Melynx

From Monster Hunter - Wiki on Neoseeker

The Melynx is known for stealing from millions of hunters. They enjoy Felvine and will take that instead of your items if you have it in your inventory. If you get an item stolen, don't worry! Attacking them and successfully scaring them off will cause them to drop the item, giving it back to you. On occasion, when the burrow underground, they may drop an item. A sparkling sphere will show up, gather it! It may be a rare item. If you do not retrieve your item in time, they will take it back to their camp. These camps are usually located in the smallest area of the map, or the one that it safest. Make your way to the camp and search the large pile of barrels, swords and other items to retrieve your lost item. These cats are related to Felynes, a lighter colored type of cat.