It has happened again

It has happened again this morning: it was 9:00 with an air temperature of -3ºC. The pond was frozen. In the area were they prefer to stay when they are active, with thinner ice because of the sun shining for longer, one of the turtles was watching me from below. As I left feeling the chill of the morning in the face, I thought of the turtle moving under there, in icy water.

I could even recognize it: it was the female

In the midday I have seen them again. It has been a sunny day. In the shadow it was chilly (9ºC), but in the spot of the pond where the sun shines for longer, the ice had melted and I have seen them with the head out of the water.

The turtles and the ice

The temperatures have dropped quite a lot since last week, specially the nocturnal ones. Although they have not finally been historical, it has been cold enough to keep the pond frozen all those days. 

It snowed again last weekend, and the ice was covered by the snow.

The aerator is proving very useful. It oxygenates de water, but it also keeps a window open in the ice. In a frozen pond, the oxygen of the air does not pass to the water. The window created by the aerator allows some contact between water and air, and it also provides the turtles the possibility to  breath air.

The birds take advantage of  the window in the ice now that it is so difficult to find liquid water 

Yesterday morning, at 9:22, with an air temperature of -4ºC , I saw the turtles under the ice. At the end of the month, the probe will tell the water temperature in that moment. I was surprised to find them at that time with that air temperature. It had not happened in other winter days, with warmer temperatures. I did not think it was an emergency situation. A frozen pond is not extraordinary for this turtle species, they have strategies to survive with very little oxygen, and possibly can survive for some weeks without oxygen (I previously talked about it and put some article links). There was also the window created by the aerator. But I thought it was curious that of all the winter days, I found them active precisely now, when the pond had been frozen for a week, so early in the morning with such low temperatures for an ectoderm. Could it be that, although they have physiological mechanisms to cope with the lack of breathing air, they try first the easiest solution? (find a window in the ice)

It is probably the female, this is close to the place she chose to hibernate. You can see her left forearm. She is facing the window in the ice.

This midday I have seen them again. The air temperature was 7ºC , but it was sunny and you could feel the sun's heat. One of the turtles stayed among the algae, in the thawed area near the aerator. The other one was moving slowly under the ice. It stayed there for about 10 minutes, then moved near the aerator and, without breathing air, she swam to the deeper water, again under the ice. If they had wanted to take air at some point, they could have done it (in fact they had many other moments of the day to do so, when I wasn't there to see it)

The dark shadow is the turtle. You can even see the yellow spots, specially on the head.

Ready to swim towards the deeper area

In the weather forecast they said the cold days will still last  for some days. The pond will remain frozen some days more.

The winter is here

Coinciding with the arrival of cold air of Siberian origin, today it has snowed.

We have been advised of a strong drop in the temperatures between tonight and tomorrow. They say it will be historic. Just in case I have protected with a piece of wood the area over the place where the female hibernates, at shallow depth.

Woods covered with snow.

So far this winter, the lowest temperature occurred on January 13,14 and 15.  It reached  2,6ºC at 10 cm and 4,09ºC at 50 cm. Probably in the next days the temperatures will be much lower.

January temperatures at 10 cm

January temperatures at  50 cm

Temperatures at ground level in January

The turtles are very inactive now. I only saw the male twice in January, in the 19th and the 21st, sunbathing. I haven't seen the female since December the 15th.

The hatchling hibernating

Yesterday I checked the hatchling that is now hibernating. It is in a bucket with little water in a well ventilated shed.  It is a cold place but protected from freezing. I put a plant and some roots that the turtle uses as a hiding place. By simply extending the neck it reaches the surface. Apparently all goes well.

December temperatures

Some time ago I talked about the data loggers that I put in the pond at 10 and 50 cm depth. They measure the temperature with a pre-programmed frequency, in this case every hour. The last day of each month I download the data. These graphics correspond to December (warmer than usual, as it happened in November)

Temperature at 10 cm depth

Temperature at 50 cm depth

November and December air temperatures, 10 cm above the ground.

Some days I found the pond partially frozen (all but the area nearer to the bubbler). The temperatures of those days at 9:00 were

19-11-12  Air -1,7ºC, at 10cm 3,09ºC, at 50cm 4,09ºC
20-11-12  Air -0,69ºC, at 10cm 2.6ºC, at 50cm 3.59ºC
28-11-12  Air -0,56ºC, at 10cm 3.59ºC, at 50cm 4.09ºC

The water was colder at 10cm. than 50cm. This is because the water temperature was lower than 4ºC. As the water cools down it becomes denser (and heavier). Thus, in the summer, the water is cooler in the bottom of the pond. This is also true for the winter... until the water temperature is lower than 4ºC. Then its density, instead of increasing, decreases. Being less dense this water occupies a  higher layer (if it was not like that, the pond would start freezing in the bottom)

Regarding the turtles, I have seen them active several days in December. Always at midday on sunny days:

04-12-2011 at 12:00. Air 7.53ºC, at 10cm 8.9ºC, a 50cm 7.6ºC. The female didn't leave the water but stayed between the vegetation with the head out of the water for several minutes.

06-12-2011 at 14:00. Air 9.04ºC, a 10cm 8.09ºC, at 50cm 6.6ºC. The male was sunbathing in the land area.

08-12-2011 at 15:37




Air temperature 9.79ºC. Water at 10cm 7.1ºC, water at  50cm 6.6ºC.

27-12-2011 at 14:00

Air temperature (in the shadow) 9.92ºC. Water temperature at 10cm 5.1ºC, water temperature at 50cm 4.58ºC. The male stayed sunbathing for an hour in the land area.

In these cases the water temperature was higher than  4ºC  and the water in the bottom was colder than in the surface. 

I haven't seen the turtles since December the 27th, when I took that picture, although the weather has not been cold nor cloudy.

The Clemmys breeding

Last April-March the male chased the female. She usually escaped, but one day I saw them mating.

Sometime later, in late May, the female's behavior changed: I often found her walking in the land area of the pen. When she realized that I was watching her, she went back to water. In the wild, when they need to nest, they migrate to look for the right place, sometimes far away from the water. Could it be that she wanted to nest?
One day I picked her up and I palpated her through the inguinal space. I managed to pass my hand smaller fingers. I gently turned her one side and the other and I thought I felt eggs, but I wasn't sure at all.

This species uses to nest in the evening and through the night. Therefore, each night, when I came back from work about 21:00 I had a look at the pond. Also in the midnight, with a torch, trying not to alarm the neighborhood.
On May the 20th, at 21:00, I found the female digging a hole. I filmed her throughout the process, until  1:30. During all this time I noticed the nocturnal life around the pond: mosquitoes, slugs, snails, ants, spiders, tarentolas...When the nest was covered, she wasn't satisfied (although it looked perfect to me). She stepped on it, paused, I thought she had finished... but she started again. More than half an hour like that.

Female nesting at night

Covering the nest with the rear legs

She made the nest among the weeds

While she covered the nest, I had time to think about the eggs. I could leave them in place, to incubate naturally, or dig them out and put them in the incubator.

Geographic variation in reproduction in a freshwater turtle (Clemmys guttata). Jacqueline D. Litzgus and Timothy A. Mousseau. http://www.laurentian.ca/NR/rdonlyres/F98DC713-A788-4A95-8CBA-C23BE8EC11DF/0/LitzgusMousseau2006Herpetol62_132140.pdf

According to this article, it is thought that they do not nest in a particular substrate or habitat but in the place where the incubation conditions are better. In some part of their range it is in under tree canopy, in other places in open areas. Sometimes they nest in woody debris or leaf litter,even under moss. In other places they nest in the soil in open areas. 
 In the pond the land area is not so variable and they have no choice. Would they have developed there? It was a very exposed place, and in the summer the soil dries and hardens. I decided to try the incubator.

There were 4 eggs. I used a Jaeger incubator with vermiculite as a substrate. I put two eggs at 30ºC and two at 25,5ºC. The humidity was high. In the beginning it all seemed to go well. A white patch appeared in the eggs and it usually means fertility. Sadly I lost the pictures of this moment.

Some weeks later my mother in law told me that one of the turtles had been digging a hole in the afternoon. I looked for the nest and I found it, although it was very well camouflaged. If she had not told me, I would have never noticed that nest. Curiously the turtles nested in the afternoon. There were three eggs. I put two at 25,5ºC and one at 30ºC.

In this species, as in many other chelonians, the sex of the hatchlings is temperature dependent.  At higher temperatures you obtain females, at lower temperatures males. In mid August I candled the eggs with a torch. I had a deception because only one of the eggs looked fully developed.

 

Infertile egg

Unlike in the previous picture, in this egg there had been some embryonic development. By now it should occupy all the egg, like the one in the next picture. All the other eggs looked like that. I incubated them for some time until they rotted (they cracked and smelled bad)

Egg ready to hatch

From this last egg, incubated for male, a very beatifull turtle hatched

Detail of the "egg tooth" that they use to open the egg from inside

I didn't put the hatchling with the adults, I wanted to have  him in a smaller space. I put him in a tank, 1 x 0,5 mt, with a water depth of 20cm and plants, logs, rocks....
The last picture is not of a real situation, I had to put the hatchling there. I have never seen him out of the water, and I have hardly seen him in the water. He hides and he does it very well.  After some days not seeing him, I looked for it. I had to take out all the plants, rocks, etc until I palpated him hidden between the plant roots. He is very shy. I offered him worms, small fish... but he didn't touch them. I don't know if he fed since he was born. In the tank there were mosquito larvae and small water snails. He also had the yolk sac reserves.
I imagine this behavior is important when you are very small and so many animals can prey on you. 
He is now hibernating in a  bucket with a plant (roots included) and little water. He hides in the roots (they could also be useful to avoid accidental drowning). It is in a shed outdoors, in a cold place but without danger of freezing.
I don't know what failed during the incubation. I think it could be the humidity since the vermiculite tended to dry, especially at  30ºC. I also wonder now what would have happened if I had let the eggs in place to incubate naturally.

Winter activity

This morning there was ice in my car's window and the thermometer showed a temperature of +2ºC. The pond didn't freeze, but it will as soon as the temperature drops a little bit more. A few hours later, in the midday, I saw the female watching me with the head out of the water, hidden in the vegetation. I touched the water to feel how cold it was, and I thought that it is really surprising that a turtle is active at such low temperatures.
Now it is the male whom I haven't seen for some time. Since the 8th of December, when he was on a log in a day without sun (although it seems sunny in the picture). In the winter I usually see the turtles underwater with the head out, but they rarely get out completely from the water. That day he did and he earned a picture.

Ectoderms are amazing. Last year a Mediterranean locust (Anacridium aegyptium) decided to spend the winter behind a net left near a window. I put a piece of insulating material to protect her a little bit more (also from my mother in law) and she used it for shelter. As turtles, she wasn't completely inactive all the winter. When she felt there was some sun, she took the opportunity to warm up. But she always stayed in that place. When the sun disappeared, she hid again. Until a day in late February when she flew away. I hope she had luck.