Asio ecuadoriensis: Giant Predatory Owls Once Lived in Ecuador

Thursday, July 23, 2020

Life reconstruction of Asio ecuadoriensis. Image credit: Sebastián Rozadilla.

An extinct species of giant owl that lived 40,000 years ago (Pleistocene epoch) and preyed on smaller owls has been identified from fossils found in the Cangagua Formation in the Chimborazo province of Ecuador.

Named Asio ecuadoriensis, the ancient bird was more than 70 cm (2.3 feet) tall and had a wingspan of over 1.5 m (4.9 feet).

It had longer and more robust legs than any other extant or extinct member of its genus Asio (typical or true owls).

“We think that the climate change that occurred about 10,000 years ago, when the Ice Age ended, was partly responsible for the extinction of these large predatory birds,” said co-author Dr. Federico Agnolin, a paleontologist with the Museo Argentino de Ciencias Naturales Bernardino Rivadavia, the Concejo Nacional de Investigaciones Científicas y Técnicas, and the Fundación de Historia Natural ‘Félix de Azara.’

The fossilized bones of Asio ecuadoriensis were collected from a small cave site Dr. Agnolin and colleagues interpreted as a fossil owl burrow.

The paleontologists also found several specimens from three extant owl species (Glaucidium sp.Tyto furcata and Athene cunicularia) and skeletal remains of different mammals, including rabbits and rodents.

Size comparison between Asio ecuadoriensis and a human (left) and the preserved material of the ancient owl species (right). Image credit: Lo Coco et al, doi: 10.1007/s10336-020-01756-x.

“The fossil owl remains of TytoAthene and Glaucidium show breakage and weathering, typical of stomach acid-derived abrasion of owls,” they said.

“This indicates that, as occurs with mammals coming from the site, they would be prey items of the owl that is the owner of the burrow.”

“The large size of Asio ecuadoriensis, as well as the absence of acid-derived weathering of the bones, may constitute indirect evidence that this species is the owner of the burrow.”

Asio ecuadoriensis is probably an owl-specialized predator,” they added.

“It is well known that owls usually prey on raptors, but predation on owls by owls is uncommon and remains poorly explored in the literature.”

“If correctly interpreted, the present contribution may constitute the first fossil evidence of owl being killed by owls.”

The team’s paper was published recently in the Journal of Ornithology.


G.E. Lo Coco et al. 2020. Late Pleistocene owls (Aves, Strigiformes) from Ecuador, with the description of a new species. J Ornithol 161, 713-721; doi: 10.1007/s10336-020-01756-x