Taily weed plays a special role in the desert ecosystem it inhabits. The weed sometimes serves a nursing role in helping other plant species become established. For animals, the taily weed produces thousands of tiny berries year-round.
Many birds, rodents, ibex and camels eat the plant or its berries. Among them is the Cairo spiny mouse, which ekes out a living in the rocky hills and hot deserts of north Africa; eating seeds, desert plants, insects and snails.
The spiny mouse eats taily weed berries, but carefully. Each berry has 5 – 9 seeds. If a seed is chewed, enzymes within activate a toxic glucosinate in the pulp, which is otherwise harmless. The tiny spiny mouse cannot afford to pay that price.
To avoid detonating this pungent mustard bomb, the spiny mouse spits the seeds out before consuming the berry. Because of the taily weed’s chemical cunning, the small seed eater is turned into a good seed disperser. Other small rodents that dine on the taily weed take the same precaution.
Because birds swallow their food whole, taily weed seeds pass through without setting off the mustard bomb.
Taily weed is the not only plant with this ploy. Mammals don’t eat chili peppers because they can’t take the heat from the capsaicin that the seeds contain. But birds don’t crush seeds when eating, so the heat of the seed is foregone.
Ishi Nobu, Spokes of the Wheel, Book 2: The Web of Life (pre-publication).
“Plant poison turns seed-eating mouse into seed spitter,” ScienceDaily (14 June 2012).