If you're hunting one particular type of mob only, "custom" works great too.
Custom Filter:
/mapfilter custom "whatever you want shown"
Turn off custom filter:
/mapfilter custom
For example if you're in Stoneroot hunting all types of witherans, and you dont want anything else to show up on your map, do: /mapfilter custom witheran and it will display all "a witheran" and "a witheran feeder" etc etc...
Note that the custom setting overrides the other settings, so while its on, you wont see anything else that you have turned on, like PCs.