Saving the Puritan tiger beetle in Connecticut
Today we’re sharing a story about the Puritan tiger beetle by biologist Laura Saucier of the Connecticut Department of Energy and Environmental Protection, originally published in the Connecticut Wildlife Magazine. Just this year our agencies have worked together with several partners to start rearing these threatened beetles in captivity.
Tiger beetles are a fascinating group of animals. There are over 100 different species of tiger beetles in North America and over 2,000 species worldwide. In their adult form, tiger beetles are hunters that chase down prey with their long legs, much like the cheetahs of the plains of Africa. They have impressive mandibles (jaws) for their small size. Tiger beetles are often the top invertebrate predator in the open habitats where they occur.
Fifteen species of tiger beetles occur in Connecticut; eight are on Connecticut’s Endangered, Threatened and Special Concern Species list due to perceived declines in their populations or habitats.
The Puritan tiger beetle (Cicindela puritana) occurs on sandy beaches in New England along the Connecticut River and in the Chesapeake Bay region of Maryland. Historically, C. puritana was documented at 11 distinct areas along the Connecticut River from New Hampshire to Connecticut, generally on beaches where large river bends result in regular deposition of sediments. Unfortunately, human-caused changes to the flow of the Connecticut River and surrounding land uses resulted in the extirpation (elimination) of Puritan tiger beetles from nine of those 11 sites by the early 1900s. Today, the New England population is comprised of the only two remaining sites in Hadley, Massachusetts, and Cromwell, Connecticut. The now small New England population is estimated to have just over 500 individuals. C. puritana also is struggling in the Chesapeake Bay region, but populations are more robust (over 1,000 individuals) and spread out over more sites.
In August 1990, the U.S. Fish and Wildlife Service included the Puritan tiger beetle for protection under the federal Endangered Species Act as a threatened species. Connecticut included the beetle under our state Endangered Species Act, listing the species as endangered in 1992. The reasons cited for listing C. puritana are: 1) within New England, only two populations remain within the former range on the Connecticut River, and 2) the Chesapeake Bay populations are under great threat due to human-caused habitat alteration.
In New England, the decline of C. puritana is primarily the result of 17 dams built on the Connecticut River above Hartford for flood control and hydroelectric power. The beetle has evolved to live in a dynamic habitat, relying on natural river processes to deposit and erode sediments, keeping areas of shoreline sandy and relatively free of vegetation. Hydropower dams especially affect suitable habitat because they artificially maintain steady flows, and the river no longer experiences periods of high flooding or natural periods of low flow. In addition to damming, shoreline stabilization (building retaining walls along the shoreline, adding rip-rap to the river bank, etc.) and recreational activities, such as extended camping on these beaches and excessive wakes created by jet-skis and speed boats, have also been cited as exacerbating stressors.
A close look at the life cycle of C. puritana reveals why they are so sensitive to changes in the hydrology of the river. From July to August, larvae hatch from eggs buried in shallow sand and excavate vertical burrows a few inches deep in sand located somewhere between the high-tide line and sparse vegetation near the crest of the riverbank. The larvae feed by anchoring themselves in their burrow with specialized abdominal hooks and waiting for prey to pass by the burrow. The larvae will grab the prey when it walks by, pulling it into the burrow. After two to four weeks, the larvae molt from their first instar to the second instar stage and deepen their burrows up to two feet down. In October, they close their burrows for an overwintering period that lasts until April. The larvae emerge in April-May and feed for a couple of months before closing the burrows again until September when they molt into the third and final larval stage. In fall, they again close their burrows to overwinter until the next spring and, in late June, adult tiger beetles emerge from their pupal burrows to feed and mate. As an adult, C. puritana is an aggressive predator, often hunting down insects and other invertebrates with surprising speed and agility. By mid-August, two years after hatching from the egg-stage, the adults begin to die off.
For the past two years, the Wildlife Division has been working with the U.S. Fish and Wildlife Service Northeast Region, Silvio O. Conte National Wildlife Refuge, tiger beetle experts, and academia to initiate recovery objectives in the Puritan Tiger Beetle Recovery Plan. Specifically, funding was secured to 1) reintroduce Puritan tiger beetles to sites within their historic range in Connecticut, and 2) initiate a captive rearing pilot program to determine if captive rearing is a viable tool for conserving this species.
This field season, third instar larvae were dug up and transplanted to two state-owned properties along the Connecticut River. The larvae were placed and monitored by tiger beetle experts to determine what percentage of the transplanted beetle larvae pupated into adults. Because this beetle requires two years to reach maturity, it will not be known until 2018 if these first transplants successfully mated and laid eggs. Researchers will dig and transplant larvae in 2017 to establish a second cohort at these same sites that will not mature until 2019. If funding is available, a second wave of transplants will be conducted beyond 2018.
Also this field season, adult beetles of both sexes were captured and brought to Richard Cronin Aquatic Resource Center located in Sunderland, Massachusetts, where a laboratory has been created to rear and house these beetles. The captured individuals will be studied by tiger beetle experts and academics to try to answer some questions, such as details of larval development, habitat preferences for egg deposition, how many eggs each female lays, adult parasite loads, and more. Given the rarity of this insect, there is so much we still do not know. Efforts will shed some much needed light on the needs of this beetle, ultimately adding to our knowledge of tiger beetle biology and rare species conservation.
Yearning to know more about the Puritan tiger beetle? Check out this post from earlier in the fall.