Editing Painted turtle (section)

===Population features===
[[File:Turtle marking.svg|thumb|upright|right|alt=two diagrams showing numbes on the outer segments of turtle shells. There are some notches and then corresponding numbered code.|Shell marking code]]

Within much of its range, the painted turtle is the most abundant turtle species. [[Population density|Population densities]] range from 10 to 840&nbsp;turtles per hectare (2.5 acres) of water surface. Warmer climates produce higher relative densities among populations, and habitat desirability also influences density. Rivers and large lakes have lower densities because only the shore is desirable habitat; the central, deep waters skew the surface-based estimates. Also, lake and river turtles have to make longer linear trips to access equivalent amounts of foraging space.{{sfn|Ernst|Barbour|Lovich|1994|p=294}}

Adults outnumber juveniles in most populations, but gauging the ratios is difficult because juveniles are harder to catch; with current sampling methods, estimates of [[Population pyramid|age distribution]] vary widely.{{sfn|Ernst|Barbour|Lovich|1994|p=295}} [[Mortality rate|Annual survival rate]] of painted turtles increases with age. The probability of a painted turtle surviving from the egg to its first birthday is only 19%. For females, the annual survival rate rises to 45% for juveniles and 95% for adults. The male survival rates follow a similar pattern, but are probably lower overall than females, as evidenced by the average male age being lower than that of the female.{{sfn|Ernst|Lovich|2009|p=211}} Natural disasters can confound age distributions. For instance, a hurricane can destroy many nests in a region, resulting in fewer hatchlings the next year.{{sfn|Ernst|Lovich|2009|p=211}} Age distributions may also be skewed by migrations of adults.{{sfn|Ernst|Barbour|Lovich|1994|p=295}}

To understand painted turtle adult age distributions, researchers require reliable methods.<ref name="Gibbons1987">{{cite journal|doi=10.2307/1310589 |last=Gibbons |first=J. Whitfield |title=Why do turtles live so long |journal=BioScience |date=May 1987 |volume=37 |issue=4 |pages=262–269 |url=http://140.122.143.143/snake/%E8%84%8A%E6%A4%8E%E5%8B%95%E7%89%A9/%E8%84%8A%E6%A4%8E%E5%8B%95%E7%89%A9%E5%AD%B8%E8%AC%9B%E7%BE%A9%E9%9B%BB%E5%AD%90%E6%AA%94/9.%20why%20do%20turtles%20live%20so%20long.pdf |jstor=1310589 |author-link=J. Whitfield Gibbons |url-status=dead |archive-url=https://web.archive.org/web/20120317030949/http://140.122.143.143/snake/%E8%84%8A%E6%A4%8E%E5%8B%95%E7%89%A9/%E8%84%8A%E6%A4%8E%E5%8B%95%E7%89%A9%E5%AD%B8%E8%AC%9B%E7%BE%A9%E9%9B%BB%E5%AD%90%E6%AA%94/9.%20why%20do%20turtles%20live%20so%20long.pdf |archive-date=March 17, 2012 }}</ref> Turtles younger than four years (up to 12 years in some populations) can be aged based on "[[growth ring]]s" in their shells.<ref name="Zweifel">{{cite book |last=Zweifel|first=Richard George |title=Long-term ecological studies on a population of painted turtles, ''Chrysemys picta'', on Long Island, New York (American Museum Novitates no. 2952) |date=1989 |publisher=American Museum of Natural History |location=New York |url=http://digitallibrary.amnh.org/dspace/bitstream/2246/5106/1/N2952.pdf |pages=18–20 |author-link=Richard G. Zweifel}}</ref> For older turtles, some attempts have been made to determine age based on size and shape of their shells or legs using [[mathematical model]]s, but this method is more uncertain.<ref name="Zweifel" /><ref name="Fowle">{{cite book |title=Highways and movement of wildlife: improving habitat connections and wildlife passageways across highway corridors. Proceedings of the transportation-related wildlife mortality seminar of the Florida Department of Transportation and the Federal Highway Administration. Report FHWA-PD-96-041 |publisher=Florida Department of Transportation (Orlando) |chapter-url=http://www.icoet.net/downloads/96paper16.pdf |author=Fowle, Suzanne C. |chapter=Effects of roadkill mortality on the western painted turtle (''Chrysemys picta belli'') in the Mission valley, western Montana |editor=Evink, G. |editor2=Zeigler, D. |editor3=Garrett, P. |editor4=Berry, J |pages=205–223 |date=1996 |access-date=2011-07-20 |archive-url=https://web.archive.org/web/20110723152641/http://www.icoet.net/downloads/96paper16.pdf |archive-date=2011-07-23 |url-status=dead }}</ref> The most reliable method to study the long-lived turtles is to capture them, permanently mark their shells by notching with a drill, release the turtles, and then recapture them in later years.<ref name="Cagle1939">{{cite journal|last=Cagle |first=Fred R. |title=A system of marking turtles for future identification |journal=Copeia |date=1939-09-09 |volume=1939|issue=3 |pages=170–173 |quote=A system to be used in marking turtles must be permanent, since turtles have a long life span, must definitely identify each individual, must not handicap the turtle in any way, and should be simple and easy to use. |author-link=Fred R. Cagle |jstor=1436818| doi = 10.2307/1436818 }} {{subscription required}}</ref><ref name=Macartney>{{cite book|title=The western painted turtle in Kikomun Creek Provincial Park (report)|date=1985|author=Macartney, M.|author2=Gregory, P. T.}} as cited in {{cite web|title=Inventory methods for pond-breeding amphibians and painted turtle|url=https://www.for.gov.bc.ca/hts/risc/pubs/tebiodiv/pond/baptml20-06.htm|publisher=Ministry of Environment, British Columbia|access-date=2017-10-06|at=3.1.3 Marking and identification|date=1998-03-18|url-status=dead|archive-url=https://web.archive.org/web/20171006212321/https://www.for.gov.bc.ca/hts/risc/pubs/tebiodiv/pond/baptml20-06.htm|archive-date=2017-10-06}}</ref> The longest-running study, in Michigan, has shown that painted turtles can live more than 55 years.<ref name="Zweifel" /><ref name="Congdon2003">{{cite journal |doi=10.1016/S0531-5565(03)00106-2 |author=Congdon, Justin D. |display-authors=4 |author2=Nagle, Roy D. |author3=Kinney, Owen M. |author4=van Loben Sels, Richard C. |author5=Quinter, Todd |author6=Tinkle, Donald W. |author6-link=Donald W. Tinkle |title=Testing hypotheses of aging in long-lived painted turtles (''Chrysemys picta'') |journal=Experimental Gerontology |date=2003 |volume=38 |issue=7 |pages=765–772 |url=http://www.cnah.org/pdf_files/251.pdf |pmid=12855285 |s2cid=12556383 |url-status=dead |archive-url=https://web.archive.org/web/20110726155606/http://www.cnah.org/pdf_files/251.pdf |archive-date=2011-07-26 }}</ref>

Adult [[sex ratio]]s of painted turtle populations average around 1:1.{{sfn|Ernst|Barbour|Lovich|1994|pp=294–295}} Many populations are slightly male-heavy, but some are strongly female-imbalanced; one population in Ontario has a female to male ratio of 4:1.<ref name="sbaa.ca" /> Hatchling sex ratio [[temperature-dependent sex determination|varies based on egg temperature]]. During the middle third of incubation, temperatures of {{convert|23|–|27|C|F|abbr=on|0}} produce males, and anything above or below that, females.<ref name="wcsu.edu-Reproduction" /> It does not appear that females choose nesting sites to influence the sex of the hatchlings;{{sfn|Ernst|Barbour|Lovich|1994|p=291}} within a population, nests will vary sufficiently to give both male and female-heavy broods.{{sfn|Ernst|Barbour|Lovich|1994|p=295}}