Otter Trail Letterbox Cave

Peter Swart
March 2019

Stephan Moser, Jessica Hitchcock and I went to explore and survey Letterbox Cave on the 25th September 2005. We parked on Marine Drive above the Otter Trail and walked down past the ranger’s hut to the trail path and then down a fisherman’s path to the coast at Grootbank, west of the Bloukrans River. Stephan Moser, Jessica Hitchcock and I followed the coastline westward past Cobblestone Cave to Strydomsloep, which is situated in a headland jutting into the sea.

Access to Letterbox Cave is difficult and should only be attempted with experienced climbers using suitable equipment. Access is along a grassy slope that ends at a rock wall. An exposed horizontal shelf allows one to progress for a further 10m along the cliff that drops away into the sea. Stephan Moser crawled along the shelf and then up a steep cliff to the steep fynbos covered slope above. He rigged the cliff with safety lines so that we could climb with protection. We explored the channel in the headland, but did not find a cave at sea level so moved on to Letterbox Cave, the entrance of which is at the base of a high cliff higher up the slope.

Description

We climbed up a steep slope along the base of the cliff to a large 15m wide entrance in the shape of a letterbox-posting hole. The entrance is partially blocked by rubble. The cave slopes steeply downward at 30 degrees for about 40 metres and then levels out continuing for a further 30 metres and then closes down.

The cave opens from the entrance into a large, sloping chamber 36 metres wide with the ceiling up to 4 metres high in places. There is a passage at the back of the chamber that continues for about 16 metres and then splits into two. The left-hand passage is a low crawl-way extending for 10 metres. It appears to widen further on, but we did not have time to excavate and get past the constriction. The right-hand passage is about 15 metres long and is formed along a vertical crack that slopes left to right from floor to ceiling.

The total length of the cave is over 80 metres from entrance to furthest recess. We found no evidence of shell midden.

Biota

There were a few (about 10) insectivorous bats (Rhinolophus sp.) in the area.

There is also a slope in the main chamber that is covered with bat guano, but the amount does not suggest a large population of bats inhabit this cave. Bats were seen flying in and out of a small passage at the left extremity of the chamber, facing inward, but again we did not have time to explore this properly. The reason for this is that access past the gully below Cobblestone Cave is tide-dependent and we had to return before the tide rose too much.

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Survey

Survey

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