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Old 19-03-2003, 09:32 PM
Kay Easton
 
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Default Counting frogs

Does anyone have any idea how to count the frogs in a pond?

For example - I counted 36 frogs in the pond today - does that mean I
have 36 frogs? Or have I got nearer 50?

can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn have I
got 20 females or could it have been laid by,say, 5 females?

How many females does each male mate with? I presume once he's
fertilised one batch of eggs, he won't just sit on the sidelines, he'll
see if he can find another female.
--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/

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Old 19-03-2003, 09:56 PM
Martin Sykes
 
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Default Counting frogs

"Kay Easton" wrote in message
...
Does anyone have any idea how to count the frogs in a pond?

Drop a grass snake in the pond. *all* the frogs will jump out. :-)

For example - I counted 36 frogs in the pond today - does that mean I
have 36 frogs? Or have I got nearer 50?

More seriously, apart from wondering why it's important, depending on how
long you spent looking you probably counted the same frog more than once.
Your presence there probably made them dive and pop up somewhere else. The
act of observation changes what you are observing.

As a rough guide, if you knew what percentage of its time a frog stayed on
the surface on average and how many frogs on average were visible at any one
time then the total number of frogs would be average visible/percentage of
time visible. So if on average there are 10 visible at any one time and they
spend only 25% of their time on the surface then you've got 40 frogs give or
take. The percentage time on the surface could be found if you've got one
easily identifiable frog you could time.

can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn have I
got 20 females or could it have been laid by,say, 5 females?

I'm pretty sure they can lay more than one batch. This is only an indication
of female numbers though and is no guide to the number of males. However, I
think frogs can change sex from male to female depending on the temperature
so it's probabably possible to work out the likely ratio of female to male
at a given temperature.

How many females does each male mate with? I presume once he's
fertilised one batch of eggs, he won't just sit on the sidelines, he'll
see if he can find another female.

A male will try and mate with anything that moves. female frogs, fish, your
hand. Doesn't help you count them though.

Short of draining the pond and catching them all though, there's so much
uncertainty in any measurement that you'll probably be plus or minus 50% of
the true value. As soon as the spawn hatches (?) your number will be wrong
again anyway.

Martin

--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/



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Old 19-03-2003, 10:32 PM
ned
 
Posts: n/a
Default Counting frogs

Kay Easton wrote:
Does anyone have any idea how to count the frogs in a pond?

For example - I counted 36 frogs in the pond today - does that mean
I have 36 frogs? Or have I got nearer 50?

can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn
have I got 20 females or could it have been laid by,say, 5 females?

How many females does each male mate with? I presume once he's
fertilised one batch of eggs, he won't just sit on the sidelines,
he'll see if he can find another female.


Nothing authoritive here, just observation.

I have found that I count many more frogs by torchlight after dark
than I see during the day.

I suspect that females do spawn more than once per season. I seriously
doubt that I have one female for every batch of spawn in my pond.

The small males seem to outnumber the females 2:1 in my pond. There is
always competition for the females. I have seen one passive female
smothered by four males all waiting for that oportunistic moment. So I
guess one clump of spawn could contain diverse genetic content.

Spawning seems to take place in 'favoured' places in the pond. So when
the female drags herself (and suitors) to that favoured place, there
is every chance that all the males in the neighbourhood could be in
attendance.

Wrap up warm when you go out with the torch. ;-)

--
ned

....... isn't it a shame that common sense
is not all that common.


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Old 19-03-2003, 11:08 PM
Kay Easton
 
Posts: n/a
Default Counting frogs

In article , Martin Sykes
writes
"Kay Easton" wrote in message
...
Does anyone have any idea how to count the frogs in a pond?

Drop a grass snake in the pond. *all* the frogs will jump out. :-)

For example - I counted 36 frogs in the pond today - does that mean I
have 36 frogs? Or have I got nearer 50?

More seriously, apart from wondering why it's important,


It's not importnat, but it's interesting.

depending on how
long you spent looking you probably counted the same frog more than once.


No, no - this was 36 simultaneous frog heads sticking out - I could see
them all so I know that none of them moved.

Your presence there probably made them dive and pop up somewhere else. The
act of observation changes what you are observing.


I approached very slowly! None of them dived. All but 5 vanished when a
kitten appeared, though.

As a rough guide, if you knew what percentage of its time a frog stayed on
the surface on average and how many frogs on average were visible at any one
time then the total number of frogs would be average visible/percentage of
time visible. So if on average there are 10 visible at any one time and they
spend only 25% of their time on the surface then you've got 40 frogs give or
take. The percentage time on the surface could be found if you've got one
easily identifiable frog you could time.


They all look the same to me ;-)


can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn have I
got 20 females or could it have been laid by,say, 5 females?


I'm pretty sure they can lay more than one batch. This is only an indication
of female numbers though and is no guide to the number of males.


Oh, quite, I realise that - that's why I asked my third question!

However, I
think frogs can change sex from male to female depending on the temperature
so it's probabably possible to work out the likely ratio of female to male
at a given temperature.

How many females does each male mate with? I presume once he's
fertilised one batch of eggs, he won't just sit on the sidelines, he'll
see if he can find another female.


A male will try and mate with anything that moves.


I don't think it has to move! One of ours was clasping the pipe to the
pump!


--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/
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Old 19-03-2003, 11:56 PM
ned
 
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Default Counting frogs

Martin Sykes wrote:
snip
However, I think frogs can change sex from male to female
depending on the temperature so it's probably possible to work
out the likely ratio of female to male at a given temperature.

Have you any corroboration for that?
Temperature will certainly dictate sexual activity but I doubt they
change sex.

--
ned

....... isn't it a shame that common sense
is not all that common.






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Old 20-03-2003, 07:44 AM
Pete The Gardener
 
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Default Counting frogs

On Wed, 19 Mar 2003 23:57:13 -0000, "ned" wrote:

Martin Sykes wrote:
snip
However, I think frogs can change sex from male to female
depending on the temperature so it's probably possible to work
out the likely ratio of female to male at a given temperature.

Have you any corroboration for that?
Temperature will certainly dictate sexual activity but I doubt they
change sex.

AFAIR temperature can affect the sex of amphibians while they're in
the egg, though not once they hatch.
--
Pete The Gardener
A room without books is like a body without a soul.

  #7   Report Post  
Old 20-03-2003, 07:44 AM
Martin Sykes
 
Posts: n/a
Default Counting frogs


"ned" wrote in message
...
Martin Sykes wrote:
snip
However, I think frogs can change sex from male to female
depending on the temperature so it's probably possible to work
out the likely ratio of female to male at a given temperature.

Have you any corroboration for that?
Temperature will certainly dictate sexual activity but I doubt they
change sex.

Just a literary, not a scientific source. In Jurassic Park ( Michael
Crichton), the all-female dinosaurs manage to breed because their DNA is
spliced with frog dna.

I've just checked though and it looks like its only true for some reptiles
and fish ( all crocodiles ) and its the developing embryo which changes, not
the adult.

Sorry.

Martin



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Old 21-03-2003, 12:32 AM
ned
 
Posts: n/a
Default Counting frogs

Amynthas wrote:

snip
At breeding time, If they are on their own they are males
looking for females, if in a clinch and the one on top smaller of
the two then a male and female, if both the same size two males,
one of whom thinks/hopes the other is a male.

Males tend to hang around the pool waiting for females,
females turn up when ready and once they've spawned go elsewhere.


I think my frogs must have read a different book.
The first frogs to appear in my pond are 'always' large well marked
females. These can arrive as early as November/December. They are
therefore 'on their own' for some time before the smaller, more
non-descript males arrive maybe 3 or 4 weeks prior to mating. Both
genders will happily remain 'on their own' until the females are close
to spawning. Then the males start getting fruity, indulging in
amplexus with all and sundry, including themselves.
After spawning, there is a period of 'recuperation' when both sexes
remain and then, I agree, it is usually the females who are first to
leave. I presume that they know there is no more work to be done, and
they leave behind the ever hopeful males.
But, generalisations are always difficult. Last year, I had a big
female still in the pool even after all the tadpoles had hatched. It
would be nice to think of her taking on a guardian role - but for the
fact she was so quick to dive for cover when frightened and I doubt
any frog is equipped to fend off a predator.

--
ned

....... isn't it a shame that common sense
is not all that common.


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Old 22-03-2003, 11:28 AM
Joe Bloggs
 
Posts: n/a
Default Counting frogs

Changing the theme slightly - Is it true or have I dreamt that frogs and
toads don't co-exist in the same pond ? I have the frogs and frogspawn, but
would like to introduce toads to the garden too. I think they have a bad
press, but I like them.
B.

Kay Easton wrote:

Does anyone have any idea how to count the frogs in a pond?

For example - I counted 36 frogs in the pond today - does that mean I
have 36 frogs? Or have I got nearer 50?

can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn have I
got 20 females or could it have been laid by,say, 5 females?

How many females does each male mate with? I presume once he's
fertilised one batch of eggs, he won't just sit on the sidelines, he'll
see if he can find another female.
--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/


  #10   Report Post  
Old 22-03-2003, 11:28 AM
andyp
 
Posts: n/a
Default Counting frogs

I have both frogs and toads in the same pond and it is only about 9' x 4'. I
have plenty of spawn from both.

AndyP

--
"Wisest are they that know they do not know." Socrates
"If more of us valued food and cheer and song above
hoarded gold, it would be a merrier world" JRR Toliken, The Hobbit
"Joe Bloggs" wrote in message
...
Changing the theme slightly - Is it true or have I dreamt that frogs and
toads don't co-exist in the same pond ? I have the frogs and frogspawn,

but
would like to introduce toads to the garden too. I think they have a bad
press, but I like them.
B.

Kay Easton wrote:

Does anyone have any idea how to count the frogs in a pond?

For example - I counted 36 frogs in the pond today - does that mean I
have 36 frogs? Or have I got nearer 50?

can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn have I
got 20 females or could it have been laid by,say, 5 females?

How many females does each male mate with? I presume once he's
fertilised one batch of eggs, he won't just sit on the sidelines, he'll
see if he can find another female.
--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/






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Old 22-03-2003, 11:29 AM
Larry Stoter
 
Posts: n/a
Default Counting frogs

Joe Bloggs wrote:

Changing the theme slightly - Is it true or have I dreamt that frogs and
toads don't co-exist in the same pond ? I have the frogs and frogspawn, but
would like to introduce toads to the garden too. I think they have a bad
press, but I like them.
B.

snips ....

You'll have problems introducing toads - they are very loyal to their
breeding areas. If you try to relocate a toad, it will probably try to
walk 'home'.

Spawn would be the best way but toad spawn is a lot more difficult to
spot.

Finally, moving amphibians around is probably not a good idea -
certainly frogs are threatened by diseases and moving adults or spawn
can easily spread disease.

--
Larry Stoter
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Old 22-03-2003, 11:29 AM
Amynthas
 
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Default Counting frogs

In message , Kay Easton
writes
Does anyone have any idea how to count the frogs in a pond?

For example - I counted 36 frogs in the pond today - does that mean I
have 36 frogs? Or have I got nearer 50?


At breeding time, If they are on their own they are males
looking for females, if in a clinch and the one on top smaller of the
two then a male and female, if both the same size two males, one of whom
thinks/hopes the other is a male.

Males tend to hang around the pool waiting for females, females
turn up when ready and once they've spawned go elsewhere.

can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn have I
got 20 females or could it have been laid by,say, 5 females?


One female produces one clump of spawn. Though occasionally if
disturbed I suppose they might spawn in two clumps. When the spawn first
hits the water it has no noticeable jelly round the outside, this is
produced as it absorbs water and once it occurs fertilization is
impossible - so the males have to be quick.

How many females does each male mate with? I presume once he's
fertilised one batch of eggs, he won't just sit on the sidelines, he'll
see if he can find another female.


How long is a piece of string? As many as he can get to.

Now the 50,000 pound question, why does someone post a
zoological query here when there is a trained zoologist somewhere in the
house?
--
Amynthas
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Old 22-03-2003, 11:29 AM
Kay Easton
 
Posts: n/a
Default Counting frogs

In article , Amynthas [email protected]
pneobeb.qrzba.pb.hx writes
In message , Kay Easton
writes
Does anyone have any idea how to count the frogs in a pond?


can one tell form how much spawn there is? Does each female lay one
batch or more than one batch - eg if I have 20 batches of spawn have I
got 20 females or could it have been laid by,say, 5 females?


One female produces one clump of spawn.


Though others here have suggested that a female might produce another
batch of spawn a week or so later - are you sure of your statememnt?

So what you are saying is we have a minimum of 36 males (the 36 I saw
waiting) and one female for every lump of spawn - say another 40, hence
76 frogs in total. But you have also offered the guess that there may be
two males for every female, which would take us up to 100 or so frogs.


Now the 50,000 pound question, why does someone post a
zoological query here when there is a trained zoologist somewhere in the
house?


I don't ask my milkman to mend my car; neither do I ask an earthworm
specialist about amphibians ;-p

But the main reason is there is a lot of expertise and knowledge on urg
and i wanted to tap into that.
--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/
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Old 22-03-2003, 11:29 AM
ned
 
Posts: n/a
Default Counting frogs

Amynthas wrote:

snip
At breeding time, If they are on their own they are males
looking for females, if in a clinch and the one on top smaller of
the two then a male and female, if both the same size two males,
one of whom thinks/hopes the other is a male.

Males tend to hang around the pool waiting for females,
females turn up when ready and once they've spawned go elsewhere.


I think my frogs must have read a different book.
The first frogs to appear in my pond are 'always' large well marked
females. These can arrive as early as November/December. They are
therefore 'on their own' for some time before the smaller, more
non-descript males arrive maybe 3 or 4 weeks prior to mating. Both
genders will happily remain 'on their own' until the females are close
to spawning. Then the males start getting fruity, indulging in
amplexus with all and sundry, including themselves.
After spawning, there is a period of 'recuperation' when both sexes
remain and then, I agree, it is usually the females who are first to
leave. I presume that they know there is no more work to be done, and
they leave behind the ever hopeful males.
But, generalisations are always difficult. Last year, I had a big
female still in the pool even after all the tadpoles had hatched. It
would be nice to think of her taking on a guardian role - but for the
fact she was so quick to dive for cover when frightened and I doubt
any frog is equipped to fend off a predator.

--
ned

....... isn't it a shame that common sense
is not all that common.




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