Is “hanging bats” a participial phrase, gerund phrase, or simple noun phrase?

Question

In the sentence "Hanging bats populate most of the caves in North America," what is the role of "hanging bats"? I believe it is a simple noun phrase containing the participle "hanging" (which modifies "bats"), while another individual referred to it as a gerund phrase.

I should mention that the quiz question is "What kind of phrase is underlined?"

Answer 1

Hanging bats is the subject. The question is which of those two words is the real subject.

We aren’t going to be out hanging bats like ornaments from a tree. If we were, then hanging would be the subject and bats the object of that hanging, and hanging therefore a gerund in the old grammar books. That would make hanging the real subject.

But it isn’t. It’s the bats themselves who are hanging from the ceilings of the the caves like so many furry stalactites. They are bats a-hangin’ — they are “bats pendant”, if you would. Therefore, hanging is here acting as an adjective, which makes it a participle in the old books. Bats is the real subject.

But it’s really just an -ing word in both cases, and not always of much use to try to figure out which particular flavor we think we’re looking at.

Answer 2

You are correct. Hanging bats here obviously means ‘bats which hang’, since hanging anything is not semantically compatible with the verb populate.

It is however possible to employ hanging bats with hanging as a gerund.

1. Hanging bats in the batrack is the batboy's task. ... Here hanging is a gerund and bats is its complement.

2. The great timber baulks over the courtyard, on which condemned criminals were executed, were known as the hanging bats. ... Here hanging is a gerund employed as an attributive noun, and the construction means ‘a bat employed in hanging’.