Be very careful with this.
A new writer submitted such a story to my writer's group. The main character, referred to as "she," took a drink, picked up her trunk, and a few other things. In the end we discover she is an elephant.
The writer's intention was to amuse us by exposing our assumptions. Unfortunately, not a single one of the half dozen reviewers was amused. Every one of us felt swindled. The writer did not expect this, and became very defensive. She did not return to the writer's group.
I think what happened is this: We readers want to feel involved in the story, involved with the character. As we read the words, we make mental images of what we're reading. We put ourselves into a reader's trance, guided by the written words. This trance is the reason we read. In general, we don't like anything that pops us out of the trance (awkward grammar, out-of-sequence actions, and so on). This story created a trance, then shattered it. That's jarring to the reader, and the writer had better have a very good reason for doing it, a reason that is worth it to the reader.
Over time we train ourselves as writers to induce this reader's trance and not violate it. If our story stars a pair of buddies from page one, and one buddy is a foot and a half taller than the other, we want to say this right away so that the reader can form the right mental image. We don't want the reader to form a mental image and invest in that for 60 pages only to discover that it's wrong. That forces the reader to stop reading, rewind, and replay events with this new mental image. It shatters the reader's sacred trance.
Mostly we writers want to create a trance and sustain it.
There are a few exceptions. When we write riddles ("thirty white horses on a red hill..."), we try to disguise the subject. Our audience knows it's a riddle, and a metaphor. When we write mysteries, we deliberately disguise the significance of the clues. But even in a mystery we wouldn't try to fool the reader into thinking that the detective was looking at a clothing trunk if she were really looking at an elephant's trunk.
So be very careful with this. For most of your story, you're trying to induce a trance. If the point of your story is to lull us into the wrong trance, and then to point out our folly, I think you're in trouble. And if this is not the main point of the story, then the rest of the story will have to offer something very special to compensate for shattering the sacred trance.