Editing Albertosaurus (section)

===Social behaviour===
[[Image:Albertosaurus Tyrrell.jpg|thumb|Bronze sculptures of a pack, RTM, designed by Brian Cooley]]
The Dry Island bonebed discovered by Barnum Brown and his crew contains the remains of 26 ''Albertosaurus'', the most individuals found in one locality of any large Cretaceous theropod and the second-most of any large theropod dinosaur behind the ''[[Allosaurus]]'' assemblage at the [[Cleveland-Lloyd Dinosaur Quarry]] in [[Utah]]. The group seems to be composed of one very old adult, eight adults between 17 and 23 years old, seven sub-adults undergoing their rapid growth phases at between 12 and 16 years old, and six juveniles between the ages of 2 and 11 years old that had not yet reached the growth phase.<ref name=ericksonetal2006/>

The near-absence of [[herbivore]] remains and the similar state of preservation common to the many individuals at the ''Albertosaurus'' bonebed quarry led Currie to conclude that the locality was not a predator trap, such as the [[La Brea Tar Pits]] in [[California]], and that all of the preserved animals died at the same time. Currie claims this as evidence of pack behavior.<ref name="currie1998"/> Other scientists are skeptical, observing that the animals may have been driven together by a drought, flood, or other reasons.<ref name=ericksonetal2006/><ref name=roachbrinkman2007/><ref name=eberthmccrea2001>{{cite journal |last=Eberth |first=David A. |author2=McCrea, Richard T. |year=2001 |title=Were large theropods gregarious? |journal=Journal of Vertebrate Paleontology |volume=21 |issue=Supplement to 3 – Abstracts of Papers, 61st Annual Meeting of the Society of Vertebrate Paleontology |page=46A|doi=10.1080/02724634.2001.10010852|s2cid=220414868 }}(published abstract only)</ref>

[[File:Albertosaurus hunting Saurolophus.jpg|thumb|left|Two ''Albertosaurus'' hunting ''[[Saurolophus]]'']]
There is plentiful evidence for gregarious behaviour among herbivorous dinosaurs, including [[ceratopsia]]ns and [[hadrosaur]]s.<ref name=horner1997>{{cite book |last=Horner |first=John R. |author-link=Jack Horner (paleontologist) |year=1997 |chapter=Behavior |editor=Currie, Philip J. |editor-link=Philip J. Currie |editor2=Padian, Kevin |title=Encyclopedia of Dinosaurs |publisher=Academic Press |location=San Diego |pages=45–50 |isbn=978-0-12-226810-6}}</ref> However, only rarely are so many dinosaurian predators found at the same site. Small theropods, like ''[[Deinonychus]]''<ref name=maxwellostrom1995>{{cite journal |doi=10.1080/02724634.1995.10011256 |last=Maxwell |first=W. Desmond |author2=Ostrom, John H. |author-link2=John Ostrom |year=1995 |title=Taphonomy and paleobiological implications of ''Tenontosaurus''-''Deinonychus'' associations |journal=Journal of Vertebrate Paleontology |volume=15 |issue=4 |pages=707–712|bibcode=1995JVPal..15..707M }}</ref> and ''[[Coelophysis]]'',<ref name=raath1990>{{cite book |last=Raath |first=Michael A. |year=1990 |chapter=Morphological variation in small theropods and its meaning in systematics: evidence from ''Syntarsus rhodesiensis'' |editor=Carpenter, Kenneth |editor-link=Kenneth Carpenter |editor2=Currie, Philip J. |title=Dinosaur Systematics: Approaches and Perspectives |publisher=Cambridge University Press |location=Cambridge |pages=91–105 |isbn=978-0-521-43810-0}}</ref> have been found in aggregations, as have larger predators, such as ''Allosaurus'' and ''[[Mapusaurus]]''.<ref name=coriacurrie2006>{{cite journal|last=Coria |first=Rodolfo A. |author-link=Rodolfo Coria |author2=Currie, Philip J. |year=2006 |title=A new carcharodontosaurid (Dinosauria, Theropoda) from the Upper Cretaceous of Argentina |journal=Geodiversitas |volume=28 |issue=1 |pages=71–118 |url=http://www.mnhn.fr/museum/front/medias/publication/7653_g06n1a4.pdf |access-date=May 3, 2009 |archive-url=https://web.archive.org/web/20090326062832/http://www.mnhn.fr/museum/front/medias/publication/7653_g06n1a4.pdf |archive-date=March 26, 2009 |url-status=dead }}</ref> There is some evidence of [[gregarious behaviour]] in other tyrannosaurids as well, as fragmentary remains of smaller individuals were found alongside "[[Sue (dinosaur)|Sue]]", the ''Tyrannosaurus'' mounted in the [[Field Museum of Natural History]] in [[Chicago]], and a bonebed in the [[Two Medicine Formation]] of Montana contains at least three specimens of ''Daspletosaurus'' preserved alongside several hadrosaurs.<ref name=currieetal2005>{{cite book |last=Currie |first=Philip J. |author-link=Philip J. Currie|author2=Trexler, David|author3-link=Eva Koppelhus |author3=Koppelhus, Eva B.|author4=Wicks, Kelly|author5=Murphy, Nate |year=2005 |chapter=An unusual multi-individual tyrannosaurid bonebed in the Two Medicine Formation (Late Cretaceous, Campanian) of Montana (USA) |editor=Carpenter, Kenneth |editor-link=Kenneth Carpenter |title=The Carnivorous Dinosaurs |publisher=Indiana University Press |location=Bloomington |pages=313–324 |isbn=978-0-253-34539-4}}</ref> These findings may corroborate the evidence for social behaviour in ''Albertosaurus'', although some or all of the above localities may represent temporary or unnatural aggregations.<ref name=currie1998/> Others have speculated that, instead of social groups, at least some of these finds represent [[Komodo dragon]]-like mobbing of carcasses, where aggressive competition leads to some of the predators being killed and even [[cannibal]]ized.<ref name=roachbrinkman2007/> The evidence of cannibalism was later reported in 2024 by Coppock and Currie.<ref>{{Cite journal |last1=Coppock |first1=C. |last2=Currie |first2=P. J. |year=2024 |title=Additional ''Albertosaurus sarcophagus'' (Tyrannosauridae, Albertosaurinae) material from the Danek Bonebed of Edmonton, Alberta, Canada with evidence of cannibalism |journal=Canadian Journal of Earth Sciences |volume=61 |issue=3 |pages=401–407 |doi=10.1139/cjes-2023-0055 |bibcode=2024CaJES..61..401C |s2cid=266279287 }}</ref>

Currie has also speculated on the pack-hunting habits of ''Albertosaurus''. The leg proportions of the smaller individuals were comparable to those of [[ornithomimid]]s, which were probably among the fastest dinosaurs. Younger ''Albertosaurus'' were probably equally fleet-footed or at least faster than their prey. Currie hypothesized that the younger members of the pack may have been responsible for driving their prey towards the adults, who were larger and more powerful, but also slower.<ref name=currie1998/> Juveniles may also have had different lifestyles than adults, filling predator [[Ecological niche|niche]]s between the enormous adults and the smaller contemporaneous theropods, the largest of which were two [[orders of magnitude]] smaller than adult ''Albertosaurus'' in mass.<ref name=holtz2004/> A similar situation is observed in modern Komodo dragons, with hatchlings beginning life as small [[insectivore]]s before growing to become the dominant predators on their islands.<ref name=auffenberg1981>{{cite book |last=Auffenberg |first=Walter |author-link=Walter Auffenberg|year=2000 |title=The Behavioral Ecology of the Komodo Monitor |publisher=University Press of Florida |location=Gainesville |isbn=978-0-8130-0621-5}}</ref> However, as the preservation of behaviour in the fossil record is exceedingly rare, these ideas cannot readily be tested. In 2010, Currie, though still favouring the hunting pack hypothesis, admitted that the concentration could have been brought about by other causes, such as a slowly rising water level during an extended flood.<ref>{{cite journal | last1 = Currie | first1 = Philip J. | last2 = Eberth | first2 = David A. | year = 2010 | title = On gregarious behavior in ''Albertosaurus'' | journal = Canadian Journal of Earth Sciences | volume = 47 | issue = 9| pages = 1277–1289 | doi = 10.1139/e10-072 | bibcode = 2010CaJES..47.1277C }}</ref>