Giant frogs build ponds for their young

Extensive construction of nurseries could explain the giantism of Goliath frogs

The gigantic Goliath frogs show for their offspring full body use. © Marvin Schäfer
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Caring Parents: The gigantic Goliath frogs build with a great body use nurseries for their offspring. As researchers have found, the amphibians lift ponds on the edge of river banks - moving up to two kilograms heavy stones. The frogs are thus the first known amphibians of Africa, which actively build breeding grounds. Perhaps this behavior is even the explanation for the special size of the frogs.

Goliath frogs reach considerable body sizes: The domestic in Cameroon and Equatorial Guinea Lurche be up to 3.3 pounds and up to 34 inches tall - the legs not counting. This makes them by far the largest frogs in the world. However, like many other amphibians, the giant creatures are increasingly threatened. This is not only because they are hunted for meat in their homeland. The destruction of their habitats, fast-flowing rivers in rainforests, the Goliath frogs.

Noticeable ponds in the rainforest

To better protect this species of frog in the future, scientists are trying to find out more about their biology. Because despite their fabulous size, the Goliath frogs are hardly explored, especially about their reproductive behavior is almost nothing known. For this reason, Marvin Schäfer from the Museum of Natural History in Berlin and his colleagues have now been looking for traces in the rainforest.

In Cameroon, the researchers searched along the Mpoula River for eggs and tadpoles of Goliath frogs. They identified 22 places where the giants apparently raised their offspring. The special feature: eggs and tadpoles of the frogs were strikingly found in small ponds on the shore, which seemed to have been artificially separated from the water flow with accumulated material and stones. What was behind it?

For their pond constructions Goliathfräs sometimes move stones weighing up to two kilograms. Marvin Sch fer

Up to two kilos heavy stones

Further observations revealed: The Goliathfräs apparently built these nurseries with a diameter of about one meter and a depth of about ten centimeters themselves. Thus, Sch fer and his team documented how the breeding places in the Over several days changed. Parent animals have three different types of structures in their pockets, as the researchers report. display

In the first type, the frogs use naturally created mini-ponds, which only free them from leaves and other disturbing material. On the other hand, the second variant requires a bit more use: The mats remove material from flat patches and haul it up to a kind of dam on the edge. Similarly, the amphibians also occur in pond variant number three. In this case, they move even up to two kilograms heavy stones to create a well-defined, round pool.

Explanation of Giantness?

But after the heavy physical work, the parental care is not over yet. As camera shots showed, the Goliathfräses also guard their eggs and young tadpoles. Especially at night, they keep watch on the edge of the ponds. "Goliathfräs are not only huge, but also loving parents, " says Sch fer. "The small ponds protect their eggs and larvae from being washed away by the current, and from rafts in the water."

Thus, the Goliathfräs are the first known African amphibians, which actively build breeding grounds for their offspring. According to the scientists, this behavior could also be a reason for the particular size of the frogs: "They sometimes move stones weighing two kilos. We believe that this painstaking activity could explain why adult frogs must be giants in the first place, "says Sch fer.

Better protection as a goal

"The fact that we've just discovered this behavior shows how little we know about the biology of even the planet's most spectacular creatures, " says co-author Mark-Oliver R del of Frogs & Friends " in Berlin. The researchers hope that with their now published results and further research, they will be able to gather the necessary knowledge to enable future sustainable protection measures for Goliath frogs and many other threatened species equalized. (Journal of Natural History, 2019; doi: 10.1080 / 00222933.2019.1642528)

Source: Taylor & Francis / Museum of Natural History

- Daniel Albat