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Extinct Teratorn (Family Teratornithidae) Fact Sheet: Behavior & Ecology

Extinct Teratorn (Teratornis merriami, Aiolornis incredibilis, Cathartornis gracilis, Argentavis magnificens) Family Teratornithidae

How Do We Know This?

Because direct observation of a fossil animal's behavior isn't possible, paleontologists use comparison and contrast with living animals for guidance. Tracks can sometimes reveal further clues to behavior. At a fossil site, the mix of plant and animal species gives clues to the ecosystem of that time and place.



  • Teratornis merriami capable of walking well and stalking but not running (Campbell & Tonni 1981)
    • More adapted for moving on the ground than condors. (Campbell & Tonni 1981)


  • Of all the teratorns, Argentavis probably was the least agile because of its very large size.
  • Argentavis probably behaved more like vultures than the other teratorns (Palmqvist & Vizcaíno 2003)
    • Probably was too large to be a strong flyer but could soar and glide efficiently at speeds of 67 kph (42 mph) (Chatterjee et al 2007)
    • Estimated dives of 241 kph (150 mph) (Chatterjee et al 2007)
    • Vultures, for comparison, soar about 61 kph (38 mph)
    • Argentavis would have had trouble taking off on level ground because of its great size
    • By running down a slope into a very slight headwind, takeoff possible (using albatrosses' technique) (Chatterjee et al 2007)
      • Couldn't take off by running on level ground - not enough wing power.
  • Teratornis merriami would have had a soaring/cruising speed of 57 km/h (35 mph) (Chatterjee et al 2007)

Interspecies Interactions

  • Hertel (1995) observed that there were many more species of Pleistocene daytime raptors in western North America than are found today, and there were twice as many scavenger birds as today; possible because of greater diversity and abundance of prey species at that time

Page Citations

Campbell & Tonni (1981)
Chatterjee et al. (2007)
Palmqvist & Vizcaíno (2003)

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