The turtle is lying on its back, can it still turn over by itself?

In his crosstalk "On Dreams", Guo Degang expressed the trouble of being a turtle: as long as someone turns it over, it will be upside down and it will be difficult to get back on its feet .

For turtles, turning over is indeed a very troublesome thing. People who have raised turtles at home know that after aquatic turtles accidentally turn over, they will use their heads to the ground and swing their limbs to quickly right themselves. But for land tortoises, because their backs are too high, it is difficult for them to use their heads to the ground to turn themselves over.

Common red-eared slider flipping itself right side up | ELKFILMZ / youtube

What happens when a tortoise flips over? Today we're focusing on two species of tortoises: the Galapagos giant tortoise (Chelonoidis niger) from Ecuador and the South African giant tortoise (Chersina angulata).

Giant tortoise rollover risk

The Galapagos Islands are home to the world's largest tortoise: the Galapagos giant tortoise . This is one of the largest tortoises in existence and only lives on a few small islands in the Galapagos Islands in South America - this archipelago also inspired Darwin's thinking about evolution.

Due to different environments, Galapagos tortoises on different islands evolved in different directions; from the perspective of molecular biology, these tortoises are already different species, not subspecies as previously thought. Therefore, they are currently recognized as a species complex .

Galapagos Don Fausto Tortoise (C. donfaustoi) | ‍Andy Kraemer

Although Galapagos tortoises look similar in appearance, they have two distinct back types: round back and saddle back . Their back type may be related to their ability to roll over.

Generally speaking, the round-backed Galapagos tortoises live in the high altitude areas of the islands, where there is hazy fog and low grass. They are very large , and some can weigh up to 300 kilograms.

Round-backed tortoise | David Adam Kess / wikimedia

The saddleback Galapagos tortoise lives in the low-altitude areas of several islands, walking on volcanic rocks and eating cacti. Adults are half the size of their round-backed relatives , and some adult saddlebacks are only one-third the size of round-backs.

The famous "Lonesome George" is a saddleback tortoise | putneymark / wikimedia

Research in recent years has shown that the saddleback shape may have evolved to make it easier for tortoises to turn over . Galapagos tortoises are too heavy and too big, and they are more troublesome than turtles (aquatic turtles) when they fall over. The inability to turn over after falling is the main cause of death for adult Galapagos tortoises and even various large tortoises.

Saddleback tortoises live on low-altitude islands, which are formed by lava from volcanic eruptions. The lava is rugged and rugged, making it easier for the tortoises here to fall and turn over. As a result, their bodies are smaller , which makes it easier for them to turn over successfully. The opening of the carapace has also gradually become larger. In order to expand the opening as much as possible, a bone plate at the front end is partially missing , which is rare in tortoises.

The missing bone plate is the first vertebral scute, which is the yellow part in the picture | Gennady Cherepanov / Paleontological Journal (2014)

Compared to round-backed tortoises, saddle-backed tortoises have extremely long necks, so when they fall on their backs, they can use their long necks to push against the ground and push themselves back up.

Tortoises open their mouths wide to threaten each other | almoh22 / youtube

The fighting race among the tortoises

The way Galapagos tortoises fight for mates is to stretch their necks and open their mouths to scare the other party, or stretch out their mouths to bite, and there is rarely any physical contact. However, the small and medium-sized tortoises distributed in South Africa and Namibia at the southernmost tip of Africa, the chest-lifting tortoises , have invented a more brutal way. Although they are completely vegetarian, the chest-lifting tortoises with abundant martial virtues have been given the name of " fighting tortoises ", and the most important thing for tortoises is to knock the other party over.

The turtle with a straight chest. Note the sharp corner of the plastron under its head | Bernard DUPONT / wikimedia

From the age of 10 when they reach sexual maturity, every spring and summer, at noon, two male tortoises will meet each other after eating and drinking. When they see each other, they will start fighting. Once the fight starts, they will often forget that their original target is the female nearby.

Since tortoises are afraid of falling, knocking each other over has become an effective tactic in the "involution" struggle of turtles . The way male tortoises fight each other is mainly to knock over or scare off their opponents - after all, they both have shells and thick armor, and as long as they retract their heads, neither side will be able to cause fatal damage to the opponent. But the tortoises are different. The front end of their plastron has evolved a bony protrusion , which is its "crowbar". This "crowbar" can not only knock over the opponent, but in extreme cases it can also act as a "sword", inserted into the opponent's body , and directly take the opponent away.

The "sword" of the turtle pierces the gap in the opponent's leg armor | Africa Geographic / youtube

After knocking down the opponent, the winner will wait for a while beside the loser. If the loser does not make any move and accepts the fact that he has been knocked down, just like the ceremony of announcing the result in a boxing ring, the winner will instantly lose interest and start to leave. But if the loser tries to turn over, the winner will immediately continue to attack (Are you convinced! Are you convinced! Are you convinced!)

Therefore, those generals who are not physically strong and often lose will choose to wait for a while, until the winner loses interest in them, and then try to turn things around.

Two turtles are fighting, one has been knocked down, and the other is still trying to "finish the job" | Witzenberg Adventures / Facebook

When two male thrushes meet, what determines the outcome? Studies have found that the length of the thrushes' "swords" does not significantly affect the odds of winning a match; instead, another inconspicuous factor determines victory or defeat - the ability to maintain flexibility and not be flipped over by the opponent. This ability is specifically reflected in the body, that is, the width of the carapace. The wider the carapace of the thrushes, the greater the freedom of movement of their hind legs, making it easier for them to flip their opponents over while maintaining their own flexibility and center of gravity .

The "sword" evolved on the plastron is not unique to the pectoral tortoise. The Angora tortoise (Astrochelys yniphora) on the island of Madagascar and the Texas gopher tortoise (Gopherus berlandieri) in North America have also evolved similar structures, and both can use "swords" to overturn opponents and compete for mating rights. These species are thousands of miles apart, but they use the same weapon. This is the power of convergent evolution .

Texas gopher tortoise living in North America｜Clinton & Charles Robertson / RAF Lakenheath

"What happens after a turtle turns over?" is not just a joke, but an important and often overlooked issue in evolutionary biology.

Author: Yuan Xia

Editor: pee pee shrimp

This article comes from the Species Calendar, welcome to forward

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