Saturday, December 17, 2011

Oh Those Unpredicatable Hermann's Tortoises

There is was, beginning to prepare my Hermann's Tortoises for hibernation/brumation. I had made darned sure that they have been well fed lately, hoping to assure they were healthy enough and of a high enough weight to withstand a couple to a few months without food at lowered temperatures (probably in the mid forties to mid fifties Fahrenheit). I also had made sure that they were well hydrated by not only supplying them with drinking water frequently but also by keeping the cypress mulch substrate in their enclosure fairly moist. I added substrate to the enclosure so that they could dig down and completely cover themselves with substrate twice their height. This was all in anticipation of not feeding them for 10 days to a week, then turning off their heat lamp for about a week, then placing them into a room where the temps are very close to what I mentioned above. They would stay there for two to three months or a bit more.

There is no reason that these tortoises absolutely must be placed into hibernation while in captivity. It is not like it will adversely effect their health if they do not hibernate, at least as far as I am aware. They do just fine without it. The thing is though, if you want to breed them and if you want the eggs to be viable and to have been fertilized by the male tortoise, them hibernation is strongly advised. Hibernation allows the male to develop sperm and apparently also allows the female to develop viable eggs (personal communication with Ed Bennett, et al). This past spring/summer my female laid two clutches of eggs, I think 9 eggs in all if I recall correctly. Only 2 of those eggs hatched, one from each clutch.  I incubated them properly so I wondered what else might have gone wrong to cause such a low hatch rate when Hermann's Tortoise eggs often have about an 80% hatch rate. I learned that not having hibernated them could have been the problem. Another factor may have been that the eggs got a bit too cool after being laid. I probably got them out within an hour or two of her laying one clutch and sooner after she laid the other but they still had enough time to cool to the temperature of the substrate which probably was in the mid to upper seventies although the surface temp was much warmer.

I woke up to a dream that she was laying this morning and I walked over to her enclosure and checked on her. To my surprise some dreams do come true. She was in the process of dropping eggs when I took a look. Of course, me dreaming about it this morning could be called coincidence but I think it was probably more an anticipatory collection of thoughts that came out in a dream due to the circumstances. The circumstances being I saw her starting to dig with her hind legs yesterday, a sure sign she is ready to lay eggs. So, yesterday afternoon, I added even more substrate to her enclosure, enough for her to feel that she had dug deep enough to have made a good nest. I was really somewhat surprised that she laid already today. The last two clutches were laid a couple to a few days after she started test digging nest sites. Tortoises and other turtles often dig test nest holes or just dig holes that for some reason they find unsuitable and they just walk away from them. That could also be due to the fact that they may not be quite ready to lay eggs but think they are ready, sort of a false labor sort of a thing. Whatever the reason, she laid them pretty quickly after her first attempts at digging a nest site this time around.

After seeing them, I did not waste any time. I got the incubator down off of the shelf, found a suitable small plastic container to hold the eggs inside the incubator and got out the long cut sphagnum moss and gave it a good soaking, then squeezed out the excess water, then put that into the plastic container. As soon as the heat inside my Hovabator incubator was at the proper temperature, I put the eggs into the substrate inside the plastic container and put that into the incubator. Time will tell if these eggs are all fertile or not. if they are, then I can expect a mixed batch of male and female Hermann's tortoises in about 75 days, give or take around 5 days. The reason I can expect a batch of mixed sex babies is because I will incubate the eggs between 86 to about 88.5 degrees Fahrenheit (1). The sex of baby tortoises is determined by temperature at a certain stage of their development. Since I will leave the temp set in that range for the whole of the development it is a good bet they will be mixed sex, that is if the eggs hatch. Last time, I am pretty sure I incubated at a slightly higher temperature range to get all females. Time will also tell if I got that right although it will be a few years before sex can be easily determined in the tortoises from the first two clutches. Right now though, I am simply hoping that all the eggs are fertile. I will be surprised if they are since they have not hibernated but as I said, time will tell.

While determination of the sex of the babies may be predictable, the breeding habits of the adults surely is not predictable. With the shortened days, cooler nights in my basement, and other environmental factors, I would have expected the two adult Hermann's Tortoises that I have to be getting ready to hibernate as opposed to be breeding and egg laying. I do not usually like surprises, seems they are more often bad ones than good. This time though, even though quite unexpected a very surprising, it was a pleasant surprise at that.

All the best
Glenn B

1) Highfield, A.C. 1994. Keeping And Breeding Tortoises In Capitivity. The Longdunn Press Ltd., Bristol.