Giant salamanders: growth factors and cold water habitat constraints

¶ … Dinosaurs and Massive Reptiles Are Gone

Giant, cold-water salamanders: Selective pressures and biodiversity

One of the great curiosities of the amphibian world is the large salamanders known as cryptobranchids. They appear to the naked eye more like prehistoric relics than the small, swift-moving salamanders with which most individuals are familiar. Of course, both large and small sizes can convey evolutionary disadvantages and advantages to a species. The giant salamanders of Asia and North America would once have been more difficult to be easily consumed as prey, unlike their smaller counterparts. Yet it is also more difficult today for these animals to find enough food to sustain them, and to conceal themselves from more intelligent predators such as humans. In the contemporary era, most amphibian species flourish when they can camouflage themselves in their environments, making a small size an advantage. But this was not always the case: during earlier phases of evolution, large sizes provided protection for these animals. However, as the biodiversity of warmer zones resulted in the creation of faster-moving and more skillful predators (including humans) the numbers of these creatures shrunk and they are now only found in colder regions.

The relatively lower biodiversity of colder environments may have reduced the threat of predators for the giant salamanders, hence their continued (albeit limited) existence today. Because of their scarcity, large amphibians are often called an evolutionary curiosity, a 'living fossil' like the hanzaki (Andrias japonicus) and the Chinese giant salamander (a. davidianus), and the hellbender (Cryptobranchus alleganiensis) of U.S.. "Creatures rather like these were certainly around when dinosaurs dominated life on land, and fossils of the family have been found much further afield than their current tight distribution - in northern Europe, certainly, where scientists presumed the lineages had gone extinct until tales of the strange Oriental forms made their way back to the scientific burghers of Vienna and Leiden a couple of centuries ago" (the living fossil...the giant salamander, 2010, Cryptozooscity).

There are fears that giant salamanders may meet the same fate as dinosaurs, given that modern life has exposed them to quick-moving, larger-brained humans who consider them a delicacy and will hunt them with greater determination than previous predators. The amphibian's size makes them "lucrative prey for hunters, who can sell the flesh for around U.S.$100 per kg (£30 per lb)," a considerable sum when one salamander can grow to over one hundred pounds (Black 2005). "They are protected species; but in China, illegal hunting is bringing them within sight of extinction" (Black 2005). Observed one conservationist: "They are easy to catch, hiding in rock crevasses during the day, and people know where to find them" (Black 2005).