expand_less Whenever you bite someone, you can attempt to grab and hold onto them with your bite.  If you succeed, next turn you can then attempt to swallow them whole.
Grab:
If a creature with this special attack hits with the indicated attack (usually a claw or bite attack), it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity. Unless otherwise noted, grab can only be used against targets of a size equal to or smaller than the creature with this ability. If the creature can use grab on creatures of other sizes, it is noted in the creature’s Special Attacks line. The creature has the option to conduct the grapple normally, or simply use the part of its body it used in the grab to hold the opponent. If it chooses to do the latter, it takes a –20 penalty on its CMB check to make and maintain the grapple, but does not gain the grappled condition itself. A successful hold does not deal any extra damage unless the creature also has the constrict special attack. If the creature does not constrict, each successful grapple check it makes during successive rounds automatically deals the damage indicated for the attack that established the hold. Otherwise, it deals constriction damage as well (the amount is given in the creature’s descriptive text).
Creatures with the grab special attack receive a +4 bonus on combat maneuver checks made to start and maintain a grapple.
 
Swallow Whole:
If a creature with this special attack begins its turn with an opponent grappled in its mouth (see Grab), it can attempt a new combat maneuver check (as though attempting to pin the opponent). If it succeeds, it swallows its prey, and the opponent takes bite damage. Unless otherwise noted, the opponent can be up to one size category Smaller than the swallowing creature. Being swallowed causes a creature to take damage each round. The amount and type of damage varies and is given in the creature’s statistics. A swallowed creature keeps the grappled condition, while the creature that did the swallowing does not. A swallowed creature can try to cut its way free with any light slashing or piercing weapon (the amount of cutting damage required to get free is equal to 1/10 the creature’s total hit points), or it can just try to escape the grapple. The Armor Class of the interior of a creature that swallows whole is normally 10 + 1/2 its natural armor bonus, with no modifiers for size or Dexterity. If a swallowed creature cuts its way out, the swallowing creature cannot use swallow whole again until the damage is healed. If the swallowed creature escapes the grapple, success puts it back in the attacker’s mouth, where it may be bitten or swallowed again.
 
Infectious Maw:
At 4th level, a famine spirit gains the swallow whole ability with his bite attack. Creatures he has swallowed take 1d6 acid damage per round + 1 per class level. Creatures who have suffered this damage come under the effects of a curse with a caster level equal to the famine spirit’s class level that urges them to consume flesh; similar to starvation damage, this damage cannot be recovered until 24 hours have passed or the target spends a full-round action consuming the corpse of a creature with Intelligence 3 or higher - until then, not even magic that restores hit points heals this damage.
He may use his class level as his base attack bonus for the purpose of grapple and swallow whole CMB and CMD checks; this stacks with base attack bonus gained from other sources as normal. He can swallow creatures up to his size category.