Bullfrog Offal

Top Photo: American bullfrog.

It’s a well known fact that red-shouldered hawks take crawfish from our wetlands. Besides actually being observed eating the crawfish, the hawks leave the claws of the arthropods on the railings of the boardwalk when they’re done. The evidence is clear.

Frogs are also on the menu. The hawks, though, don’t typically leave frog parts on the boardwalk as a record of their passing.

Last week, I was confronted by a mystery while walking down the boardwalk into Explore the Wild. A good amount of internal organs and other other body parts was left on the railing and walking surface of our boardwalk. My first thought was red-shouldered hawk as predator. That was the easy part. I’d seen red-shoulders hunting from the trees and boardwalk at the edge of our wetlands many times. No problem.

But what was the creature whose parts were laid out in front of me? and why had the hawk left so much uneaten?

It didn’t take very long to determine that what I was looking at was a frog. And, judging by the amount and size of the offal on the boardwalk, it was a large one.

Looking at photos of skeletal frogs and images of their internal organs confirmed that yes, it was a frog. The clincher was a small portion of a frog’s jaw resting on the railing. On one side of the object I could see a bit of the maxillary bone and teeth of the frog. The other side showed green skin. Two of our local frogs become quite large and may or may not have a green upper lip, bullfrog and green frog.

Green frog.
Green frog.

Another piece of the puzzle was staring at me from down the boardwalk, though I didn’t know it at the time. Some dozen feet or so from the pile of apparent frog pieces was a backbone with what, I was later to learn, was a urostyle still barely attached to it. A urostyle is a unique feature in amphibians. Its an extension of the spinal column made up of fused vertebrae and lies between two modified ilia (hip bones) of a frog or toad. Confirmed identity.

In the following photos I’ve labeled select parts of the frog as best as I could. While I’m not certain as to their anatomical identity, I’m fairly confident.

Stomach, or colon.
Humerus (upper arm).
Various internal organs, liver, lung, etc.
Piece of jaw with skin of upper lip.
Inside of jaw showing teeth and maxillary bone (same piece as above).
Urostyle broken off to right (hip bone not shown).

As mentioned, there are both green frogs and bullfrogs in the area. They both get large, though bullfrogs tend to be larger. Some green frogs have green upper lips, some are mottled, some are plain brown. The same goes for bullfrogs. However, bullfrogs tend to be either green or brown on the lip, not mottled. Most of our local bullfrogs have green upper lips.

With the great amount of internal organs left behind this had to be a very large frog. Due to the frog’s lip color and amount of the offal on the boardwalk I think our unfortunate victim was a bullfrog, a large male if I were pressed.

As to why so much of it was left behind, pieces that any predator would gobble up with wildness? The hawk, and I’m pretty sure it was a red-shouldered hawk which preyed upon the frog, must have been disturbed, and it must have been disturbed by a human. A hawk, or owl, or fox, or coyote would have eaten what was left behind, no doubt.

I picture the event playing out thusly. A red-shouldered hawk was perch-hunting from the railing, locked onto a big bullfrog at the water’s edge and dropped in on it. The raptor then flew up to the boardwalk railing with its prize and began to pull the amphibian apart. At the same time, a human was beginning their descent of the boardwalk. Keeping an eye on the intruder, the hawk began to rip the frog to pieces, hastily gulping down the chunks as it ripped and tore.

The human got closer. The ripping, tearing and gulping became more frantic until finally the hawk grabbed as much of the frog as it could in its talons and took off across the wetland to find a peaceful location to finish its meal, leaving quite a bit of material behind in the process.

I came along sometime later, saw the leftovers, photographed the items and began my investigation.

There’s nothing like a good mystery!

1 response to Bullfrog Offal

  1. An interesting and unusual post. What most surprised me was your casual mention of the teeth in the jaw. I had no idea that some frogs have teeth! This led me down a bit of a rabbit hole. I found out that the ones that do have teeth only have them on the upper jaw, and they aren’t “true” teeth (although none of the articles I found explained why they aren’t). What was really interesting is that there is one species in the Andes that does have true teeth. I has them on both upper and lower jaws, but its ancestors didn’t. It reevolved them! Here’s the wikipedia article: https://en.wikipedia.org/wiki/Gastrotheca_guentheri

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