Bee

Sealed honey essentially never spoils. Its water content is low (~17%) and bound to sugar, its pH of 3–4.5 is acidic, and bee enzymes add hydrogen peroxide. Microbes can't survive, so millennia-old honey is found unspoiled in Egyptian tombs.

When bees are repeatedly exposed to explosive scents followed by sugar water, they eventually extend their tongues at the smell alone. A real device was built with 36 trained bees in sensor cartridges as an explosive detector. Training a dog takes months, but bees need only a few hours.

Honeybees can understand that zero is smaller than 1, 2, 3, or 4.