For decades, scientists have viewed octopuses as unromantic loners, with mating habits nearly devoid of complex behavior. But new research has found that at least one species of octopus engages in such sophisticated lovemaking tactics as flirting, passionate handholding and keeping rivals at arms’ length. Biologists witnessed an array of complex mating behaviors as they snorkeled two meters or less above the shallow reefs of northern Sulawesi in Indonesia.