Eidolon Swallow Whole Evolution

Question

I am currently working on building a level 20 Summoner NPC. He has a quadruped eidolon roughly based around the idea of a Cerberus-like three headed bear.

At current build, the eidolon has 36 evolution points available in which I have spent them on

(evolution / times taken / evolution cost)

1. Head/2x/4ep
2. Bite/2x/2ep
3. Bite 1.5/3x/3ep
4. Claws/1x/1ep
5. Improved Damage/1x/1ep (bite)
6. Pounce/1x/1ep
7. Rend/1x/2ep
8. Swallow Whole/1x/3ep
9. Breath Weapon/1x/4ep (cone acid)
10. Large/1x/4ep
11. Huge/1x/6ep
12. Grab/1x/2ep
13. Reach/1x/1ep (bite)
14. Poison/1x/2ep (bite)

The feats I gave him are as follows

1. Cleave
2. Combat Reflexes
3. Hammer the Gap
4. Intimidating Prowess
5. Lunge
6. Power Attack
7. Snatch
8. Noxious Bite

As I understand to use swallow whole I have to have Grab to use Swallow Whole

Grab (Ex)

Source: PRG: APG

An eidolon becomes adept at grappling foes, gaining the grab ability. Pick bite, claw, pincers, slam, tail slap, or tentacle attacks. Whenever the eidolon makes a successful attack of the selected type, it can attempt a free combat maneuver check. If successful, the eidolon grapples the target. This ability only works on creatures of a size one category smaller than the eidolon or smaller. Eidolons with this evolution receive a +4 bonus on CMB checks made to grapple.

Swallow Whole (Ex)

Source: PRG: APG

An eidolon gains the swallow whole ability, giving it the ability to consume its foes. If the eidolon begins its turn with a creature grappled using its bite attack (see the grab evolution), it can attempt a combat maneuver check to swallow the creature. The creature can be up to one size category smaller than the eidolon. Swallowed creatures take damage equal to the eidolon’s bite damage each round plus 1d6 points of bludgeoning damage. A swallowed creature keeps the grappled condition but can attempt to cut its way free with a light slashing or piercing weapon. The amount of damage needed to cut free is equal to 1/10 the eidolon’s total hit points. The eidolon’s AC against these attacks is equal to 10 + 1/2 its natural armor bonus. If a swallowed creature cuts its way out, the eidolon loses this ability until it heals this damage. Alternatively, the swallowed creature can attempt to escape the grapple as normal. Success indicates that it has returned to the eidolon’s mouth, where it can attempt to escape or be swallowed again. The eidolon must possess the grab evolution, tied to a bite attack, to take this evolution. The summoner must be at least 9th level before selecting this evolution.

But after looking at everything I'm curious if Snatch negates the need for grab which in turn frees up two evolutions points for something else such as Trample or Wings?

Snatch

Pathfinder RPG Bestiary

This creature can grab other creatures with ease.

Prerequisite: Size Huge or larger.

Benefits: The creature can start a grapple when it hits with a claw or bite attack, as though it had the grab ability. If it grapples a creature three or more sizes smaller, it squeezes each round for automatic bite or claw damage with a successful grapple check. A snatched opponent held in the creature’s mouth is not allowed a Reflex save against the creature’s breath weapon, if it has one.

The creature can drop a creature it has snatched as a free action or use a standard action to fling it aside. A flung creature travels 1d6 × 10 feet, and takes 1d6 points of damage per 10 feet traveled. If the creature flings a snatched opponent while flying, the opponent takes this amount or falling damage, whichever is greater.

Answer 1

No, Snatch does not negate the need for the Grab evolution.

There are three components at play here.

1. The functional capability of automatically initiating a grapple on hit
2. The "grab" special attack, which grants that capability
3. The Grab evolution, which grants the grab special attack

So #3 gives you #2, and #2 gives you #1.

From the Snatch feat (emphasis mine):

The creature can start a grapple when it hits with a claw or bite attack, as though it had the grab ability.

So Snatch grants #1 from the list above, but not #2 or #3.

From the description of the Swallow Whole evolution (emphasis mine):

... The eidolon must possess the grab evolution, tied to a bite attack, to take this evolution. ...

So the Swallow Whole evolution requires #3 as prerequisite.

Snatch lets you grab without having the grab special attack. But the Swallow Whole evolution explicitly requires the Grab evolution, so you can't use Snatch to qualify for Swallow Whole.