Large herd of nutria recently trapped in Mendota wildlife area

The state has spent the past five years tracking a destructive pest to California agriculture.

The nutria is a big rodent that thrives in wetlands and wildlife areas.

Recently a big herd of nutria was detected in Fresno County.

The Mendota wildlife area is roughly 50 miles west of Fresno. Scientists knew there were nutria in the water but the amount they've trapped so far surprised them.

Nutria were first detected in Central California in 2017. They feed on vegetation and crops. The big rodent can also destroy the banks of ditches, lakes, and other bodies of water.

Greg Gerstenberg has led the nutria eradication project for State Fish and Wildlife since its beginning.

"We went down at the end of summer and worked Mendota wildlife area and pulled about 220 out of there over about a four-week period."

More trapping will take place early next year in the waterways south of Mendota. Gerstenberg says the site is under control.

"Mendota, the Fresno slough and Mendota wildlife area are surrounded by mostly ag ground so we can get those and they're not gonna go anywhere."

In the past five years, Gerstenberg's team of 30 has trapped and euthanized 3,380 nutria. The main focus has been on the wetlands north of Los Banos.

Its mission has been to keep nutria out of the San Joaquin Delta. "We have detected nutria in the Delta up on Sherman Islands, so that's not good news. That's quite a ways further north than our previous detection. There are more wetlands and difficulty in finding nutria in the Delta than an isolated wetlands."

The biggest stumbling block for the team is getting permission to trap on private property. It can take months to track down property owners who live out of the area.

"You can clean five miles of river and if you have one parcel that has a pond on it and you don't have access to it they can just keep coming and re-infect that area where you've worked."

Nutria can reproduce in a little over four months. While most have been removed from Merced County Gerstenberg says full eradication is still years away.

According to State Fish and Wildlife, nutria were brought to California for the fur trade in 1899 but it never caught on. The state believed the animal was eradicated in the 1970s.

One final note, Greg Gerstenberg is retiring Friday after 35 years with State Fish and Wildlife.