On a mid-April evening, herpetologist Joe Martinez walked slowly through the darkness of Mount Auburn Cemetery, his headlamp illuminating the road in front of him. Three Harvard graduate biology students followed close behind.
Martinez stopped to point out a monument to Nathaniel Bowditch, an early American mathematician and navigator.
“A lot of famous people are buried here,” Martinez said.
Suddenly, Martinez heard something. He asked the students to listen. A distant chorus of high- pitched single note whistles drifted through the cool night air and across the rolling landscape dotted with headstones and crypts.
“Ah, this is good. Sweet stuff to hear,” said Martinez. “If you listen very carefully in the distance, those are peepers.”
Until last year, explained Martinez, spring nights were silent in the cemetery. Then he and Patrick Fairbairn, a member of the Watertown Conservation Commission, decided to launch a project to reintroduce spring peepers, gray treefrogs, and American toads to Mount Auburn.
Martinez said the idea struck him when he and Fairbairn were at Dell Pond, the cemetery’s only vernal pool, observing the migration of spotted salamanders, and noting the complete silence of the place.
The quietness was in contrast to virtually every other vernal pool they visited in Massachusetts. The small temporary ponds, formed by fall and spring rains and melting snow, are the primary breeding habitat for a variety of frog and salamander species, and typically resound with loud choruses of male frogs calling for mates in the spring.
“We wondered if it was possible to bring in some spring breeding frog species to bring a bit more life to the place,” said Martinez.
So Martinez, who works in the herpetology department at Harvard University’s Museum of Comparative Zoology (although Harvard is not involved in the project), drafted a proposal to reintroduce the amphibians to Mount Auburn, and obtained approval from the Watertown Conservation Commission, Mount Auburn Cemetery, and a license from the Massachusetts Division of Fisheries and Wildlife to capture and transport tadpoles.
“We have undertaken many habitat creation and enhancement projects over the past two decades,” Paul Kwiatkowski, Mount Auburn Cemetery’s conservation and sustainability manager, said in an email. “And when Joe Martinez proposed the re-introduction program, it fit perfectly with our stewardship goals.”
Kwiatkowski said those goals include protecting and enhancing the cemetery as a resource for wildlife.
Martinez feels the project is important on several levels, including increasing the biodiversity of a unique urban nature reserve, enhancing the visitor experience by allowing visitors to see frogs and toads and hear them calling, and as an educational resource for local schools.
Richard Primack, a conservation biologist at Boston University who is not involved with the project, said that by seeing and hearing frogs in an urban area, people understand the connections between the quality of the environment and the ability of species to live in an urban environment.
“If the frogs are able to live, to some extent it means that the environment is also clean and healthy,” Primack said in an email. “And people will be motivated to be concerned about protecting the environment.”
Mount Auburn was consecrated in 1831 as the nation’s first garden cemetery. Kwiatkowski said removal of trees and shrubs beginning in the late 1800’s to create ornamental Victorian landscapes, and turf and lawn installations in the 1900’s, might have contributed to the frogs’ disappearance.
If habitat destruction didn’t do the frogs in, Martinez guesses heavy pesticide use in the 1950’s and 1960’s probably did.
And with the urbanization of Watertown and Cambridge, which share the cemetery, there were likely no remaining local populations of vernal pool breeding frogs and toads to repopulate the area.
Martinez estimates that toads, spring peepers, and gray tree frogs have been absent from Mount Auburn for 50 years or more.
He decided to put tadpoles into Dell Pond, as opposed to releasing adult frogs and toads, because some animals have a homing instinct and might try to get back to where they came from. Martinez said when tadpoles metamorphose into frogs and toads during summer, they would regard the cemetery as their home.
In preparation for the new arrivals, Fairbairn said Mount Auburn Cemetery installed a variety of wetland plants in and around Dell Pond, which improved terrestrial and aquatic habitat for the toads and frogs by increasing cover and forage.
Each spring from 2011 to 2013, Martinez collected toad tadpoles at wetlands in Norwell and South Weymouth. Martinez said he put nearly 6,000 toad tadpoles into Dell Pond, in addition to about 150 spring peeper tadpoles. He also started introducing gray treefrog tadpoles last spring, and will add more this year and next.
Martinez said there is a high mortality rate for frogs, toads, and tadpoles due to predation and other factors, so only a small percentage of the tadpoles he releases are likely to survive to adulthood.
To monitor the success of the project Martinez listens for toads and spring peepers calling, which means they’ve gotten to reproductive age. He also looks for eggs and tadpoles in the water, and for metamorphs on land – tiny frogs and toads that have recently metamorphosed from tadpoles.
His work is paying off. Newly metamorphosed toads from breeding Mount Auburn toads were first seen in 2014, and this is the second year in a row Martinez heard spring peepers calling at Dell Pond, and saw adult toads in the area.
The ground crew also reports each time they see a toad, and Martinez said toads have now been spotted pretty much all over the 170 acre cemetery.
Martinez said this is going to be his legacy.
“These are my children, if you will.”