Wild gibbons plan their travel pattern according to food types of breakfast

Abstract

Planning for the future is a complex skill that is often considered uniquely human. This cognitive ability has never been investigated in wild gibbons (Hylobatidae). Here we evaluated the movement patterns from sleeping trees to out-of-sight breakfast trees in two groups of endangered skywalker gibbons ( Hoolock tianxing ). These Asian apes inhabit a cold seasonal montane forest in southwestern China. After controlling for possible confounding variables including group size, sleeping pattern (sleep alone or huddle together), rainfall and temperature, we found that food type (fruits or leaves) of the breakfast tree was the most important factor affecting gibbon movement patterns. Fruit breakfast trees were more distant from sleeping trees compared with leaf trees. Gibbons left sleeping trees and arrived at breakfast trees earlier when they fed on fruits compared with leaves. They travelled fast when breakfast trees were located further away from the sleeping trees. Our study suggests that gibbons had foraging goals in mind and plan their departure times accordingly. This ability may reflect a capacity for route-planning, which would enable them to effectively exploit highly dispersed fruit resources in high-altitude montane forests.

Eco-evolutionary dynamics of gut phageome in wild gibbons (Hoolock tianxing) with seasonal diet variations

“…Before the study, both groups were well habituated to observers and all individuals were distinguished by their fur color, body size, and shape of the white eye brow. We followed the adult female of each group (A2 in group NK and B2 in group BC) for on average eight days per month, each day from the time gibbons left their sleeping trees in the morning until they returned to the sleeping trees in the afternoon 63 , 64 . During follows, we recorded all feeding activities (5-min scan and ad libitum), recording the start time, end time, food species and food type (e.g., leaves, fruit, flower, animals, and others) of each feeding bout for the focal individual 25 .…”