Would bats, or other echolocation-based creatures be able to see in a storm?

Question

I came across a situation in my campaign where our druid used a Sleet Storm to obstruct the view of some bandit archers. As a summoner, I decided to send my eidolon in and start summoning Earth Elementals to enter the storm and bash the bandits to death, as Earth Elementals and my eidolon have tremorsense.

Our GM accepted this as reasonable, based on the tremorsense description.

However, our druid wanted to then summon dire bats, which have blindsense. According to the pathfinder definition, blindsense would work in a sleet storm, but we all know that bats use echolocation, and not "blindsense".

It doesn't make sense for Paizo to create a million types of "visions" and "senses" in their books (as every creature is slightly different), so should dire bats be able to see in a sleetstorm (knowing bats truly have echolocation, and not blindsense)?

Answer 1

Dire Bats have blindsense, not echolocation

The statblock for the Dire Bat lists only Blindsense, not echolocation.

When playing a game like pathfinder, you have to make some allowances for the system to work. Stats, turns, and actions are a simplification (with sometimes ridiculous implications) of real-word scenarios.

Thus, when it comes to creatures (especially in combat, which can already drag on) it's best to trust the stat block implicitly. This serves a few purposes

1. It saves non-experts from having to do research: If the GM isn't an expert on bats, then all he needs to do is know the keywords used on the stat block and he's good to go. Something like a bat is one thing (most people are aware of echolocation at this point), but when it comes to Green Slime knowing whether the creature is completely immobile or not is obscure trivia, and could start a table argument. For the purposes of combat, it's best to trust the statblock and agree that the slime isn't going anywhere, and the bat can see in any condition.

2. It could affect balance: Sometimes stats don't make a ton of sense. Why does damage for some weapons change between some editions of D&D, but not other weapons? Did steel get less sharp and more pointy? Rather than explore minutiae it's generally best to trust the designers of the system that they made things the way they are. If you start worrying about how rain, snow, sleet, dust, and fog affect echolocating creatures different you could wind up inadvertantly making bats weaker than intended (after all, there are a lot of ways to conjure up some of those things, and some aren't even magical).

Besides...

In the real world we're not really sure if storms mess with echolocation in the first place

We know that bats don't like to be out in the rain, but we're not entirely sure why. There's been some research done, but due to limitations in the equipment used they were unable to test echolocation hypotheses. The researchers did determine that the caloric cost of flying as a wet bat vs a dry one was around twice as high, which would be a serious factor, but aside from wind-levels pathfinder doesn't try to address adverse weather conditions much in Flight, and certainly doesn't model the difference between how rain affects a Duck and a Bat very well.

Answer 2

To answer your question: Yes, they should. But let me explain a bit more on this topic.

The only reference to echolocation is this spell. Which has more exceptions than rules that we can use as backup. The spell cannot be used as reference as how dire bats percieve their enemies.

Strong winds and storms do affect blindsense if the creature's entry says they use that sense. What sense each creature's use is left to GM's discretion, but Blindsense clearly says:

Blindsense (Ex)

Using nonvisual senses, such as acute smell or hearing, a creature with blindsense notices things it cannot see. The creature usually does not need to make Perception checks to pinpoint the location of a creature within range of its blindsense ability, provided that it has line of effect to that creature. Any opponent the creature cannot see still has total concealment against the creature with blindsense, and the creature still has the normal miss chance when attacking foes that have concealment. Visibility still affects the movement of a creature with blindsense. A creature with blindsense is still denied its Dexterity bonus to Armor Class against attacks from creatures it cannot see.

Format: blindsense 60 ft.; Location: Senses.

Note how it says usually doesn't need to make Perception checks, that means it doesn't need to make checks just as a regular person doesn't need to see someone 30 feet away in front of them. But if something does affect their perception, specially regarding the sense which they use to see enemies, they should require perception checks if the GM decides it is obstructing their perception in some way or another.

Notice how most weather effects do cause some penalty to perception checks, while Windstorms and Hurricanes are particularly harsher:

Strong Wind: Such gusts impose a –2 penalty on ranged attack rolls and on Perception checks.

Severe Wind: Perception checks are at a –4 penalty.

Windstorm: Perception checks that rely on sound are at a –8 penalty due to the howling of the wind.

Hurricane-Force Wind: Perception checks based on sound are impossible: all characters can hear is the roaring of the wind.

However, Sleetstorm is not an actual storm. Spells do what their description says they do, followed by their spell school, followed by the general rules for spells on the Magic chapter, followed by the remaining rules of the game.

Pathfinder is an exception-based ruleset, meaning that specific overrides general rules. Okay, lets read what Sleetstorm does:

Driving sleet blocks all sight (even darkvision) within it and causes the ground in the area to be icy. A creature can walk within or through the area of sleet at half normal speed with a DC 10 Acrobatics check. Failure means it can't move in that round, while failure by 5 or more means it falls (see the Acrobatics skill for details).

The sleet extinguishes torches and small fires.

Okay, so the spell blocks all sight, but it says nothing about hearing or smells, thus those senses are completely ignored by the spell, they will work as if nothing was actually happening on the area of effect.

About real-world bats, keep in mind that the ruleset cannot emulate every creature sense we have in the real world, or we would have creatures that can see 17 million colors or that can smell the proteins on their preys, or even see ultraviolet or ultrared wave lengths. And we would need to memorize all those rules.

Instead, it tries to create a few rules that can cover a lot of those non-human senses, in a way that we can easily memorize, or reference, what the creature can actually sense (darkvision, blindsight, blindsense, tremorsense, etc).

Note, aswell, that dire-bats do not exist in our world, so they could have laser beams instead of claw attacks and they would still be a valid fantasy creature. Albeit scarier.