|“||Strangle can be used against adjacent humans unprotected by strangle-resistant armor, items, or abilities.||”|
– In-Game Description, XCOM: Enemy Within
Seekers, if cloaked can perform a Strangle attack that allows them to latch on (actually occupying the same tile as its target) and paralyze their prey while the damage mounts each turn; Strangle causes 2 initial Damage and 1 for every turn there after. A friendly unit that survives a Strangle attack (whether by dislodging or killing the Seeker) will suffer a turn "Catching Breath" (-75% Movement and -50% Aim). The Bioelectric Skin gene mod and the Sniper's Battle Scanner, and a Psionic using Telekinetic Field can all reveal stealthed Seekers thus preventing them from using their Strangle ability. The Respirator Implant, Chitin Plating and many of the advanced body armors confer immunity to strangulation.
In Multiplayer, Strangle will only work against human enemies, including EXALT, but doesn't require the Seeker to be stealthed to be used.