Scientists at the South Pole found that female penguins make males pay to have sex with them. Payment is in the form of stones, which the females need for nest platforms. The researchers on the Antarctica’s Ross Island observed that paired females sneak away from their mates and approach the nests of unpaired males. After mating, the female grabs a stone to take back to her nest. Sometimes merely flirting with the single males will win femailes a stone.