You mean forerunner are crocodiles? Nah.
Sentience refers to utilization of sensory organs, the ability to feel or perceive subjectively, not necessarily including the faculty of self-awareness. The possession of sapience is not a necessity. The word sentient is often confused with the word sapient, which can connote knowledge, consciousness, or apperception. The root of the confusion is that the word conscious has a number of different usages in English. The two words can be distinguished by looking at their Latin roots: sentire, "to feel"; and sapere, "to know".
All things which can feel can be killed by halo, thus, they are flood hosts. Flood elephant or crocodile? wow.