Errata needed: Detect magic and supernatural abilities

The spell detect magic is terribly unclear when it comes to supernatural abilites.

Supernatural abilities are defined as "magical but not spell-like. Supernatural abilities are not subject to spell resistance and do not function in areas where magic is suppressed or negated (such as an antimagic field). A supernatural ability's effect cannot be dispelled and is not subject to counterspells."

This establishes that they are magic.

Detect magic has the line "If the items or creatures bearing the auras are in line of sight, you can make Knowledge (arcana) skill checks to determine the school of magic involved in each. (Make one check per aura: DC 15 + spell level, or 15 + 1/2 caster level for a nonspell effect.) If the aura eminates from a magic item, you can attempt to identify its properties (see Spellcraft)."

This established that the spell can detect magical nonspell effects. And what is a magical effect that is not a spell? A supernatural ability.

However, the rest of the spell only tells the Aura Strength and the Duration of a Lingering Aura for spells and items. Which can lead to the impression that it only works on the auras of spells or items and nothing else, if one gives the spell just a single read.

The spell description should at some point include the words "supernatural abilities" to finally and completely remove all ambiguity.
I think basing the aura strength on the HD of the creature would be a good solution. Like making the effective level of a supernatural ability equal to half the creatures HD.

What is a "magical aura", exactly?

Also a good question. ^^

The D&D FAQ actually adressed this very issue and says that supernatural abilities are detected and have a caster level equal to the HD of the creatures who used them. For aura strength and duration, the rows for magic items are to be used.

I assume that Paizo intended for the spell to work in PF the same way it works in D&D. So unless it's a design descision by them to change it, it would be the same for Pathfinder. Either way, it should be noted in the spells description.

I marked for FAQ. From a house-rule perspective, I assume that any Su or SLA registers on Detect Magic.

Magical Aura is something you emit and has different Strength levels

If you are say Cloaked in Invisibility

Someone turns on Detect Magic

1st Round: Presence or absence of magical auras.

2nd Round: Number of different magical auras and the power of the most potent aura.

3rd Round: The strength and location of each aura. If the items or creatures bearing the auras are in line of sight, you can make Knowledge (arcana) skill checks to determine the school of magic involved in each. (Make one check per aura: DC 15 + spell level, or 15 + 1/2 caster level for a nonspell effect.) If the aura emanates from a magic item, you can attempt to identify its properties (see Spellcraft).

Now here is the Kicker you can actually Track someone in Invisibility

Lingering Aura: A magical aura lingers after its original source dissipates (in the case of a spell) or is destroyed (in the case of a magic item). If detect magic is cast and directed at such a location, the spell indicates an aura strength of dim (even weaker than a faint aura). How long the aura lingers at this dim level depends on its original power:
Original Strength Duration of Lingering Aura
Faint 1d6 rounds
Moderate 1d6 minutes
Strong 1d6x10 minutes
Overwhelming 1d6 days

So depending on the str of the Magic involved will determine the aura

SLAs and SUs are treated as Spell casting they can be Canceled with Anti Magic Spells and Effects and for all Purposes they are using the Given Spell.

So with all this Information an SLA and an SU ability will leave an Aura... Using the Hit Dice of the Creature or given caster Level will determine the Potency of the Aura... If the ability is EX it will not leave an Aura

But this could mean that a creature will still glow with a dim illusion aura after the invisibility spell ends. It does not neccessarily mean that any magical aura leaves an afterimage in the air where it passed through.
But even if so, tracking someone this way who is trying to flee would be rather difficult. Every time you turn a corner, you have to concentrate for 3 rounds to pick up the trail, and it only stays for 1 to 6 rounds after the person passed through the space.

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Important to note here, that detecting a doppelgangers or succubusses "faint transmutation aura" does not make their change shape ability pointless. Which is one of the most common arguments people have against it.

They just have to avoid being scaned by ramaining inconspicious and avoiding places where random detect magic scans might happen, or they have to assume an identity that wouldn't make anyone suspicious for having a magic item.
An amulet of natural armor +1 or a cloak of elvenkind would result in the same magical aura as seen by anyone casting detect magic.

Also, since the effect is disrupted by an antimagic field, it means there has to be magical energy present to maintain the new form. It also reverses when the creature dies, so it's a "permanent" effect, not an "instantaneous" one.

This established that the spell can detect magical nonspell effects. And what is a magical effect that is not a spell? A supernatural ability.

Not necessarily. A magical non-spell effect could be a magic item. A +1 sword for example.

Detect Magic only detects functioning spells and magical items. Supernatural abilities, despite being magical, wouldn't detect with Detect Magic. If Detect Magic could do that, then it would say so on the table that shows the auras strength.

Jeraa
You are correct except for the SLAs and SUs that say Constant

Then you could track them at all times...

The only other Time they will be present is on use... Now the Use would fall under the rule for Lingering Aura unless you are present at the time it was used.