This may seem like the start of a joke (to get to the other side, right?) but it actually has a serious answer and some complex systems at play. 

On April 1, 2025 a friend and I went to Indian Creek Nature Center for an afternoon birding trip. While we didn’t see too many birds - a singular Song Sparrow, some Buffleheads, and a lot of Canada Geese - we did encounter a whole bunch of frogs. We heard them first. I thought the cacophony was a massive flock of Geese flying towards us and I moved my binoculars to the ready position. But the Geese never showed. As we kept walking, the sound got louder and louder, with no obvious source. At the peak we found a vernal pool to our left, and a bunch of ripples with two little eyes poking out from the center - frogs! My first thought was, “I missed Big Night!”

Mobility and migration is a critical factor and facet in the lives of many animals. For example, Red-winged Blackbirds, humpback whales, and monarch butterflies all undertake long migrations to avoid harsh northern winters, find more abundant resources, and, in the case of the whales, reproduce. However, not all migrations are hundreds or thousands of miles long. In fact, there’s a group of local animals going through a short but impactful migration right around now. 

Amphibian species (the amphibian class encompasses frogs, toads, salamanders, newts, and caecilians) are ectotherms, meaning that they can’t moderate their own body temperature, and rely on external environmental conditions. This is why you will often find frogs and turtles (who are in the reptile class but are also ectotherms) basking on the shore or on a log when it’s sunny out. By contrast, mammals (like us humans) are endotherms and able to regulate our own body temperature through metabolism. 

So how does an animal that relies on the warmth of the sun to move around and get food make it through the long, harsh North Country winter? They overwinter either underground or underwater. Those that shelter underground go through a process called brumation - essentially an amphibian equivalent of hibernation. This gives them protection from the extreme cold, and also slows their body’s functioning to preserve energy. Wood frogs actually freeze over and their heart stops beating! But once spring comes they thaw right back out - look it up!

The strategies that amphibians use to survive through the winter could be a blog in itself. However, in this blog I want to focus on what happens when they thaw out - Big Night. This is the night of mass movement of frogs and salamanders as they migrate from their overwintering site to the vernal pools where they breed. Vernal pools are temporary seasonal pools of water in the forest. They hold water in the spring, but dry up in late summer. This drying up is important, as it means that fish (who would be predators of amphibian larvae) cannot live in these pools. Amphibians must reach these vernal pools in a timely manner to successfully lay their eggs and give their young enough time to reach maturity.

Two factors determine when Big Night occurs - temperature and moisture. As I mentioned before, being ectothermic means that warmer temperatures are important for amphibians to have enough activation energy for extensive movement. For the movement undertaken during Big Night, the temperatures must be at least 40 degrees Fahrenheit. Second, moisture plays a part. Amphibians’ skin is thin and permeable because they use it for part of their respiration (breathing). For their skin to work well it needs to maintain a certain level of moistness, so they do best in environments where moisture is readily available. On a rainy night, expect to find a lot of amphibians! So overall, Big Night occurs when it is consistently over 40 degrees and raining. 

Big Night also isn’t always just one night. It can occur in a series of nights when the conditions are right, or even in waves separated by some number of days. It all depends on the weather. 

During Big Night, a large number of frogs and salamanders - common species you may find are wood frogs, spotted salamanders, and Jefferson-blue spotted complex salamanders - move between their overwintering site in the forest to vernal pools. The issue is that unlike species that migrate through the air and sea, amphibians have to deal with roads crossing through their path. Roads cause habitat fragmentation, creating barriers that divide up habitat that once was continuous. This disrupts the natural patterns, like migration, that many species undertake seasonally and present serious and novel risks. 

Roads pose a serious issue for more species than just amphibians. Many mammals and birds are commonly killed on roads, either from hunting or scavenging around the road like many raptors tend to do, or from trying to cross the road to reach a new habitat, like deer and racoons. In today’s world, roads and cars are a deeply embedded tool in society and our everyday lives. It may be unavoidable, and sometimes even safer, to hit an animal on a road. 

There are ways to minimize this risk, some of which you may be familiar with. Signage, either year round or seasonally can be beneficial to alert drivers to hotspots of wildlife crossings. In these areas, reduce your speed, and pay more attention to the road and its surrounding habitat. Wildlife crossings are another design to reduce road mortality. These are frequently below the road and are designed as a passageway for smaller species like amphibians, reptiles, and small mammals to move between habitats. Above road bridges for animals to cross highways also exist. While wildlife crossings are beneficial, they are not a fix-all. The space may be dark, small, or unnatural which can present as unsafe to many animals. When designing a wildlife crossing, the ecology of the target species must be considered for maximum effectiveness. 

During Big Night, frogs and salamanders often need to cross a road to reach their destination. Considering the quantity of individuals in motion and their slow speed, amphibians are at high risk on these nights. This is where humans can help out! There are many groups and volunteers who collaborate each spring to help amphibians cross the road. The DEC (Department of Environmental Conservation) is in their 17th year of the Amphibian Migration & Road Crossings Project in the Hudson Valley. In that time, volunteers have documented 20+ species of amphibians with 58,000 live amphibians crossing the roads, and 24,000 killed by cars. 

If you’re an amphibian enthusiast and want to help out our migrating friends, I encourage you to read the Amphibian Migrations and Road Crossings Project Volunteer Handbook, and/or watch the Volunteer Training videos they’ve created. While we are not located near the Hudson Valley and can’t contribute officially to the project, their resources include all the important information for monitoring and helping amphibians during Big Night, and you could still use their data sheet (the last 2 pages of their handbook) to collect information. If you go out to look for amphibians, be sure to follow their advice: bring a bright flashlight, go with another person, wear a reflective vest, and stay alert on the roads. If you move an amphibian, bring them to the side of the road that they are facing. Note that if you touch an amphibian, your hands must be clean (no lotions or bug sprays). If you have to drive at night and the conditions are right for amphibian movement, reduce your speed and keep watch for amphibians as best you can. 

While I may have missed out on the main Big Night, amphibians will still be crossing roadways throughout the spring. If you want to find these amazing creatures, visit a local trail and keep an eye out for a variety of frogs and toads, and look under logs and rocks for salamanders. Make sure you return any amphibians you find or habitat you move back to how you found it. In the end, the answer to the question “why did the salamander cross the road” really is “to get to the other side.” However, this movement is purposeful and no simple feat for these extraordinary amphibians. 

Photos included at the top of this blog are Encounters from Nature Up North's website. These were shot and shared by Tracey Thomas, Troy Parla, and Liz Anderson.