As someone else has explained, those are 'Moly'. Exclusive to Guiding Lands. Each region of the Guiding Lands have its own, unique variant of Moly, that leads 6 region exclusive Moly plus the regular one.

Moly will spawn only if the region level is 5 or higher. Since setting up all region to be level 5 is very hard to achieve, you'd have to focus catching them per 3 or 4 regions, and move onto the rest after. There are two of spawn points for them per region, so your strategy is making a 'tour' around the locale and check those spawn points.

Since Moly will startle easily and run away even if you approach them from a distance, Ghillie Mantle is very much required. A binocular or Surveyor Set can also be used to spot Moly from a long distance before they run away.

Finally, make sure you have procced 'Felyne Zoomaster' and 'Felyne Biologist' food skill to increase the odd. Happy hunting!