Tag Archives: T. rex

Dinosaur Mating Dances

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This illustration shows theropods engaged in scrape ceremony display activity, based on trace fossil evidence from Colorado. Photograph: Lida Xing/AP

This illustration shows theropods engaged in scrape ceremony display activity, based on trace fossil evidence from Colorado. Photograph: Lida Xing/AP

Geologist Martin Lockley reports that there is now evidence that some dinosaurs engaged in ritual ‘scraping’ dances as foreplay to mating. “We know they had feathers and crests and good vision,” Lockley said, speaking of theropods… They were visual animals, but there’s never been any actual physical evidence that their anatomy and behavior was co-opted for fairly energetic display. This is physical evidence.”

In a paper published on Thursday in Scientific Reports, Lockley and his co-authors compared the patterns to those left by puffins and ostriches, and deduced that the marks did not represent nests or digging for water or food.

Link to full story: Dinosaurs performed dances to woo mates, according to new evidence .

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The semester is over, so let’s get back to work on Dinosaur Island!

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My name and office listed among many of the professors who taught me in grad school.

My name and office listed among many of the professors who taught me in grad school. (Click to enlarge.)

I’ve had a wonderful time teaching computer science at the University of Iowa as a Visiting Assistant Professor but now the semester is over and it’s time to get back to work on Dinosaur Island.

Most professors assign reading at the beginning of the semester, but I want to share a number of great academic papers that have been forwarded to me and I am just now getting time to read.

First is a fascinating and very important paper by Dr. Nathan P. Myhrvold entitled Revisiting the Estimation of Dinosaur Growth Rates (it can be downloaded here). Myhrvold writes, “The analyses reported here find that only a few dinosaur growth data sets exhibit a marked slowing of growth with age and that most previous qualitative assumptions of asymptotic growth were incorrect.” And, “Mature individuals seem to be missing or underrepresented in the data on a wide range of taxonomic groups, including ornithopods, theropods, ceratopsians, hadrosaurs, sauropods and prosauropods.” In essence, Myhrvold suggests that some dinosaur growth rates are lower than previously thought. Dinosaur Island is – for lack of a better phrase – “An Excel spreadsheet for dinosaurs.” By this I mean that Dinosaur Island was designed to play ‘what if’ with various models of dinosaur behavior, growth, food consumption, etc. Below is a portion of the dialog box in Dinosaur Island where the user can change the rate of growth and food consumption requirements for a T. rex.

Portion of a dialog box that allows the user to change the rate of growth and food consumption variables for a T. rex (screen shot from Dinosaur Island).

Portion of a dialog box that allows the user to change the rate of growth and food consumption variables for a T. rex (screen shot from Dinosaur Island).

My recent work on creating an equation for calculating the probability of a dinosaur detecting another dinosaur by scent (see New scent detection algorithm integrated into Dinosaur Island link here) has brought some welcome feedback. Paleontologist Dr. Jordan Mallon kindly forwarded the Science article Nostril Position in Dinosaurs and Other Vertebrates and its Significance for Nasal Function by Lawrence M. Witmer can be downloaded here (note, subscription needed to download) and Evolution of olfaction in non-avian theropod dinosaurs and birds by Zelenitsky, Therrien, Ridgely, McGee and Witmer) can be downloaded here.

Skull and fleshed-out restorations of the head of the nonavian theropod dinosaur, Turannosaurus, rex, in left rostrodorsolate ral view showing the bony nostril and varying views of the position of the fleshy nostril. (A) Skull, showing the bony nostril; note also the narial fossa on the bone's adjacent to the opening. (B) Head showing the caudal position of the fleshy notril typically depicted in most scientific and popular restorations. (C) Head showing the nostral position of the fleshy notril supported by the data presented here. From Science 3 August, 2001 (click to enlarge).

Skull and fleshed-out restorations of the head of the nonavian theropod dinosaur, Tyrannosaurus, rex, in left rostrodorsolate ral view showing the bony nostril and varying views of the position of the fleshy nostril. (A) Skull, showing the bony nostril; note also the narial fossa on the bone’s adjacent to the opening. (B) Head showing the caudal position of the fleshy nostril typically depicted in most scientific and popular restorations. (C) Head showing the nostril position of the fleshy nostril supported by the data presented here. From Science 3 August, 2001 (click to enlarge).

Witmer writes, “…there may be more to nostril position than just its role in conveying an airstream across the nasal apparatus. Olfaction remains important in many extant anmiote groups, being intimately associated with critical behaviors (e.g. feeding, reproduction, predator detection, territoriality), and it has been argued that some dinosaurs had significant olfactory capabilities.”

Zelenisky, et. al writes, “… our results show that olfaction continued to become relatively more important during the transition from non-avian theropods to early neornithines, thus indicating that olfaction was another significant sensory modality during early avian evolution.”

I would also like to mention two other articles that have been forwarded to us: Intra-guild competition and its implications for one of the biggest terrestrial predators, Tyrannosaurus rex by Carbone, Turvey and Bielby (download here) and Eulerian-Lagrangian model for predicting odor dispersion using instrumental and human measurements by Schiffman, McLaughlin, Katul and Nagle (download here). The Schiffman, McLaughlin, Katul and Nagle article presents a model for odor dispersal in swine confinement facilities. It did not include an equation, but the results seem similar to my own work here. However, my equation produces a more ‘bulbous’ dispersal pattern (NB: changing the values M and the multiplier (1.5) of WindSpeed (or adding a multiplier to (90 – angle)  would create a longer and thinner detection area that is similar to the Eulerian-Lagrangian model).

Carbone et. al writes, “As an active large prey specialist, feeding on herbivores of similar or grater mass, T. rex would have had feeding habits consistent with prey size selection patterns found in extant mammalian carnivores. We propose that this is the most likely feeding strategy for T. rex.”

Two other articles that are of special importance to our research are Binocular vision in theropod dinosaurs by Kent A. Stevens (can be downloaded here) and Relative brain size and behavior in archosaurian reptiles by James A. Hopson (can be downloaded here).

Stevens (who is also a computer scientist) did work in modeling reconstructions of various dinosaur heads and then calculating their binocular field of vision. We used this paper for the default values for field of vision for T. rex (see New sight and smell variables added to Dinosaur Island). Stevens writes, “… Tyrannosaurus… had cranial designs that afforded binocular fields between 45-60º in width similar to those of modern raptorial birds.  He also writes, “One might therefore envision an alert, hungry Tyrannosaurus rex raising its head to maximum height, its keen olfactory sensitivity catching the scent of living prey and not just carrion… In particular, due to its great scale and broad frontal vision, Tyrannosaurus rex, of all sighted observers to have ever lived, might have experienced the most spectacular view of the the three-dimensional world.”

Hopson, in his paper on dinosaur behavior, observes, “…the brains of dinosaurs fall within the expected range for reptiles of their body size.” And, “The larger ceratopsians, with their great horned heads, relied on active defensive strategies and presumably required somewhat grater agility than the tail-weaponed forms, both in fending off predators and in intraspecific combat bouts.” Hopson also observes, “The best evidence for the existence of coordinated group behavior in dinosaurs is provided by multiple trackways that show the parallel movement of several or many individuals in the same direction.” And, later, “…smaller tracks are toward the center of the group and the largest are at the periphery. This suggests that the largest adults sheltered the vulnerable juveniles at the center of the herd.”

We are always very happy to receive email; especially when a link to a fascinating article (like those above) is included. Please feel free to forward scholarly articles that are relevant to the development of Dinosaur Island to Ezra [at] Dinosaur-Island.com.

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New AI enables T. rex to anticipate prey’s future location.

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Trex looking 40 secs into future

In this screen capture from the Dinosaur Island AI testbed program a T. rex (John, left) is stalking an Edmontosaurus (Muffie). The long yellow line intersecting the shorter yellow line is where John anticipates that Muffie will be 40 seconds in the future and he is planning accordingly. The blue lines are angle of vision arcs (140 degrees for Edmontosaurus, 55 degrees for T. rex). John can see Muffie. Muffie cannot see John. Click to enlarge.

We recently added ‘blinders’ to the dinosaurs by restricting their ‘vision’ to accurate angles calculated from the position of their eye sockets in their skulls (see new sight and smell variables added to define dinosaur species).

After restricting the T. rex’s vision to 55 degrees we observed some unexpected behavior: while pursuing prey a T. rex would occasionally ‘lose sight’ of his target and not be able to reacquire it. Upon investigation we discovered that the cause of this was that the T. rex would advance, single-mindedly, towards where the prey is now. Under some circumstances, and if the simulation’s ‘time slices’ were sufficiently larger (> 8 seconds), and if the prey moved away at an oblique angle, or disappeared behind a hill, it was possible that their prey was no longer observable within the restricted angle of vision.

The solution was to give the T. rex the ability to anticipate and calculate its prey’s position in the future.

If we simply wished to use ‘cheating AI’1 the solution would be trivia. Because the current goal for every dinosaur is stored in memory a ‘cheating AI’ could simply look up the objective for its prey and arrive there first. That is not what we did.

Instead, if the T. rex sees a prey animal and begins stalking it the future position of the animal at X seconds2 in the future is calculated given the prey animal’s bearing, current speed, expected terrain traversal and anticipated slope traversals.

Again, we must ask: are we making the T. rex too smart? At this point; we must be pushing the extreme levels of dinosaur calculations and planning abilities. However, as a predator – and there is solid evidence that T. rex was, at least, occasionally a predator –  he must have possessed the ability to calculate future positions of prey animals. Furthermore, he must have been very familiar with his hunting territories and, consequently, possessed a priori knowledge about terrain and slopes.

This AI technique probably makes a hunting T. rex in Dinosaur Island the most advanced NPC (Non Player Character) in all current computer games.

SmallRule

1) Cheating AI: There are numerous examples of ‘cheating AI’ in computer games. Without going into specific details, some of the more common methods include giving the computer AI information that should be hidden (such as enemy unit positions and intentions) and weighting random factors in the computer’s favors. See also Artificial intelligence (video games) and The Computer Is a Cheating Bastard.

2) X seconds: we are currently using 40 seconds as the future point in time for anticipated position calculations.

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Creating a combat model for T. rex versus Edmontosaurus regalis.

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A T. rex is attacking an Edmontosaurus while it's companions flee (screen capture of the AI test bed program). Click to enlarge.(screen capture of the AI test bed program).

A T. rex (Bob) is attacking an Edmontosaurus (Julie) while its companions (Gertie & Muffie) flee (screen capture of the AI test bed program). Click to enlarge.

We are at the point in the development of the AI routines for the inhabitants of Dinosaur Island where it is time to make decisions about the combat models used to determine the resolution of hostile encounters. As shown in the screen capture of the Dinosaur Island AI testbed program (above), the simulation is placing the dinosaurs in various appropriate states such as: resting, eating, looking for food, looking for water, stalking prey, moving towards water, moving towards food, drinking, fighting and fleeing.

My first thought on the subject of modeling combat between T. rex and Edmontosaurus regalis, the first two resident species on the island, was that it would be handled similar to ‘melee combat’ models that I had previously used for my wargames.

Below is a page from the manual for UMS II: Nations at War explaining the 20 variable equation used to decide combat between tactical units.

The 20 variable equation used to calculate combat in our UMS II: Nations at War (c. 1992). (Scan from user's manual). Click to enlarge.

The 20 variable equation used to calculate combat in our UMS II: Nations at War (1989). Scan from user’s manual. Click to enlarge.

I was envisioning something similar for Dinosaur Island until I happened to see this video (below) which includes a sequence (starting at 4:45) describing hypothetical Edmontosaurus and T. rex combat.

What I took away from the video was:

  • Edmontosaurus regalis  is bigger than I thought. I understood the size mathematically and that they could easily grow up to 13 meters (~ 40 feet) but it wasn’t until I saw this video that it was put in perspective, “they were as big as a railroad car.” And, “they could look into a second story window.”
  • The tail of an adult ‘bull’ Edmontosaurus regalis  was a formidable weapon.
  • T. rex, like many predators, would have preferred to attack adolescent or sick animals rather than encounter a full-size, and potentially lethal, ‘bull’.
  • The correct pronunciation is Ed-MONT-o-saur-us. I’ve been saying it wrong for the last six months!

While there is still debate about whether T. rex was a predator or a scavenger (“Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly sauropods, although some experts have suggested it was primarily a scavenger. The debate over Tyrannosaurus as apex predator or scavenger is among the longest running in paleontology.” – Wikipedia) we know of at least once case where a T. rex tooth was found in an Edmontosaurus tail that had healed from the attack (“T. rex Tooth Crown Found Embedded in an Edmontosaurus Tail – Predatory Behaviour?” “The healed bone growth indicates that the duck-billed dinosaur survived this encounter.  In February of this year, researchers from the University of Kansas and Florida reported on the discovery of evidence of a scar on fossilised skin tissue from just above the eye of an Edmontosaurus.  In a paper, published in “Cretaceous Research”, the scientists concluded that this too was evidence of an attack of a T. rex on an Edmontosaurus.”). From this we can conclude that:

  • Sometimes T. rex did attack a living Edmontosaurus.
  • Sometimes the Edmontosaurus survived the attack.

Furthermore, we know that some T. rex had suffered bone injuries during their lifetime (“An injury to the right shoulder region of Sue resulted in a damaged shoulder blade, a torn tendon in the right arm, and three broken ribs. This damage subsequently healed (though one rib healed into two separate pieces), indicating Sue survived the incident.” – Wikipedia) consistent with the type of damage that a 5 meter long tail (described as being “like a baseball bat,” in the above, video) could inflict.

In other words, combat between T. rex and Edmontosaurus regalis was not a foregone conclusion. Indeed, it was entirely possible that the Edmontosaurus could walk away unscathed while the T. rex could suffer some broken bones.

The AI for Dinosaur Island will reflect this. When deciding if the T. rex will attack the AI will have to analyze the T. rex‘s chances of victory and potential injuries (risk versus reward) considering the size of the T. rex, the age of the T. rex, the health of the T. rex, the size of the prey, the age of the prey and the health of the prey. And, when the two dinosaurs actually engage in combat the tactics employed by both will probably decide the outcome.

If the T. rex can sneak up on the Edmontosaurus until they are within 50 meters or less and then close the distance with a rush the advantage would certainly lie with the predator. If the Edmontosaurus has forewarning of the impending attack it would either attempt to flee or stand its ground and assume a defensive posture.

There is reason to believe that both Edmontosaurus and T. rex had well developed olfactory bulbs in their brains and smell was an important sense for both animals. We will add wind (and wind direction) to Dinosaur Island and incorporate this into the AI routines that control the dinosaurs. Predators will attempt to get ‘upwind’ of their prey; prey animals will ‘sniff’ the wind and respond if they smell a T. rex even if they can’t see it (see “Dinosaurs, tanks and line of sight algorithms” here).

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