Tiger Beetles From Thriving Monomoy Colony Transferred To New Jersey Beach

By: Tim Wood

Topics: Monomoy National Wildlife Refuge , Conservation

One of 196 tiger beetle larvae taken from South Monomoy to Sandy Hook, N.J. recently. PHOTO COURTESY OF RODGER GWIAZDOWSKI

CHATHAM – Twenty years ago, 23 larvae of the federally threatened northeastern beach tiger beetle were taken from a beach on Martha's Vineyard, the last known population in New England, and released on South Monomoy Island. Subsequent transplanting of tiger beetle larvae from the Vineyard to Monomoy took place annually through 2004.

To say that the tiger beetles took to Monomoy would be an understatement. The population on the National Wildlife Refuge is now the largest outside of the Chesapeake Bay region, numbering an estimated 8,000 individuals.

Two weeks ago, 196 tiger beetle larvae were dug up from South Monomoy and brought to the Sandy Hook section of the Gateway National Recreation Area in New Jersey, where they were released with the hope of establishing a new population.

Both Monomoy and Sandy Hook have natural, protected beaches, “the right size and shape” for tiger beetles, said Dr. Rodger Gwiazdowski, adjunct professor in the Department of Environmental Conservation at UMass, Amherst, owner of Advanced BioConsulting in Shrewsbury and principal investigator of the northeast beach tiger beetle recovery project. Like other species that depend on unspoiled beaches, tiger beetles were once abundant from Massachusetts to New Jersey and along the Chesapeake Bay. A 1910 paper describes dense swarms of the insect off Atlantic City, Gwiazdowski said, but after World War II, increasing recreational use of beaches, off road vehicles and shoreline changes, including beach stabilization structures such as revetments, led to the extirpation of the beetle, which lives its entire lifecycle on the beach.

In New England, a private beach on Martha's Vineyard, with no foot traffic or vehicles, held the last population of tiger beetles. An adjacent public beach has no tiger beetles, which demonstrates the impact humans have had on the species, Gwiazdowski said. Isolated Monomoy proved a perfect habitat for the beetle, which is an apex predator in the insect world. The recent translocation to Sandy Hook is the most significant step in the preservation of the species, which was listed as threatened in 1990 and could be upgraded to endangered, in two decades, Gwiazdowski said. A similar attempt to introduce tiger beetle larvae to Sandy Hook from the Chesapeake Bay population failed, presumably because of the differences between the bay and ocean habitats.

“It was a good try but it didn't work,” he said.

The historic size of the population on Monomoy, an ocean beach like Sandy Hook, offered the opportunity to establish a new population of the species within its historic range.

“Monomoy is one of the last vestiges of the way our coast used to look,” said Matthew Hillman, manager of the Monomoy National Wildlife Refuge. “That's why it's a hot spot for everything from plovers to seals to beetles. It's a small piece of land but has an outsized role in preserving these species.”

Adult tiger beetles are about a half an inch long with a bronze-green head and thorax, with white or tan forewings sometimes covered with gray-green lines. The beetles go through three larval stages, spending the one- to two-year period in vertical burrows in the sand. During this stage they are ambush predators, Gwiazdowski said, snatching prey as it passes their burrow.

“They have some of the fastest response time of any inspect,” he said.

Mature adults emerge in June and July and scavenge on dead fish, crabs and insects. The beetles mate and lay eggs from late June to August; the females are believed to lay eggs at night in shallow burrows in the mid to high tide zone, according to a Fish and Wildlife Service fact sheet. Not much is known about the mating process, Gwiazdowski said. The jaws of the male fit into grooves on the female thorax, he said, “and he hangs on. If she can toss him off, then he's weak and they won't mate.”

Beach raking that occurs in many areas robs the beetle of the prey that live within the tangle of vegetation, Gwiazdowski said. Carcass of birds, seals and other sea life often found on undisturbed beaches are a rich source of food for the tiger beetle.

“You can draw a straight line from a dead seal to more tiger beetles,” he said.

The recent collection on Monomoy was supposed to involve 15 people, with the goal of gathering 150 tiger beetle larvae. But the COVID-19 emergency cut the number of people involved to four; nonetheless, they collected 196 larvae, an indication of the robust population.

Resources for monitoring the Sandy Hook population are limited, Gwiazdowski said.

“We know exactly how many we put out, so as we start to observe adults, if we see a comparable number, we know most of them survived,” he said. The next step will be determining the mating success of the surviving beetles.

“We're just gong to try and see how it works,” said Gwiazdowski. “If it doesn't work well, we'll have a number of conversations and try to understand why. Was it the translocation or the ecology?”