Rhinos

That armor-plated look is an illusion — a rhino's hide is thick but sensitive enough to sunburn, which is why they spend so much of the day wallowing in mud that dries into a natural sunscreen. The horn isn't bone at all but compacted keratin, the same material as your fingernails, and it grows back if worn down. Fewer than 30,000 rhinos remain across all five species, making the ones in front of you ambassadors for a fight still very much underway.