Goats adjust their feeding behaviour to avoid the ingestion of different insect species

Ungulates feed on plants that are often inhabited by insects. Goats (Capra hircus Linnaeus, 1758) can efficiently avoid the ingestion of setae-covered noxious, caterpillars while feeding, but it is unknown how they respond to non-toxic insects. We filmed and analysed the behavioural responses of goats to smooth, innocuous silkworms (Bombyx mori (Linnaeus, 1758)) while feeding. The goats successfully sorted the silkworms apart from the food despite their tendency to cling to the leaves. Although the goats exhibited behaviours similar to those displayed with noxious caterpillars, the frequency of the behaviours doubled and a new behaviour appeared. The goats detected silkworms using tactile stimulation, obtained by repeatedly touching the leaves with their muzzles. This behaviour enabled them to pick silkworm-free leaves (leaving 73% of silkworms behind). If the goats picked up leaves with a silkworm, then they shook it off. When shaking was unsuccessful, they employed a new behaviour, filtering, in which they physically blocked the silkworm with their lips while consuming the leaves. Silkworms that entered the mouths of goats (rare) were spat out. These findings demonstrate that ungulates are capable of adjusting their feeding behaviour to accurately detect and avoid the ingestion of different insect species.