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Two new papers
For those, like me, who search for applicabilities of natural selection processes across time, I recommend:
Tamara Grand, 2002. Foraging-predation risk trade-offs, habitat selection, and the coexistence of predators. American Naturalist 159(1):106-112
Tamara Grand, 2002. Alternative forms of competition and predation dramatically affect habitat selection under foraging-predation-risk trade-offs. Behavioral Ecology 13(2):280-290
Both papers by Tamara are fascinating excursions into IFD, ideal free distribution, and, as she notes in the first paper, IFD is a tool for interpellating data: predator-prey systems' persistence, protandry, and partial migration. Together with the research of Kathreen Ruckstuhl on bighorn sheep (read: small ceratopsians for avenues of thought and speculation), one can develop scenarios for allowing one to, in part, take the leap of imagination with game theoretics, as it were, and speculate about logical behaviour systems among dinosaurs. The second paper is ripe (forgive the words, but I do not know how else to phrase it) with images. She stresses that predators, in the main, hunt where there is plentiful prey in concentrated areas, and, in turn, the potential meals will distribute themselves relative to predation vulnerability. In turn, habitat selection will change as will body size and morphology, although spatial fixation !
predation risk will create general uniformity of size. What one has, in effect, is a "game" between predator and prey (for those who appreciate the influence John Nash has had, however indirectly, on dinosaur "game" theoretics, PBS on 28 April 2002 will have an excellent profile of his "beautiful mind"), and mathematical models are constructable: IFD + IBMs (individual-based models) may provide one with the mental tools for inferring dinosaur behaviour (they are being applied to subsaharan theropods, such as the vultures, and, using biochemical computer simulations of "velociraptorine"/"dromaeosaur" locomotion, deductions are provisional for pre-K/T dinosaurs).
What Tamara gives the reader: two forms of competition, four forms of predation > eight ecological scenarios for "walking" unseen among our imagination's re-creation of theropod "packs":
vulnerability- and frequency-dependent predation, the possibility of cannibalism-as-predation among Coelophysis colonies (and similar information centres), the kleptoparasitism of G.A. Parker, and R.D. Holt's provocative ideas re: intraguild predation (read: competitions between variably sized theropod taxa in the late Cretaceous). Contrary to Horrorwood film makers, IFD gives one a way of speculating re: not only how herbivorous dinosaurs selected habitat, but how the habitats were used in coexistence with stalking predators (who, like Neophron in Juan Negro's paper this week in Nature, may have had yellow heads [not red as in Valley of the T. rex] from consuming excrement mixed with flesh of prey). Thus, larger bipedal ornithischians would have foraged in open areas (they could presumably run, perhaps out-run a large tyrannosaur, or escape a "pack" of dromaeosaurs/velocirap-
tors), while quadruped ornithischians may, in fact, have preferred more heavily forested areas where food resources would be coupled with their defensive mechanisms. Phil Tippett, in his "Prehistoric Beast", showed such a scene, of a foraging centrosaur in a redwood forest confronting a tyrannosaur: who would have more moving room? It could be a centrosaur, in such a situation, may have used a combination of trees and its own skull structure to defend itself (morphological/behaviour traits being transmitted through generations of ceratopsians). Tamara makes an interesting point: varieties of behaviour may appear before morphological changes (cf. R.L. McLaughlin's work on "adaptive peaks" and "alternative foraging tactics"), morphological specialization resulting from habitat selections. Thus, morphologically similar dinosaurs may (as is observable among extant theropods today, using IDF theory) have exhibited dissimilar behaviours.