A thought after an operation to save toads: an intervention with good intentions, may under certain conditions be harmful.
My daughter asked us to take some tadpoles with us, so that she can watch their development while growing them at home. At first I refused and explained to her that this was a violation of nature, but she convinced me by saying that after they turn into young toads, we will return to the place and release them. I searched in the junkyard and found electrical wire and scraps of fabric from which I improvised a net. It is easy to describe my daughter's joy when she managed to catch tadpoles and carefully thread them into a liter and a half bottle full of egg water. Suddenly she drew my attention to the scattered small shallow puddles in the area, separate from the main body of the swamp - and containing dozens, if not hundreds, of tadpoles, some of them actually fluttering in the mud. In my estimation, these puddles would have dried up completely, the very next day. We will save them said the girl, collected another amount into the bottle and several dozen more and transferred several rounds from the puddles to the body of the egg.
At home, we transferred the contents of the bottle, which included swamp water and about 25 tadpoles, to a large jar - one that goldfish used to swim in. They don't lack food. In the water we saw lots of tiny creatures and we occasionally diversified by adding tiny pieces of meat, chicken and fish. My daughter devoted time to observing them and even gave names to some of them, according to various hallmarks and behavior patterns she claimed to have detected in them. She actually recognized them over time.
As you know, first the amphibian tadpoles grow the back legs and then the front legs and then the tail starts to shrink (if they are among the tailless ones, and not, for example, salamanders or newts). It was really interesting to follow their development.
At some point, we came to the conclusion that they were already transitioning from gill breathing to lung breathing (and skin) and then we moved them to an aquarium (we switched to female because linguistically, tadpoles are male and frogs, toads, and frogs are female) in the middle of which was a pile of gravel grains, so they could choose whether to be in the water or outside of them.
About two months have passed since we collected the tadpoles from the egg and they have all become adults - green toads the size of a small fingernail. They fed on things that were in the water and also on mosquitoes and flies that were attracted to the aquarium. A few days later we noticed two that looked different. We checked and identified that those two are common elk. My daughter was very proud that, on her initiative, two woodpeckers were saved, which are probably more rare, in the same environment, and they certainly would not have survived if we had not raised them at home.
They grew a little more and the time has come to return them to their natural environment. The girl wanted to keep holding them until winter, and see how they grow. I convinced her that under our treatment conditions, we might miss out and they might pay for it with their lives in the dry summer.
We returned to the swamp, or rather no swamp, because it was impossible to tell that there was once a swamp here. The ground, even in the lowest places, was as dry as a board and everything was covered with vegetation. Who knows how many tadpoles have dried to death here, said the girl as she took the twenty or so toads and the two ladybugs out of the box. The tiny amphibians jumped into the thick vegetation in order to find a place protected from the sun and possibly holes to hide in. We tried to follow the elk because we knew they were supposed to find a tree to climb, but we lost eye contact with them in the thicket of vegetation.
While the "frogs" were disappearing, I began to ponder out loud and try to explain to my daughter that even if we contributed in some way to increasing the amphibian population in the area, then it is possible, and precisely this kind of action could cause the population to decrease.
This is on the assumption of having a certain genetic trait, saving a large amount of tadpoles and repeating it for many seasons. Then when the manipulation is stopped, the population is reduced to lower levels - also in relation to the initial state.
Anyone who thinks they can offer the explanation for this, is welcome to write it in the comments.
25 תגובות
I agree with Aryeh Seter's position.
But in my opinion the change is not genetic, frogs that can be called "genetic sloths" do not develop.
They can be called "behavioral lazy", because they were raised in captive conditions, and hence they did not develop behavioral abilities that promoted them against dangers, they developed lazy behavior. and survive less well in the wild.
Arya Shalom
Although I joined the respondents two years late, but. I think you will be interested in my story and "my" frogs.
20 years ago my son (then 17 years old) brought home a green toad. We put her in a small fish pond. I suggested that he bring another one, and maybe you will be a daughter or a partner for the lonely frog. And so it was. For 20 years they have been spawning and breeding at my place. I fight every year to save the tadpoles from the fish in the pond. In their wisdom, they moved to spawn on the cover of the swimming pool, which is close to the fish pond. On the cover of the swimming pool develops a swamp rich in leaves and insects... mosquito worms
And more... when my husband decides it's time to remove the cover on the swimming pool - I have two weeks to move hundreds of tadpoles to another pool. It's really a saga of rescuing tadpoles...brown, shiny, full of life and movement, tiny and chubby. And when they sometimes fall outside the net or the bowl, I collect them with the help of a leaf pushed under their body and pick them up one by one. All this takes place in my home, in Safed, on Mount Canaan. And for six months I hear the song of the frogs.
I call them song frogs - because their croaking is so gentle and beautiful, and reminds of nature... (as opposed to other ugly croaking of other toads) I must already have a unique Canaanite species with unique genetics.
Tzah - your hypothesis is incorrect. The toads and the elk didn't miss taking shelter for the summer, because they don't need special shelter. The elk live on the trees and they must have jumped there immediately and the toads - there is nothing to worry about them - they live even in the desert and we brought them to an environment that has a lot of vegetation and shade.
As far as I understood from the description - it is possible that the population that came from captivity delayed the stage of taking shelter for the summer and actually did not survive at all for this reason.
To clarify - I was not talking about breeding toads in captivity. My theoretical rescue project is expressed in the fact that every season, shortly before the swamp dries up, the tadpoles are collected, raised to the young adult stage and then released into the environment.
The sloths then do not die - on the contrary. Their percentage in the population is increasing. The general number is also increasing, but the natural living environment limits the total amount, but the percentage of laziness in the population is constantly increasing. When the manipulation is stopped, the sloths die and the population shrinks below the size it was before the rescue operations began.
True, but this does not change the fact that the total number (in the specific case described - not in the principle case I described) will be greater than it would have been without the rescue operation - even excluding the lazy ones who died.
But the percentage of industriousness in the population will decrease because the lazy, who without rescue, are all dead - survive.
I didn't notice that you said that in the wild the sloths die out before they have time to reproduce.
In any case - if the conditions you provide for the toads in captivity allow them all to survive - then there won't be fewer industrious toads in captivity. In fact there will be at least the same number of industrious toads as there would have been had they not been taken into captivity.
Therefore - even if when you return the toads to the wild - even if all the sloths die - there will still be more toads left than there were without the rescue operation.
Laziness will not prevent the culture of the lazy in captivity, or alternatively in the rescue centers, because the lazy are also saved and not allowed to dry up.
lion:
The scenario you described is a special case of what I referred to in the following sentence "Over many generations, genetic development can occur, but during individual generations - even if a mutation occurs in one of the animals that gives an advantage in the conditions of captivity but becomes a limitation in a free life - it cannot yet spread to parts significant of the population."
As a principle, I don't think that the example you gave is so good because laziness will prevent the culture of the lazy even in captivity, but the principle - as a principle - remains true.
What genetic trait will decrease the toad population after ongoing tadpole rescue operations? First we will clarify and say that a one-time rescue of about 25 tadpoles, as described in the article, will not cause any harm. The theoretical possibility I was thinking about - damage to the size of the population, will only occur if the genetic trait I was thinking about actually exists and only if saving tadpoles is implemented on a large scale and over many seasons. Obviously, in the case of a population in a state of extinction, any rescue operation will be blessed.
What is the manipulation we do when we save tadpoles? We add toads to the population, which would otherwise dry out and die in the tadpole stage. Suppose there is a genetic trait of agility versus laziness in regards to the speed of reproduction and development. Agility is the ability to lay eggs as quickly as possible - immediately after the first rains and/or rapid development of the tadpole until the toad stage. And then when we save masses of tadpoles, we save a lot of sloths among them. As a result, the percentage of lazy people in the population is increasing. After several generations, if the rescue operations are stopped, the sloths, whose relative number is now large, do not survive and the population decreases. That's all - just a thought exercise in evolution.
What genetic trait will decrease the toad population after ongoing tadpole rescue operations? First we will clarify and say that a one-time rescue of about 25 tadpoles, as described in the article, will not cause any harm. The theoretical possibility I was thinking about - damage to the size of the population, will only occur if the genetic trait I was thinking about actually exists and only if saving tadpoles is implemented on a large scale and over many seasons. Obviously, in the case of a population in a state of extinction, any rescue operation will be blessed.
What is the manipulation we do when we save tadpoles? We add toads to the population, which would otherwise dry out and die in the tadpole stage. Suppose there is a genetic trait of agility versus laziness in regards to the speed of reproduction and development. Agility is the ability to lay eggs as quickly as possible - immediately after the first rains and/or rapid development of the tadpole until the toad stage. Then when we save masses of tadpoles, we also save sloths among them. As a result, the percentage of lazy people in the population is increasing. After several generations, if the rescue operations are stopped, the sloths, whose relative number is now large, do not survive and the population decreases. That's all - just a thought exercise in evolution.
lion:
Thanks for the compliments.
It's hard for me to describe a scenario where an activity like the one you did - even if it continues over several generations, will lead to the result you fear.
I'm talking about fear because if I understood you correctly - that's all there is - that is - you haven't seen a phenomenon of this kind, but you are afraid that it will happen (I still have some doubt as to whether this is what you meant because you asked for an "explanation" and it is customary to ask for an explanation only for a phenomenon that is known to occur And not to mention that it might not happen at all).
Genetic development can occur over many generations, but during individual generations - even if a mutation occurs in one of the animals that confers an advantage in captivity but becomes a limitation in free life - it cannot yet spread to significant parts of the population.
As the link provided by Assaf describes - the way you have taken is indeed an acceptable way to save species that are in danger of extinction.
Of course, there may be very unlikely scenarios in which an action like the one you have taken will result in a reduction of the population (such as, for example, a situation where you took captive or left in the territory a very unbalanced population in terms of males and females and returned the captives only after they had already "missed" reproductive cycles)
to Aria
To improve your feeling see:
http://www.sciencedaily.com/releases/2010/08/100817111833.htm
Michael Rothschild - Welcome back. Your presence affected the responses - both in quantity and level. Please comment on the quality of this article.
With all the damage that man has contributed to the environment
It follows that man is enemy #1
And not nature.
So if the tadpoles were cute enough to save them, and take them to grow at home.
They are most likely the surviving generation, possessing superior genetic traits.
Yair - I mentioned the possibility of changing genetic frequency in the population, after a massive manipulation that will take place over many generations.
At the beginning of the 20th century, researchers moved newts or salamanders from low areas to high mountains. The animals reacted with significant changes and the generations after them also differed from their low altitude form. After several generations, the descendants of the immigrants were returned to their original living areas and returned to their original form. The changes were at the hormonal level. It is ridiculous to think that half a generation of changing conditions might bring about some kind of change in the population.
lion
At the beginning of the twentieth century, attempts similar to yours were made. Two animals from sea areas were moved to mountain areas. Many changes appeared in them. After several generations of living in mountain areas, the animals were returned to the coast, and see it's no wonder, they returned to their original form. You have nothing to worry about, the life of the jar for one generation did not give an advantage to any garden and did not change anything in the Holon puddle before its construction.
Arya, in any given environment an equilibrium is reached between the available resources and the amount of plants (and plants) of all the types it supports, therefore there is no permanent state of "unlimited food".
Yehuda,
A few important points that should be emphasized in your answer: one, after the return to the wild, the tadpoles that were raised at home (under favorable conditions) will for a while take the place of some of the others that were raised wild (the total amount that the environment can support is limited, and for a while the "domesticated" ones will have a size advantage ). The second, the genes that are not so good for survival and survived in the "domesticated" will be inherited to the next generation and prevent the passage of "good" genes in their place. Third, the sex of the individuals is determined in most cases in amphibians according to the environmental conditions, and hence the male/female ratio that was returned to nature violated the ratio appropriate to the environmental conditions there.
In any case, Aryeh, an interesting experiment with little damage to the environment and gives a subtle hint of what man is doing to the human genome...
It is possible that the domestic breeding environment caused the development of a unique microbial flora on the body of the animals and these can carry and spread this unique flora among the population, for better or for worse (most likely for the worse).
It is also possible that actually "rescuing" a group that would probably continue to live and produce fertile and competitive offspring resulted in the introduction of negative genes into the population that would have caused individuals carrying it not to reach the adult stage and produce offspring that would continue to spread the gene. Of course these genes are in the population anyway (otherwise how did they get to the tadpoles in the first place) but actually bringing them to a mature stage increases the significance of their distribution (whether significantly or not, we don't know since we don't know the survival ratios of this special ecosystem).
You will see a disruption in a private or communal life cycle, a disruption in predator-prey relationships, if the amount returned is large enough compared to the amount that survived in the field.
The bottom line,
I don't think it really made any real change that harmed the population and on the contrary, now there is a girl with dreams of tadpoles and frogs - which will probably remain in her memory for many years and will also be passed on to her children when the time comes. Somewhere in this chain, one of them might be able to take care of the conservation of wetlands. In my feeling - the two-life population benefited in any case.
Greetings friends,
Ami Bachar
Yehuda - I do not believe that there is an advantage in obtaining food for the "domesticated" tadpoles since in my opinion there is an abundance of food available in the swamp.
You gave an advantage to the garden of Beyot. The domesticated tadpoles who didn't know how to look for food survived and even this gave them a certain advantage over the wild tadpoles who worked hard to get food. So in nature, the amount of tadpoles that didn't know how to look for food increased, and thus the entire group was flawed. Continuing the domestication operation or stopping it will not stop the general reduction of the frog population. Only after the cessation of domestication for several generations will the situation return to normal.
That's my opinion
Good night
Sabdarmish Yehuda