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Hutan’s 2023 Annual Report

Marc Ancrenaz, on behalf of the HUTAN team, March 2024

The Orang-utan Research team encountered and closely followed 15 wild orang-utans, securing 325 hours of direct observations on the animals at our intensive study site. We confirmed the presence of healthy resident females, including Mallotus (Jenny's second youngest daughter, 18 years old in 2023) and Muticus her 2.5-year-old daughter):

Oceanne (9 years old, Jenny's latest daughter); Wawa (8 years old, Maria's latest daughter); Manis (14 years old), who gave birth to Paduk on 29.05.2023; and Felicity (Juliana's last daughter).

In terms of diet, the top five species consumed by orang-utans at our site included Ficus sp. (26.3% of feeding bouts), leaves of the climber Spatholobus sp. (13.6%), Maranthes corymbosa (13.1%). Disopyros sp. (ebene wood: 9.5%), and the fruits of the climber Gnetum sp. (8.6%). Most nests were identified in the ironwood tree (Eusderoxylon zwagerii), a hardwood belonging to the Lauraceae family.

Our site showed a slight increase in orang-utan density, with about 1.4 ind./km sq. This rise may be due to the younger females reaching maturity and attracting more males.

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