Lurking in the rivers and streams of the eastern United States is an animal that is equal parts off-putting and adorable—the hellbender. The largest salamander in North America, (third largest in the world behind the Chinese giant salamander and Japanese giant salamander) this oozy oddity has an average length of two feet from snout to tail.
It occupies a range stemming from New York near Lake Ontario to northern Georgia, even reaching as far west as southern Illinois. The species and its ancestors have occupied this ecological niche since the late cretaceous period, around 65 million years ago—about the same time lake sturgeon have been around in the Great Lakes.
Also like the lake sturgeon (as well as opossum shrimp) hellbenders are sensitive to their surroundings. Temperature, dissolved oxygen, the swiftness of the water itself, and the presence of large rocks all contribute to whether or not hellbenders occupy an area. They’re most active during the night, (like another “ugly” aquatic creature, the burbot ), feeding once the water has cooled, about two hours after dark. They eat crayfish, other small fish, dead fish, even other hellbenders and their eggs. This cannibalism contributes to controlling the population density in an area.
Usually solitary animals, hellbenders will congregate from late August to mid-September for mating season. The males lure the females into their burrows and prevent them from leaving until they have deposited their eggs while the males simultaneously fertilize the eggs.
After the eggs are laid, the male hellbenders force the females out of the burrow and take over. The males rock back and forth to circulate the water and increase the oxygen available to the eggs and protect them from predators—which can include other hellbenders.
Newborn hellbenders have true gills, but as they grow older, respiration is achieved mainly by breathing through capillaries found along skin folds that run along their back and belly.
Little is known about the average lifespan of hellbenders. Some in captivity have lived to be as old as 29, but there is speculation that those in the wild can live for 50 years or longer.
Hellbenders have been in decline for a while and are considered Near Threatened by the International Union for the Conservation of Nature, with many populations already considered endangered or extinct. Habitat destruction and disease are thought to be the major contributors to their falling numbers. Now many states, agencies, and institutions have developed conservation programs to help bring awareness to the plight of the hellbender.
INVASIVE SPECIES EDITION—Where we take a moment to explore the species that threaten the Great Lakes region.
They may not be what comes to mind when you think of invasive carp, but grass carp can have drastic and lasting impacts on aquatic ecosystems and water quality. Originally from eastern Asia, they have been introduced the world over as a biocontrol for aquatic weeds and can now be found in over 70 countries.
This wide range is made possible by their versatility—not unlike the hydrilla they are sometimes employed to eliminate. Grass carp can live in water temperatures from below freezing to over 100ºF, can survive in brackish waters, and are able to tolerate low-oxygen environments.
While they live mostly in slow moving and still waters, eggs are spawned in fast rivers, and must remain suspended for two to four days before they hatch. From there, grass carp grow quickly—as much as 10 inches in the first three months. An adult can grow to be upwards of 4 feet in length and more than 50 pounds on a diet of mostly aquatic weeds. But they have also been known to consume detritus, insects, and other invertebrates as well.
Grass carp were first brought to the U.S. in 1963 when they were imported from Malaysia and Thailand to aquaculture facilities in Alabama and Arkansas. Their first release into the wild is believed to have happened three years later when some escaped from the U.S. Fish and Wildlife Service Fish Farming Experimental Station in Stuttgart, Arkansas. Planned introductions began in 1969 in an effort to control nuisance plants. By the end of the 1970s, grass carp had been introduced in 40 states. Today it can be found in 45 states, with well-established populations throughout the Mississippi River Basin.
Grass carp are a highly regulated species, and for good reason. Because they are so adept at consuming plants, there is a risk that these veritable aquatic lawnmowers might leave a waterbody completely devoid of plant life and wipe out the food supply for other fish, insects, and waterfowl. A lack of plant life can also spur on algal blooms, which in turn lower oxygen levels. And without roots to keep sediment secure, the water is likely to become muddied, and spawning beds for other fish can be destroyed.
Because of these and other risks, grass carp used for weed control are sterilized by shocking the eggs with drastic changes in either temperature or pressure. But this process is not 100 percent effective, and fish sometimes escape into the wild. In some states, including Illinois, the use of grass carp is restricted to private ponds or pools. Those thinking about using the fish for personal use are encouraged to explore other weed-control options.
INVASIVE SPECIES EDITION—Where we take a moment to explore the species that threaten the Great Lakes region.
What was originally seen as a decorative and easy-to-maintain aquarium plant is now one of the most noxious weeds in the U.S. Sold under the name “Indian star-vine” in the late 1950s, Hydrilla verticillata was first introduced after live samples were shipped from Sri Lanka to a Florida aquarium dealer. More than half a century after careless disposal into Florida’s waterways, hydrilla can now be found throughout the south and along the east coast, with populations extending inland to the Great Lakes region. Isolated communities have also been found in Idaho and Washington.
This spread is not surprising since hydrilla is unusually hardy and versatile. It can grow in as little as a few inches of water or as much as 20 feet. It requires very little light to thrive and is just as happy in a nutrient-rich environment as one deprived of nutrients almost all together. It can even grow in slightly salty conditions or in water as hot as 81°F. And while it can spread through seeds, hydrilla is also able to grow from stem fragments as well as tubers that can lie dormant for up to four years. Taken together, it’s little wonder that this perennial is found on every continent except Antarctica.
Hydrilla’s unique biological characteristics give it a leg up over many native plants in the Great Lakes region. For example, its early sprouting season and ability to grow rapidly leaves less light for natives later in the spring, making it harder for them to grow once they begin to sprout.
These same characteristics also make it a nuisance to other aquatic wildlife and humans. Growing as long as 30 feet, hydrilla vines form dense mats that alter the water’s pH and oxygen levels, which in turn makes it difficult for some fish species to reproduce and grow. These mats can also impede irrigation, hinder recreation, and clog water intakes to power plants.
Efforts to contain hydrilla have been historically cautious out of fear that the robust plant may mutate or develop a resistance to chemical herbicides—a fear that was realized when fluridine-resistant hydrilla was found in Florida. Today the Asian hydrilla leaf mining fly, weevils, and even the invasive grass carp are used to manage hydrilla invasions. These and other methods cost states millions of dollars a year.
In recent years, Illinois and Indiana have banned the sale, barter, and transport of hydrilla. Water gardeners, aquarium hobbyists, and others can learn how to recognize the plant—and distinguish it from the invasive Brazilian elodea—with our species WATCH card.
We’ll have more species spotlights on aquatic invaders throughout May in honor of Illinois Invasive Species Awareness Week.
Where we take a moment to explore some of the unique and impressive species that call the Great Lakes home. Sun-gazer. Squirrel of the marshes. Smallest heron in the Americas. Measuring about a foot in length and weighing in at less than 4 oz., the least bittern is widely spread but rarely seen.
Least bitterns make their homes among the reeds of dense wetlands. Even with a migratory range from southern Canada to northern Argentina, the bittern remains elusive, making it hard for wetland managers to get an idea of their numbers.
Migrating to the Great Lakes each summer to breed, least bitterns fly only at night. And as if that didn’t make visual identification difficult enough, they also prefer to flee from predators and approach their nests on foot. On top of it all, least bitterns are well camouflaged. When threatened, the bird will freeze and point its head upward, exposing vertical striping on its throat that allows it to blend in with its surroundings—thus the nickname “sun grazer.” They will even sway in the breeze to match the motion of the reeds.
Elusive as they are, least bitterns are more often heard than seen—a low cooing from the males and a ticking from the females is the best way to “spot” them. Nests are made by constructing platforms of reeds above the water. Even these are camouflaged. A canopy of surrounding marsh plants is crimped in place above the nest. But the 4-5 eggs laid every season won’t be in the nest for long. Over the span of roughly 50 days, the chicks will hatch, fledge, and leave the nest to start hunting on their own.
Like squirrels leap from branch to branch, least bitterns walk among the reeds 2-3 feet above the water, allowing them to hunt in areas well outside the wading range of larger birds. Balancing on a reed, they strike down with their long bills to catch their prey. Their diet consists of fish like minnows and perch, insects, frogs and other small amphibians, invertebrates, crayfish, and even mammals like shrews and mice.
We’ll have more species spotlights in the coming weeks. In the meantime, check out our spotlight on lake sturgeon.
Where we take a moment to explore some of the unique and impressive species that call the Great Lakes home.
Skin like a shark, feeding habits akin to those of a whale, and a lifespan comparable to our own—the lake sturgeon is a peculiar species indeed. Found in large lakes and rivers, this toothless, whiskered bottom feeder is the largest, longest living, and one of the most ancient species in the Great Lakes. With an average length of 3-5 feet and a weight of 10-80 pounds, some lake sturgeon have grown to be 8 feet long and 300 pounds. Males typically live around 50 years while females’ lifespans range anywhere between 80-150. And with origins during the late cretaceous period, this species has remained relatively unchanged since the time of the triceratops and the tyrannosaurus rex.
The lake sturgeon’s skeleton is partly cartilaginous. Its body has no scales and is lined with five rows of bony plates called skutes—one on top and two rows along each side. Two pairs of fleshy sensory organs called barbels hang from its shovel-like snout like whiskers to help the lake sturgeon find prey. Its diet consists primarily of benthic organisms—small bottom-dwelling creatures like mussels, snails, crustaceans, aquatic insects—but they have been known to eat small fish. With no teeth, the lake sturgeon uses its snout to dig up whatever prey it finds and then sucks it up through its protractile mouth, filtering out sediment through its gills while digesting the organic material.
As hardy as the lake sturgeon may seem, its population suffered almost incalculable losses in the late 19th century. Initially thought of as a nuisance fish that damaged fishing equipment, lake sturgeon were slaughtered en masse. They’d be buried on shore or lined up to dry in the sun like stacks of timber and later used as fuel for steam ships due to the high oil content of their meat. Over time, lake sturgeonmeat and eggs became prized commodities, leading to overfishing and an eventual collapse in population.
Recovery has historically been a challenge due to the lake sturgeon’s naturally slow reproductive cycle, with males only reaching maturity around 15 years of age and females at closer to 20. This in combination with lake and river pollution, habitat loss, and dam activity blocking access to spawning grounds has lead to a long decline of lake sturgeon populations across the U.S. and Canada. As a result, lake sturgeon are listed as an endangered, threatened, or species of special concern by 19 of the 20 states where they are found.
But in recent years, some populations have started to rebound. State and Canadian governments now enforce strict policies that limit the number of sturgeon caught each year. Spawning habitats have been constructed, watersheds have been stocked, and eggs have been raised in artificial cultures. People are also encouraged to report any sightings of lake sturgeon to help get a better idea of their numbers.
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