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Phenology - the calendar of nature

Tracking the seasons in the Sepilok-Kabili reserve.

While the UK enjoys a mast fruiting season, the forests of Sabah are in a quieter phase, with few fruits to be found. For the orangutans in the Sepilok-Kabili reserve, that means more time searching, more clever foraging, and a bigger challenge to find food.

Behind the scenes, our team is hard at work monitoring these seasonal changes through phenology, the study of when natural events like leafing, flowering and fruiting occur.

Every week, observers including Rico, Arnold and Sylvitus walk designated transects and trails, tagging trees and carefully noting which ones are producing young leaves, flowers or fruits. They classify the observations: low, medium, or high - building a detailed picture of the forest’s food availability.

Rico, Arnold & Sylvitus phenology trial

The latest report from the team showed young leaves starting to appear on several key trees, while flowering and fruiting remained very low, with no ripe fruits observed. Each tally helps us understand how orangutans adapt to seasonal scarcity and which parts of the forest they explore.

This work is painstaking but invaluable. By tracking phenology, our team gathers the data needed to anticipate challenges, plan support and protect both the orangutans and the forest they rely on.

Recent observations:

Young leaves: Obah, Kunau-Kunau, Obah Nasi, Lantupak, Simpoh Laki, Kayu Malam, Aglia, Kondolon (Class 1); Kayu Malam (Class 3)

Flowering: Simpoh Laki (Class 1)

Unripe fruits: Medang (Class 1)

Ripe fruits: None observed

Simpoh Laki Flower 1

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