If you’ve ever tried to spot a marbled salamander in the wild, you know it’s no easy task. These elusive amphibians belong to the genus Ambystoma, commonly known as “mole salamanders”, a fitting name for creatures that spend most of their lives underground or tucked beneath logs, out of sight and out of reach. Their secretive nature makes them notoriously difficult to study, especially once they’ve transitioned from aquatic larvae to terrestrial adults.
But every fall, nature gives us a rare window of opportunity.
Unlike most of their salamander cousins who breed on a rainy spring night, often called the “Big Night” by salamander fans, marbled salamanders flip the script. On cool, rainy autumn nights, before the frost sets in, adults emerge from their subterranean hideouts and make their way to dry vernal pool edges. There, they lay eggs in anticipation of winter rains that will eventually fill the pools and submerge the developing eggs. This unique breeding strategy gives their young a head start come spring, allowing them to dominate the pool and even prey on the eggs and larvae of other amphibians.
Since 2016, the Field Conservation team at Zoo New England has been working to reintroduce these unique amphibians to their former home in the Middlesex Fells, where they became locally extinct in the 1920s due to deforestation and industrial activity in and around the Reservation. Longtime readers will recall the exciting moment in 2023 when a survey by our partner organization Earthwise Aware documented the first larval marbled salamanders to hatch in the Middlesex Fells in 90 years – proof that our reintroduction was taking hold. Nighttime surveys for adult salamanders have also confirmed the presence of breeding adults and maturing young adults on the landscape. Yet, in all likelihood, this reintroduced population remains small and vulnerable to disturbance as they build up their numbers. A bad breeding year or two or a seemingly-small change in their vernal pool habitat could wipe them out all over again. This means we need to keep checking up on the salamander population every year to stay alert for potential problems.
This fall, our team at Zoo New England has again returned to the Middlesex Fells, armed with flashlights, rain gear, and the marbled salamanders did not disappoint. 11 individuals were spotted near the edges of the pools, their striking black-and-white patterns gleaming in the wet leaf litter.
Each sighting is more than just a delightful encounter, it’s a valuable data point. Because these salamanders spend so much of their lives hidden, fall surveys are one of the few reliable ways to estimate population sizes and monitor their health. Every individual we find helps us better understand their distribution, breeding success, and the challenges they face in a changing environment. Seeing reliable numbers of adults and sub-adults each year not only tells us that our reintroduced individuals survived, but also that individuals across multiple age classes are still out there, which lays the foundation for a healthy population. In the future, we hope to use this successful reintroduction as a model for similar efforts, first at other pools in the Middlesex Fells and then at other sites where the species was known to breed in the past.
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