Hellbender

The hellbender, also known by the name hellbender salamander or snot otter, is one of the largest salamander species in the world. It is a fully aquatic amphibian that constitutes the genus Cryptobranchus and is closely related to other species like the Chinese and Japanese giant salamanders. Hellbenders are divided into two subspecies, including the Ozark hellbender (C. a. bishopi) and the Eastern hellbender (C. a. alleganiensis). The Ozark subspecies can be distinguished by its smaller body, darkly spotted chin and larger black patches on its back. These aquatic salamanders are usually found in the eastern and central parts of the US.

Physical Description and Appearance

Size: As the largest amphibian species in North America, the hellbender measures 9.4-15.7 in (24-40 cm) from its snout to vent. The total length of its body is roughly 12-29 in (30-74 cm).

Weight: An adult hellbender can weigh anywhere between 3.3 lbs and 5.5 lbs (1.5 kg and 2.5 kg), making it the fourth heaviest amphibian on Earth after the Chinese and Japanese giant salamanders and the giant slippery frog.

Color: Its color varies from reddish-brown, olive-brown, to grayish brown, and sometimes, entirely black while its underbelly is usually paler than the rest of the body. Some specimens have dark mottling on their upper sides.

Body: It has a flat head with beady eyes, slimy skin, wrinkled and flattened body, and a paddle-shaped tail. Although it has working lungs, gill slits are sometimes retained. Only the immature hellbenders possess true gills.

Legs: It has four short and powerful legs, with four toes on its forelegs and five toes on its hind legs.

Distribution

The territory where hellbenders exist ranges between the southern region of New York and the northern region of Georgia. It includes parts of Pennsylvania, Ohio, West Virginia, Virginia, Maryland, Illinois, Kentucky, Tennessee, Indiana, South Carolina, North Carolina, Mississippi, Alabama, Missouri, Arkansas, Kansas, and Oklahoma.

What Kind of Habitats do Hellbenders live in

Hellbenders are usually found under large, irregularly shaped rocks or boulders, which remain partially submerged in the cold, swiftly moving streams. They typically avoid slow-moving waters that have slab rock bottoms or muddy banks. These salamanders may leave their habitat if the boulders or rocks are disturbed or removed.

Lifespan

Captive hellbenders have a life expectancy of about 29-30 years, but researchers have found that some individuals may live for more than 50 years in the wild.

Diet

These aquatic salamanders primarily prey on crayfish and other small fish species. They tend to eat more crayfish during the summer when crayfish are more active. They may also feed on tadpoles, insects, and the eggs of other hellbenders.

Behavioral Characteristics

• Hellbenders are somewhat nocturnal, as they are most active after dark and hunt at night. During the day, they remain hidden under flat rocks or boulders in streams.
• They are solitary salamanders that live alone, except the breeding season.
• Once these salamanders find a favorable habitat, they generally do not go too far away from it (except for hunting and breeding). They are territorial and will protect their homes from other individuals.
• Although they can swim in the water, they typically walk along the bottom of the stream with their sturdy legs.

Adaptations

• Their brown skin with dark patches acts as natural camouflage, helping them to blend in with the surroundings thereby avoiding potential predators.
• They have a flattened body, which offers very little resistance to shallow, fast-flowing water, assisting them in moving upstream as well as crawling or walking into the narrow spaces under boulders or rocks.
• Although they have poor eyesight, the hellbenders have light-sensitive cells on their bodies that help them see. The cells on their tails help them to safely stay under boulders without the tails poking out and giving their hiding position away.
• Like all fish species, hellbenders possess a lateral line system that helps them detect vibrations and hunt in the water.
• The numerous skin folds along the sides of a hellbender’s body give it the extra surface area to facilitate the extraction of oxygen from water. Thus, the hellbender breathes through its skin.

Mating and Reproduction

The breeding season of hellbenders starts in late August-early September and may last till the middle or end of November. Unlike most salamanders, these giant aquatic amphibians reproduce by external fertilization. At the start of their mating season, the males dig a saucer-shaped brooding site under a log or rock, with its entrance pointing downstream.

They remain in their nesting site, waiting for a female and defending the burrow from other males. When a female hellbender approaches the brooding site, the male leads or drives it into the burrow and prevents it from leaving until it lays all the eggs.

The female lays about 150-200 eggs, each having a diameter of 18-20 mm, over two to three days. As it lays eggs, male hellbender positions itself either slightly above or alongside the eggs and sprays them with sperm, while moving its limbs and swaying its tail to scatter the sperm uniformly.

After all the legs are laid, the male forces the female to leave the nest. It then guards the eggs and incubates them by rocking backward and forward and then undulating its skin folds. The incubation may last for about 45-70 days.

What does the Baby Hellbender look like

The hatchlings are typically 25-33 mm long, and they do not have any functional limbs. For the first few months, they get their nutrition and energy from the yolk sac.

Conservation Status

The population of hellbenders has been declining at a dramatic rate in most of the locations throughout their range. Some of the causes that have helped in creating this decline include blocking of migration routes, destruction of habitats due to the construction of dams, disease, pollution, siltation, and sedimentation. While the IUCN Red List has classified the hellbenders as ‘Near Threatened’, the US Fish and Wildlife Service has listed the Ozark hellbender as an endangered species.

Several conservation efforts have been initiated to improve their population. In November 2011,  an Ozark hellbender was first bred at the St. Louis Zoo. Head-starting programs, which include the collection of eggs from their natural habitat and raising them in captivity for reintroduction in the wild at a stage of least vulnerability, have started in Ohio and New York. In April 2019, the eastern hellbender was officially selected as the state amphibian of Pennsylvania.

Interesting Facts

• The hellbenders are often mistakenly called mudpuppies. Even though the mudpuppies are amphibians, they possess external feathery gills that are absent in hellbenders.
• Both the subspecies, Ozark and Eastern hellbenders, are found in only the US state of Missouri.
• The simple lungs in hellbenders help in buoyancy control instead of breathing.