SCIENCE LAB SCREAM : SALAMANDER CANNIBALS

 

Threat To Their Species 

Devastated environment turns salamander fathers into cannibals.

The hellbender salamander has been called a lot of names, mud devil being among the more polite. And now, perhaps, it may be called a cannibal, according to new research into the parental habits of these giant amphibians.

An eight-year study of hellbenders living in the rivers of southwestern Virginia has found that male salamanders, which ordinarily care for unhatched salamanders, are increasingly consuming their own eggs in areas near decimated forests.

When nearby trees are felled, pollutants flow into rivers, changing water chemistry in ways that seem to be altering paternal behavior, the researchers said. Infanticide is becoming so widespread that eastern hellbenders - the largest salamanders in North America at two feet long and weighing up to five pounds [ 60 centimeters and 2.25 kilograms ] - may be on the cusp of eating the species into extinction.

'' If you have rates of cannibalism this high, then that alone is enough to explain many of the population declines we've seen,'' said Bill Hopkins, an ecologist of Virginia Tech who led the research. The findings will appear in The American Naturalist.

Eastern hellbenders once thrived in 15 states. The numbers have dwindled over the past 15 years, however, and researchers have struggled to explain why. Habitat loss, disease, poaching and climate change all probably contribute.

The practice of eating one's own offspring, known as filial cannibalism, is common among species that like the eastern hellbender, have evolved a parental system in which fathers provide the bulk of early care.

Eating eggs with low chances of survival helps the salamander conserve energy in lean times and improves their chances of surviving long enough to make more and stronger babies in the future.

But Dr.Hopkin's research suggests that cannibalism may be on the rise. 

'' They're exhibiting this behaviour that was once adaptive,'' said Hope Klug, an environmental biologist from the University of Tennessee at Chattanooga, '' but it's no longer adaptive, due to this rapid environmental change.''

Dr. Hopkins and his colleagues set up hundreds of underwater nest boxes in three rivers across southwestern Virginia. From 2013 to 2020, they monitored each box, tracking what happened to egg clusters left in the boxes.

In areas with lush forest cover, males ate their entire spawn about 14 percent of the time. But this happened more than three times as often wherever trees had been cut down. [ Elie Dolgin ]