All right class.....

[Jeff_Favelle]

Topic : Inbreeding. Here's a quote from Frank R. (sorry FRank! :D) at www.varanus.net on locality monitors and how they interact. What does this make you feel about "inbreeding" in captive reptiles. Put ALL biases aside and think purely from the standpoint of the quote.

Several years ago, I gave a talk on the cutural aspests of monitors. What "cutural" means here is, the behavioral particularities(differences) of any givin isolated population of the same species. That is, different populations of one species can and do have very different behaviors, such as shelter choice, food preference, etc. To a point of effecting physical traits, size and reproduction. This produces a tribal quality. For instance, one tribe will not reconize the other tribe as being the same. This is without question true with many species. On a side note, this may not be of importance to a scientist, it should, but it is of prime importance to a captive breeder. It should also be of prime importance when trying to understand species as a whole.

[Brock]

So what you're saying is: if you inbreed a species to a point. or excessively, the genetical stress will cause it to become somewhat like a new species and if someone were to buy your inbred animals, their pure animals wouldn't recognize it and may attack it?

Sorry, I must understand the statement before I can make my own, although I am against inbreeding.

-Brock

[Jeff_Favelle]

So what you're saying is: if you inbreed a species to a point. or excessively, the genetical stress will cause it to become somewhat like a new species and if someone were to buy your inbred animals, their pure animals wouldn't recognize it and may attack it?


LOL! Nope. I'm not saying that! Ha ha, not even close. :D

[NiagaraReptiles]

I'll take a stab at that.......

I think Jeff's point is to illustrate that "inbreeding" occurs naturally and quite regularly, and that it may even play a part in the evolution of a species.

The argument against "inbreeding" often includes or imply's that it is not natural, and doesnt' occur. Well, what about social animals that are born and raised in social groups?

I could keep writing until I'm blue in the fingers, but I don't see the point. There is plenty enough argument in the fact that for over 25 years, Leopard Geckos have been inbred. How about all of the wonderful Australian fauna that is on the market today, it's not like breeders can import wild caught animals to deversify their lines........Regarding the two examples I've given, can anyone say that there has been anything bad come of all this?

I guess the bottom line is reptiles are not mammals. Yes, inbreeding has been proven to be harmful with mammals and I think that is just carried across the board and applied to reptiles as well.......

Just my $0.02

[Kyle Barker]

I agree, however most species of reptiles probably react differently. I've heard some pretty nasty outcomes from excesive dumerils boa inbreeding. But then he's talking about monitors. I have often wondered the same about the australian species, beardeds especially. I bet they are the most inbred of all herps, but dont "seem" to be affected by it unlike some others.

[eyespy]

Bearded dragons are most definitely showing inbreeding problems, and there is some suspicion that cornsnakes might be as well. Beardies' clutch sizes and neonate sizes are on a steady decrease, incidences of lung and liver abnormalities are climbing, cancer and diabetes are starting to become bigger problems, and they are showing decreased resistance to parasites and viruses. When I first started working with bearded dragons in March 1985 it was not unusual to see 5 inch hatchlings, now it can be hard to find them over 4 inches long with good muscle tone. We used to consider an average clutch size to be 25-35 eggs and now the averages we see are 18-27.

Cornsnakes are beginning to show a lot of decreased virus resistance as well and there have been adenovirus and paramyxovirus endemics in cornsnakes. Lipomas, a type of fatty tumor, are also being reported in greatly increased numbers.

[NiagaraReptiles]

Clutch and egg sizes decreasing "on average" is a negative effect of inbreeding? I think it's more influenced by imporper diet and husbandry......smaller adults = smaller egg/clutch sizes.

As for other abnormalities and health issues, the captive population is growing tremendously. How many people have you heard of that had at least one clutch of beardie eggs this year alone? Also, with a growing population comes increased health "abnomalities", just the same with people.

I'd be interested to know the research that was done to come up with these averages as well. I don't think the law of averages can really apply here. I know several breeders that produce hundred of babies (talking about beardeds here in particular) and never have a problem beyond the odd "small" hatchling. I also think this is a perfectly natural occurance, not related to inbreeding at all.

I realize you are coming from a medical standpoint, which is great, but I'm sure you hear a lot more about the problems and such than the people that are keeping their animals with no health problems to report.

As for my thoughts on decreased resistance, I agree with you. Most reptiles have incredible resistance to just about anything given they are healthy to begin with, and are being kept properly. This is something they have developed over thousands of years of exsistance. After several generations of captive propogation this begins to work backwards. If the threat is not present, there is no need for the defense. In some cases, incomplete nutrition in captive diets also play a role here, but that is not related to the topic.

I guess I'm up to $0.04 now ;)

[Dom]

Maybe just to add to all the possible causes of such problems might be the simple fact that in natural accurences, reptiles usually have many babies and only a few survive to breeding hood.. this automatically gets rid of the week ones..

In captivity .. even the runt or the weak one will often pull through and be alound to genetically reproduce...

I personally think there is many factors that can lead to many of the above enlisted problems.. its not just inbreeding

just my 2 cents as well

[reverendsterlin]

another thing to consider is animal mobility. with snakes many have a range restricted to a few miles. with lizards there is increased mobility. I think over the eons mama nature has selected against less mobile species having much inbreeding reactions. With corns we are often maintaining genetics with involving heavy mutation that would not survive in the wld. Before I will accept that 'inbreeding' is affecting corns I want the tests to compare inbred normal lines against other morphs. I suspect that the data won't support the claim of problems.

[casacrow]

I like Dom's point. By allowing the weaker ones to grow and reproduce we may also be allowing weaker genetics to be passed on. I believe the same thing is happening to people. Those with weak hearts are surviving heart attacks and are producing children with weaker hearts. Kind of like reverse evolution.

[eyespy]

I donate all deceased reptiles from my rescue or the ones that patients of the surgical clinic sign over to the University of Pennsylvania's genetics labs so that hopefully they can get a grant to map reptilian genomes. They do see lots of broken chains in the genes of the beardies and corns I donate.

But until they get the funding and the samples needed to map the genome we don't know how much is inbreeding vs. mutations that occured on incubation. Most of the tissue samples they are researching right now are from unhealthy individuals, they need tissue samples from thousands of healthy ones for comparison.

That weak heart example doesn't pan out that much in real life. Most vital organ defects are acquired rather than genetic, and even when genetic that's generally a recessive trait. If there is that large a pool of recessives getting together and furthering weak hearts in their offspring, that's a sign of a bigger problem than just letting the weak ones survive. Just where did all those recessive genes suddenly come from?

True weak hearts from birth are very rare, all those heart attack survivors are generally folks with lifestyle-related problems. Children learn bad habits from their parents and the lifestyle-related problem is passed down, but not genetically.

When you do find a true congenital defect, many of those are the result of a problem when the embryo was forming, and that's not going to pass down to the next generation.

[C.m.pyrrhus]

IMO, it seems that most herps in a small way are inbred no matter where you look. Species that collect in smaller "colonies", such as in montane species L.p.pyromelana and C. cerberus, tend to stick to smaller colony populations, and are mating more or less with aunts, uncles, sisters and fathers. They do not spread out and find new "bloodline mates." They stick to the same basic area, if not the same exact mountain slope they were born on. Even live most their lives in the same rock pile their whole life. This has been the way of life for many many years for these wild populations. As for C. atrox and others with wider homeranges, the "family genepool" is wider spread, so they may have mated with aunts, cousins and even wider "bloodlines" that these more localized reptiles have. Still, in the wild, there is not many problems when it comes to inbreeding, if any at all.

There are species that have been isolated from the mainland species they "broke from" 15,000 years prior, and are still going strong, and some have found new ways of adapting to seperate living conditions. But there is no proof even in these populations to suggest that inbreeding did any ill effects on their survival. They did what reptiles do best and that was evolve to better condition themselves for their new situation.

Now with beardeds, the American ancectors were just a handful of lizards, and now has broken out into many from those original parents. There is more of a controlled study group there to trace. But, it seems to me that there is no real hard evidence to show that these animals are doing poorly from this, and whats to say what would happen with new bloodlines introduced? If they have gone into a downword spiral from it, what would fresh bloodlines do anyhow? You would still see a strong introduction of these "manipulated" problems in the offspring. So what would be the point to breed new bloodlines to a weakened genepool?

[Linds]

Originally posted by eyespy
Bearded dragons are most definitely showing inbreeding problems, and there is some suspicion that cornsnakes might be as well.

As far as I know, there have been no actual studies as to the effect of inbreeding, both selective and careless. I would be more inclined to lean towards husbandry than I would to inbreeding. In captivity everything is changed. Different bacterial exposure, reduced exposure to parasites as well as no natural parasite control factors, reduced excercise, as well as no matter how hard we try, we can never come close to giving them the variety they feed on in the wild (with a few exceptions).
In the wild inbreeding is very natural. Adding new blood is actually more of a foreign incident. Especially with all the insular species. Locality specific animals are loaclity specific for a reason. They are all bred together and have done so for ions. As mentioned above, inbreeding has brought them to the level they stand at today.
For reptiles (ie-corns) that have a lot of morphs, they do seem to have a lot more abnormalities and the like. People often attribute this to inbreeding. However does anyone stop to think that perhaps these morph animals are genetically weak in the first place? Most morphs do not last more than a heartbeat in the wild. It is considered a defect.
For animals (ie- beardies) that started off with a relatively small population and have had no new blood added, abnormalities may also be quite high. Has anyone given any thought to the fact that since survival of the fittest has been taken away, many of the breeding specimens were not prime examples and combined with the small foundation population, increases the effect of poor blood.
Everyone is so quick to point the finger at inbreeding, but IMHO, there are a gazillion other possibilities that are being overlooked.

[Scales Zoo]

There was another post about inbreeding, and reptiles, and I put forth the possibility of weak snakes not being removed from the breeding program with natural selection.

I'm not saying inbreeding doesn't have it's affects - it might, and we do not intend to inbreed reptiles ourselves but....

Look at how many generations of corn snakes can be bred in 20 years. Many current captive are probably close to 10, and in some cases even 20 generations removed from any wild ancestry.

Look at all the faulty genetics that can be passed on, because often the most prettiest go on to breed, not the most healthy or thrifty.

In the wild, runts, poor feeders - etc, usually are the first animals that are killed.

People usually mention australian species, and how they must be so inbred because no new blood has been available. Some of those pythons weren't bred until they were close to 10 years old, in many cases one could have a baby blackhead or diamond that is only 3 generations from a wild ancestor.

And then, don't forget, that just because it may be illegal, doesn't mean that "new blood" hasn't been introduced to some countries in the past.

Ryan

[eyespy]

Kathryn Tosney is a developmental biologist at the University of Michigan. She's working on a study of inbreeding in bearded dragons but more as a hobby than an actual research project, I believe. She imports beardies from Germany where there is less morph-craziness to compare with high-colored bloodlines here in the US and compares embryonic development.

Here is one of her hypotheses she posted on the Pogona newsgroup about a trend she's noticing in the inbred dragons she's been studying:

http://groups.yahoo.com/group/pogona/message/35779

It's a fairly controversial hypothesis because broken tail rings are often seen in animals that appear perfectly healthy. But inbreeding causes changes on a cellular level first so it can take many generations to show external defects.