Re: [vernalpool] An interesting observation from Michigan

This is an interesting paper about wood frog tadpoles preying on spotted
salamander embryos. Not a precise response to your species specific
question, but related.

http://www.jstor.org/discover/10.2307/3893392?uid=3739696&uid=2&uid=4&uid=3739256&sid=47698848996237

I hope interested people can find the full version somewhere online.

When this paper came out, it changed our former understanding of what
tadpoles eat. The food chain is much less predictable than we used to
think. I bet it happens with green frogs too.

Scott Smyers

On 4/6/2012 8:39 AM, Leo Kenney wrote:
>
> Hi Folks,
>
> VPA received the question below this week. With permission, I am
> throwing it out to the community. I have already visited one long
> hydroperiod pool this spring with a substantial population of green frog
> tadpoles. The water level was lower than usual but still over 4 ft in
> the deepest area. The tadpoles were grazing at the wood frog egg rafts
> but didn't seem to be any more predaceous than in other years. Has
> anyone else seen green frog tadpoles completely remove wood frog eggs.
> Or is something else going on here? Is this observation an answer to an
> earlier observation about "missing frog eggs"?
>
> Leo
>
> Quote begins:
>
> Hello. I'm hoping you are willing to to take the time to read my account
> below and lend some expert insight into what I'm finding to be
> unsettling developments on our vernal pool.
> We've lived on property in lower Michigan for 23 years with a one-acre
> vernal pool and use it annually for education purposes. This past hot
> stretch in March provided water temperatures that were comfortable
> enough to swim in, where in every other March, a wade through it is a
> numbing experience. This year, we've noticed, for the first time ever,
> that there were absolutely no fairy shrimp in the water. Could the
> unusually warm water have killed the larval shrimp immediately upon
> hatching?
> On another unsettling note, due to warming... Every year, in addition to
> 6 other species of frogs breeding on the pond, green frogs attempt to
> breed there. Since greens do not begin breeding until May, peeper,
> chorus, wood, leopard and Am toads are well into their breeding cycle
> with tadpoles growing in the pool. Green tadpoles appear to take about 3
> months to grow and metamorphose. Tadpoles that hatch from eggs laid
> later in the summer do not make it. Either the vernal pool dries out and
> kills them, or, if there is shallow water remaining in the pool at the
> onset of winter, the green frog tadpoles are winter-killed.
> Through the wimpy winter of 2011-12, the shallow water on the pond went
> through several periods of freezing and thawing instead of the permanent
> freeze of any past normal winter. The green frog tadpoles did not
> winter-kill. Then the wood frogs laid their eggs 3 weeks ahead of
> schedule. I made a youtube video of their breeding action on March 16. A
> few nights later, I waded to the location where hundreds of eggs masses
> could be found. I shined the flashlight on them to reveal large green
> frog tadpoles engulfing them. The light scared them and they darted into
> the grassy depths below. A few days later, I waded to the same spot. It
> was as if the eggs were never laid. I believe the green frog tadpoles
> ate the entire season's breeding effort of the wood frogs. In any other
> year, wood frog tadpoles are abundant. This year, we have not seen a
> single one, and only a couple of tiny peeper tadpoles, which are
> also always abundant.
> It appears starkly obvious that green frog tadpoles overwintering
> successfully in a vernal pond is very detrimental to the breeding
> success of wood frogs. By extension, the early spring presence of green
> tadpoles is most certainly detrimental to the breeding success of other
> frog species and of the mole salamanders, too. On your site you list
> some obligate vernal pool species of amphibians. They cannot breed
> successfully in waters occupied by fish. It appears to us that the green
> frog tadpoles are playing the role of "fish" in a warming vernal pond.
> With the apparent inevitability of climate change, it is easy to imagine
> more such warm winters ahead and the associated mass declines and local
> extinctions of all amphibians that rely on vernal pools for reproduction.
> Can you point to any research or past findings that corroborate what
> we've noticed here, or offer any other comments? Thanks a lot for your
> time.
> Jim McGrath,
> Nature Discovery
> Williamston, MI
> www.naturediscovery.net <http://www.naturediscovery.net>
> naturedisc@cablespeed.com <mailto:naturedisc%40cablespeed.com>
>
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>
>
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--
Scott Smyers, M.S.
Senior Scientist
Oxbow Associates, Inc.
P.O. Box 971
Acton, MA 01720
978-929-9058 ext. 203
978-314-6027 cell

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