18

Following the Mole (Salamander) Trail

A Forty-Year Cross-Country Journey

Standing knee-deep in a temporary woodland pond, I lifted my dipnet from the water to find an odd creature with smooth skin, four legs, and big floofy, feathery, bright-red external gills wriggling in decaying leaves and muck in the net’s bottom. I had never seen such an animal before: I was bamboozled by a larval Mole Salamander (Ambystoma talpoideum). For me, this encounter was what James Joyce and Joseph Campbell called aesthetic arrest: the larva’s gill arches and body were painted with gold flecks of shiny iridophores. The highly vascularized, bushy gill filaments—when viewed under a dissecting microscope—circulated oval-shaped red blood cells that moved along arterial pathways like bumper cars. I was hooked.

Thus began what would become a life-long passion for, and research focus on, salamanders—especially mole salamanders of the family Ambystomatidae. Unlike many others, I didn’t become enamored with amphibians and reptiles until I was a young adult and enrolled in an undergraduate field ecology course at Mississippi State University. As part of a class field project to study ecological interactions in temporary (ephemeral) woodland pond ecosystems, I sampled a small pond with a dipnet, looking for amphipods and isopods (my assignment in the class). I found plenty of my targets but, more importantly, I found a new passion to study mole salamanders, which would take me to three corners of the continental United States during the course of my career.

Later that year, I returned to the same pond one winter night. The darkness was enshrouded in a cold but gentle rain—perfect salamander weather. As I approached the pond, the water’s surface bubbled in the light of my headlamp. I ran a dipnet through the pond, only to struggle underneath the weight of its contents as I lifted it out of the water. Dark, purplish salamanders poured over the edge of the dipnet. As I sorted through my catch, I realized that I had stumbled upon an en masse breeding aggregation of another species, the Spotted Salamander (Ambystoma maculatum). Scores of 10-in salamanders, their purple bodies punctuated with bright orange and yellow spots, looked up at me with dark round eyes and blinked in the bright light of the head lamp. I had never seen such a sight before, nor have I seen it again in the 40 years since.

It turned out that there was yet a third species of Ambystoma that used this little pond for breeding. The Marbled Salamander (A. opacum) capitalizes on temporary ponds like this throughout its expansive distribution, ranging from New England to northwest Florida, then west to eastern Texas, Missouri, southern Illinois, Indiana, and Ohio. This widespread distribution would afford me the opportunity to work with this species at multiple points in my career as I moved around the country. I focused study on this species, along with Spotted and Jefferson Salamanders (A. jeffersonianum), in New York’s Hudson Highlands when I became an assistant professor at City College of the City University of New York. Many years later, a discovery of populations close to where I currently live in northern Florida allowed me to rekindle my fondness for Marbled Salamanders and examine how this species is faring at the extreme southern end of its range.

I soon left Mississippi for graduate school in Louisiana where the same three species—Mole, Spotted, and Marbled Salamanders—co-occurred. This set the stage to continue addressing questions I initially posed in my undergraduate days, but there was just one hitch: I had a hard time finding them. I searched the university’s museum records for historic localities and found hot spots of collections at key locations, in one instance resulting in 300 adult Marbled Salamanders crammed into gallon jars filled with preservative. I thought, Oh, boy! This must be a great spot for Marbled Salamanders! A visit to the site exceeded my expectations: the habitat was perfect. The next summer, before the fall salamander breeding season, I hauled left-over plywood boards from construction sites out to the dry pond depressions to provide cover under which gravid females could nest and lay their eggs. But it was not meant to be: I never found a single salamander over the years that I checked the area. I eventually found another field site, but the sad realization sunk in that, most likely, the collector had taken all adult individuals as they arrived at the site to breed. All 300 salamanders in the collection were stockpiled over a short period of time, confirming my suspicion. The worst of it was that no research had ever been done with those animals; the extirpation of that population was in vain.

Following graduate school, I was fortunate to pursue a postdoctoral research position in Oregon. With its mountainous terrain, cool temperatures, lush evergreen forests, and beautiful waterfalls, rivers, and lakes, living in the Pacific Northwest had always been my pipe dream. Plus, species of mole salamanders that were new to me lay in wait! Fieldwork with the Long-Toed Salamander (A. macrodactylum columbianum) proved to be one of my biggest adventures yet. My main study site with this species was a high-altitude ephemeral pond south of Sisters, Oregon, nestled in the Cascade mountain range. Like many montane amphibians, this salamander breeds at snowmelt just as soon as the pond’s surface is free of ice. In warmer months, one could drive right to the pond; however, in the winter and spring, getting to the pond required skis or snowshoes. Having never skied before, I chose the latter option. The uphill trudge through wet, heavy snow at high elevation proved a challenge for someone acclimated to the swamps of Louisiana. However, the effort paid off when we reached the pond: we found a couple of dark, slender adult salamanders, decorated with gold across their backs, swimming in the ice-cold water. I knew nothing about how this species bred. I found out, however, when I lifted a submerged flat rock and found clusters of freshly laid eggs clinging to its underside.

I continued to visit the pond as the season progressed. Remarkably, hatching of the larval salamanders coincided with a prolific bloom of plankton (copepods and cladocerans)—food for the larvae. As the days grew longer and the water warmed, the plankton population eventually crashed. I noticed that the larval salamanders were very thin and had disproportionately enlarged heads. What could they possibly be eating in this prey-depauperate pond?

I collected some larvae to examine in the laboratory. I sacrificed a big-headed morph and discovered that it had significantly enlarged vomerine teeth, just like the known cannibal morph in some populations of the Tiger Salamander (A. tigrinum nebulosum). Remarkably, after about a month in the lab—reared in isolation from other larvae and fed plentiful prey—a group of wild-collected, big-headed individuals transitioned to more normal looking larvae with smaller, rounder heads, fuller bodies and limbs, and reduced vomerine teeth. Based on this morph’s similarity to that of A. t. nebulosum, I concluded that this population of Long-Toed Salamanders likely developed cannibal morphs in a prey-depauperate environment.

Regrettably, my stint in Oregon came to an end too soon. I moved to New York for my first academic job and more field studies with a trio of Ambystoma. But that, too, changed when an opportunity arose to get closer to my family in Mississippi. Thus I moved back to the South—then again (back to Louisiana)— and again! I finally settled in Florida, with the rare opportunity to work with the highly imperiled Frosted Flatwoods Salamander (A. cingulatum). This time, however, the motivation was very different, as this species was quickly slipping into oblivion. The focus of my work shifted to conservation. Using drift fences and funnel traps, my team and I began catching adults as they migrated to wetlands to breed, marking and measuring them before releasing them into the pond. This technique would allow us to follow individual growth and survival over time, thus providing an estimate of how well populations were doing. We also began capturing free-swimming hatchling larvae and moving them to water-filled mesocosms to enhance their growth and survival in that predator-free and prey-enriched environment. Once larvae metamorphosed, we marked and released them at their natal pond. Only time will tell if this head-start approach is working.

The panhandle region of Florida is considered a biodiversity hotspot, yet, with rare exceptions, the region (as well as the rest of the state) lacks ponds supporting multispecies assemblages of Ambystoma, as I had experienced elsewhere. Indeed, Spotted Salamanders don’t occur in Florida, and Marbled Salamanders— occurring at the extreme southern edge of their range—are only patchily distributed along a few river drainages in the panhandle region. I longed to see a Marbled Salamander again and finally had the opportunity nearly a decade and a half after moving to Florida. One fall I descended into the dry basin of a seasonally flooded swale on the west side of the upper Suwannee River; the basin was ringed with saw palmetto and dotted with decaying logs of varying sizes underneath a canopy of cypress trees. The ground was bare other than a carpet of cypress leaf litter. In late November, the temperature was still unseasonably warm, and it had not rained for many weeks. The habitat was perfect, but would there be any salamanders given the warm and dry conditions? Many logs had to be turned to get an answer to that question, but, eventually, my friends and I turned a log to uncover a pair of female Marbled Salamanders sitting on a communal mass of developing embryos—a double clutch! Repeated visits to different parts of the expansive dry swale revealed only a few more salamanders. Did a viable salamander population still exist here? Were there only a few salamanders because of the dry conditions? Would the winter rains eventually fill the depressions and allow the larvae to hatch?

With so many species experiencing declines and facing the threat of extinction, so-called common species with broad distributions—like the Marbled Salamander—are typically not even on the radar of concerned conservation biologists. However, anecdotal reports of more and more common species are indicating that they, too, are likely declining. Populations at range edges—like the Suwannee River population of A. opacum—are especially vulnerable. Empirical studies are beginning to reveal that climate change is leading to both expansions and contractions of species’ distributions. As the impacts of climate change escalate, field guides will undoubtedly have to be revised to reflect shifting distributions of many species.

As I sat by the overturned log admiring the pair of female salamanders and their communal clutch, I debated whether I should roll the log back over and leave them be or whether I should collect the females and their eggs, rear the larvae to metamorphosis myself, then later return them to their natal site. I flipped a mental coin and collect animals won. As I later watched the larvae grow and develop, I knew I had made the right choice: the rains never did come, and any eggs left on the landscape perished, resulting in another year of complete reproductive failure for that population. Final score in the game of ecological roulette? Environmental uncertainty one, salamanders, zero.