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Overlooked 2001 paper on dinosaur threat displays




Peter L. Hurd & Magnus Enquist, 2001. Threat display in birds. Canadian Journal of Zoology 79(6):931-942.   Coupled with Gregory Paul's new book -- a spectacular array of ideations, causing one to hope that he will revise, update, and re-release his 1988 volume (still quite useful) -- the Hurd/Enquist paper puts to rest the idea that threat displays are behavioural handicaps among dinosaurs. With apologies to John Hutchinson, one can close one's eyes, e.g., scale up an Egyptian vulture to ca. 18 feet high, and imagine threat displays exhibited by a feathered theropod in a Gregory Paul landscape.  I say displays...because, as Hurd/Enquist document, theropods have up to  six such displays, gradated temporally so that, as it were, when a taxon is at maximum aggression, the display is quite remarkable. The dinosaur literature has numerous papers on threat d! ! isplays of a descriptive nature, but Hurd/Enquist provide the scholar with paradigms of explanation (Magnus Enquist, in the 1980s, published a group of papers interlinked with the present study). Thus, there is a complex array of "game" theoretic interactions between dinosaurs: the signals may be misinterpreted, causing one dinosaur to (using a colloquial alliteration) to "up the ante". The flurry of displays (some are what V. Crawford & J. Sobel in 1982 termed "costless signals", or A. Spence's 1973 "handicap signals") can be composed of a signal and receiver (mating rituals), or actual  displays of physical threat. The agonistic morphogenesis of  dinosaurs is, hence, a combination of strategy and motivations, and, as Peter Hurd has written in his dissertation in 1997 (Game theoretical perspectives on conflict and biological communication, Stockholm University), among dinosaurs there is a difference between threat displays and "performance" displays, the former ! ! linked with cognitive processes of the theropod in interpreting whether a possible opponent's ability and motivation are  providing probabilities of attack.
As Hurd/Enquist stress, much work is necessary among field dinosaurologists (I still like the adjective, because in studying a living dinosaur, "paleo" is not applicable) to use rigorous game theoretics to establish models of understanding the sequences and compositions of alternating displays between dinosaurs.