The largest-ever reintroduction of an endangered tiger beetle happened quietly in the morning of October 19th, 2017, on a foggy beach in the Connecticut river. These beetles are the rare Puritan Tiger Beetle, Cicindela puritana , or “PTB” as tiger beetle experts call it. This species is listed as federally threatened and state endangered due to a century of human use that has changed the Connecticut River’s flow. This change has reduced desired habitat, and left only one viable population of PTBs in New England. This reintroduction of more than 700 laboratory-reared PTB larvae is only part of a multi-year, team-project to establish sustainable populations of PTB in the Connecticut River.
This project, which is supported by the Cooperative Recovery Initiative program and based at the Richard Cronin Aquatic Resource Center in partnership with Silvio O. Conte National Fish & Wildlife Refuge, unites a seasoned team of over 30 Federal & State wildlife officials, professional Biologists, Academic partners, students, and generous volunteers. Together, this group is pioneering methods to acquire land, captive-rear larvae, manage habitat, and use field-techniques to ensure the survival of PTB throughout one of the largest rivers in the Northeast.
To restore a healthy river ecosystem that includes these tiny apex predators, lab-reared PTB reintroductions are key to establishing new populations. To do this, the PTB team uses aerial “butterfly” nets to carefully collect adult beetles from the single source-population. The adult beetles mate and lay eggs in the lab, which hatch into larvae that grow progressively larger through 3 growth phases, called instars. In the wild, it takes about 2 years for PTB larvae to reach their third instar, but in the lab, this time can be reduced to just a few months.
The reintroduction sites were carefully selected by the PTB team. Finding good habitat requires expertise to determine sediment size, beach slope, and the abundance and diversity of prey that PTBs prefer. To be reintroduced, PTB larvae are transported to the site, each in their own small sand-filled vial, and released into plotted-areas on the beach where they immediately dig vertical tunnels in the sand to develop through their instar stages.
Over the next 2 years, the PTB team will revisit the reintroduction sites to count the number of PTB burrows and adult beetles, which will indicate the success and survival rate of the lab-reared PTBs.
Stay tuned for 2018 updates on the PTBs!