PRELIMINARY REPORT
The Mulu Caves 2025 expedition has recently concluded its work in Gunung Api, with significant finds high above Blackrock totalling over 3km. 10 cavers from the UK, Malaysia and the US spent 3 weeks in Mulu.
Due to time constraints this year’s expedition was concentrated into a single 9 day camp with resupply halfway through. A team of 6 stayed for the entire duration with a team of 3 doing the resupply.
The main find of the expedition was called ‘Reputation’ and was a large fossil passage connected to Armistice totalling 1,926m, though is still open at the end. This broadly followed the north south dip in the bedding. A few leads were explored from here, dropping down the strike, leading to a further 756m in which a branch appears to cut across the bed and a large fossil passage 20m wide remains open and is in clear need of further exploration. The significance of this find is that it opens up an entirely new area to cave exploration and suggests the potential of Clearwater to be much larger and longer than previously thought.
Additional work was done on 2023’s important find, the Velodrome, where a 30m bolt climb was completed. This led into 200m of large passage, with 300m or so of small but very well decorated passages (including an Aragonite calcite ‘chandelier’). It also would provide a good vantage point for photographing the Velodrome. A further lead going down the strike was explored in Defiance totalling 127m.
All finds were surveyed to BCRA Grade 5d. No sampling was conducted on this expedition. Of ecological note, it appears the Swift habitat extends further into the cave than previously thought, and as such so does much of the invertebrate life. This would be sensible for future study.
I am happy to report that there were no significant medical incidents and that all exploration was carried out in a safe and effective manner.
The expedition would like to thank both the National Park staff and the Sarawak Forestry Corporation for their understanding and willingness to help – there was an unfortunate miscommunication and misunderstanding leading to 9 days waiting for the permit to come through. We really do appreciate the expedited modified permissions and these expeditions would not be possible without their support.
Discoveries Log
Date – Name – Length (m)
12-18/11/25 – Reputation 1,926
18/11/25 – Swift Sarcophagi 756
15/11/25 – Hysterectomy Heights 554
16/11/25 – Yeastwater 132
21/11/25 – Skylight Rift 56
19/11/25 – Canopy View Cave 50
*note: a small amount of the length will be reduced when added to the master survex model as
there will be some duplication.