BALTIMORE, Md.— The Center for Biological Diversity today formally notified the Trump administration that it intends to sue the federal government for deciding not to protect American horseshoe crabs under the Endangered Species Act.

The Center and 25 other organizations petitioned the National Marine Fisheries Service in February 2024 to protect horseshoe crabs, who live along the Atlantic and Gulf coasts. They are threatened by overharvesting, including for the biomedical industry. But the Trump administration denied protections on Feb. 18.

“Horseshoe crabs have helped so many people and saved so many lives, but Trump officials seem to believe these incredible animals aren’t worth saving from extinction,” said Danny Waltz, a senior attorney at the Center. “The science shows that horseshoe crab populations have crashed, and they face growing threats from overharvesting and habitat loss. We can’t let reckless politicians keep these ancient and iconic creatures from getting the protections they so urgently need.”

Not a single plant or animal has been protected under the Endangered Species Act since Trump took office again in 2025.

Nearly twice as old as the dinosaurs, horseshoe crabs have been crawling ashore for more than 450 million years. They are brown, body-armored arthropods with 10 eyes and a long, spiked tail. Each spring horseshoe crabs lay their eggs on beaches in massive spawning events.

Horseshoe crab populations have plummeted by more than 70% in recent decades because of overharvesting and habitat loss. A growing threat comes from biomedical companies, which drain the blood of horseshoe crabs for drug safety testing — even though synthetic alternatives are available, approved and used widely in Europe and Asia. Biomedical harvests have doubled in the past seven years, with more than 1 million horseshoe crabs harvested in 2024.

Horseshoe crabs are also harvested for use as bait by the commercial whelk (edible carnivorous snails) and eel fisheries. Even though horseshoe crab populations have fallen to historic lows, fishing regulators have proposed increasing the amount of horseshoe crabs that can be harvested.

In addition, development and sea-level rise are threatening horseshoe crabs and their spawning beaches across their entire range from Maine to Louisiana.

In its negative finding on the Center’s petition, the Service ignored these threats and cherry-picked results from an inaccurate and fundamentally flawed data model that has been repeatedly challenged by the scientific community. It also failed to consider studies that show dangerously low and declining levels of horseshoe crabs across most of their range.

The International Union for Conservation of Nature’s horseshoe crab specialist group has determined that the species will go extinct this century without significant conservation action.

As horseshoe crabs have declined, so have other species like endangered sea turtles, fish and birds. The red knot, a shorebird species that feeds on horseshoe crab eggs during their 19,000-mile migration from South America to the Arctic and back, was listed as threatened under the Endangered Species Act in 2015. That listing decision cited horseshoe crab overharvesting as one of the contributing factors to the red knot’s decline.

“Horseshoe crabs watched the dinosaurs come and go, but now they face their greatest threat yet: us,” said Waltz. “Fortunately, we also have the power to save horseshoe crabs by protecting them under the Endangered Species Act.”