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.

Water fleas (Daphnia sp)

Water fleas are crustaceans that feed on microscopic algae. I put some in the pond in the beginning, when the water became green a few weeks after making the pond. They are a quick, very effective and ecological solution against this sort of algae. In two weeks the water was crystalline. I used Daphnia  magna, one of the biggest, it can reach  3 mm . I tried to make some pictures in the pond but I didn't succeed.

They are small but they don't pass the net

Water fleas

Fish and Daphnia don't make good friends.  I put some fish to control the mosquitoes and they ate all the Daphnia. I don't know if it would be possible to keep both if there were a few fish. Then I don't know if those fish would be useful against the mosquitoes or they would prefer feeding on Daphnia.  Curiously, in spite of the Daphnia extinction in the pond, the green algae didn't come back. Maybe it was due to nutrient competition with plants (they had grown quite a lot)

Water quality

Initially I used a homemade filter. It was an Eheim pump put inside a 5lt water bottle with filter foam and a mesh in the bottom. The water was forced to pass the foam. It worked for some time until it started clogging, especially when I put duckweed in the pond. In addition the plant roots tangled with the mesh. The turtles made a refugee in that place and I didn't want to destroy it because of cleaning the filter. One day it clogged completely .Since then the plants do the filtration. And they do it well. The water looks crystalline and the regular ammonia, nitrate and nitrite checks are always correct.  Somewhere there are nitrifying bacteria that do their job. The low animal density as well as not leaving uneaten food in the pond also help.

Plants do the filtration and offer refugee to the turtles

Regarding the oxygen levels, I have the feeling that they are correct, but it has not been checked. I would like to do it  but I don't think it is easy at amateur level. 

In a pond the water oxygenates mainly by diffusion from atmosphere and by photosynthesis. If the water moves, especially if it hits a rock or forms bubbles, the pass from atmospheric oxygen to the water increases. In the pond there in no pump mowing the water. There are aquatic plants that make photosynthesis. When the filter stopped working I didn't see signs of lack of oxygen. I had doubts whether to connect it again or not, but it was summer and I wanted to know if the water stratified. A pump would avoid a thermal water stratification. I finally put an aerator. It makes a column of bubbles but doesn't move the water as a pump would.

Aerator bubbles

If there was no oxygen fish and nitrifying bacteria would die. The water would stink and the ammonia levels would rise up. There would be fermentations... nothing of this has happened.

My doubt is whether the oxygen levels are normal or low. I have never seen the fish gasping, not in winter nor in the summer. Neither in the early morning, when the oxygen levels in the water are the lowest because of plant consumption during the night.
Certain situations can deplete the oxygen levels in a pond. For instance when the pond surface freezes the atmospheric oxygen does not reach the water. This is not a problem in my pond. It freezes often in the winter nights, but it usually thaws, at least partially, during the day. Since I made the pond the maximum time that it has been frozen without thawing is four days. The aerator also creates a window in the ice.

Frozen pond

Another situation that depletes the oxygen in the pond is the organic matter decomposition. A plump tree drops the leaves over the pond in autumn. Although I pick up most of them, some go to the bottom.

Water stratification can also reduce the oxygen levels. When it happens, there are two different temperature (and density) water layers in the pond. Water circulates independently in each layer. The deepest one does not mix with the higher one, the oxygenated one. If there is also some decaying matter in the bottom, it is possible that there is anoxia in the deepest layer. I am measuring the temperatures to see what is happening in the winter, but in the summer there was not a permanent stratification, so I don't expect it in the winter neither.

If there were many green microscopic algae in the water, sometimes there is anoxia during the night or if, for any reason, the die suddenly. They are not a problem in my pond.

If there were too many fish they could deplete the oxygen levels, especially in the summer when the warm water has less oxygen and the fish use more. I have few fish and belonging to small sized species.

In the event that there were punctual problems with the oxygen levels, would it affect the turtles? I don't think so.

If there was less oxygen than normal in the water in the summer, it would not affect them because they have no limitation to pulmonary respiration and the extrapulmonary respiration in this season is negligible. Extrapulmonary respiration is the one that takes place when the exchange of oxygen/CO2 is between the skin/mucous membranes and water instead of lungs and air.

If there was less oxygen than normal in the water during the winter, it would cause more problems. Clemmys guttata usually hibernates underwater and can go without breathing air for several months (they don't do this  in my pond). It uses extrapulmonary respiration, probably cloacal in this species (other species use the skin or the pharynx mucose membranes).  Their metabolism is very depressed at low temperatures and the oxygen needs are so minimal that the extrapulmonary respiration provides enough. But the oxygen levels in the water must be normal. What happens if the water has little oxygen?
Clemmys guttata uses to hibernate in shallow ponds, without flowing water, that frost for several months and rich in decaying  organic matter. Precisely because they hibernate in such ponds, that tend to run out of oxygen, this species is  thought to belong to the anoxia tolerant group of turtles.When there is not enough oxygen in the water to meet the needs of the turtle by cloacal respiration, or when the oxygen is completely depleted,  the turtle switches to anaerobic metabolism. How does a turtle survive without oxygen (some species up to 5 months) is fascinating. Some links about it:

Hibernation: Poikilotherms (Storey) http://http-server.carleton.ca/~kbstorey/417-r-els.pdf

Physiology of hibernation under the ice by turtles and frogs (Jackson and Ultsch) http://www.mnf.uni-greifswald.de/fileadmin/Zoologisches_Museum/Hildebrandt/Dokumente/Hibernation_under_Ice_Frogs_Turtles_Jackson_2010.pdf

Life in a shell: A Physiologist's View of a Turtle (Donald C. Jackson)

So just now I keep the pond with an aerator and the plants. I will try to put a tube with more air exits  to increase oxygenation. If possible I will avoid using a pump because I don't want to loose the temperature gradient that forms in the water during the summer in the hottest hours.

Yesterday I saw the female. I had not seen her since early November. She was between the plants, with the head out of the water. I have discovered that she now hides in shallower water, about 10-15cm. I don't think the ice can reach her there, but I would be more assured if she were in a deeper place.



The female in her new refugee

Pond depth and August water temperatures at different levels

The pond has two levels, one at 50 cm and another at 20-30cm. When I had to decide the pond depth I relied on the information I found in articles and books. Some of them:

Habitat and Temperature Selection of Clemmys guttata in a Northern Population (Jacqueline D.Litzgus and Ronald J.Brooks)

The ecology of overwintering among turtles: where turtles overwinter and its consequences (Gordon R. Ulstch) http://www.seaturtle.org/PDF/Ultsch_2006_BiolRevCambPhilosSoc.pdf

COSEWIC Assessment and Update Status Report on the Spotted Turtle Clemmys guttata in Canada http://dsp-psd.pwgsc.gc.ca/Collection/CW69-14-382-2004E.pdf

The book “Turtles of the United States” (Ernst and Lovich)

In the wild they live and hibernate in shallow water. In the north of their range the hibernation is very long, up to 7 months. They spend more than half of their lives hibernating.

In Pennsylvania they hibernate in ponds or running waters 10-25cm deep. In those shallow places the ice thaws out quickly in spring and also in warm winter days, temporarily interrupting the hibernation of the turtles. In Maryland they hibernate in ponds about 4,5mt long with a depth in the middle of about 60-90cm. The turtles select the shallower areas at the edges of those ponds, with a depth of  10-15cm .In Florida they possibly do not hibernate.

In my pond I think the situation is similar to the one of the southern populations. They hibernate but not continuously if the weather conditions are favorable. To date, I have seen the male every day. Usually in the midday. When he hides, he does it under the roots of a cattail (Typha angustifolia) at a depth of 15-20cm. I haven't seen the female since November the 8th. I know she hibernates deeper, about 30cm, also in  cattail's roots.

Last year I even saw one of them moving under the ice in January. Later, also in January but with the ice already melted, I saw them again. A different situation from the seven months of Ontario hibernation I think.



Moving under the ice

To facilitate the transition from one level to another, I used stones. From the second level to the ground there is a gentle slope. All of this facilitates the movements of the turtles at low temperatures, when they are not so agile. It also helps them if they have been under hypoxia or anoxia. Then they can emerge very lethargic.

The water temperature is also related to the pond depth. I had curiosity to know the water temperature at different depths in the summer, as they are sometimes very hot. I measured temperatures in the deeper place (50 cm) and in shallower places (10 cm). I used signatrol data loggers configured to measure the temperature every hour. http://www.signatrol.com/Products.aspx?i=1

Data logger enclosure

Data loggers underwater at 10 and 50 cm

1-15  August 10 cm

1-15  August 50 cm

15 -31 August 10cm

15-31 August 50cm

The pond is not in a particularly windy area and there is no pump that moves the water. In August the highest temperatures at any depth occurred between 16:30 and 18:00. The cooler ones at any depth between 8:30 and 10:00. In the cooler hours the temperatures at 10cm and 50 cm were very similar. In contrast, in the warmer hours there were between 2 and 7 degrees of difference. It would seem that in the summer there is some thermal stratification of the water layers during the day, but it disappears during the night. I imagine there should be more water and a bigger depth to achieve a true water stratification.http://ohioline.osu.edu/a-fact/0007.html

In August 19th at 17:00 there was the maximum water temperature of the summer. It reached 31,61ºC at 10 cm depth and 24,63ºC at 50 cm. A 6,98ºC difference. This is interesting because it means that the turtle had the option to move to cooler water, and the temperature there was not excessively high in the hottest day of the summer. The highest temperature at 50cm. was 25,64ºC the 21th of August between 18:00 and 20:00.

In a study taken in Pennsylvania, the turtles started aestivation when the water temperature reached 30ºC.They aestivated in aquatic habitats (in the bottom of ponds and streams or in Muskrat burrows) or in terrestrial habitats (buried or under vegetation). It could last 100 days.

In the pond I only once witnessed what looked like an aestivation. It was two years ago and I didn't measure the temperatures.It was in the summer and the male dissappeared for two weeks, until I found him buried under some leaves in the shady part of the land area. He has not repeated this behavior.

I usually see a marked activity decrease in the summer. I just see them in the mornings, sometimes late afternoon. I also see them when I water the pond to compensate the evaporation looses. They become very active moving around and walking in the shallower areas.