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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/ |
#2
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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/ |
#3
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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. |
#4
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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/ |
#5
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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. |
#6
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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
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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 |
#8
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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. |
#9
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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
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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/ |
#11
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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 |
#12
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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 |
#13
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Counting frogs
In article , Amynthas Nzlagunf@f
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/ |
#14
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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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