In the deep sea, partners are so hard to find that in some anglerfish the tiny male bites onto a female and never lets go. Their tissues and then their blood supplies merge, and the male, fed by her, shrinks to little more than a pair of testes. To avoid rejecting him, these species have lost major parts of their immune system, something unheard of in other vertebrates.
In 2022, a young tagged bar-tailed godwit flew from Alaska to Tasmania in about 11 days of nonstop flight, covering 13,560 km without eating, drinking or landing. Before departure, these birds pile on huge fat reserves and shrink their digestive organs, which are useless during the journey.
To escape rivals, a dung beetle rolls its ball of dung in a straight line. At night, it holds its course using the glowing band of the Milky Way. In a planetarium, researchers showed that beetles rolled straight under a starry sky but wandered aimlessly when the galaxy was switched off. It was the first animal known to navigate this way.