Turtles are famous for their slowness, but you'd be slow too if you were lugging a heavy shell 24/7. Imagine carrying a humongous backpack full of bricks wherever you go. Then imagine a bad guy is chasing you! Still wearing the backpack, you have to run for your life. Good luck with that. Everyone knows how it feels to be weighed down physically, and the metaphorical heaviness of negative emotions—such as depression, frustration, despair, and fear—is also readily understood. In "Turtle," images and metaphors connoting heaviness or lightness weave through the poem, supporting key themes (see "Freedom and Confinement" in the "Themes" section). How does the turtle bear up under the heaviness of constant physical challenges? How does she seem to respond emotionally to those challenges?
Lines 5-6: You know those heavy footlockers, the kind students use to ship their stuff off to college? Maybe a couple of friends (who work out regularly) will offer to carry it up the three flights of stairs to your dorm room. But if you have to drag the footlocker yourself, the turtle feels your pain (and then some). She has to drag her "packing-case" all the "places" she goes, and there are never any buff guys around to help her out. As a metaphor, the packing-case represents both the physical weight of the turtle's shell and the constant burden of struggling to stay alive.
Lines 6-7: Remember "Climb Every Mountain," that song from the musical The Sound of Music? Ryan's turtle might find the song more depressing than inspirational, since "almost any slope / Defeats her modest hopes." The imagery in these lines implies physical heaviness (the turtle's weight causing her to slide back down the slope) as well as emotional heaviness (the discouragement resulting from the failed attempt).
Lines 12-13: "Load of pottery" provides yet another metaphor for the turtle's weighty shell and life burdens, but for the first time, an image of lightness offsets the idea of heaviness. Feathery-light "wings" would offer the turtle escape from the exhausting weight of her own body, freeing her from the mud that would trap her, the slope that would block her, the ditch that would swallow her, and all the nameless predators that would just love for her to make a misstep. But she can't even imagine a life with wings.
Line 14: Still, the turtle may have a top-secret weapon under wraps, an anti-gravity super-power charged by the alternative energy sources of "levity"—a different kind of lightness—and "patience." Whether these hidden powers are energetic enough to lighten up all the heaviness in the poem is up to you to decide. (For more on these ideas, check out the "Detailed Summary" and "Themes.")