InstitutionalAnimal Care and Use Protocol AS023

LITERATURE CITED

BROWN L AND D W MACDONALD 1995 Predation ongreen turtle Chelonia mydas nests by wild canids atAkyatan Beach Turkey Biological Conservation7155ndash60

ERNST C H AND R W BARBOUR 1989 Turtles of the worldSmithsonian Institution Press Washington DC

ERNST C H J E LOVICH AND R W BARBOUR 1994Turtles of the United States and Canada Smithso-nian Institution Press Washington DC

GYURIS E 1994 The rate of predation by fishes onhatchlings of the green turtle (Chelonia mydas)Coral Reefs 13137ndash144

HATCHER R T 1984 River otters in Oklahoma Proceed-ings of the Oklahoma Academy of Science 6417ndash19

HORNE B D R J BRAUMAN M J C MOORE AND R ASEIGEL 2003 Reproductive and nesting ecology of

the yellow-blotched map turtle Graptemys flavimacu-lata implications for conservation and manage-ment Copeia 2003729ndash738

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageselection on size of hatchling turtles Ecology812290ndash2304

KOTENKO T I 2000 The European pond turtle (Emys

orbicularis) in the Steppe Zone of the UkraineStapfia 6987ndash106

LANSZKI J M MOLNAR AND T MOLNAR 2006 Factorsaffecting the predation of otter (Lutra lutra) onEuropean pond turtle (Emys orbicularis) Journal ofZoology (London) 270219ndash226

MACDONALD D W L BROWN S YERLI AND A FCANBOLAT 1994 Behavior of red foxes Vulpes vulpescaching eggs of loggerhead turtles Caretta carettaJournal of Mammalogy 75985ndash988

RIEDLE J D 2001 The ecology of the alligator snappingturtle Macrochelys temminckii in Oklahoma MSthesis Oklahoma State University Stillwater

SHACKELFORD J AND J WHITAKER 1997 Relative abun-dance of the northern river otter Lutra canadensisin three drainage basins of southeastern OklahomaProceedings of the Oklahoma Academy of Science7793ndash98

SLOAN K N K A BUHLMANN AND J E LOVICH 1996Stomach contents of commercially harvested adultsnapping turtles Macrochelys temminckii ChelonianConservation and Biology 296ndash99

SWINGLAND I R AND M J COE 1979 The naturalregulation of giant tortoise populations on AldabraAtoll recruitment Philosophical Transactions ofthe Royal Society of London 286B177ndash188

Submitted 21 December 2006 Accepted 31 March 2007Editor was Mark Eberle

610 The Southwestern Naturalist vol 52 no 4

recently become reestablished Therefore aspopulations of northern river otters increasedue to reintroduction and other managementpractices their effect on communities of turtlesshould be closely monitored

We thank B Harding S Kasson D Moore and JSanchez for field assistance K Graves B Fillmore andothers at Tishomingo National Fish Hatchery providedthe captive-reared turtles released at Sequoyah Nation-al Wildlife Refuge We also thank K Backues and theTulsa City Zoo for volunteering time and resources tosurgically determine sex of turtles prior to release SFox M Lovern and D Riedle provided valuablecomments on the manuscript and A Cheville providedtranslation of the resumen Work was conducted underan Oklahoma Department of Wildlife Conservationpermit and Oklahoma State University InstitutionalAnimal Care and Use Protocol AS023

LITERATURE CITED

BROWN L AND D W MACDONALD 1995 Predation ongreen turtle Chelonia mydas nests by wild canids atAkyatan Beach Turkey Biological Conservation7155ndash60

ERNST C H AND R W BARBOUR 1989 Turtles of the worldSmithsonian Institution Press Washington DC

ERNST C H J E LOVICH AND R W BARBOUR 1994Turtles of the United States and Canada Smithso-nian Institution Press Washington DC

GYURIS E 1994 The rate of predation by fishes onhatchlings of the green turtle (Chelonia mydas)Coral Reefs 13137ndash144

HATCHER R T 1984 River otters in Oklahoma Proceed-ings of the Oklahoma Academy of Science 6417ndash19

HORNE B D R J BRAUMAN M J C MOORE AND R ASEIGEL 2003 Reproductive and nesting ecology of

the yellow-blotched map turtle Graptemys flavimacu-lata implications for conservation and manage-ment Copeia 2003729ndash738

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageselection on size of hatchling turtles Ecology812290ndash2304

KOTENKO T I 2000 The European pond turtle (Emys

orbicularis) in the Steppe Zone of the UkraineStapfia 6987ndash106

LANSZKI J M MOLNAR AND T MOLNAR 2006 Factorsaffecting the predation of otter (Lutra lutra) onEuropean pond turtle (Emys orbicularis) Journal ofZoology (London) 270219ndash226

MACDONALD D W L BROWN S YERLI AND A FCANBOLAT 1994 Behavior of red foxes Vulpes vulpescaching eggs of loggerhead turtles Caretta carettaJournal of Mammalogy 75985ndash988

RIEDLE J D 2001 The ecology of the alligator snappingturtle Macrochelys temminckii in Oklahoma MSthesis Oklahoma State University Stillwater

SHACKELFORD J AND J WHITAKER 1997 Relative abun-dance of the northern river otter Lutra canadensisin three drainage basins of southeastern OklahomaProceedings of the Oklahoma Academy of Science7793ndash98

SLOAN K N K A BUHLMANN AND J E LOVICH 1996Stomach contents of commercially harvested adultsnapping turtles Macrochelys temminckii ChelonianConservation and Biology 296ndash99

SWINGLAND I R AND M J COE 1979 The naturalregulation of giant tortoise populations on AldabraAtoll recruitment Philosophical Transactions ofthe Royal Society of London 286B177ndash188

Submitted 21 December 2006 Accepted 31 March 2007Editor was Mark Eberle

610 The Southwestern Naturalist vol 52 no 4