Can a single casting of Dispel Magic dispel every creature conjured by a Conjure Animals spell?

Question

Yesterday in a game, my character cast Conjure Animals and summoned 8 wolves†. On the baddies' turn, one cleric was about to cast Dispel Magic, but the DM changed his mind, deciding that the 8 wolves could not be considered a single magical effect. Personally, I agree with this, but I'm wondering if that stands up to the rules:

Can a single casting of Dispel Magic dispel every conjured creature from one spell at once?

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† I'm aware of the debate over who picks the animals; my DM ruled that I could pick.

Answer 1

No, it only ends the spell on a single target

We can extrapolate an answer based on how dispel magic interacts with spells like bless:

From the Sage Advice Compendium:

If dispel magic targets the magical effect from bless cast by a cleric, does it remove the effect on all the targets? Dispel magic ends a spell on one target. It doesn’t end the same spell on other targets.

Since the conjure spells actually bring creatures into the Prime Material plane and in essence holds them there, a dispel magic will only end the magic on a single creature; the rest would still have the magic to keep them present.

Answer 2

No, dispel magic works on each creature independently.

Here is an excerpt from the Sage Advice Compendium:

[...] a spell like conjure woodland beings has a non-instantaneous duration, which means its creations can be ended by dispel magic and they temporarily disappear within an antimagic field.

Only the creatures summoned who happen in to an antimagic field disappear, not all 8 if you happen to target just one. I have to imagine this holds true for dispel magic as well, though the wording is open to interpretation. It would be pretty nasty if an increasingly powerful spell could just be rendered completely useless with a single casting of dispel magic.

Answer 3

I no longer agree with my answer but instead with the one presented above by Slagmoth, but leave it here for you to read and make your own decision:

My argument is that yes casting a Dispel Magic on one of the creatures ends the whole spell.

Conjure Animals:

3rd-level conjuration

You summon fey spirits that take the form of beasts and appear in unoccupied spaces that you can see within range.

Each beast is also considered fey, and it disappears when it drops to 0 hit points or when the spell ends.

Conjure animals is a 3rd level spell that summons a number of fey spirits in the form of beasts and when it ends all the animals disappear together. Therefore it is a single magical effect, no matter how far apart the animals get, or how far from the caster they get. For instance the spell ends when the caster loses concentration and all the animals disappear as one. It is a single magical effect. This is a key point.

Dispel magic:

Choose one creature, object, or magical effect within range. Any spell of 3rd level or lower on the target ends.

The key point is that, as with any spell, if any part of a target is in range of a Dispel Magic you can target it.

Therefore if you can cast a Dispel Magic on any one of the fey spirits that are there because of the conjuration spell, you have targeted the magical effect, the spell ends and all the creatures disappear as one.

Targeting the caster does not end the spell as they are not part of the magical effect nor do they have the spell "on" them, despite the need for their concentration.

Answer 4

After reading the previous answers and thinking about it from the perspective of the way magic works, as well as the wording of the spell, I believe that there are 2 possible ways of applying dispel magic in this case. If you target one of the summoned creatures, a creature who has been brought to this place by the magic of the spell, as it says, "Any spell of 3rd level or lower on the target ends." This means spell that is keeping the creature here ends. But the other creatures remain - you ended the spell on that one creature. However, if you target the caster with dispel magic you will dispel the entire spell as it is his concentration and magical energies that are the focus of the spell.