In an ecological trap, natural cues lead animals to forage or breed in a place that is no longer beneficial, putting them at great risk. Since 2000 ecologists have identified more than two dozen such traps. They include polarized glints of sunlight that make glass look like water to insects. In early 2017 researchers revealed the first evidence of a trap in the ocean. Young African Penguins, an endangered species that breeds in South Africa and Namibia, seem hardwired to follow signals up the coast (yellow lines) in search of anchovies (purple) and sardines. Because those species are overfished, however, the food is not there—and 80 percent of the juveniles are dying. Those who do survive manage to find their way south again. But then “they have chicks that will go and get stuck in the trap,” says ecologist Richard Sherley of the University of Exeter in England, who led the study. “It just becomes an extinction vortex.”