Peanut The Squirrel's Owners Pursuing Legal Action Over Viral Controversy

The owners of Peanut the squirrel are still in an emotional whirlwind after their beloved social media star was seized and euthanized by authorities in New York ... and now they're readying to fight back, TMZ is told.

Mark Longo and his wife, Daniela, tell us they are already in the process of legal action ... but they cannot give too many more details at this point. But ML makes it crystal clear ... "Peanut did not die in vain!"

Their story went national after they accused the state of abusing power and wasting taxpayer funds to seize and kill Peanut -- all because of some anonymous claims ... which ML says were all total BS.

Since that time ... the couple has been inundated with messages on social media -- people sharing their sorrow over the news, and their anger over the allegations.

Mark tells us his heart is broken ... but also full of warmth over the outpouring of support from strangers all over the country, which he believes will help get the answers he is demanding of county and state officials.

Mark previously told TMZ ... officials from the New York State Department of Environmental Conservation showed up at his doorstep Wednesday with a search warrant signed by 4 state agencies and a judge.

Peanut and one of the couple's pet raccoons were taken away ... both have since been euthanized as a result of rabies testing.

Peanut happily lived with him for 7 years, spreading joy on the internet with funny and wholesome videos, becoming his best friend in the process, he told us.