Re: impacts are cool!

["Tony Canning" <tonyc@foe.co.uk>]

On Oct 30,  9:16pm, Chris Campbell wrote:
> Subject: Re: impacts are cool!
> Tony Canning wrote:

> > What is the source of your assertion that frogs are the first to go?
>
> Mostly their use at the moment as an indicator species; frogs are dying
> like wildfire around the globe and most other things are doing okay, so
> I take that as pretty solid support for my assertions.
>

Some populations of some species of frogs are in big trouble, yes.

But, US Fish & Wildlife Service lists as threatened or endangered:

Mammals 73 spp
Birds 96
other reptiles 35
Amphibians 16
Fish 111

So I wouldn't agree that other groups are doing okay.

 Many (but not all)
> > amphibian populations are currently in decline - acid rain may be a
> > factor in some cases, certainly not all.
>
> Or chemical pollutants, or a variety of other things, yes.
>

Particularly pesticides, which hopefully were not an issue, K/T.

> > Don't forget that the majority of amphibians can survive long periods
> > at very low temperatures without food - we're talking months, even
> > years here.  If the asteroid hit in November the most northern populations
> > would already be safely in hibernation where they could ride out the worst
> > few months of the impact consequences.
>
> Don't forget the climate at the time, though, which IIRC was much warmer
> globally than it is now.  I don't even know if hibernation would be a
> strategy at the time!
>

Well, if ever got near freezing anywhere in the world amphibians would
have hibernated.  I've not heard anyone suggest the whole planet had a
tropical climate


> > Maybe frogs are tougher than we think..
>
> Then why are they dying in droves?
>

A lot of people are working on that right now, and there's no simple
answer.  part of the problem seems to be that very large fluctuations
in population are normal for anura, so an environmental whack at a low
point can finish them off.  This makes them rather poor environmental
indicators in my opinion, except as part of very detailed, very long-
term studies.

Many populations of amphibians are doing fine.  Personally, I'm more
surprised that mammals made it through K/T event than frogs.  After all,
only a few members of a species need to survive, and explosive breeding
(some toads produce 10-20,000 eggs) enable rapid recovery.  It probably
helps if most of your predators have been blown away too.

Tony

tonyc@foe.co.uk