On November 9th, 2016 we learned about

Learning about the past with regurgitated rodent bones found in owl pellets

Before an owl goes out hunting for the night, it’s likely to make room for its next meal by horking up undigested materials swallowed when it last ate. These pieces of bone, fur and feathers get captured in the in the bird’s proventriculus, a sort of pre-stomach that lets the owl easily regurgitate things its gizzard can’t digest. The owl isn’t vomiting up food really, since their bodies just can’t make use of these pieces of tougher anatomy from their prey. Paleoecologists, on the other hand, are finding owl pellets to be of great utility, as they act as a biological record of smaller species from the last few hundred-thousand years, collected and sorted by the owls living at the time.

Many species of owls live and regurgitate their pellets where they won’t really be protected, but Australian masked owls (Tyto novaehollandiae) archive their pellets in the caves some individuals live in. In some cases, caves have been found with pellet debris hundreds of thousands of years old, piled up in layers almost like sedimentary rock that paleontologists use to date fossils. The bones and bits found in the pellets can similarly offer a wealth of information about various time periods, even though they’re mostly collections of animals small enough for an owl to eat.

In the case of Australia, pellets can help reveal the story of what the ecosystem looked like before and after the arrival of European colonists. When those settlers arrived, they cleared large amounts of land to plant wheat for food, greatly disrupting the ecosystem that was previously in place. This can be seen in pellets by looking for shifts in what rodents were living at the time, and what seeds those rodents had in the mouths or their fur when they were picked up by an owl. One of the most useful, and thankfully durable, parts of a body are the teeth, which provide information about an animal’s diet and help identify which species a jumbled skeleton might be. These identifications can then be referenced against other data to see what animals lived where, and when.

Rodent bones as record-keepers

The small rodents can also provide information about historical climate change. Their relatively quick and high reproduction rates allow them to react quickly to changes in climate as they scramble to keep pace with wherever their favorite foods might be growing. So again, the types of prey and the seeds those animals might have with them in owl pellets can help provide data about environments from relatively recent history that is otherwise difficult to document.

This line of research has wider applications than just measuring the impact of Europeans in Australia 200 years ago. Owls and falcons around the world package these remains into handy pellets, assuming they’re roosting in spaces that can help preserve them from the elements. It also highlights the role even ‘mundane’ animals like mice or moles play in ecosystems, transporting seeds in an ecosystem, helping to preserve biodiversity. Not bad for a bird’s leftovers.

Source: How Bird Vomit Helps Us Understand History by Emily Graslie, The Brain Scoop

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