The Video:
https://www.youtube....eature=youtu.be
Reign of the den master: Biologists video seldom-seen breeding behavior of hellbenders
Eastern hellbenders are super-secretive – active mostly at night, living under submerged rocks, camouflaged so subtly that even by day these giant salamanders, the largest in North America, disappear into the cobbled beds of the cold mountain streams they inhabit.
All of which makes the recent video of a hellbender guarding a “nest rock” even more amazing.
Wildlife biologist Thomas Floyd of DNR’s Nongame Conservation Section and Dr. Shem Unger, a postdoctoral researcher at UGA's Savannah River Ecology Laboratory, were looking for larval hellbenders Sept. 5 as part of a State Wildlife Grants project exploring the impact of sedimentation levels on young salamanders. But in the bend of a rain-swollen creek on the Chattahoochee National Forest, the snorkelers saw the head of an adult male hellbender protruding from a gap in the rocks.
The scientists watched, fascinated, as the male defended the site against male and female hellbenders trying to get in. The male even bit a large female. Undeterred, she slipped past him.
Floyd says the male was a den master, a large, dominant male that controls access to a prime nest site. “We just happened to be at the right place at the right time. If we had been there just 30 minutes before or after, we would have missed seeing the whole event.”
Possibly drawn by pheromones and maybe by habit – hellbenders can live more than 50 years and “who knows how long these particular hellbenders have been doing this skit,” Floyd said – the females were trying to enter the nest to deposit eggs. Out of sight, the den master would externally fertilize the clusters, much like native trout in north Georgia streams do.
The other males also had reproduction in mind. Adding their milt could extend their family line.
Unger said that while little is known about the breeding biology of hellbenders in the wild, genetic research conducted in another state recently confirmed multiple parentage of a nest guarded by a single male. It has been widely believed that only one male and one female contributed to each nest. The genetic evidence, however, suggests the story is more complex.
Either multiple females enter and deposit eggs in the same guarded nest, or multiple males, possibly smaller “sneaker males,” help fertilize eggs in that nest – behavior common in other amphibians. Although multiple paternity has not been confirmed in hellbenders, “the entry of multiple males under a single nest rock suggests this,” Unger said.
“Our video is the first known documentation of this behavior in Georgia.”
Floyd said other males and females tried several times to access the nest rock through other entrances. “Two males and two females made it in.” (One of the smaller males quickly fled the nest rock, possibly forced out by the den master.)
The den master will guard the eggs “through hatching until the larvae are ready to leave the nest, probably into March,” Floyd said.
Considering that habitat loss has hellbenders on the decline, den masters and the nests they guard are critical to the species, and part of a seldom-seen aquatic “skit” that can now be watched by all.
Love nip?
It’s not clear why this den master nipped the large female trying to enter the nest site.
Floyd’s theory is that maybe female suitors are not quickly discerned from male intruders, and the den master’s guard helps ensure that only the strongest or smartest mates make it into the nest.
Added Unger, “The den master likely has an overriding instinct to defend his nest rock, biting all intruders. Clearly in hellbenders, love hurts!”
Nest rocks
- During late summer, males begin excavating saucer-shaped depressions under flat rocks.
- Suitable nest rocks have a sizable cavity underneath and few entrances. Dominant males defend these sites.
- Females attracted or lured to the nest deposit from 450 to nearly 1,100 eggs in a single compact cluster, with the eggs strung together, similar in appearance to a pearl necklace. Occasionally, several females will oviposit in the same nest.
- Following external fertilization of the eggs, the male guards the clutch from predators until hatchlings disperse from the nest rock.
- In Georgia, hellbender breeding season lasts from about mid-August to late October.
- Repeatedly disturbing habitat by flipping or moving rocks in streams is detrimental. DNR surveys a stream for hellbenders only once every several years and never in breeding season.
Information provided by the Georgia Department of Natural Resources. Sign up for this newsletter at http://www.gadnr.org/