The full barrel shroud should be quiet enough on a Marauder.
I built a custom suppressor for my BSA Lonestar, but the biggest benefit was a slight accuracy improvement.
Prairie dogs don't seem to mind if I use a suppressor or not. The most important thing is to keep the pellet subsonic and quiet. Field Target Trophy pellets are loud and inaccurate. Animals pay more attention to ballistic crack than muzzle blast.
Shooting in town without arousing the neighbors is the main reason to have a suppressor, but the .25 cal air rifle as powerful as a Marauder isn't an "in town" air rifle anyway.
Shrouds and suppressors hold in moisture and can rust your barrel if you don't do the right things after a shooting session. I'd rather have the BSA muzzle break than the suppressor they make. The Marauder gives you no option as the suppressor is a permanent attachment. My "in town" air rifle is my old Sheridan Blue Streak, as I have variable power and enough power for very short range. Barrel rust is not an issue due to the brass barrel and there is no mandatory oiled patch through the barrel after firing and before storage to prevent barrel rust.
There is a very notoceable condensation blast from my BSA Lonestar when it fires, and I live in an arid state and have less moisture in my air cylinder than most people, so there is no way I would leave a suppressor full of moisture attached after a shooting session. This is something that sours me on the Marauder a bit. All air rifles with permanent barrel shrouds should have stainless steel or hard brass barrels. Otherwise, pull an oiled patch through the barrel and store the rifle muzzle downward like all rifles with permanent suppressors should be stored.
I have seen air rifle suppressors that were rusted out, so you can imagine what the barrels must look like. I made my BSA suppressor from PVC, brass and stainless steel because of the moisture issues. The suppressor is stored in a plastic bag separate from the rifle when its in the rifle case.
FWIW, no suppressor is legal when in the hunting field in Montana, whether for firearm or air rifle and no matter if you are compliant with BATF or not (Under Montana law you can build your own suppressors for firearms, but the BATF says they supercede Montana law. Montana does not agree, and the issue has yet to be tested in court. Nobody in Montana will turn you in, and the BATF seems to not want to scout around at this point. They have no say regarding air rifles anyway, but game wardens do as it's a hunting regulation issue and not a firearms/air arms "right to own" issue.)
Technically, it is illegal to hunt in the field in Montana with a stock Benjamin Marauder, which is why I own a BSA Lonestar .25, among other reasons. To be legal, you will have to remove the barrel shroud if hunting in Montana, but I have yet to hear of anybody getting in trouble. Air rifles are still not taken seriously here .....except for some of the locals who have seen what my BSA Lonestar can do at ranges they thought were impossible for air rifles. A former hunting guide was in awe of my rifle. That also includes a couple of BLM rangers who happened across me on BLM land. They wouldn't care if your air rifle was suppressed or not, but they DO care if you drive a vehicle where you should not. They are serious about illegal vehicle access and land erosion.
Like I said, the prairie dogs seem to not care one way or the other, so the suppressor is dead weight and a liability.