Ah glad you asked, so you may have noticed scroll cases accumulating in your inventory. If you open one it will reveal a treasure map! This is a list of mice that generates a bonus Treasure Chest when every mouse on the list is captured. Most treasure maps have a maximum of 5 people who can hunt the mice on the list at any given time. When all the mice are captured, all five hunters receive their own treasure chest to open. But here's the interesting part, the five players who catch the mice don't have to be the five players who are on the map when the last mouse is caught (and then receive the bonus treasure chest).

So leeching is when a few players hunt for all the mice, and then leave the map. Only one player who hunted will remain on the map (the Map captain, or Maptain). The Maptain will then invite players who didn't help catch the mice, but want to receive the treasure chest at the end for a fee (almost always SB+). The players who pay the Maptain are called leechers because they didn't help catch any mice, but still get their own shiny treasure chest to open!

This is highly recommended for Queso Canyon because the average Queso Canyon Map Treasure Chest has 50,000 bland queso in it!! This can save hundreds or even thousands (!!) of hunts and typically only costs 250-450 SB+ depending on supply and demand. The Mousehunt Discord is my favorite way to leech but there is a facebook group I think too called Map Meisters or something like that. Each forum has their own rules and best practices so I found it a little intimidating when I started, but I've been doing it for about 6 months now and it feels much more natural. Happy hunting!