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I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.

They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.

So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it?

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    $\begingroup$ The same with fish - how on Earth do they find their way to isolated lakes?! ! I love this question. +1 $\endgroup$ – AliceD Aug 2 '15 at 10:12
  • $\begingroup$ I have read that hurricanes can carry animals up into them and displace them. en.wikipedia.org/wiki/Rain_of_animals#Frogs_and_toads $\endgroup$ – Ro Siv Aug 2 '15 at 15:24
  • $\begingroup$ First, i would look at statistics: just because (hypothesis) you visit 1000 watering holes /marshes a year and they have frogs in them it doesn't mean that its a common occurrence; Second, i think froglings (yeah, i know :D ) hatch whenever there is rain, grow, mate and deposit new eggs that survive droughts. Now, these can be relocated by earth movements and birds and wind (i don't think frog rains could help with this level of dispersal). Basically, they don't end up in remote areas; They were already there in some form. $\endgroup$ – sergio Aug 3 '15 at 13:44
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    $\begingroup$ You would understand it much better when you consider the fact that your question encompasses a geographical aspect more than a biological one, the biological aspect being the creation of a new habitat. Migration/dispersal of offsprings from their parents depends much more geographical aspects such as lay of the land or climate. These links may be of some interest. goo.gl/JL1vp3 , goo.gl/agcr0d , goo.gl/6vb6yp $\endgroup$ – FoldedChromatin Aug 4 '15 at 5:39
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    $\begingroup$ @OneFace - I'm not and if I were, it still does not explain why fishes inhabit new puddles formed after the universal flood :) $\endgroup$ – AliceD Aug 5 '15 at 0:58
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This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.

Definition: From the Wiki

Technically, dispersal is defined as any movement that has the potential to lead to gene flow.

It can be broadly classified into two categories:

  1. Density dependent dispersal
  2. Density independent dispersal

The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)

From the wiki:

Density-independent dispersal

Organisms have evolved adaptations for dispersal that take advantage of various forms of kinetic energy occurring naturally in the environment. This is referred to as density independent or passive dispersal and operates on many groups of organisms (some invertebrates, fish, insects and sessile organisms such as plants) that depend on animal vectors, wind, gravity or current for dispersal.

Density-dependent dispersal

Density dependent or active dispersal for many animals largely depends on factors such as local population size, resource competition, habitat quality, and habitat size.

Currently, some studies suggest the same.

This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.

Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)

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I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it?

Why not? In wet weather, the conditions would be just fine for an enterprising amphibian to go exploring, perhaps driven by predators or lack of available resources, not to mention Ro Siv's comment about wind-borne dispersal of animals. Birds of prey may also pick up small animals, fly away with them, then drop them for whatever reason.

You are also neglecting the fact that these organisms have existed for millions of years, and the landscape has changed tremendously in that time, with glacial periods interspersed with interglacials every 20-50,000 years or so. As glaciers melt, large lakes form, and as those dried the organisms were dispersed across the land into smaller bodies of water. Streams and rivers form, transporting aquatic life forms, and may dry out and form isolated ponds, or they may be blocked for any number of reasons (mudslides, earthquakes, volcanic eruptions, beaver dams, fallen trees, etc.). As erosion and landscape remodeling occur, all traces of the original body of water may be erased, except for the wide distribution of similar organisms.

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    $\begingroup$ Yes, but marshes have come and gone on an almost yearly basis (or over several years, maybe a decade or so). We're not talking eons here. $\endgroup$ – Octopus Aug 2 '15 at 20:56
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    $\begingroup$ @Octopus marshy areas tend to remain marshy areas over the short term (decades to centuries) unless acted upon by an outside force, such as the rerouting of a water supply or human activity. I'm not sure what you mean by coming and going on an almost yearly basis - could you give some examples? Also, as I mentioned in my answer, during prolonged wet weather (maybe over a week or more), frogs and other amphibians could travel relatively long distances with ease. I'm not terribly close to wetlands, yet I often find frogs in my yard during/after a long rain that are no longer there when it's dry. $\endgroup$ – MattDMo Aug 2 '15 at 23:25

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