A “Big Night” is coming to Harvard, and it is something worth seeing. The conditions need to be just right to trigger this salamander and frog party. When the so-called Big Night occurs, it is one heck of an amphibian party! But like most wild parties, there can be casualties.
Amphibians, such as the Jefferson, blue-spotted, and more common spotted salamanders, wood frogs, and spring peepers, overwinter in burrows, under logs, or sheltered by leaves. Once the ice melts and the ground is no longer frozen, they are awaiting the right conditions for their mass migration to their breeding pools. This usually happens in early to mid-March after dark, when it is raining and the outside temperature is above 40 degrees. Instincts, triggered by exact weather conditions, act as a sort of flash-mob alert. The eager, lustful crowd descends on the party spots, and it is there, under cover of night, that some rather salacious activity occurs within these once calm and virtuous pools.
Let’s consider the beautiful spotted salamanders, which people rarely get to see. Not surprising to me, the males arrive at the pools first, forming large groups called congresses. As the females arrive a couple of hours later, some males will leave the congress to court the females. All of this activity can be easily witnessed by finding a vernal pool on Big Night. And I encourage you to do this; it makes for a fun family activity. You just need to dress for the cool rainy conditions and bring a modified light source. (In order not to interfere with the salamanders’ activities, red light should be used.) It is easy to walk along the shore of the pool and, while shining your red light into the clear water, see all of the activity below the surface. But the first step is to locate a vernal pool.
There are lots of vernal pools in Harvard. What is a vernal pool? As the name implies, it is a pool that forms by winter snowmelt and rain, generally in depressions in the woods. The most important factor is that the water must dry out at some point during the year. If it has permanent water in it, it will develop pond life, which will encourage fish and other species that will devour the salamander eggs and larvae, preventing them from completing their life cycle. You may have a vernal pool right in your backyard and not know it. You might discover one by going out on Big Night and seeing if there are amphibians migrating toward any large pool of standing water on your property.
Eggs to adult before pool dries
The amphibians must complete their life cycle, from eggs, to larvae, to emerging adult, before the pool dries up. We have had some very dry spring seasons over the past two years, and that undoubtedly reduced the population of young that became adults in this area. Amphibians tend to return to the vernal pools in which they were born, so it is important to protect these pools as habitat. Generations of amphibians will know only one vernal pool, so it is a vital lifeline for them.
An action that you can take to protect the salamander and wood frog population is to act as a crossing guard. The amphibians migrate fairly long distances to reach these vernal pools, and their migration often takes them across roadways. The migration casualties can be lessened, to some degree, by residents who act as “crossing guards” in areas where roads and vernal pools are in close proximity. Also, if you are driving after dark in early to mid-spring on a rainy night, look closely at the roadway to avoid crushing the amphibians. Salamanders are particularly tough to see because they are mostly dark and low to the ground. I find it very sad to see the casualties on the roads after Big Night. Last year, some caring folks on Nextdoor Harvard posted the locations where many salamanders were spotted (pun intended) crossing the roads and volunteered to help escort them across the roads to avoid oncoming cars. This is one small feel-good activity that you can do to promote the health of the amphibian population. And it will enable you to witness (and hold!) some rare species that you would otherwise likely never get to see. Putting up signs notifying drivers is another strategy, though of unknown legality.
On Nextdoor Harvard, we can crowd-source notification of the exact date of Big Night when it occurs. I’ll post some locations of vernal pools that are on public property so you can see them for yourself. If you are aware of any other vernal pools, please add to the list with some instructions on how to find them. And then we can be extra careful when driving near them. Or maybe even stop and be self-appointed chaperones to the party attendees.
Marc Sevigny is a trustee of the Harvard Conservation Trust.
