Penguins ‘propose’ with rocks.

Much like humans, penguins also propose with rocks — but not the ones sold at jewelry stores that cost three months’ salary. Instead, male penguins scour the barren Antarctic beaches for the perfect pebble to present to their preferred partner. To be clear, these stony gestures have little to do with romance; rather, these gift exchanges  serve a more practical purpose related to nest-building.

Given the dearth of twigs, brush, and other foliage in their cold-weather environments, species such as the gentoo, chinstrap, and Adélie penguins use the small stones to elevate their eggs off their ground. The more rocks, the better and sturdier nest to protect eggs from potential flooding caused by melting snow.