On a scorching summer day in Darwin, Australia, I stood 10 feet abreast of a 17-foot-long, 1,200-pound adult male saltwater crocodile—the world's largest reptile. It stared me down with eerie, catlike eyes, its chest heaving periodically to exhale a loud blast of spent air through its nostrils like a locomotive purging steam. Perhaps, I thought, my colleagues and I were taking our research beyond the realm of sensibility. I had worked with crocs many times before but never with such a massive one. Sweat pouring off me, I shuffled forward, armed with only a handful of electronics and a four-foot-long PVC pole capped by a device that would measure the force of the animal's bite.