Stalker: Call of Pripyat → Quests → Anomaly Research
Apparently, the devices that measure anomalous activity have a negative effect on the mutants; they suddenly become very angry when they sense these devices. And they become dumb. We've been tasked (by scientists, of course, who else?) to install a specially tuned device in the very center of the "Bitumen" anomaly (remember, there are quite a few "Zharoks" there) and wait for it to measure the results.
During the experiment, hordes of snorks will be swarming us, and any careless step risks falling into the anomaly. However, this can be used to our advantage by positioning ourselves relative to the snorks so that their jumping trajectory runs right through the anomalies. This greatly simplifies the task.
Source: gamer.ru
See also:
Ocean biom is Terraria
Fallout Tactics: Osceola
Phosphorus. Three Different Species