A request by @verdeviento@mander.xyz for some more info on talons.

Owls are a type of raptor. The origin of the word raptor comes from the Latin word rapere, which means “to seize.” That is because for a raptor, their feet are key to their survival. They catch their food, they’re used for grooming, and they’re the main line of defense.

Basic Anatomy

There are many differences in owl leg and foot anatomy when compared to other birds.

Owl foot and leg bones are shorter and thicker than other birds. This allows for a thicker muscular structure, even greater than that of most eagles many times greater in size. This sturdiness also helps the feet and legs withstand impacting their prey at high speed.

A is a hawk leg bone, B is an owl leg bone

Another advantage owls over other raptors is calcification of the leg tendons. This hardening occurs in areas of high stress. It allows more structural support in areas that need it and serves as a calcium reserve should a bone injury occur. These structures are called sesamoids.

Owl tendons are also arranged in a way that they are tensed when the bird is relaxed. This is the opposite of how our hands work. To grip tighter, we need to exert more and more force, but the owl just has to use energy to release its grip. This allows them to exert maximum force holding onto prey with minimal effort. It is also what lets them stay gripped to their perch when they sleep without falling off. They must consciously let go to relax their grip.

This article has some good animations on the way the tendons lock up the grip. Animated gifs work for me on Boost, but not Liftoff so I’ll just put the link here so I know everyone can look at it.

Owls are zygodactyl, meaning they have toes that are arranged in a 2 rear facing / 2 front facing, as opposed to most birds which are anisodactyl, with a 3 rear facing / 1 front facing arrangement. Owl toes are also of equal length, as opposed to having one longer toe in front. Owls do have the ability to move their fourth toe to either the front or back to allow force to be distributed in different ways.

Typical bird foot

Owl 2 by 2 grip

At the end of their toes are the talons. Owl talons are made of keratin, just like our fingernails. They have a hard outer layer and a soft inner layer, which makes them very hard, but also maintain some flexibility.

Inner and outer talon layers

Owl talons vary in size by species, but they are relatively long compared to their toe size. This increases the leverage in can apply. The Eurasian Eagle Owl has talons that can be up to 4 inches / 10 cm long.

Eurasian Eagle Owl feet

Grooming

Preening is an important part in owl grooming as it maintains the integrity of their feathers. Owls use their feet to arrange feathers, remove debris and parasites, and spread oils throughout the feathers.

Most birds have a ridge on their talons that aid in this, but the Barn Owls have evolved serrations that look and act like a comb.

Barn Owl talon

Another view

Hunting

Why do owls hunt with their feet and not their beaks? Owls have short and rather weak beaks. The tip is curved and can generate a good amount of tearing force, but it is not good for offense or defense. By using the feet, they not only have much great mechanical advantage, they also keep any danger as far from their face as possible. Owl eyes and ears are their means of locating food, so they need to keep them protected.

Owls will swoop down on prey with their talons spread to allow the maximum grabbing area possible. Many hunt at night and cant actually see their prey, so this increases the odds of being on target. The 2 by 2 toe arrangement allows maximum gripping force to be evenly distributed. With the toe that can move from back to front, they can adjust their grip if they somewhat miss their mark. The undersides of the feet are also highly textured to add additional grippiness. The feet are also covered with many sensory nerves to detect vibrations in the air or on the ground, so that also helps them “see” without being able to see.

Splayed talons to increase grabbing area

Grippy surface of foot

Once they have their grip on their prey, they do not use their talons to kill like hawks or eagles do. All the combined mechanical advantage of their bones and tendons is used like a hydraulic press to finish off their prey. Most eagles and hawks have much less grip strength because they do use their talons to kill. A Bald Eagle only has half the grip strength of a Great Horned Owl, even though the eagle is much larger.

Owl grip strength is not to be overlooked. The Great Horned Owl is one of the strongest birds, with a grip strength approaching 500 psi / 3450 kPa. An adult human can grip around 150 psi / 1025 kPa. A pitbull bite is less than 250 psi / 1700 kPa, and only when we reach dogs the size of an English Mastiff do we reach dogs large enough to generate as much gripping force as a Great Horned Owl. To compare sizes, an adult Mastiff is over 200 pounds / 90 kg, where a GHO weighs 3 pounds / 1.4 kg.

GHO vs Mastiff size comparison

  • luky
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    1 year ago

    i wonder if arm wrestlers can keep up with the owls grip strength. like arm wrestlers mostly train grip strength. my guess is that professional arm wrestlers could reach 400psi

    • anon6789@lemmy.worldOP
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      1 year ago

      After skimming some arm wrestling and grip strength from posts, it looks like 300 pounds on a hand Dyno will put you in legend territory, but I don’t know if that’s straight pounds or psi it’s measuring, so I can’t say it’s apples to apples.

      Those guys weigh a bit more than a 3 pound owl though, so either way the owl is very impressive!

      • luky
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        1 year ago

        yeah, obviously. that was never a question. i just wondered if a human could reach that strength regardless of strength to weight ratio

        • anon6789@lemmy.worldOP
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          1 year ago

          Maybe the hand dyno is in psi…

          I found this on a zoological site and I’d think they’d measure the comps the same way as the owls, and 440 would be 1.5x the strength of a buff dude…

          Link

          It is estimated to be 1.5 times physically stronger than humans to pull weight and jump.

          Chimpanzees are adapted for strong grip because of their arboreal lifestyle. Their grip strength is estimated to be 441 lbs (200 kg).

          A chimpanzee can also bench press a weight of 1,250 to 2,000 lbs, which is 5 to 8 times greater than the weight an adult large man can bench-press (250 lbs).

          • luky
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            1 year ago

            lol. I am trying to imagine an owl wrist curling a long barbell. Anyways thank you for looking that up

    • p3n@lemmy.world
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      1 year ago

      I think that everyone is misunderstanding pressure and what psi (pounds per square inch) is measuring. This is force applied over a surface area. There are two ways to increase pressure: 1. Increase the force 2. Decrease the surface area.

      I assume that 500 PSI is being measured at the very pointy tips of the Owl’s talons. This demonstrates their ability to pierce and grab their prey but it is misleading.

      I can easily generate 5000 PSI by stabbing with a sharp knife. That is not the same thing as what everyone is thinking of as “grip strength” which is like closing the Captains of Crush grip trainers. There is no way an owl could close the No. 4 CoC (365 lb) note this isn’t 365 PSI, this is 365 lb. Meaning you can generate 365 lb of force with your closing grip. If you could apply that force to a talon that came to a point of .001 square inches, you would generate 365,000 PSI

      • luky
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        1 year ago

        true. forgot about that. psi is unknown to me but bar or pascal is