Caught in the Act

Wayne Groesbeck
Vice Chair
Muskegon River Watershed Assembly

Evolution works over eons, and it’s unusual to catch nature tinkering with a new adaptation. It can, however, happen: when the giant panda switched from a normal omnivorous bear diet to eating bamboo, a front leg bone started to morph into a thumb so it could grasp bamboo stalks. The Muskegon River has its own example of an animal in transition. This animal is so inconspicuous that most humans have never seen one and are unaware that it exists.

Necturus Maculosis has gills but isn’t a fish, and has legs but isn’t a lizard. Instead, it’s an amphibian with relatives that lay their eggs in water but live on land like a good salamander should. In the prehistoric past, its ancestors were some of the first vertebrates to attempt to live out of water. Some scientists speculate that its habitat at some point took a turn for the wetter and its food supply became more exclusively aquatic, leaving this critter with an unlikely assortment of land and water adaptations. We call it the mudpuppy, and its closest relatives, the hellbender of northern Appalachia and the axolotl of Mexico, are similarly amphibians caught in the act of heading in a new direction.

Mudpuppies grow throughout their lives and can reach a length of 24 inches in a 20 year lifespan, though most live to only half that size and age. Food is not the limiting factor: if worms, snails, larval insects and crayfish become scarce, mudpuppies simply become less active to burn fewer calories. How well they thrive is determined by how much oxygen is dissolved in their water. Their respiratory system is caught between land and water: they have an air chamber which isn’t quite a lung, but they can surface and gulp enough air to last them for hours. If lifted from the water, that air escapes and makes a sound something like a puppy’s bark, hence “mudpuppy.” More routinely, they extract oxygen from water by waving their feathery external gills. These bright red blood filled organs sprouting from an olive brown salamander give them a startling appearance.

Mudpuppies can survive under ice and are most often seen when caught by ice fishermen using insect larvae for panfish bait. In Spring, females lay 50 to 100 eggs under flat rocks or other underwater structure. Females, which must be 5 years old to reproduce, will guard their eggs aggressively, and this is when they are most vulnerable. Their eyesight may be dim, but they are otherwise protected by glands which secrete a thick layer of slime, making them both slippery and unpalatable. Michigan requires that they be returned to the water if caught.

Because of their structure and behavior, these bizarre residents are sensitive to water quality and are considered an indicator species by scientists. We should therefore be pleased that mudpuppies thrive in our watershed, while they are threatened in many others, as confirmed by multiple surveys. Unfortunately, this creates for us a management dilemma. Downstream from our hydro dams, our river places together a problematic mix of babies: young lake sturgeon, larval sea lampreys, and mudpuppy hatchlings. This is where the river is periodically treated with an oxygen depriving chemical to kill the larval lamprey, but also has the potential to kill many young sturgeon amd mudpuppies. Some readers may recall that, partnering with the Ottawa Nation and the U.S. Fish and Wildlife Service, the MRWA participated in a sturgeon rescue prior to the Muskegon’s last lampricide treatment. Young sturgeon are hard enough to spot and capture; rescuing mudpuppies is virtually impossible. Since mudpuppies and sturgeon are both slow to mature and reproduce, our management skills are challenged.

Information for this article was obtained from Michigan State University Cooperative Extension Services; Herpetological Resource and Management LLC; The Panda’s Thumb by Stephen Gould; and the National Geographic website.