Editing Tyrannosaurus (section)

===Population estimates===
[[File:Upper Cretaceous Hell Creek dinosaur census 2.svg|thumb|Chart of the time-averaged census for large-bodied dinosaurs from the entire Hell Creek Formation in the study area]]
According to studies published in 2021 by Charles Marshall et al., the total population of adult ''Tyrannosaurus'' at any given time was perhaps 20,000 individuals, with computer estimations also suggesting a total population no lower than 1,300 and no higher than 328,000. The authors themselves suggest that the estimate of 20,000 individuals is probably lower than what should be expected, especially when factoring in that disease pandemics could easily wipe out such a small population. Over the span of the genus' existence, it is estimated that there were about 127,000 generations and that this added up to a total of roughly 2.5 billion animals until their extinction.<ref name="nytimes2021"/><ref name="Marshall2021"/>

In the same paper, it is suggested that in a population of ''Tyrannosaurus'' adults numbering 20,000, the number of individuals living in an area the size of California could be as high as 3,800 animals, while an area the size of Washington D.C. could support a population of only two adult ''Tyrannosaurus''. The study does not take into account the number of juvenile animals in the genus present in this population estimate due to their occupation of a different niche than the adults, and thus it is likely the total population was much higher when accounting for this factor. Simultaneously, studies of living carnivores suggest that some predator populations are higher in density than others of similar weight (such as jaguars and hyenas, which are similar in weight but have vastly differing population densities). Lastly, the study suggests that in most cases, only one in 80 million ''Tyrannosaurus'' would become fossilized, while the chances were likely as high as one in every 16,000 of an individual becoming fossilized in areas that had more dense populations.<ref name="nytimes2021">{{Cite news|url=https://www.nytimes.com/2021/04/15/science/tyrannosaurus-rex-population.html |archive-url=https://ghostarchive.org/archive/20211228/https://www.nytimes.com/2021/04/15/science/tyrannosaurus-rex-population.html |archive-date=December 28, 2021 |url-access=limited|title=How Many Tyrannosaurus Rexes Ever Lived on Earth? Here's a New Clue.|first=Kenneth|last=Chang|newspaper=The New York Times|date=April 15, 2021}}{{cbignore}}</ref><ref name="Marshall2021">{{Cite journal|title=Absolute abundance and preservation rate of Tyrannosaurus rex|first1=Charles R.|last1=Marshall|first2=Daniel V.|last2=Latorre|first3=Connor J.|last3=Wilson|first4=Tanner M.|last4=Frank|first5=Katherine M.|last5=Magoulick|first6=Joshua B.|last6=Zimmt|first7=Ashley W.|last7=Poust|date=April 16, 2021|journal=Science|volume=372|issue=6539|pages=284–287|doi=10.1126/science.abc8300|pmid=33859033|bibcode=2021Sci...372..284M|doi-access=free}}</ref>

Meiri (2022) questioned the reliability of the estimates, citing uncertainty in metabolic rate, body size, sex and age-specific survival rates, habitat requirements and range size variability as shortcomings Marshall et al. did not take into account.<ref>{{Cite journal|last=Meiri|first=Shai|date=2022|title=Population sizes of T. rex cannot be precisely estimated|url=https://escholarship.org/uc/item/8mj4015f|journal=Frontiers of Biogeography|volume=14|issue=2|language=en|doi=10.21425/F5FBG53781|s2cid=245288933|doi-access=free|archive-date=February 4, 2022|access-date=February 8, 2022|archive-url=https://web.archive.org/web/20220204051249/https://escholarship.org/uc/item/8mj4015f|url-status=live}}</ref> The authors of the original publication replied that while they agree that their reported uncertainties were probably too small, their framework is flexible enough to accommodate uncerainty in physiology, and that their calculations do not depend on short-term changes in population density and geographic range, but rather on their long-term averages. Finally, they remark that they did estimate the range of reasonable survivorship curves and that they did include uncertainty in the time of onset of sexual maturity and in the growth curve by incorporating the
uncertainty in the maximum body mass.<ref>{{Cite journal|last1=Marshall|first1=Charles R.|last2=Latorre|first2=Daniel V.|last3=Wilson|first3=Connor J.|last4=Frank|first4=Tanner M.|last5=Magoulick|first5=Katherine M.|last6=Zimmt|first6=Joshua P.|last7=Poust|first7=Ashley W.|date=2022|title=With what precision can the population size of Tyrannosaurus rex be estimated? A reply to Meiri|url=https://escholarship.org/uc/item/8vv2g57c|journal=Frontiers of Biogeography|volume=14|issue=2|language=en|doi=10.21425/F5FBG55042|s2cid=245314491|doi-access=free|hdl=10852/101238|hdl-access=free|archive-date=January 21, 2022|access-date=February 8, 2022|archive-url=https://web.archive.org/web/20220121045413/https://escholarship.org/uc/item/8vv2g57c|url-status=live}} [[File:CC BY icon.svg|50px|class=noviewer]] Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=October 16, 2017 }}.</ref>