captive breeding in general

[Otterwoman]

Would people agree that once you have a species that breeds in captivity, that succeeding generations will be easier and easier to breed in captivity? not only because natural selection would favor the ones that would breed in captivity, but maybe other things, like ones that breed would be less upset that they didn't return to their natal pool, or captive breeding favors the individuals that have less difficult to meet triggers (light, temp, water). Or probably these are things that natural selection would choose for/against.
But there might be other factors, like the ones that are raised in captivity are less stressed by the captive (vs. wild) environment. I am wondering about these things in connection with my Tarichas. I have a bunch that are wild caught, and I have some that I raised from eggs. I'm wondering if the ones I'm raising will be more likely to breed, when they reach breeding age, than the wild caught ones, even after I have had the wild caught ones a long time (which I haven't yet). These questions might be obvious to those of you with a background in animal biology, but they are things I'm just starting to think about. If anyone wants to offer facts or speculations, please do!

 

[Lasher]

I would speculate that captive born and raised specimens would be more comfortble in their enclosures, less stressed, and more likely to breed than a wild specimen stressed by its introduction into a captive environment.
Though I would have thought a wild animal would 'adapt' to a captivity in time.

Having said that I once had a pair of Green Anoles start mating a week after they were bought(seperatley - maybe pets really do mimic the behaviour of their owners!). I've also had wild caught paddle tails and firebellies mate, but that was after I'd had them for a year or two.

 

[Otterwoman]

Maybe the anoles had been primed in the wild, and the stress of captivity couldn't stop them.
The question is, did they mate the NEXT year.

 

[Jake]

I've noticed that with my Xenopus leavis the captive born frogs will spawn more readily than the giant imported ones. I think you're right about the granulosas possibly being easier to breed if they were c.b. I am also raising some c.b. granulosa morphs and have eggs hatching right now.

 

[Lasher]

Maybe the anoles had been primed in the wild, and the stress of captivity couldn't stop them.
The question is, did they mate the NEXT year.

They did indeed, and the year after. Following that I sold them(which was a pitty, I was quite attached, had to due to moving), I heard from the new owner a few months later, they were still at it!

 

[Jennewt]

This is a tough one to even speculate on. While CB animals may be more accustomed to captivity and thus more likely to mate, there are other factors. There are some inborn biological triggers - some species need to be cold for a period of time before they will breed, for example - and these would probably be the same for WC and CB animals.

There are a couple of factors that might make CB animals less prolific. One is age - WC animals are likely to be full adults, and may even be 10+ years at the time they are acquired. Older animals generally produce more eggs. So it would take CB animals many years to catch up in fecundity.

I think there is also a tendency for CB animals to be weaker - in SOME cases. We could hope that if they get a good diet and conditions, CB animals might be just as strong or stronger. Certainly they have fewer parasites to hold them back. But from various things I've observed and/or read, CB animals often end up having a shorter lifespan for whatever reasons.

 

[Daniel]

I think there is also a tendency for CB animals to be weaker - in SOME cases. We could hope that if they get a good diet and conditions, CB animals might be just as strong or stronger. Certainly they have fewer parasites to hold them back. But from various things I've observed and/or read, CB animals often end up having a shorter lifespan for whatever reasons.

Jen - this is absolutely new to me I have to admit. Do you have any statistical sources on that thing?

After all I can see some changes in cb-animals in higher generations (admittedly reduced to Axolotls). Some of them can be triggered to mate and lay eggs throughout almost all of the year (I can remember how difficult this was some generations ago).

But maybe that this can not be generalized because Axolotls have been cb for quite some generations.

 

[Otterwoman]

So it would take CB animals many years to catch up in fecundity.

Although I was thinking, with better nutrition that they would hopefully be getting as cb animals (more quantity and more regular availability) they would mature earlier. Like people (girls) are reaching reproductive maturity at younger and younger ages thanks to nutrition.

 

[ben_tajer]

Like people (girls) are reaching reproductive maturity at younger and younger ages thanks to nutrition.

Isn't that also partially attributable to estrogen pollution?

 

[Azhael]

Probably the fact that they reach sexual maturity in an "unnatural" short period of time is one of the reasons that shortens their life span. I remember hearing someone say that female chameleons in captivity usually became pregnant at a very young age, which lead to a drastic stop of growth, usually cases of egg-bounding, and ultimately a shorter life. It probably happens something similar with caudates.
One thing that i would like to point out too, but mostly ask to more experienced breeders, is about the
"strength" of sexual behaviour in captive animals. It may just be my imagination, but i´ve seen newts displaying courtship in nature and the males were just desperate. The whole courtship was energic, and they would chase the female as fast as they could. In captivity though i remember when i was kid, stupid, and ignorant, that the newts i caught did court each other...but it was a weak version of it.
I´ve also noticed that my male C.orientalis courts in a rather lazy way...
First time they bred, little time after i got them he was energetic and fast....but this time even if he has been sexually active for months, his courtship is lazy and he´ll only tail fan every once in a while. I remember the wild newts fanning for loooong periods of time to anything that moved.
So, anyone with anything to say about that?

 

[Mark]

In my opinion captive breeding doesn't produce weaker animals than wild counterparts. The big difference is that weak animals have a much higher survival rate in captivity and therefore occur in greater numbers. I think it's likely the quality of the eggs and resulting larvae would be similar in the wild. The differences between a strong animal and a weak animal would in most cases be undetectable to the keeper. In the wild only the toughest make it to adulthood and breeding age. For species that lay large numbers of eggs it would seem sensible to raise the larvae in conditions that were as close to a wild environment as possible. We'd have far fewer metamophs but they would be of a high quality.

I can't see how reaching sexual maturity earlier would be a negative thing. It's just tied in with an increased growth rate due to plentiful food and temperature. I remember reading that P.waltl kept in mixed groups were generally smaller than those kept in same sex groups. Breeding somehow inhibits growth - maybe this is due to the ease of finding a mate. In the wild stronger, larger animals would naturally have more success than smaller ones. In captivity this doesn't follow due to the enclosed environment.

 

[grunsven]

Two things are lacking in this discussion in my opinion.

CB animals are probably lack parasits and pathogens common among wild animals.

Inbreeding is a problem that can reduce fecundity and longevity of caudata in captivity. Many breeders are not fully aware of this problem.

 

[Otterwoman]

Isn't that also partially attributable to estrogen pollution?

Whenever I've read about this subject, that hasn't been brought up. I'm not saying it's not possible, however. I've read about this affecting other animal species (non-human).

 

[Abrahm]

Narrowing this down to any small set of factors would be a really difficult thing to do. It would be anawfully great project for a graduate student or research university, though I could see the experimental setup being difficult.

Although I was thinking, with better nutrition that they would hopefully be getting as cb animals (more quantity and more regular availability) they would mature earlier. Like people (girls) are reaching reproductive maturity at younger and younger ages thanks to nutrition.

Isn't that also partially attributable to estrogen pollution?

I think estrogen mimicking compounds in the environment are more contributing to the feminization of animals than speeding up sexual maturity. I would imagine estrogen mimickers could be playing a role in faster sexual maturity. A lot of the early sexual maturity in humans has to do with diet. High energy diets with low exercise means that girls are reaching puberty faster by reaching their trigger weights faster.

In my opinion captive breeding doesn't produce weaker animals than wild counterparts. The big difference is that weak animals have a much higher survival rate in captivity and therefore occur in greater numbers. I think it's likely the quality of the eggs and resulting larvae would be similar in the wild. The differences between a strong animal and a weak animal would in most cases be undetectable to the keeper. In the wild only the toughest make it to adulthood and breeding age. For species that lay large numbers of eggs it would seem sensible to raise the larvae in conditions that were as close to a wild environment as possible. We'd have far fewer metamophs but they would be of a high quality.

I definitely agree with Mark here. All the selective pressures being placed on animals in captivty are man created. It would be relatively easy to select for hypersexuality by constantly mating easy to breed animals. All you would need is time. I think it would difficult to select as nature does for the high quality traits considering all the factors involved.

I can't see how reaching sexual maturity earlier would be a negative thing. It's just tied in with an increased growth rate due to plentiful food and temperature. I remember reading that P.waltl kept in mixed groups were generally smaller than those kept in same sex groups. Breeding somehow inhibits growth - maybe this is due to the ease of finding a mate. In the wild stronger, larger animals would naturally have more success than smaller ones. In captivity this doesn't follow due to the enclosed environment.

Was there any papers on this? It would be really interesting to see what the cause was. Could it be some sort of feedback loop mechanism where (for example) male animal growth is slowed by the presence of female pheromones or hormones? I could see such a mechanism used to keep populations from out growing resources. Its effect would be amplified in the home aquaria as these compounds could easily be allowed to build up.

Inbreeding is a problem that can reduce fecundity and longevity of caudata in captivity. Many breeders are not fully aware of this problem.

Couldn't inbreeding just as easily produce more fecund animals by reinforcing those traits, possibly at the expense of others, like longetivity?

 

[Jennewt]

OK, so here's an attempt to summarize all the factors. My conclusion is that there is no way to generalize whether CB animals will breed more or less. Some of these factors are totally unproven, but are at least semi-plausible.

Factors that would make CB animals MORE reproductive (compared to WC LTC):
Better acclimation or adaptation to captive conditions.
Fewer parasites.
Earlier sexual maturity, resulting in earlier mating and more offspring.

Factors that would make CB animals LESS reproductive (compared to WC LTC):
Inbreeding, resulting in more animals that are weaklings.
Lack of "natural selection" of the fittest, resulting in more animals that are weaklings.
On average, younger age.
Possible shorter lifespan due to various factors .
Earlier breeding may inhibit growth or shorten lifespan.

 

[grunsven]

Couldn't inbreeding just as easily produce more fecund animals by reinforcing those traits, possibly at the expense of others, like longetivity?

No it can't

Every animal has 2 copies of every gene. Some genes have one wrong copy but as you also have a good copy that does not matter (you still have the recipe). These errors are all very rare. That is: the chance of having a wrong copy of a specific gene is tiny but as there are very many genes every individual has quite a few.
If two unrelated animals breed both will give some errors to the offspring but the change they give a wrong version of the same gene is very very small. HOWEVER if these two animals are related the chance of them having the same error is much larger and if they both give this faulty gene to the offspring (25% chance per gene) this offspring will not have a working version of this gene. Thus is less healthy.

Another aspect is increased homology. Many genes have multiple versions and an animal often has two different copies. This can for instances give two different versions of an enzyme. One working better at high temperatures and one working better at low temperatures. Or one version helps against one virus while the other protects against another virus. If the parents are closely related the chance an animal has two identical copies is large. Therefore it is less flexible and less healthy

Inbreeding has been shown to:
-reduce immune system functioning
-reduce growthrate
-reduce longevity
-reduce fertility
etc.


This is a crude explanation but this is in short what inbreeding does. Giving problems with rare lethal/bad genes and less flexibility as a result of homologies.

 

[Lasher]

One thing I feel the need to point out is that while inbreeding produces infant animals with less genetic diversity, it does not nescaserily produce inferior or weaker animals, particularly if your only talking a few generations, and the effects are far less pronounced in 'lower order' animals.

People have been inbreeding plants, fish and food stock animals for centuries to combine, strengthen and continue desired traits in the animals. The most certain way to maintain a particular trait is to breed it with creatures of the same bloodline as their known to carry the same gene(be it dominant or recessive). For example plants have been interbreed for more attractive flowers, higher crop yeilds, tolerances and resistances to particular environmental factors. The same is true of decorative fish, selectively breed for colour, fin types etc.

As far as creating 'weaker' animals goes its simple - dont breed sub standard stock. In each generation you allow only the strongest most desirable animals to reproduce. If you just dump a load of caudites into a tank and let them go at it for a couple of years you probably would end up with the amphibian equivalent of a Texan.

Thats not to say you dont have to cross breed to introduce fresh genetic material into the line from time to time, though its done carefully.

 

[pete]

OK, so here's an attempt to summarize all the factors. My conclusion is that there is no way to generalize whether CB animals will breed more or less. Some of these factors are totally unproven, but are at least semi-plausible.

Factors that would make CB animals MORE reproductive (compared to WC LTC):
Better acclimation or adaptation to captive conditions.
Fewer parasites.
Earlier sexual maturity, resulting in earlier mating and more offspring.

Factors that would make CB animals LESS reproductive (compared to WC LTC):
Inbreeding, resulting in more animals that are weaklings.
Lack of "natural selection" of the fittest, resulting in more animals that are weaklings.
On average, younger age.
Possible shorter lifespan due to various factors .
Earlier breeding may inhibit growth or shorten lifespan.

I have to agree with Jennewt in that you can't predict what you're going to get. I think there's plenty of evidence that captive breeding over time places a new selective pressure on a species, but the overall outcome is influenced by several environmental and genetic factors available to your captive breeding pool.

Although I think some attention must be given to the relativity of the terms "more/less reproductive" and "easier to breed" in this discussion. For instance, is a breeding pair that breeds earlier, producing fewer eggs, but more frequently, more or less reproductive than a pair that reproduces seasonally, later in life and generates large volumes of eggs. Is the former or the second case "easier to breed". It is very much dependent on your environment and personal desires, and even more complicated if you consider human factors that affect survival of the progeny.

 

[pete]

Oh, and personally Dawn, I think you can and will select over time animals that will breed easier in captivity for you, but I don't know how many generations it would take before you see an effect when compared to wild caught species.

 

[Alex Tsukanov]

Excuse me please if my question deviates from the subject but I should like to ask about initialization of the division of unfertilized eggs of tailed amphibians under the influence of electricity?

(this question from "Multilingual Caudata Dialogue": http://urodeles.forumpro.fr/multilingual-caudata-dialogue-c8 )