Of the four tomato plants we have, one is being attacked by an unknown
animal. It only eats the tomatoes themselves but takes rather large
bites out of them. My wife (the gardener) says the bites may be caused
by a hornworm (?) except there are no other signs of hornworms so she
rules that out.

She thinks it may be a rodent. I suppose there may be mice around. Do
mice eat tomatoes? These bites are roughly 5 mm x 3 mm. Any other ideas?