Date: 4/28/17 8:11 am From: Reames, Clark -FS <creames...> Subject: Re: Why do Great Egrets dunk and shake frogs before eating them?
I wonder how often a bird such as a great blue heron in the process of tossing, biting, and re-positioning will actually lose his grip and drop his catch where it makes an escape? Knowing how slippery a wet fish is, one might think all the manipulation would be risky especially when you are standing in knee deep water. Of course this is my anthropomorphic view from my experience as a fisherman. Obviously, a hard bony bill is a better tool for gripping a slippery fish than the palm of my hand. :)
From: Keith Newton [mailto:<keithnewton...>]
Sent: Thursday, April 27, 2017 6:14 PM
To: Reames, Clark -FS <creames...>; <ARBIRD-L...>
Subject: Re: Why do Great Egrets dunk and shake frogs before eating them?
Clark, My thoughts were something close to yours. I don't know anything about birds salivary glands, and or how they manage to swallow fish as large as they sometimes do, and or how the true frogs which can be a bit clammy after they are out of the water. However, I had a series of photos of a Great Egret catching a Western Lesser Siren about 12" long. After catching it, he tossed it around mouthing it pretty well for about 1 minute 30 seconds before dunking it in the creek, but then went back to tossing and biting again for another 3 minutes 40 seconds longer before swallowing it. I would assume that they don't seem to care whether something is actually dead before swallowing it, but probably would have been drier when it finally swallowed it than just before it dunked it. I think I've read that most salamanders can exude some poison through their skin to avoid some predators.
I find it hard to NOT think of this from our squeamish human perspective of swallowing something alive that is going to be down there wiggling around for gosh knows how long. It seems like frogs and some fish are extremely hard to kill. However it might be that they die quicker down in their gullet than outside. A trick I had learned for dispatching a large fish that you need to process quickly that you know will be trashing around messing up the boat cockpit is to hold the gill flaps closed, then pour a little spirits like rum in their mouth. When it hits the gills, it goes instantly into their bloodstream, and that is the end of the fight. I would imagine that whatever digestive juices are down there which are strong enough to break down something like a 1.5# pickerel swallowed head first, which will be regurgitated in pieces for chicks sometime later, probably would have the same effect as the rum.
I'll bet there are other photographers on the list who would have series of images with time signatures that could add to this conversation and give more perspective. I'm not an expert, so this is speculation, or my 2¢.
On Apr 27, 2017, at 4:12 PM, Reames, Clark -FS wrote:
So I gather from this that white ibis can ingest cane toads with no ill effects? I wouldn't think that a quick rinsing would reduce the toxicity much at all. Maybe the dunking just helps to lube the frog to slide down the gullet easier or something as simple as the bird shifting its grip on the frog to reposition it to swallow. Of course I am just speculating here...
From: The Birds of Arkansas Discussion List [mailto:<ARBIRD-L...>] On Behalf Of Ragupathy Kannan
Sent: Tuesday, April 25, 2017 6:37 PM
To: <ARBIRD-L...><mailto:<ARBIRD-L...> Subject: Why do Great Egrets dunk and shake frogs before eating them?
Hi Andrew and Mobirders,
I think that Chis may be close to right. But, I am not sure and I haven't
come across that in the lit. either.
Here's a thought: maybe they're breaking up some bones so that it will
go down easier !
Larry, in Joplin.
Lawrence Herbert <certhia13...><mailto:<certhia13...> 4-25-17.
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I have seen this in Australia with a White Ibis eating a Cane Toad. Cane Toads are extremely toxic to mammals at least, and a lot of frogs have toxins in the skin which are easily capable of making a human feel ill. I know from personal experience that you can get sick from just eating food with hands with have handled frogs. But if you wash your hands first, even rather briefly, it seems to eliminate the risk, so I would guess a lot of the toxins might be very water soluble, and that it might be quite a good idea to wash the frog first. Repeated processing might work well with things like toads where substantial glands can exude toxins for extended periods.
On 4/25/2017 10:57 AM, Andrew Reago wrote:
I've witnessed a number of Great Egrets capture frogs and eat them, but I've also watched as they have dunked the frogs over and over in the water, shaking the frogs in between dunks, before eating them. What are they doing? If they did it just a few times, I'd think they were cleaning the frog, but repeatedly doing it? I can't find anything online.
Anyone know? Any ornithologists out there study this behavior?
St. Louis MO
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