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A Wilder View: Wildlife claws helping determine the past

claws
Posted at 10:31 AM, Jan 18, 2023
and last updated 2023-01-18 12:31:25-05

MISSOULA - The wildlife we see around today can help scientists learn what prehistoric animals may have done.

This edition of A Wilder View looks at why looking at the claws of wildlife is helping determine the past.

Pretty much every animal you see has claws or nails and wildlife use these as tools to greatly help out their day-to-day life. Claws are important for understanding wildlife’s behavior because it’s a part of their body that directly interacts with their habitat.

Cheetahs use their claws like cleats to gain traction when sprinting after an animal. Some marsupials have claws only used as an undeveloped embryo to climb into their mother’s pouch that are later shed and new ones are grown to help with hopping or digging.

These amazing abilities of claws start with just two different parts.

"One is the core which is the bony part, and the other is the keratin sheath, and then so together they form the whole claw structure,” explained UC-Davis lecturer Dr. Tracy Thompson.

Keratin is the same thing fingernails, hair and feathers are made out of.

Thomson focused his PH.D. research on functional morphology, the study of the shape of structures to determine or understand their function.

"I think of it kind of like tools. If you go into a tool closet you got your shovels, picks, and screwdrivers, and all of these tools and you can kind of guess or infer what each of those tools is used for from their shape. "

What Thompson did for his dissertation was create a method so we can look at claws and accurately describe what they are used for. Since we can’t witness prehistoric animals’ behavior, he must assess how modern animals use their claws and infer what they used them for.

"It allows us to then have a framework in which to infer or understand fossil organisms which we can’t observe any more,” Thompson said.

His research allows them to correctly classify known animals by 95%.

"Which means that we can take a fossil organism now and insert them into that analysis and have a 95% confidence that we are correctly interpreting what that fossil organism is doing,” noted Thompson.

This research can be quite tricky. In modern animals, we can see the claw sheath easily, that part that goes over the bone. But fossils usually don’t have the sheath and just the bone, which means Thomson must carefully piece together what a sheath would be like on a fossilized bone.

"And so, trying to take this structure and use it to interpret what this is doing. That’s apples to oranges,” Thompson said. “The claw with a sheath might look or appear very different than a claw without the sheath."

Thomson also had to tackle another critical issue in the biological realm. That being researchers often put wildlife in some sort of category based on where they live or what they do in their environment.

"They would classify organisms as eating other things, living in trees or running on the ground,” Thompson said.

But Thompson says these categories are not functions, it's really a lifestyle, "a cat and a hawk are both predatory, but they catch their prey in very different ways when it comes to the claw usage."

A bird of prey that catches — let’s say a rabbit — wraps its whole foot and claws around the rabbit to grasp it in a similar fashion of a bird grabbing a branch.

"So instead of a tree bird and a predatory bird those should be the same category because the claws are being used in the exact same way to grip a branch or to grip a rabbit,” Thompson explained. “Although there is mostly overlap between mammals and birds."

Thomson found there is more variability in claw usage for birds and the main reason is because they can fly.

"Because the birds are specializing the hind limb claws because they can fly they can really hone in on a very specific very targeted shape to do a very specific thing. Whereas mammals, they, need to run and climb or have to run and catch prey."

Thomson had to reinvent the way scientists categorize species based on their claw function to get this to work. It was all done with a specific goal in mind.

"My goal all along was really to provide a foundation for people to use and apply to fossils,” Thompson said. “I’m a paleontologist at heart and I want to be able to understand what past organisms are doing."

Thomson researched this for years and hopes future researchers will build upon this using it as a foundation.

"That for me is really valuable. Being able to take something and contribute it to the body of knowledge, for humanity, that could be of use,” Thompson concluded.