May 26, 2018 | Updated: 09:54 AM EDT

New Sensitivity Study May Reveal ‘Terror Birds’ Hunted In Packs

Apr 11, 2015 06:30 PM EDT

News this week revealed a frightening new addition to the fossil record-a "Terror Bird" species known more scientifically as Llallawavis scagliai (aka Scaglia's Magnificent Bird). But in spite of its massive size and terrifying stance, this top-tier predatory may not have been the most well-adapted hunter that it could be... That is, unless it was hunting in packs.

Known to be up to 10-feet-tall in height, flightless, and with massive beaks evolved to pulverize their prey, Terror Birds were some of the most predominant predators of South America during the Cenozoic Age. But in spite of all of this, current research has pointed towards the group of birds known as "phorusracids" and said that the fossils recovered may reveal that the birds were far more brute than evolutionary brawn. Not adapted to forage or hunt, perse, many terror bird skulls reveal fused joints and vertebrae which limited the birds' ability to be flexible in search of prey. But with the additional fusing of their upper palate, as well, what the birds lost in flexibility they gain in strength, as they could use these unique structures to pummel their prey and pulverize carcasses.

But with new fossils come new studies, and with the discovery of Llallawavis scagliai, researchers have taken aim at interpreting sensory abilities of these large birds from the intricate skeletal structures in the near 95% complete structure discovered in Argentina. In a new study published this week in the Journal of Vertebrate Paleontology, lead researcher of the study from the Centro de Investigaciones en Ciencias de la Tierra in Córdoba, Argentina, Dr. Federico "Dino" Degrange says that the new fossil may allow them to give a voice to terror birds, in a way. They may not be able to track down their screech, but they can narrow it down to a specific frequency, and the researchers say that it is far lower than any other birds living today.

"The discovery of this species reveals that terror birds were more diverse in the Pliocene than previously thought" Degrange says. "It will allow us to review the hypothesis about the decline and extinction of this fascinating group of birds." 

CT scans of the bird's inner ear, in conjunction with the complete voice box and trachea that the paleontologists uncovered, reveal that Terror Birds may have been big, but they were low-frequency too. While the researchers are unable to say definitively that the birds were of the quiet variety, they are able to say that their sensitivity was most likely limited to the frequency range between 3800 and 4230 hertz. Though this may be what they would expect to find in larger animals, as low-frequencies propagate across longer distances with little attenuation, the researchers believe that it may also allow for insight into the behavioral studies of Terror Birds.

"The mean hearing estimated for this terror bird was below the average for living birds" Degrange says. "This seems to indicate that Llallawavis may have had a narrow, low vocalization frequency range, presumably used for intraspecific acoustic communication or prey detection."

If this limited communication had evolved within the Terror Birds' family, then perhaps it may also reveal that the birds hunted in packs, a mere notion believed by many paleontologists. But at 10-feet-tall, with beaks that can pulverize bone, could you imagine a scarier sight?

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