California wildlife biologists have caught two rare Sierra Nevada red foxes in three weeks, a feat they say is a “huge” step to understanding the animal listed as threatened in the state in 1980.

A nearly 9-pound (4-kilogram) female walked into a trap this week near Manzanita Lake in Lassen Volcanic National Park. A 10-pound (4-kilogram) male was captured Feb. 13 just outside the park, the Sacramento Bee reported Thursday.

Scientists in 2018 intensified their study of the animal, but had not been able to capture a red fox until now.

“This is huge,” said Jennifer Carlson, an environmental scientist with the California Department of Fish and Wildlife.

Biologists took blood samples and put tracking collars on the animals before returning them to the wild.

Electronic tracking will allow biologists to know more about the size of the elusive red fox’s home range and hopefully learn more about den sites and reproductive rates.

“We know so little about this animal, and we have never found a den — ever,” Carlson said.

Carlson estimated there are around 20 individuals in the Lassen group, likely too few to sustain a population under ideal conditions.

The Sierra Nevada red fox once roamed widely in the upper mountain sub-alpine zones of California’s Sierra Nevada and Cascade ranges, but its abundance and distribution has declined dramatically in the last century. In addition to the Lassen population, a group exists at Mt. Bachelor in central Oregon, experts say.

The Sierra Nevada red fox requires a specific high-elevation habitat that has been shrinking. Another threat to its future is in-breeding, Carlson said.

Scientists are collecting fox scat and hair samples to build a database that will help them understand the animals’ genetics and how the individual Lassen foxes are related.