The Mimics have a really cool ability: they can manipulate time and reset a time loop to their own satisfaction.
Both have killed an Alpha and ingested their blood, which gives them the same time looping skills as a Mimic.
In fact, it really is in their blood, as both Cage and Vrataski find out the hard way.
There are two components to the Mimic’s looping strategy: the Omega, the hive mind that coordinates all of the Mimic grunts, and the Alpha, specialized Mimics connected to the Omega.