Rastreo

Rastreo (芳ばしい (ラストレオ), Rasutoreo; Spanish for "Tracking", Japanese for "Savoury") is an ability exclusive to, and who use Hollow powers.

Usage
Rastreo is the innate ability that all Hollows possess, allowing them to "sense" the spiritual pressure of another target. It is more rudimentary than either the used by 's, or the standard spiritual pressure sensing ability used by the majority of spirit beings and Psysis. To a Hollow, their existence is one of constant hunger; much like how an animal lives, a Hollow spends its time in search of prey almost constantly. Because of this, they are equipped with the ability to detect the scent of a target's soul. Rather than sensing directly the strength one's spiritual pressure, to a Hollow, each and every soul has a scent. The larger and more robust a target's collection of spiritual energy, the more delicious and appetizing that particular soul smells to a Hollow. The souls of Shinigami, such as, or with an unnaturally large amount of spiritual energy, such as the  , smell especially succulent.

Differing species have differing scents as well; the scent of a Hollow usually repulses that of another Hollow, as they are not driven to eat each other except in the rare occasion a is formed. The scent of a human is close to, yet distinct enough from a Shinigami that a Hollow with even mild self-awareness can tell the difference, though the scent of a Quincy is identical to that of a human. Much like unique spiritual signatures, individuals possess scents unique to themselves, even among their species; as such, a skilled user of Rastreo can find someone based on the unique scent of their soul.

Naturally formed Arrancar utilise this method of spiritual sensing; the Pesquisa that Arrancar are typically shown with is a method developed by Aizen's Arrancar army. Shinigami who wield Hollow powers unlock this ability naturally, though it is not one frequently simply due to a Shinigami's training; they will instinctively use their superior method of detecting the spiritual pressure of another over tracking the scent of a soul. Furthermore, for an inexperienced Shinigami, new to Hollow powers, it can cause them to run wild, rampaging in their Hollow form until they become a beast of pure destruction that will have to be dealt with as a Hollow.