On rainy spring evenings, have you ever encountered large numbers of salamanders and frogs crossing the road? Do you ever wonder where they came from and where they are going? New Jersey’s forests are home to a group of amphibians that breed in small, temporary wetlands called vernal pools. Within northern New Jersey, this group includes wood frogs, spotted salamanders, and Jefferson salamanders.
These salamanders are elusive, often concealed under foliage, moss, or in burrows created by small creatures. They belong to the Ambystomatidae family, earning the nickname “mole salamander” due to their subterranean tendencies. Feeding primarily at night on various invertebrates like earthworms and insects, they, along with wood frogs, play crucial roles in forest ecosystems as vital links in the food chain and are indicators of ecosystem health. Emerging from winter hibernation during rainy nights in late winter and early spring, they embark on journeys to vernal pools for mating and egg-laying, marking the onset of the amphibian migration.
If you follow us or any other wildlife organizations on social media, you may have noticed that our posts these last few days have been inundated with amphibians. It may seem like odd timing, given that our early breeders (wood frogs, spotted, and Jefferson salamanders) completed their crossroad migration last month. But the reason is simple – it’s Amphibian Week!
Close up of an American toad that hitched a ride during this year’s crossing. Photo Credit: Nikki Griffiths
Globally, amphibians are disappearing faster than any other vertebrate group. The International Union for the Conservation of Nature (IUCN) estimates that 41% of amphibian species categorized for their Red List are currently facing extinction. That estimate is likely conservative, given that these creatures are often small and difficult to survey, rendering many species data deficient. This is concerning from multiple perspectives. From an ethical standpoint, we don’t want any wildlife to go extinct except maybe, in my extremely biased opinion, certain types of ticks… (I began my career as a moose technician and saw firsthand the terrible consequences that winter ticks have on these behemoths). Beyond that though, amphibians are tasked with a lot of responsibilities and carry out their work efficiently and without complaint. The list is inexhaustive but here are a few things that amphibians are doing for us and our planet as we speak: filtering water, sequestering carbon, eating pests (like mosquitos!), serving as prey for countless predators, helping researchers study regeneration (with hopeful applications to the future of organ transplants), aerating the soil in your garden, indicating where water sources have been contaminated by pollutants, and giving everyone who meets them a reason to smile.
We’ve made it to the final “super species” in our “superhero” series though, like in the last post, we’re spotlighting an adaptation that aligns with one of the more notorious residents of Gotham City. Our local frog has all the chill, while this DC villain needs to chill… quite literally, as his sub-zero body temperature must be maintained to ensure his survival. Cryogenics expert, Dr. Victor Fries- better known as Mr. Freeze, had admirable intentions when he began his experimentation with ice. Unfortunately for him, accidental exposure to chemicals altered his physiology, necessitating the use of an air-conditioned suit and spurring a life of crime motivated by tragic desperation. The compound responsible for his transformation is thought by some to be glycerol, which also happens to be the key to the winter survival strategy of our favorite early breeding anuran- the wood frog (Lithobates sylvaticus).
Animals living in temperate climates must find ways to cope with the cold temperatures and reduction of food resources, characteristic of the winter season. Some species deal with winter by not dealing with winter… instead they migrate to milder conditions farther south. This is a path commonly taken by birds. Other animals have adapted to have a large body mass. This reduces their surface area and enables them to hold onto heat more efficiently. As a former moose biologist, I’m happy to give them a quick nod here. Many strategies exist across the natural world to increase the odds of persistence, but we’re here to talk about amphibians and, it’ll probably come as no surprise to you that they aren’t employing either of the aforementioned tactics.
Wood frogs are a vernal pool obligate species; they must have access to these temporary wetlands in order to breed and complete their lifecycle, but they don’t live in them all the time. Therefore, we do refer to them as migratory, but they only cover about ¼ to ½ mile during this annual pilgrimage, so temperature differences are negligible. Most frogs and salamanders in New Jersey endure the colder months by entering brumation- the “cold blooded” equivalent of hibernation. In this state, animals can drop their body temperature and metabolism to conserve energy. Some species burrow and use the ground as insulation. Others brumate in streams and ponds since water cools at a slower rate than air. Wood frogs cover themselves in leaf litter (for camouflage) and spend the winter comfortably as frog-cicles. That’s right- they essentially freeze solid and thaw once air temperatures become favorable again.
Under normal conditions, when a cell freezes, ice crystals form internally. These solids can then expand, which damages organelles and ultimately ruptures cell membranes. This leads to cell death. Compounded by damage incurred in blood vessels and dehydration, this would be a fatal situation for most animals. Wood frogs have found a hack to get around these devastating consequences.
A recently thawed wood frog huddled beneath a leaf. Photo credit: Nikki Griffiths.
As temperatures drop, wood frogs continue to produce urine but cease voiding it. Instead, the urine is concentrated into urea, which floods the frog’s bloodstream. The liver also goes into overdrive, manufacturing vast quantities of glucose, which causes their blood sugar to skyrocket as high as 100x normal levels (a better understanding of how this frog can avoid negative health effects under such conditions could certainly contribute to diabetes research in humans). The urea and glucose create a mixture that acts almost like antifreeze. Once ice crystals begin to form around the blood cells and internal organs, this homemade antifreeze infiltrates, allowing for the retention of water and protecting the frog’s cells from desiccation and explosion. They can maintain this state for up to 8 months.
This brumation strategy earns wood frogs the “northernmost amphibian in the western hemisphere” superlative as they can be found up past Gates of the Arctic National Park in Alaska.
The 2023 Amphibian season has begun! Drive carefully one upcoming rainy nights. Photo credit: Nikki Griffiths.
That’s a wrap on Mr. Freeze and our Super Species! The Amphibian Crossing is now in full swing. If you are going to be driving after sunset along roads that border ponds in the upcoming rains, watch out for migrating frogs and salamanders. Collisions with motor vehicles can decimate local populations rapidly so please slowdown!
I felt confident, after the mild conditions that we experienced in January and much of February, that March would skip the “lion” phase of the well-known adage and come in and out like a lamb. I was clearly incorrect…
In anticipation of the amphibian migration, I thought it would be fun to write about some of the most unique adaptations displayed by three early-breeding vernal pool obligates that we target during our Crossing program. These species require access to temporary wetlands in order to complete their life cycles and are thus at greater risk of motor vehicle collisions than other amphibians that don’t rely on these resources. As I started drafting this, I kept thinking about parallels between the behaviors that I chose for each species and superheroes/villains whose background and abilities relate. And so, I’m kicking off this series with our very own Wonder Woman, the Jefferson Salamander.
Citizen science projects are an amazing way for volunteers to contribute to ongoing research projects. By using volunteers scientists are able to extend the data collected for projects, and help more wildlife. The Amphibian Crossing Project is one of the ways CWF works with volunteers to protect imperiled wildlife.
The salamanders and frogs in East Brunswick got an early start to their migration season by crossing this week on February 15. David Moskowitz found spotted salamanders, wood frogs, dozens of spring peepers, and one wood frog crossing the temporarily closed section of Beekman Road in the early evening rain.
“This is the earliest they’ve ever moved – by about a week – in the 12 years I’ve been closing the road,” said Moskowitz.
East Brunswick has closed the road for a few nights each late winter/early spring when conditions are just right. While all amphibian species are vulnerable, spotted salamanders are a species of special concern in New Jersey.
Photo by David Moskowitz
Conserve Wildlife Foundation partners with certain municipalities and the Division of Fish and Wildlife’s Endangered and Nongame Species Program on salamander crossings in northern New Jersey. This is a key initiative among CWF’s amphibian projects.
The East Brunswick crossing offers the best opportunity for the public to take part and see these salamanders and frogs up close. Check their website for the next expected crossing and share the road with a salamander!
Waterloo Village in Byram Township, Sussex County is more than a tourist attraction and local gem, it is also home to the largest cross-road amphibian migration in New Jersey. Each spring, frogs, toads, and salamanders stir from their hibernation to make their way to their breeding sites. Some of these sites, like the one at Waterloo, are vernal pools – small, temporary bodies of water that appear in early spring as snow melts and rain and groundwater gathers, and disappear throughout the summer as they evaporate. The ephemeral nature of these pools can’t support fish, which would prey on amphibian eggs and larvae. Vernal pools therefore provide some protection for amphibian offspring, with many species such as wood frogs and spotted and Jefferson salamanders – both of which are listed as New Jersey species of Special Concern – relying exclusively on these vernal pools for breeding.
The greatest challenge for amphibians breeding at Waterloo Historic Village is crossing Waterloo Road. Living in the most densely population state takes a toll on many species of wildlife in the form of habitat loss, degradation, and fragmentation. Each year, many amphibians become victim to vehicular collision as they move from their hibernation sites across Waterloo Road to the vernal pool in which they reproduce. Amphibians may be disproportionately affected by vehicle-caused road mortalities compared to other wildlife because of their tendency to migrate en masse to breeding sites. These annual road mortalities can have devastating effects on amphibian population sizes, especially for the local at-risk salamander populations. In fact, as little as about 10% annual risk of road mortality in spotted salamanders can lead to the local extinction of an entire population.
Wood Frog eggs. Photo courtesy of MacKenzie Hall.
To address this problem, the Conserve Wildlife Foundation of New Jersey (CWF) and the New Jersey Endangered and Nongame Species Program (ENSP) organized amphibian rescue efforts. Since 2002, dedicated volunteers have assisted frogs, toads, and salamanders across Waterloo Road during the busiest migration nights. This aid has proven effective in reducing amphibian road mortalities, but it is not a permanent solution to the problem. Efforts are underway to construct under-road tunnels to help guide amphibians safely across Waterloo Road. These tunnels will provide safe passage for these critters throughout the breeding season, including on their migration back into the woods where they will hibernate. Since this return migration is more sporadic and less weather-dependent than migration to the vernal pool, it is much harder to protect amphibians as they make their way back to the forest.
This year, CWF scientists have begun the initial phases of research to understand current amphibian population sizes and the impact of vehicle traffic on these animals at Waterloo. Scientists and volunteers have been out 7 days a week since amphibian migrations began in late February to tally daily roadkill on Waterloo Road. This study will be used to evaluate changes to frog, toad, and salamander populations as the under-road amphibian tunnels are installed. CWF scientists have also conducted egg mass counts in the vernal pool at Waterloo Village to estimate the current population sizes of the different amphibian species in the area. Having this knowledge will allow CWF to improve on future projects to minimize road-related human-wildlife conflicts.
Spotted Salamander egg mass. Photo courtesy of MacKenzie Hall.
Along with improving conditions for amphibians in this location, CWF’s work at Waterloo Village will serve as an example of New Jersey statewide initiatives to reconnect wildlife habitat as a part of the Connecting Habitat Across New Jersey (CHANJ) program. The goal of CHANJ is to make our state landscapes more permeable to wildlife movement so that all of New Jersey’s residents – human and wildlife – will have the space they need to thrive.
In an effort to bring people and wildlife together in a positive way at Waterloo Village, CWF scientists are leading educational walks for the public and local schools. Through hands-on interaction, local residents can learn about and appreciate the remarkable wildlife right in their own back yards and what they can do to support conservation efforts.
All New Jerseyans can help wildlife this season by planting native plants for their gardens, building bat boxes where bats can roost, and, of course, by keeping an eye out on the roads, especially on warm, rainy nights when amphibians might be migrating.
CWF Vernal Pool Walks Connect New Jersey Residents with Rare, Seasonal Marvel
by Lindsay McNamara, Communications Manager
Spring Peeper photo by Andrea Proctor.
We all know that “April showers bring May flowers,” but the earlier rains of March stir up beauties of a different kind. When the first spring raindrops hit the barely-thawed ground and night falls on the forest, frogs, salamanders, and toads emerge from their winter burrows. These amphibians – the spotted salamanders, wood frogs, spring peepers, and others – are anxious to get to their breeding pools and lay their eggs. The waters that they choose are called vernal pools because they fill with rainwater, snowmelt, and rising groundwater in early spring but then dry up as summer advances. The pools are thus temporary and cannot support fish, meaning fewer predators for the amphibian eggs and young.
In the northeastern United States, vernal pools are home to over 500 species. In New Jersey, these pools are critical habitat for amphibians, reptiles, invertebrates, migratory waterfowl, raptors, and songbirds. All 14 of New Jersey’s frog species use vernal pools to breed and two endangered salamander species breed exclusively in vernal pools, including Cape May’s eastern tiger salamander.
The new generation of amphibians must race to complete metamorphosis and leave the vernal pool before the water does. Under perfect conditions of warm, thawing, nighttime rains, there may be hundreds or even thousands of amphibians moving at once toward the same breeding pool. The darkness and the rain allow them to move stealthily over the landscape, hidden from predators like the owl and raccoon.
CWF’s Kelly Triece organized a series of walks through the vernal pools of Waterloo Village in Sussex County, New Jersey, and showed residents the unexpected creatures swimming in the pool’s shallow waters. Kelly led the exploration of an ecosystem that most people will never see! Participants listened to the songs of Spring Peepers and discovered salamander eggs, fairy shrimp, and other unique creatures as the evenings set in. Here are photos from her walks:
CWF biologist Kelly Triece educates participants on the natural resources of Waterloo.
CWF biologist Kelly Triece looking for wildlife in the vernal pool.
Spotted Salamander Eggs! Photo by Kelly Triece.
Green Frog photo by Kelly Triece.
Examining the wildlife found in the vernal pool after dark.
Road Closures Help Amphibians Migrate to Vernal Pools to Breed
Conserve Wildlife Foundation is excited to celebrate Amphibian Awareness Month during March 2015! Follow us on social media and be sure to check your email (sign up for our list) for weekly stories on the amphibians of the Garden State and our work to protect them.
On the night of March 14, Conserve Wildlife Foundation Communications Coordinator Lindsay McNamara attended the first closure of Beekman Road this season. Beekman Road, in East Brunswick, New Jersey, is closed to traffic about two or three nights for six to twelve hours each spring by Friends of the East Brunswick Environmental Commission(Friends of EBEC). Friends of EBEC organizes these road closures to maintain local biodiversity.
In the woods on either side of Beekman Road, vernal pool habitat exists. Vernal pools are temporary woodland ponds that fill with water during the winter and spring and dry out in the summer. These vernal pools are extremely important for a number of amphibians in the area. Spotted salamanders, wood frogs, green frogs, spring peepers, Fowlers toads and chorus frogs all rely on the vernal pools for breeding.
Some amphibians, like spotted salamanders and wood frogs are entirely dependent on the vernal pools for breeding. They leave their winter hibernation spots in upland forests and migrate (often in large groups) to the vernal pools. Research suggests that these species follow the same migratory paths each year, often traveling distances of as much as 1,000 feet from their hibernation spots.
At the vernal pool, mating occurs, eggs are deposited by the females, and the adults leave the habitat and venture to the surrounding woods. The adults spend their summer in these wooded areas before slowly retreating back to their winter hibernation areas, and the natural cycle begins again.
Unfortunately, the migrating amphibians need to cross Beekman Road to get from their hibernating spots to their vernal pool breeding grounds. Road kills during this journey significantly reduce salamander and frog populations and can lead to local extinctions at breeding ponds.
Friends of the East Brunswick Environmental Commission has worked together with a number of partners to close Beekman Road to traffic during nights when amphibian migration is extremely likely. These road closures help protect migrating salamanders and frogs as they move across Beekman Road to their breeding vernal pools.
Friends of EBEC consider a number of variables before they decided to close the road. A wide range of factors trigger salamander migration including the amount and timing of rainfall, the date, the temperature of the air, the temperature of the ground, the availability of open water on the vernal pools, the depth the salamanders are migrating, soil moisture and many others. Interestingly, studies have shown that males typically migrate first and arrive at the vernal pools before the females. It seems females need a higher average air temperature to stimulate their movement than the males.
Volunteers are encouraged to come on these rainy nights to help the amphibians cross the road. Bring your friends, your family and don’t forget a flashlight, to the next road closure of the season! Updates are posted on the Friends of the East Brunswick Environmental Commission’s blog.
These road closures are a great way to protect local biodiversity and educate New Jersey residents about wildlife in their state. Conserve Wildlife Foundation, in partnership with the New Jersey Division of Fish & Wildlife’s Endangered and Nongame Species Program, lead a number of Amphibian Crossing volunteer programs across New Jersey. Join us!
by MacKenzie Hall, Amphibian Crossing Project Coordinator
This small vernal pool in Hopewell is ready for things to start hoppin’.
For the 98 volunteers signed on to help with this year’s amphibian road-crossing efforts, yesterday brought on the first flurry of excitement. Forty degrees! The promise of nighttime rain! Saturday’s soaker had helped to get the ground thawing, though many of the amphibians’ breeding pools were still capped in ice. The conditions weren’t going to be perfect, but surely some eager salamanders would be enticed to come out from their winter burrows and set off on migration. And when their tiny feet hit the pavement of peril, we were gonna be there gosh dernit!
So our “scouts” got ready for night (and rain) to fall, to go check on a dozen or so road-crossing hot-spots in northern and central NJ. Then, as volunteer Phil Wooldridge of Warren County put it, we experienced a little deja-vu. The rain started later, the temperature was colder. North of Route 80, snow and sleet fell instead. We amphibian crossers have gotten used to the shakiness of weather forecasts, and to the somewhat complex combination of triggers that set an amphibian migration in motion. At any rate, we basically got skunked last night.
The only sign of life came from Hampton, in Sussex County, where Sharon and Wade Wander found a single Jefferson salamander crossing the road to his ice-covered breeding pool. Tough little salamanders, those Jeffs. Our first one of 2012 came out during a wet snowfall, too, around 2:00 am on February 24th.
The town of East Brunswick was also counting on last night’s forecast when they decided to close Beekman Road – a town road bisecting an amphibian migration path. The town’s Environmental Commission has coordinated the closure for the past 10 years to protect the spotted salamanders, wood frogs, and other migrants on 4 to 10 nights every spring (read about it here). Even there, only one male spotted salamander was seen making his way to the pool.
So, we’ll keep doing our best to predict the amphibian migration and to be in the right places when it happens. Clearly the big long nights are still in front of us.
To learn more about our Amphibian Crossing Project and experience the migration through video, please visit our “Amphibians Crossing!” webpage.
