A and B which, which stands for which?

Solution 1:

Without punctuation, the sentence is somewhat ambiguous, as pointed out in the other answer.

However, as written, the sentence would most likely be understood as follows:

     "Which" modifies neither "voles" nor "field mice".

     The word "animals" is modified by:

• "which you do not see"

       and

• "like field mice and voles"

Solution 2:

There is a certain ambiguity, which you would normally use punctuation to prevent. Let's try some examples.

There are numerous small animals - like field mice and voles - which you do not see.

It is the small animals you do not see. Field mice and voles are examples. 'which' modifies the animals. Replacing the dashes with commas gives the same meaning.

There are numerous small animals - like field mice and voles which you do not see.

There are numerous small animals, and field mice and voles (which you do not see) are examples. You may see the other animals. "Which" modifies field mice and voles.

There are numerous small animals like field mice, and voles which you do not see.

There are 1) numerous small animals like field mice 2) voles which you do not see. "Which" modifies voles.

Without punctuation context and sense is most likely to give you the meaning.