20 Animal Journeys That Still Defy Explanation

The return is almost unbelievable until you see the fish fighting upstream. Sockeye salmon hatch in freshwater, grow, migrate out to the ocean, and then come back years later to spawn. Their navigation appears to involve a layered system: magnetic cues may help guide long-distance ocean movement, while smell and local environmental signals help them locate the waters tied to their early life. By the end, the journey becomes physically punishing. They push against the current, leap obstacles, avoid predators, and change dramatically as spawning nears.