Editing Common snapping turtle (section)

==Ecology and life history==
Common habitats are shallow [[pond]]s or [[streams]]. Some may inhabit [[brackish water|brackish]] environments, such as [[estuary|estuaries]]. These sources of water tend to have an abundance of [[aquatic vegetation]] due to the shallow pools.<ref>{{Cite journal |last1=Piczak |first1=Morgan L. |last2=Chow-Fraser |first2=Patricia |date=2019-06-01 |title=Assessment of critical habitat for common snapping turtles (Chelydra serpentina) in an urbanized coastal wetland |url=https://doi.org/10.1007/s11252-019-00841-1 |journal=[[Urban Ecosystems]] |language=en |volume=22 |issue=3 |pages=525–537 |doi=10.1007/s11252-019-00841-1 |bibcode=2019UrbEc..22..525P |s2cid=78091420 |issn=1573-1642|url-access=subscription }}</ref> Some describe them as habitat generalists<ref>{{Cite journal |last1=LaGrange |first1=Seth M. |last2=Kessler |first2=Ethan J. |last3=Li |first3=Zhuang |last4=Morrissiey |first4=Flavio |last5=Merchant |first5=Mark |date=2023 |title=Bite-Force Scaling across Size Classes in the Alligator Snapping Turtle (Macrochelys temminckii) and the Common Snapping Turtle (Chelydra serpentina) |url=https://bioone.org/journals/southeastern-naturalist/volume-22/issue-sp12/058.022.0sp1228/Bite-Force-Scaling-across-Size-Classes-in-the-Alligator-Snapping/10.1656/058.022.0sp1228.full |journal=Southeastern Naturalist |volume=22 |issue=sp12 |pages=440–456 |doi=10.1656/058.022.0sp1228 |issn=1528-7092|url-access=subscription }}</ref> as they can occupy most permanent bodies of water.<ref>{{Cite journal |last1=Reese |first1=Scott A. |last2=Jackson |first2=Donald C. |last3=Ultsch |first3=Gordon R. |date=2002 |title=The Physiology of Overwintering in a Turtle That Occupies Multiple Habitats, the Common Snapping Turtle ( Chelydra serpentina ) |url=http://www.journals.uchicago.edu/doi/10.1086/342802 |journal=Physiological and Biochemical Zoology |language=en |volume=75 |issue=5 |pages=432–438 |doi=10.1086/342802 |pmid=12529844 |issn=1522-2152|url-access=subscription }}</ref> Common snapping turtles sometimes bask—though rarely observed—by floating on the surface with only their carapaces exposed, though in the northern parts of their range, they also readily bask on fallen logs in early spring. In shallow waters, common snapping turtles may lie beneath a muddy bottom with only their heads exposed, stretching their long necks to the surface for an occasional breath. Their nostrils are positioned on the very tip of the snout, effectively functioning as snorkels.<ref name="Hammer, D.A. 1972">Hammer, D.A. (1972). ''Ecological relations of waterfowl and snapping turtle populations''. Ph.D. dissertation, Utah State University, Salt Lake City, UT. 72 pg.</ref>

Common snapping turtles are [[omnivore|omnivorous]].  Important aquatic scavengers, they are also active hunters that use ambush tactics to prey on anything they can swallow, including many [[invertebrate]]s, [[fish]], [[frog]]s, other [[amphibian]]s, [[reptile]]s (including snakes and smaller turtles), unwary [[bird]]s, and small [[mammal]]s.<ref>{{Cite journal |last1=Bergeron |first1=Christine M. |last2=Husak |first2=Jerry E. |last3=Unrine |first3=Jason M. |last4=Romanek |first4=Christopher S. |last5=Hopkins |first5=William A. |date=August 2007 |title=Influence of feeding ecology on blood mercury concentrations in four species of turtles |journal=Environmental Toxicology and Chemistry |volume=26 |issue=8 |pages=1733–1741 |doi=10.1897/06-594r.1 |issn=0730-7268 |pmid=17702349|s2cid=19542536 |doi-access=free }}</ref><ref name=ADW>{{Cite web | url=https://animaldiversity.org/accounts/Chelydra_serpentina/ | title=Chelydra serpentina (Common Snapping Turtle) | website=[[Animal Diversity Web]] }}</ref> In a recent study, young common snapping turtles showed that their lower bite force matches their active foraging behavior, meaning they have to travel and seek out more prey to make up for their inability to eat some items.<ref>{{Cite journal |last1=LaGrange |first1=Seth M. |last2=Kessler |first2=Ethan J. |last3=Li |first3=Zhuang |last4=Morrissiey |first4=Flavio |last5=Merchant |first5=Mark |date=2023 |title=Bite-Force Scaling across Size Classes in the Alligator Snapping Turtle (Macrochelys temminckii) and the Common Snapping Turtle (Chelydra serpentina) |url=https://bioone.org/journals/southeastern-naturalist/volume-22/issue-sp12/058.022.0sp1228/Bite-Force-Scaling-across-Size-Classes-in-the-Alligator-Snapping/10.1656/058.022.0sp1228.full |journal=Southeastern Naturalist |volume=22 |issue=sp12 |pages=440–456 |doi=10.1656/058.022.0sp1228 |issn=1528-7092|url-access=subscription }}</ref> In some areas adult common snapping turtles can occasionally be incidentally detrimental to breeding [[waterfowl]], but their effect on such prey as ducklings and goslings is frequently exaggerated.<ref name="Hammer, D.A. 1972"/> As omnivorous scavengers though, they will also feed on [[carrion]] and a surprisingly large amount of aquatic vegetation.<ref name=ADW/>

[[File:Snapping_turtle_eggs_md.jpg|thumb|left|Eggs]][[File:Juvenile Snapping Turtle IBSP.tif|thumb|A juvenile common snapping turtle (''Chelydra serpentina'') on a hiking path at [[Illinois Beach State Park]] ]]
Common snapping turtles have few predators when older, but eggs are subject to predation by [[crow]]s, [[American mink]], [[skunk]]s, [[fox]]es, and [[raccoon]]s.<ref name=Oddie-2015>{{Cite journal |last1=Oddie |first1=Melissa A.Y. |last2=Coombes |first2=Suzanne M. |last3=Davy |first3=Christina M. |date=April 2015 |title=Investigation of cues used by predators to detect Snapping Turtle (''Chelydra serpentina'') nests |url=http://dx.doi.org/10.1139/cjz-2014-0264 |journal=Canadian Journal of Zoology |volume=93 |issue=4 |pages=299–305 |doi=10.1139/cjz-2014-0264 |issn=0008-4301|url-access=subscription }}</ref> Egg predators use three types of cues to locate turtle nests:
*Visual cues – seeing where the female has dug the soil for the nest chamber and seeing the turtle
*Tactile cues – soft surface around the nest site
*Chemosensory cues – scent of the musk of the female that she leaves on the surface of the soil as she digs<ref name=Oddie-2015/>

As hatchlings and juveniles, most of the same predators will attack them as well as [[heron]]s (mostly [[great blue heron]]s), [[bittern]]s, [[hawk]]s, [[owl]]s, [[Fisher (animal)|fisher]]s, [[American bullfrog]]s, large [[fish]], and [[snakes]].<ref name="VHS" /> There are records during winter in [[Canada]] of hibernating adult common snapping turtles being ambushed and preyed on by [[northern river otter]]s.<ref name="Brooks">{{cite journal |last1=Brooks |first1=R.J. |last2=Brown |first2=G.P. |last3=Galbraith |first3=D.A. |year=1991 |title=Effects of a sudden increase in natural mortality of adults on a population of the common snapping turtle (''Chelydra serpentina'') |journal=Canadian Journal of Zoology |volume=69 |issue=5 |pages=1314–1320 |doi=10.1139/z91-185}}</ref> Other natural predators which have reportedly preyed on adults include [[coyote]]s, [[American black bear]]s, [[American alligator]]s and their larger cousins, [[alligator snapping turtle]]s.<ref>Ernst, C.H., & Lovich, J. E. (2009). ''Turtles of the United States and Canada''. Baltimore: Johns Hopkins University Press.</ref> Large, old male common snapping turtles have very few natural threats due to their formidable size and defenses, and tend to have a very low annual mortality rate.<ref name="Brooks" />

These turtles travel extensively over land to reach new [[habitat]]s or to lay [[Egg (biology)|eggs]]. Pollution, [[habitat destruction]], food scarcity, overcrowding, and other factors drive snappers to move; it is quite common to find them traveling far from the nearest water source. Experimental data supports the idea that common snapping turtles can sense the Earth's magnetic field, which could also be used for such movements (together with a variety of other possible orientation cues).<ref>{{Cite journal|last1=Landler|first1=Lukas|last2=Painter|first2=Michael S.|last3=Youmans|first3=Paul W.|last4=Hopkins|first4=William A.|last5=Phillips|first5=John B.|date=2015-05-15|title=Spontaneous Magnetic Alignment by Yearling Snapping Turtles: Rapid Association of Radio Frequency Dependent Pattern of Magnetic Input with Novel Surroundings|journal=PLOS ONE|language=en|volume=10|issue=5|pages=e0124728|doi=10.1371/journal.pone.0124728|issn=1932-6203|pmc=4433231|pmid=25978736|bibcode=2015PLoSO..1024728L|doi-access=free}}</ref><ref>{{Cite journal|last1=Congdon|first1=Justin D.|last2=Pappas|first2=Michael J.|last3=Krenz|first3=John D.|last4=Brecke|first4=Bruce J.|last5=Schlenner|first5=Meredith|date=2015-02-27|title=Compass Orientation During Dispersal of Freshwater Hatchling Snapp Turtles (Chelydra serpentina) and Blanding's Turtles (Emydoidea blandingii)|journal=Ethology|language=en|volume=121|issue=6|pages=538–547|doi=10.1111/eth.12366|bibcode=2015Ethol.121..538C |issn=0179-1613}}</ref>

This species mates from April through November, with their peak laying season in June and July. The female can hold [[spermatozoa|sperm]] for several seasons, using it as necessary. Females travel over land to find sandy soil in which to lay their eggs, often some distance from the water. After digging a hole, the female typically deposits 25 to 80 eggs each year, guiding them into the [[nest]] with her hind feet and covering them with sand for incubation and protection.<ref name="el.erdc.usace.army.mil">{{Cite web |url=http://el.erdc.usace.army.mil/emrrp/turtles/species/comsnap.html |title=US Army Corps of Engineers, Engineer Research and Development Center, Environmental Laboratory: Common Snapping Turtle (''Chelydra serpentina'') |access-date=2013-05-23 |archive-url=https://web.archive.org/web/20130331020305/http://el.erdc.usace.army.mil/emrrp/turtles/species/comsnap.html |archive-date=2013-03-31 |url-status=dead }}</ref> These eggs have a leathery, flexible shell and they typically measure only 26–28 mm in diameter.<ref>{{Cite journal |last1=Blackburn |first1=Daniel G. |last2=Lestz |first2=Luisa |last3=Barnes |first3=Madeline S. |last4=Powers |first4=Kathryn G. |date=2019 |title=How do embryonic turtles process yolk? Evidence from the Snapping Turtle, Chelydra serpentina (Chelydridae) |url=http://www.nrcresearchpress.com/doi/10.1139/cjz-2018-0205 |journal=Canadian Journal of Zoology |language=en |volume=97 |issue=6 |pages=495–501 |doi=10.1139/cjz-2018-0205 |issn=0008-4301|url-access=subscription }}</ref>

Incubation time is temperature-dependent, ranging from 9 to 18 weeks. One study on the incubation period of the common snapping turtle incubated the eggs at two temperatures: 20&nbsp;°C (68&nbsp;°F) and 30&nbsp;°C (86&nbsp;°F). The research found that the incubation period at the higher temperature was significantly shorter at approximately 63 days, while at the lower temperature the time was approximately 140 days.<ref>{{Cite journal |last=Yntema |first=C. L. |date=June 1968 |title=A series of stages in the embryonic development ofChelydra serpentina |url=https://onlinelibrary.wiley.com/doi/10.1002/jmor.1051250207 |journal=Journal of Morphology |language=en |volume=125 |issue=2 |pages=219–251 |doi=10.1002/jmor.1051250207 |pmid=5681661 |s2cid=37022680 |issn=0362-2525|url-access=subscription }}</ref> In cooler climates, hatchlings overwinter in the nest. The common snapping turtle is remarkably cold-tolerant; radiotelemetry studies have shown some individuals do not hibernate, but remain active under the ice during the winter.<ref name="el.erdc.usace.army.mil"/> In addition to incubation time, temperature also affects sex determination. It has been shown that females develop at low and high temperatures, while males develop in the intermediate temperature range. <ref>{{Cite journal |last1=Schroeder |first1=Anthony L. |last2=Metzger |first2=Kelsey J. |last3=Miller |first3=Alexandra |last4=Rhen |first4=Turk |date=2016 |title=A novel candidate gene for Temperature-Dependent sex determination in the common snapping turtle. |journal=Genetics |volume=203 |issue=1 |pages=557–571 |doi=10.1534/genetics.115.182840 |pmc=4858799 |pmid=26936926}}</ref> Fall temperatures had a positive effect on clutch size and clutch mass, whereas spring temperatures had no impact.<ref>{{Cite journal |last1=Hedrick |first1=A.R. |last2=Klondaris |first2=H.M. |last3=Corichi |first3=L.C. |last4=Dreslik |first4=M.J. |last5=Iverson |first5=J.B. |date=March 2018 |title=The effects of climate on annual variation in reproductive output in Snapping Turtles (''Chelydra serpentina'') |url=http://dx.doi.org/10.1139/cjz-2016-0321 |journal=Canadian Journal of Zoology |volume=96 |issue=3 |pages=221–228 |doi=10.1139/cjz-2016-0321 |issn=0008-4301|url-access=subscription }}</ref>

Common snapping turtle hatchlings have recently been found to make sounds before nest exit onto the surface, a phenomenon also known from species in the South American genus ''[[Podocnemis]]'' and the [[Ouachita map turtle]]. These sounds are mostly "clicking" noises, but other sounds, including those that sound somewhat like a “creak” or rubbing a finger along a fine-toothed comb, are also sometimes produced.<ref>{{cite journal|last1=Geller|first1=G.A.|first2=G.S.|last2=Casper|year=2019|title=Late term embryos and hatchlings of Ouachita Map Turtles (Graptemys ouachitensis) make sounds within the nest|journal=Herpetological Review|volume=50|issue=3|pages=449–452}}</ref><ref>{{cite journal|last1=Geller|first1=G.A.|first2=G.S.|last2=Casper|year=2019|title=Chelydra serpentina (Snapping Turtle) hatchling sounds| journal=Herpetological Review| volume=50| issue=4| pages=768–769}}</ref> 

In the northern part of their range common snapping turtles do not breathe for more than six months because ice covers their hibernating site. These turtles can get oxygen by pushing their head out of the mud and allowing gas exchange to take place through the membranes of their mouth and throat. This is known as extrapulmonary respiration.<ref name="Edqvist">{{cite web|url=http://www.tortoisetrust.org/articles/snappers.htm|title=Tortoise Trust Web – Conservation and Ecology of Snapping Turtles|first=ULf|last=Edqvist|website=www.tortoisetrust.org|access-date=3 April 2018}}</ref>

If they cannot get enough oxygen through this method they start to utilize anaerobic pathways, burning sugars and fats without the use of oxygen. The metabolic by-products from this process are acidic and create very undesirable side effects by spring, which are known as oxygen debt.<ref name="Edqvist"/> Although designated as "least concern" on the [[IUCN]] redlist, the species has been designated in the Canadian part of its range as "Special Concern" due to its life history being sensitive to disruption by anthropogenic activity.<ref>{{cite web|last=COSEWIC|title=Species Profile – Snapping Turtle|url=http://www.sararegistry.gc.ca/species/speciesDetails_e.cfm?sid=1033|work=Species At Risk Public Registry|publisher=Government of Canada|access-date=24 February 2012|archive-url=https://web.archive.org/web/20130610233749/http://www.sararegistry.gc.ca/species/speciesDetails_e.cfm?sid=1033|archive-date=10 June 2013|url-status=dead}}</ref>