Reptile & Amphibian Forums

I haven’t had the chance to respond to some questions that were asked last week in the “ breeding frequency of females” thread, and thought I would do so here.

As far as field studies showing breeding in alternate years; Shine, Madsen, Harlow, Grigg, Slip, and Ross have all published articles on this subject. Female water pythons (L. fuscus) have been shown by field studies to typically produce eggs only every other year. Female diamond pythons in their natural environment have been shown to produce eggs at two and sometimes three year intervals. It’s obviously the increased access to food in captivity that shortens the recovery period and allows for more frequent breedings.

Medium size pythons like carpets can be bred in consecutive years in captivity if the eggs are pulled for artificial incubation because the major energy drain is in the maternal incubation, not in the egg production. Carpets have been shown to have some endothermic thermoregulatory incubation ability, but they cannot keep it up 24 hours per day over the entire incubation period if exposed to cool night time temps. They rely on basking behavior to supplement heat production for incubation in the wild. Australian pythons also have a lower maternal incubation temp than many other python taxa, and so likely spend less energy maintaining incubation temps. In captivity, with 24 hour controlled ambient temps, their maternal incubation energy expenditure can be kept to lower levels than would occur in the natural environment. Their weight loss could more rapidly be regained and they could possibly be bred every year, but that would probably not be productive for more than a few years, if that. For the larger python species, it is extremely difficult for them to regain the lost body mass from maternal incubation in the 6 months before the next breeding season begins.

The smaller python species, like Antaresia sp. and Python regius, use behavioral thermoregulation either by basking and transfer of retained heat to the egg mass, or by choosing nest sites that are in about the proper incubation temp. range. These incubating females do not produce any heat endothermically, and therefore their energy expenditure is relatively small compared to the much larger endothermic maternal incubating species. Additionally, with their much smaller body mass, it is much easier for them to recover and replace this lost body mass, and these smaller species could probably be more successfully bred in consecutive years than any of the other python taxa.

Pulling eggs for artificial incubation makes a huge difference, and some of these pythons have been breed with fair success on a yearly basis over the short term. However, with average pre-ovulation weight to hatching weight losses for the larger maternally incubating python species in the 30 to 35% range, breeding every other year is probably in the best interest of their health. Thanks,

Kelly

Thanks for the info...I'll have to go check out some of those articles

So if you did have a larger python that you wanted to breed every other year, and she ovulated anyway, would you breed her? Along the same lines, if your care is good enough (proper temp gradient/liberal feeding etc) so that your females are ovulating every year, do you think that people should hold back from them to "force" them to lay every other year.

I am not jabbing, just playing devils advocate because its something that interests me. This is a perfect example of a debate that takes place in different forms in many areas of this hobby...just what is best for our animals???

On the one hand, nature is harsh and I hope that we can provide a better life for our captives. On the other hand what makes a better life? Maybe what is best for the animal is the harsh conditions it evolved to live in.

Cheers

My large Carpondro that produced the freaky looking babies last year was a late breeder. She bred with the male last April and into May, finally laying in August. I did artificial incubating, but the female....although eating like a horse, did not put her weight back on in time. She and the male are kept together, and although I was able to see the copulations a few times last fall, I thought she wasn't going to take. Much to my surprise, she laid 16 slugs last week, and looking back, the signs were there. Too soon and not enought body mass, I believe. Ah well, at least the plumbing still works, and I'll see if she can produce this year coming.
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1.1 Blackheaded pythons
1.1 Woma
4.2 Aussie Olives
1.1 Timors
1.1 Bloods
1.1 Balls
2.2 IJ Carpets
1.0 Coastal Carpets
1.2 Macklotts
1.2 F2 Carpondros
2.0 Jungle Carpet
0.1 Carpondro
0.1 Jungle/Diamond cross
.1 Brazilian Rainbow boas
0.1 child, CB
0.1 wife, WC

I have a friend that had an interesting breeding experience with a large female retic back in the 1980’s. She was wild caught as a neonate in the early 70’s and it was definitely not very common to successfully captive breed retics in the early 80’s. However, this female was able to produced fertile clutches in 4 consecutive years. He always used artificial incubation, but each year the clutches got smaller, even though she continued to grow larger. After the fourth clutch, and by far the smallest, she was noticeably thinner than normal, and she never produced eggs again, even though yearly copulations occurred.

In their natural environment, large female retics typically breed every other year, and possibly every third year during lean times. Additionally, as a wild female retic gets older and larger, their clutch size also increases. So even if a python in captivity is capable of producing fertile eggs in consecutive years, it can be seen from the example above that it is not necessarily in the best interest of the snakes health. Jaykis gives a good example of what can happen when the female is unable to recover sufficient body mass to produce viable ova. It is not for certain that this was the cause of the failure, but the evidence definitely points toward it.

So to answer your question, I personally do not allow large female pythons contact with males every year. I do not believe that it is natural for them to breed annually, even if they can be pushed to do so in captivity. Healthy, well fed females in captivity may produce follicles every year when not in direct contact with a male, but most are induced ovulators, and the follicles typically do not develop into mature ova unless the female is actively courted by a male. Immature follicles are absorbed by the female if the stimulus for them to form mature ova is not present. As I mentioned in the earlier post, the smaller python taxa do not expend as much energy as the larger species, and with their smaller body mass, they are better able to recover from a previous years breeding, especially if the eggs are pulled and incubated artificially.

Kelly