Feral Slimes are a special kind of largo that is hostile towards Beatrix.
Feral slimes are largos with a mean streak that will attack a rancher on sight. It's not known what exactly causes a largo to become so grumpy that it goes feral, but it's suspected that they've simply gone too long without a bite to eat. Like so many things with slimes, food is everything.
If a feral slime eats, it will revert to a normal largo.
Feral slimes can pose a serious risk to ranchers if they're not dealt with quickly, or avoided altogether. Feral slimes will attempt to bite ranchers at close range or jump in the air and try to stomp them with their... butts? In any case, a rancher needs to act fast and feed the feral slime something tasty to avoid such troubles.
Feeding a feral slime not only calms it down, but also produces plorts in the same manner as a largo. Though, there are certainly easier ways out there to acquire plorts!
- Pink Rocks - In the canyon that leads to the Sandy Area and in a path behind a Slime door that leads to the area with the Mosaic Slime statue puzzle in the Glass Desert. (Replaces the Boom Rock Largos during the day)
- Also spawn in the Dry Reef - Ring Island Vault.
- Boom Rocks - In a path behind a Slime door that leads to the area with the Mosaic Slime statue puzzle in the Glass Desert. (Replaces the Pink Rock Largos at night)
- Pink Phosphors - On the island between the Dry Reef and the Moss Blanket (only at night) next to the first Tabby Gordo, and in the cave that leads to the Indigo Quarry (all times of day).
- Pink Booms - In a ravine on the way to another section of the Moss Blanket with flowers.
- Pink Rads - In the area with cliffs after the broken bridge in the Indigo Quarry. (Replaces the Boom Rad Largos during the day)
- Boom Rads - In the area with cliffs after the broken bridge in the Indigo Quarry. (Replaces the Pink Rad Largos during the night)
- Rock Tabbies - In the area accessed by going through little islands near the Grotto's teleporter that has a blue Treasure Pod. (?)
- Honey Hunters - In the Feral Path. (Replaces the Boom Hunter Largos during the day)
- Boom Hunters - In the Feral Path. (Replaces the Honey Hunter Largos during the night)
- Hunter Largos - Possibly anywhere in the Moss Blanket, due to the hunter's trait that when a hunter slime eats other slime's plort, or when other slimes eat a hunter slime's plort, the slime in question becomes feral.
- Saber Largos - Found everywhere in The Wilds.
- Feral slimes are easily recognisable from the flashing red sparks, the shadows on their faces, and grumpy face and red eyes.
- All naturally occurring feral largos can eat Meat. So if you're adventuring, try to bring some Meat with you, in case of a Feral Slime.
- On Adventure Mode, Feral Slimes also have an Area of Effect buttstomp attack; if you see a feral jumping in the air, it's preparing to whomp you! They also make a distinct sound when launching.
- The Pulse Wave upgrade is effective on largos; if in doubt, try to shoot them into The Slime Sea.
- As a last resort, you can feed a feral slime a plort it doesn't produce to cause a Tarr outbreak; since a horde of Tarr can be dispatched with Water or Ancient Water, which makes them easier to deal with feral slimes.
- Feral Slimes are said to be the result of Largo Slimes being grumpy due to going a long period of time without food. However the only largo that can naturally revert to a feral state when agitated are Hunter Largos. They used to do this before 0.2.0, but this was removed from the game since it didn't feel right. 
- Currently the only slimes that have no naturally-occuring feral counterpart are the Crystal, Quantum, Mosaic, Tangle and Dervish Slimes.
- 1.1.0 - The Wilds are added, and all slimes that spawn are Saber Largos which all spawn feral.
- 0.6.0 - More Pink Rock and Boom Rock Ferals have been added.
- 0.5.0 - A Hunter Largo can now revert to a feral state if sufficiently agitated.
- 0.4.0 - Rock, Tabby, Boom, Hunter and Honey Hunter Ferals have been added. Also, now only the Crystal and Quantum Slimes have no feral counterparts (not counting the hunter largos).
- 0.3.5 - Now a Hunter Feral can be made by creating a Hunter Largo; Feral Slimes will stay feral after reloading the game.
- 0.3.3 - They no longer produce normal slime sounds.
- 0.3.2 - Slimepedia Entry added.
- 0.3.1 - Grumpier, angrier redesign with addition of a stomp attack; They no longer follow you after being calmed.
- 0.3.0 - More Feral Slimes were added into the game.
- Before 0.2.0 - Implemented.
- ↑ http://forums.monomipark.com/viewtopic.php?f=3&t=2735&p=23566 - A Monomi Park dev states this.