Tag Archives: scent

Best T. rex hunting strategy may have been a direct attack.

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Even when stalking upwind a T. rex is frequently able to get within 40 meters before being detected. (Screen capture, click to enlarge.)

Even when stalking upwind a T. rex is frequently able to get within 40 meters of the prey before being detected. (Screen capture, click to enlarge.)

After five weeks at the Bone Marrow Transplant center at the University of Iowa Hospital I’m finally back home and working on Dinosaur Island again!

As part of my work on scent ‘plumes’ or ‘cones’ and the ability of prey animals, like the Edmontosaurus, to detect the scent of a nearby T. rex and respond accordingly, I was wondering if it would be beneficial for a T. rex to adopt a hunting strategy in which it purposefully maneuvered downwind of the prey and then attacked. Consequently, I created a simulation in the Dinosaur Island AI test bed program (see screen shot above) with one T. rex (Bob) and one Edmontosaurus (Gertie), entered wind direction and velocity (as shown by the plume) and let the AI control Bob’s hunting with two different methods:

  1. An AI routine that maneuvered Bob downwind of Gertie and then attacked.
  2. An AI routine that maneuvered Bob directly towards Gertie using the fastest path (considering for terrain and slope).

After running a small number of tests today (about 25) it appears that the maneuvering downwind of the prey strategy is not as beneficial as I would have thought. Frequently Bob was observed by Gertie while maneuvering downwind. But, more importantly, when Bob adopted strategy #2 (the direct rush), Gertie didn’t smell or see Bob until he was within less than 40 meters.

Keep in mind that these experiments are just preliminary and, most importantly, they only involve a T. rex stalking an isolated Edmontosaurus (who almost always traveled in herds) but this is still food for thought. When a T. rex encountered a single isolated prey animal, it’s best hunting strategy was probably a direct rush.

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New scent detection algorithm integrated into Dinosaur Island.

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The finished equation for determining the probability of a dinosaur detecting the smell of another given wind direction, velocity, distance and bearing. Click to enlarge.

The finished equation for determining the probability of a dinosaur detecting the smell of another given wind direction, velocity, distance and bearing. Click to enlarge.

Above is the equation for calculating the probability that one dinosaur can smell another dinosaur given the wind direction, wind velocity, distance and bearing of dinosaur one to dinosaur two. A great deal of work went into this equation and I must thank my good friends and colleagues, Alberto Segre and Mike Morton, for all their help, feedback and encouragement.

Below are examples of the output of the equation with various wind direction and wind velocities:

Results of the equation showing likelihood of detecting a scent at a specific location given the wind direction and wind velocity. Each square is 100 meters. Click to enlarge.

Results of the equation showing likelihood of detecting a scent at a specific location given the wind direction and wind velocity. Each square is 100 meters. 

Results of the equation showing likelihood of detecting a scent at a specific location given the wind direction and wind velocity. Each square is 100 meters. Click to enlarge.

Results of the equation showing likelihood of detecting a scent at a specific location given the wind direction and wind velocity. Each square is 100 meters. 

Results of the equation showing likelihood of detecting a scent at a specific location given the wind direction and wind velocity. Each square is 100 meters. Click to enlarge.

Results of the equation showing likelihood of detecting a scent at a specific location given the wind direction and wind velocity. Each square is 100 meters.

Below is a screen capture from Dinosaur Island showing the results of the new scent detection algorithm (coupled with the newly added olfactory acuity variable, see New sight and smell variables added to Dinosaur Island).

Screen capture of Dinosaur Island with new scent detection algorithm integrated.

Screen capture of Dinosaur Island with new scent detection algorithm integrated into the AI. Note AI output on right (highlighted by red box): Gertie, the Edmontosaurus, cannot see Jim, the T. rex, but she can smell him. Click to enlarge.

While developing the scent detection algorithm and reading about the extent and frequency of injuries sustained by T. rex (broken ribs appear in about 25% of known T. rex fossils) it seemed very likely that an old T. rex (and T. rex did not achieve sexual maturity until their twenties) had to be a very cautious hunter. An Edmontosaurus regalis tail could break T. rex ribs if the Edmontosaurus was aware that the T. rex attack was imminent. As we will see in the next post, a smart hunting T. rex must have had to employ clever tactics to avoid both visual and olfactory detection as it approached its prey.

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