Saru is a sensible extraterrestrial creature in the “Star Trek: Discovery” (Star Trek) series, a representative of Kelpiens, the race of aliens, who have a strong sense of self-preservation (Saru feels danger at a subconscious level), due to the fact that they have been hunted for centuries.
According to his words: "We were hunted and kept in cages like animals."
This innate ability is both a positive and negative feature at the same time, because at a difficult moment an alien starts taking decisions based on his inner fears without logic and common sense.
Saru's career developed well: at the moment, he is a Starfleet officer (state organization). He served aboard the USS Shenzhou as a lieutenant until the ship was destroyed by the Klingons. In six months he was appointed the first officer for the USS Discovery (the most important space ship for the Starfleet), whose captain is illustrious Gabriel Lorca.
The role of Saru in "Star Trek: Discovery" was masterfully performed by Doug Jones.