Prior versions of this ability required the druid to be in either [bear] or [cat form]. This is no longer the case.
Patch 6.0.2 (14-October-2014): Survival Instincts is now available only to Feral and Guardian Druids.; Survival Instincts no longer requires or forces the Druid into Cat or Bear Form, and now lasts 6 seconds (down from 12 seconds) with a 2-minute cooldown (down from 3 minutes), and can have up to 2 charges (up from 1 charge).
/Patch 4.0.1 (12-Oct-2010): Cooldown increased to 5 minutes, up from 3 minutes. Duration decreased to 12 seconds, down from 20 seconds. Now, instead of adding to health, this ability now grants 60% damage reduction for it's duration.
Patch 3.1.0 (14-Apr-2009): Cooldown reduced to 3 minutes, down from 5.
Patch 3.0.8 (2009-01-20): Now temporarily grants you 30% of your current maximum health for 20 sec. (Old - 30% of your maximum health). The extra health from this ability now persists in all forms, but the ability can only be activated in Cat Form, Bear Form, or Dire Bear Form. This prevents the health gain from occurring multiple times if constantly shapeshifting.
Patch 3.0.3 (04-Nov-2008): Survival Instincts will no longer be on the Global Cooldown.