[Tweeters] Hooded Merganser/Rough-skinned Newt update

[pond at whidbey.com]

Than you John, and also to Dan McDougall-Treacy for taking the time to share what you know about this. Very appreciated.

I am fascinated by this (and concerned for our prized newt population. Other than your photo of the Ring-necked Duck at Ridgefield, and Chantal Jacques photo from 2017 (location isn't identified), here are a couple of themes I see:

PNW Islands: Whidbey, Orcas, Salt Spring, Vancouver.
Thrashing
10 minutes or so of thrashing before swallowing

We stock trout in our pond each year for the wildlife - I am going to have to pay more attention to the process of Mergansers eating trout. I can't say I've ever seen them with a newt-sized trout before. Maybe the deed is done quickly and without the attention-getting thrashing.

Thanks again,

Sego Jackson
Whidbey Island

-----Original Message-----
From: John Riegsecker <jriegsecker at pobox.com> 
Sent: Friday, March 1, 2024 3:25 PM
To: Sego Jackson <pond at whidbey.com>; tweeters at u.washington.edu
Subject: Re: [Tweeters] Hooded Merganser/Rough-skinned Newt update

All,

In February 2014, I photographed a female Ring-necked Duck eating a rough-skinned Newt at Ridgefield.

https://skygardener.zenfolio.com/p657549207/h24deca4f#h3eb0569f

I of course was curious of the outcome.  I asked Dennis Paulson about this, and he and Gary Shugart were very helpful in pointing me to the literature and getting in contact with some other folks.

Don McVay sent me an email referencing an early Tweeters post:

https://tweetersarchives.org/2003/March/12140357How%20do%20they%20do%20that%3F.html

In response to that, someone sent him an email

Begin Quote:

"The Rough-skinned Newt (Taricha granulosa) on Vancouver Island, British Columbia, has low levels of TTX. . . . Skin extracts from these newts are at leat one thousand times less toxic than those obtained from Rough-skinned Newts from the Willamette Valley, Oregon (Brodie and Brodie, 1991).  Studies suggest that they have lost most or all of the TTX toxicity.  It is of interest that the Common Garter Snake (Thamnophis sirtalis) a newt predator that is resistant to newt poison in mainland areas, has either lost or not evolved significant resistance on Vancouver Island, where newt toxicity is low."

The full reference citation:  Brodie, E.D., III, and E.D. Brodie, Jr. 
1991.  Evolutionary response of predators to dangerous prey: Reduction of toxicity of newts and resistance of garter snakes in island populations. Evolution, 45:221-224.


End Quote:

More along those lines here:

https://journals.plos.org/plosbiology/article/file?id=10.1371/journal.pbio.0060060&type=printable

My best guess would be that you are far enough north that the newts are not very toxic and the Hooded Merganser is fine.

On 3/1/2024 1:16 PM, Sego Jackson wrote:

> This morning, I (again) happened to see from our bedroom window that 

> the Hooded Merganser was thrashing away at a Rough-skinned Newt. This 

> time I was determined to see if it swallowed it or not. After watching 

> for 10 minutes, it drifted behind some vegetation on the near edge of 

> the pond, and out of sight. So I ran outside and positioned myself 

> where I could watch it and within 5 minutes it swallowed the newt.  So 

> it is consuming them and not just playing around.

> 

> And assuming it swallowed the first two times too, what I note is that 

> from first noticing the merganser has a newt to it having “finished 

> the job” has been about 15 minutes each time. I have no idea how long 

> the merganser had hold of the newt before I noticed in each case.

> 

> Anyone know what a merganser typically does with prey? Is the 

> thrashing the prey about and time to get it down typical for other merganser prey?

> 

> Sego Jackson

> 

> Whidbey Island

> 

> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for 

> Windows

> 

> 

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--
John Riegsecker