Princeton Salamander Crossing Brigade

Meet the Princeton Salamander Crossing Brigade. They joined together one warm, rainy night last week with a shared mission to help the local amphibians safely reach their breeding grounds up along the Princeton ridge.

Their objects of affection and devotion are frogs like this one, 

and salamanders like this. Due to land preservation efforts that began with the donation of Herrontown Woods nearly 70 years ago and continue to this day with a critical initiative to save the 90 acre Lanwin tract, there is still enough forest and clean water along the ridge to sustain these charismatic and ecologically important creatures. After long winter dormancy, it's these first warm, rainy nights that stir wood frogs, spring peepers, and spotted salamanders to action. 

Their goal is to reach the vernal pools that dot the woodlands of the ridge, where they will gather to mate and lay clusters of eggs before withdrawing back into the forest. Only one thing stands in their way. 

 

Herrontown Road dates back to the early days of Princeton. It rides the top of the ridge, winding around the back side of Herrontown Woods. Hundreds, perhaps thousands of amphibians, seeking the vernal pools in which they were born, unknowingly risk being crushed when they cross this strip of pavement. A spotted salamander can live more than 20 years, so that each loss has consequences for decades to come.

Interest in taking action to help the amphibians, many of which are females carrying eggs, has been growing. This is our first year placing signs along the road, in an appeal to drivers to slow down and keep an eye out for the little creatures. Trish Shanley of the Ridgeview Conservancy introduced us to Charlotte Michaluk and her sister Sonja, who have been studying amphibians and received grant funding to make these signs.

We also had some signs hand-painted by Boy Scout Troop 43.

Inge Regan of the Friends of Herrontown Woods created a series of signs that add up to a message, inspired by the Burma Shave signage that once dotted American roadsides. 

We can hope drivers will respond to signage, 

but all too frequently, the result is this, 

 

and this. 

Even the most careful driver is unlikely to see this little frog, a spring peeper. Much of the damage done to nature by human activity is unintentional. Good will and good intentions are not enough.

In some places in the state, roads are closed on these first warm, wet nights so that amphibians can cross safely. It's also possible to build tunnels under the roads. But none of this is as yet possible for Herrontown Road.

Thus, it was time to don reflective vests, acquire strong headlamps and good raincoats, and gather at dusk to help the amphibians survive their road crossings. 

We first received training at a workshop led by staff of the Sourland Conservancy, ConserveWildlifeNJ, and Somerset County Parks Commission, who taught us basic safety protocols and how to pick up the amphibians. First and foremost, get off the road when a car is approaching, and it's important not to have any hand lotion that could harm the amphibians' sensitive skin.

Over time, FOHW board member Inge Regan has brought together a passionate group of experts and novices, students and teachers, neighbors and FOHW members, all of whom communicate by text via a whatsapp group, sharing knowledge and photos, planning action, and generally cheering each other on. Hopewell teacher Mark Manning and Princeton native Fairfax Hutter have been lending their expertise, along with Lisa Boulanger, a neighbor who has essentially adopted Herrontown Road, regularly picking up litter and protecting the wildlife. Also a font of knowledge is Princeton High School teacher Mark Eastburn, who along with his students has gotten involved. 

One PHS student, Bhavya Yaddanapudi, is conducting research on vernal pools in Herrontown Woods. 

Helping with the crossing, as Daniela Gonzalez of PHS discovered, offers a chance to get up close to animals that are otherwise elusive, spending most of their lives hidden under leaves and logs in the forest.

Inge Regan's son Dylan also lent a hand, highlighting the multi-generational nature of the enterprise. As Inge reported in an email: "On our biggest night, 2/28/24, we had 15 volunteers out. We had over 121 passing cars, and we were able to save 40 amphibians. There were 49 DORs."

DOR stands for "dead on the road" -- amphibians run over by vehicles.  

The following day, Bhavya's father, writing on the WhatsApp group, captured the sentiments of everyone involved:

"Was great to see so many come together last night. The DOR stats are startling to say the least, witnessing was even more painful. Pls count me in for any efforts to bring change to our town policies that can minimize this carnage. Thanks again for including us." 

Lisa's Salamander Rescue

This spring in late April, I received a surprising email from my friend LisaB who lives out next to Autumn Hill Reservation, across from Herrontown Woods. An amphibian had mistaken the water sitting on top of her swimming pool cover for a vernal pool, and laid a cluster of eggs there. My somewhat informed guess? Spotted salamander eggs. 

What to do with this unexpected gift? The salamander was not completely off-track in having laid its eggs in a puddle suspended over a swimming pool. Through uncanny luck, the swimming pool's owner happens to care deeply about the amphibians that inhabit the woods behind her house.

Lisa had contacted me back in March--March 15 to be exact--to report that the frogs in the neighborhood had been on the move the night before. "This was definitely Herrontown frog migration night," she reported. "Dozens on the road at 5:30a, all headed" towards Herrontown Woods to mate and lay eggs. "I only saw them in a relatively narrow band of ~a half mile, from the entry to Autumn Hill to the curve at Stone Hill Church. They were mostly moving in the dark early this morning--by 7am they were gone. Hope that protects them to some extent. Traffic picks up after 7." She suggested we organize next spring to serve as crossing guards for amphibians needing to cross Herrontown Road to get to their mating grounds, as is done elsewhere in the state.

On May 25, Lisa sent me a report on what she had decided to do with the salamander eggs, which otherwise would have been lost when the maintenance crew came to service the swimming pool. Since it's inappropriate to remove salamander eggs from a nature preserve, Lisa took this backyard gift as a rare opportunity to see salamander development up close.

"I put some in a deep vernal pool in Herrontown Woods and hung on to a few. They live outside in a tank so they get all the usual temperature variations, plus bonus mosquito larvae to eat. They seem to really like live blackworms, which I am now growing in my fridge (uh, don't tell my kid). I'd love to see one develop spots, which takes a few weeks after transformation. They already have puny little front legs!"

On June 24, another update:
"Salamander larvae are starting to transform! Losing their gills and showing their spots. Voracious carnivores!"

And on July 7, more detailed reports begin about the salamanders' metamorphosis, mixing affection with the close observation honed in her career as a scientist: "The two that transformed first flew the coop. For now I put lids on the tanks, so the next three to transform are still here. Some cool things I didn't know:"

1) "As they start to transform, their GILLS start to develop bright yellow spots just before they regress."

2) "Each one has a unique spot pattern that coalesces and intensifies as they transform, which makes them easy to tell apart. Not sure what nucleates the spots."

"This sequence of photos, taken two days apart, shows the development of spots on a transformed salamander."

"They become very shy once they transform. The larvae are just hanging out in the water column. I know they're about to transform when I look in the tank and I can't find them. The ones that have transformed are always burrowed under the moss. Interesting, for a stage with what looks like aposematic coloring ("don't eat me! I'm brightly colored and probably toxic!"). Probably they aren't actually toxic, and so the bright yellow spots pretty strongly select against anyone who is ever out in the open."

3) "The darkness of the larval stage seems influenced by substrate--ones raised on light rocks are lighter in color than ones raised in a pile of leaf litter. Not sure if it's a developmental camouflage or they're just dark because they're eating/covered in leaf gunk. "

"Man, do they eat a lot of blackworms! 1/8 lb so far."

Here are spots developing on a "new guy." Photos taken on days 1,2,3, 6, and 7.

By mid-July, thoughts turned to what to do with the salamanders once they've grown. "Technically I think I'm not supposed to release them, given there is some risk of introducing new pathogens into the local population (e.g., from the worms I feed them, which came from afar). Two did escape, though, so that ship may have sailed."

The Watershed Institute didn't have room. Salamanders apparently, and fortunately, given the potential danger to wild populations posed by poaching, don't make very good pets. They prefer to remain hidden, and can live up to 20 years. Many have toxins in their skin, and can easily absorb harmful oils and chemicals on our skin if we touch them. 

Finally, Lisa reached out to the Mercer County wildlife center, which then reached out to the senior biologist from the New Jersey Division of Fish and Wildlife Endangered and Nongame Species Program, who gave the following advice:

"From what I’ve read below I consider this to be a pretty low risk release and would recommend her to release them as near as she can to reasonable habitat by her property and best case would be to release them during the late morning when there’s some rain or release them an hour or so after sunset during a rain." 

One thing I've learned while putting this post together is that spotted salamanders (Ambystoma maculatum) have a longer incubation period than most species. Most vernal pools dry up once the trees leaf out. Only a few stay wet enough long enough to sustain the larvae until they metamorphose into juveniles.

Lisa sent a link describing how spotted salamander eggs incorporate algae into the body of the embryo. They become solar salamanders. The algae symbiotically provides energy and eats the salamander's waste. The algae fades away during the larval stage of the salamander.

Thanks to LisaB for all these photos and information. One more thing she shared speaks to why this was such a meaningful experience for her:

"I've been turning over stones looking for salamanders since I was a kid, and have seen hundreds of Eastern Redbacks. Once, when I was <10, one of the other kids found what I now know was probably a spotted salamander, and came running to tell the others (we thought they were lying about a salamander the size of a hotdog). That was the closest I've come to seeing one, despite the fact that they are all over here, until 40+ years later one decided to lay eggs on our pool cover."