Pi studies the three-toed sloth as part of his zoology thesis at the University of Toronto. For him, the sloth symbolizes understanding, love, and healing. The sloth could also be like a mirror for Pi, the sloth is like him, a miracle.
In chapter 1:
"I chose the sloth because its demeanor-calm, quiet, and introspective-did something to sooth my shattered self."
"...the three-toed sloth, such a beautiful example of the miracle of life, reminded me of God"