To dissect the observation, the team designed a new study that allowed hummingbirds to choose between a feeder with plain sugar water and an identical feeder containing sugar water laced with one of three chemicals: cuticular hydrocarbons found on honey bees’ exoskeletons; formic acid, a defense chemical released by Formica ants; and (Z)-9-hexadecenal, the ant aggregation pheromone they’d used in the bee study. The birds avoided feeders that smelled of the latter two, but not those that smelled of honey bees or a common food additive. “For specific contexts such as danger, they are responding to odors that are associated with . . . chemicals produced by insects,” says Wilson-Rankin. “They might not have many [olfactory] neurons, but they use those neurons to avoid dangerous [situations].”

— Ecologist Erin Wilson-Rankin studies olfaction in hummingbirds. Read more in Even the Tiniest of Birds Use Smell in Some Situations at The Scientist.

A landmine-hunting rat that was awarded a gold medal for heroism for clearing ordnance from the Cambodian countryside has died.

Magawa, a giant African pouched rat originally from Tanzania, helped clear mines from about 225,000 square metres of land – the equivalent of 42 football pitches – over the course of his career. [...] Belgian charity Apopo trained Magawa to detect the chemical compounds in explosives by rewarding him with tasty treats – his favourites being bananas and peanuts.

— Read more in Landmine-hunting hero rat dies in Cambodia after stellar career at The Guardian. Hat tip to Jalapeno!