The cold winter has arrived, and clean water turtles will hibernate under the frozen lake, altering their metabolism and absorbing oxygen from the water through… their rear ends.
Turtles are cold-blooded animals, meaning their body temperature changes with the external environment. If the water temperature is 1 degree Celsius, then the turtle’s body temperature will be the same.
However, turtles have lungs and breathe normal air. So when the freezing winter comes and the water surface becomes ice-covered, how can turtles breathe if they can’t surface? The answer lies in the relationship between the turtle’s body temperature and their internal metabolism.
The body temperature of turtles changes according to the external environment.
When in cold water, turtles have a slower metabolism. The colder the weather, the slower their metabolism becomes, which means they require less energy and oxygen.
Therefore, when turtles hibernate, they rely on the energy reserves in their bodies and absorb oxygen from the water by moving parts beneath their skin that are rich in blood vessels. This way, turtles can get enough oxygen for their minimal needs without having to use their lungs to breathe. And the area with the most blood vessels in a turtle’s body is… their rear end.
To be precise, turtles do not breathe through their rear end. That’s because they don’t actually have a rear end. Instead, they have a multi-functional opening called a cloaca, which is used for reproduction and laying eggs as well as expelling waste. However, this “back door” also plays a role in a basic respiratory process, simply put, “breathing through the rear end.”
According to Craig Franklin, a wildlife physiologist at the University of Queensland (Australia), during respiration through the cloaca, turtles pump water through the openings of the cloaca into two pouch-like organs called bursae, which function like underwater lungs for turtles. Then, oxygen from the water diffuses through the bursae’s spines and into the turtle’s bloodstream.
However, respiration through the cloaca is very inefficient compared to normal aerobic respiration, and all turtle species can breathe more easily using their lungs. Therefore, “breathing through the rear” is only seen in a few freshwater species to cope with particularly difficult breathing environments, such as fast-flowing rivers or frozen ponds.
So, it is not wrong to say that turtles can breathe through their rear end.
However, the ability of turtles to endure through the winter is also limited. Adult turtles cannot withstand the freezing cold of the outside air, as such weather conditions can lead to ice crystals forming in their bodies, resulting in death. This is why clean water turtles often hibernate in water, where their body temperature remains stable and never freezes.
In fact, only the water surface in contact with the air freezes. The water in the lake generally maintains a stable temperature throughout the winter, making it very suitable for some cold-blooded animals to hibernate underwater.
However, while hibernating there, turtles face two challenges: they cannot surface for oxygen, and the limited oxygen in the lake must be shared with other aquatic animals.
As winter progresses, the oxygen levels in the lake gradually deplete, leading to hypoxic or anoxic conditions. Some turtle species can survive in low-oxygen conditions, but others cannot.
Some turtle species can survive in low-oxygen conditions, but others cannot.
The snapping turtle and the painted turtle endure the winter underwater by altering their metabolism to avoid the need for oxygen. However, if this persists for too long, it poses a lethal risk to these turtles, as acid will accumulate in their muscle tissues from the metabolic shift.
But how long is considered “too long”? For snapping turtles and painted turtles, they can survive underwater during the frigid winter for about 100 days or more. In terms of tolerance to low-oxygen conditions, painted turtles are virtually “unmatched”, as they deal with acid accumulation in their bodies by using calcium from their shells to neutralize the acid.
By spring, when these turtles end their hibernation, their bodies are almost entirely muscle. Due to the high levels of lactic acid in their muscles, their mobility is further diminished, making them easy prey for predators. Turtles will need some time in early spring to boost their metabolism and eliminate all the lactic acid in their muscles before they can return to normal activity.
In Ontario, where winter lasts a long time, many turtle species hibernate for more than half of their lives.
For biologists, the ideal working periods are spring and summer when animal activity peaks. However, in Ontario, where winter lasts a long time, many turtle species hibernate for more than half of their lives.
Researching how these turtles function during winter is crucial for biologists to carry out conservation and habitat protection efforts, especially as 2/3 of current turtle species are listed in the Red Book with a high risk of extinction.
A research team has attached a small device to turtle shells to monitor their temperature during hibernation. The results showed that these turtles hibernate in groups and return to the same spots every winter.
However, this is only a small part of what the research team can observe regarding the survival process of turtles during the cold winter.
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