A few years ago, a couple of ecologists were on holiday in Ecuador and visited the Yasuní National Park. While they were absorbing the beauty of one of the most biologically-intense places on Earth, they saw an amazing sight – a thickset solitary bee delicately drinking tears from a river turtle’s eyes.

Confused? As it happens, most of the salt on Earth is concentrated in the ocean, so many terrestrial herbivores struggle to find enough nutrients to satisfy their cravings. This is why some herbivores frequent ‘salt-licks’ and why you often see butterflies or moths hovering on faeces or carcasses. Continue reading →