The terrapin incubating outdoors hatched

The egg that was incubating outdoors has hatched. But I have to confess that I cheated. 

There was a problem: now that autumn is near the sun goes lower and my neighbor's house makes a shadow on the nest area until noon. At the same time the day is shortening and the last days were cool. Last week I couldn't resist any more and I dig the nest to see what was going on.

The egg was buried at a depth of  4,5cm. It looked all right, alive. I torched it and I saw there was a terrapin, but it didn't move and I didn't not if it was alive.  Part of the egg looked empty and I thought the terrapin was immature . I put it in the incubator at 28ºC. To my surprise, next morning, before the 24 hours, the terrapin was hatching. 

Now I regret having taken the egg as it has altered the experiment. Anyway, seeing the graphs and thinking about what has happened, I am sure the terrapin was already fully developed and it just needed some temperature to hatch. I am sure it would have hatched last weekend as it has been quite warm. Next summer I will be more patient.

 

The data logger has always been with the egg

Watching the terrapin has been a pleasure, but this time I was even more interested in the data logger data. Just a brief description of the situation:

• The nest was at 4,5 cm depth. The data logger just by the egg.
• The hottest days I watered the nest area, just in case it dried too much (it was very exposed to the sun and it has been a very hot summer). But I didn't want to alter the nest temperature. So I watered in the morning, when passed the night, the ground had lost the heat accumulated during the day.
• In September there was a stormy afternoon. For a couple of hours it rained so much that I thought it could be too much even for a terrapin hatch.
• I put a data logger on the surface, to measure the air temperature. I couldn't put it exposed to the sun as it would overheat and the data would be wrong. So I protected it with a piece of wood but letting the air pass. The measured temperature is the one of the air about 7 cm from the ground. It is not the same than the one of the weather stations. These measure the temperature in standardized conditions so that they can compare the data in all the country. I have measured the temperature of a microclimate, an specific area of the pond, very close to the nest. In this case, the radiating temperature coming from the ground, the stones... can affect the data logger, but this is a more real situation for a terrapin, that would also experience those radiating temperatures. It is useful to compare what is happening inside the nest and outside the nest.

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And these are the temperatures that this data logger has measured , in the shadow, close to the nest, between the 1st of July and the 31st of August.

The maximum temperature has been 43,73ºC. The minimum 12,11ºC. The mean temperature 25,2ºC. Almost every day temperatures were over 30ºC, often over 35ºC. The minimum have moved between  15 and 22ºC but one day they reached 12,11ºC.

And these are the temperatures of September from day 1 to a couple of days after hatching.
 

The mean temperature has been 18,54ºC. The maximum 32,38ºC and the minimum 10,99ºC.
 

And this is what was happening underground, at 4,5 cm depth, in the nest, from the beginning of incubation until the end (the last peak corresponds to the incubator)

 

The maximum temperature has been 32,75ºC the 21st of August. That day, on the shadow, temperatures reached 43,73ºC. I don't know the ground surface temperature over the nest, exposed to the sun, but I am sure it was much higher than the 43,73ºC. It is curious to see how does the temperature go down at just  4,5 cm depth.

The minimum temperature has been 14,36ºC. On the shadow the temperature was 10,99ºC.

During the incubation the temperatures were below  22ºC part of the day as you can see in the graph. Some days they were over the 28ºC. Five days they passed the 30ºC and three days they passed the 32ºC.

16 days the temperatures were below 18ºC for some hours, five days, also for some hours, they were below 16ºC.

Four days the maximum temperature didn't reach the 22ºC.

The mean temperature during the incubation has been 22,69ºC.

Would you buy an incubator like that?

Is it a male or a female?

In this species sex determination depends on the temperature when the gonads are developing. In Ernst&Lovich book it says at 22.5-27ºC males predominate, while over  30ºC they are always female. But as you can see in the graph we don't have a constant temperature. In a same day the temperature changes a lot. You can begin the day at incubating temperatures for male and at noon reach incubating temperature for female.

There are more peaks below than over 28ºC. It looks like male.

On the other hand, it is said that sex determination takes place in the middle third of incubation, when the gonads are developing. The incubation lasted 83 days. It started on the 1st of July. The middle third corresponds to the period between July the 28th and August the 24th. I will look at what happened in that period.

In the beginning I thought I needed the mean temperature.

The mean temperature in the middle third of incubation, (July 28 to August  24) is 24,61ºC.

Then I thought you can calculate it another way. Ernst and Lovich talk of incubation temperatures between 22.5ºC and over 30ºC. Gunther Köhler says 23-30ºC (in a very interesting book: Incubation of reptile eggs). As we see in the graph the egg has been below 22,5ºC several hours. Under this temperature the egg stops or slows dowm development. If we ignore those temperature when we calculate the mean incubating temperature, the result is 25,2ºC, not that much higher.

The mean temperatures are low. It looks again as it is a male. But there is something that I think is strange: we have had one of the hottest summers for decades. Common sense says if you have a very hot summer, the eggs are probably going to be females. In the middle third of incubation , the air temperature in the shadow has been almost every day over 30ºC, often over 35ºC and sometimes over  40ºC. The minimum temperatures have been most of the days over  20ºC and when they were below it, it was only for a few hours. This means heat. In spite of this, it looks as though it is a male. What happens in Canada, what sort of summers do they have? What are the air temperature needed (specially nocturnal) to reach a mean temperature of 29-30ºC in the nest?.

Maybe it is not the mean temperature what is important. Maybe it is the peak temperatures in a certain moment, or a number of hours over a certain temperature, or something else. At the end, what is happening in natural incubation is very different from artificial incubation.

Anyway I won't know until the terrapin reaches sexual maturity of I find information about it in a book or an article.

Talking about sex, someone told me you could sex Clemmys hatchlings by the chin color. I haven't found any conclusive difference between males and females at that age.

Female 2012

Male 2012

Female 2012

Male 2011

Regarding hatchlings coloration, the older ones already have the yellow spots. A comparison between a recently hatched and the ones born last month. With time the color appears.
 

Born yesterday, rounded in shape, with very pale spots

Born in August, already flattened and with the spots already yellow

I have also noticed that some of the hatchlings have the 5th vertebral scute spot orange instead or yellow. Some terrapins also have the supracaudal scutes brown reddish instead of black.