Shapes of lava tube caves in Vietnam

The lava tube caves we explored in the Dong Nai province of south Vietnam in  Feb 2014 were generally not very extensive. Having said that, the expedition in 2013 found the longest lava cave in SE Asia, Hang Doi 1 Km 123, at 437 m. It continues the other side of the depression and that cave is 112 m. If these are considered to be one cave, then the length would be 549 m. However, lava tube specialists count the caves as being separate.

There are many small volcanoes in this area. Generally they are quite small hills with flat tops, the  volcano cones are heavily eroded. The resulting lava streams between Tan Phu and Dinh Quan are extensive and cover several square kilometers.

There are numerous lava tube caves, accessible through roof collapses. The cave passages were formed quite close to the surface, hence the numerous roof collapses.  This means the caves have been dissected and are short.

Most of the caves are of characteristic oval shape.

Most of the entrances were very small, as a result of the roof collapse forming a mass of breakdown

 

 This entrance was blocked by thick bamboo

This was one of the bigger entrances -

Typical passage shapes -

Views of the roof -

And some "lavatites"

rich colours

 

See more on :
Dong Nai lava tubes part 2
Dong Nai lava tubes part 1
Fauna in lava tubes


© Liz Price
No reproduction without permission

Cave fauna in lava tubes in Vietnam

The lava tubes we explored in south Vietnam are quite rich in cave fauna, mainly invertebrates. We were based in Than Phu, in Dong Nai province, about 125 km northeast of Ho Chi Minh City in south Vietnam. We were there in February which is the dry season and the whole area was incredibly dry.

We saw very little fauna above ground, just the occasional lizard. There was far more life underground, in the cooler and damper lava tubes. However the tubes are quite warm compared to limestone caves.

There was no water in any of the tubes we visited, though some had damp mud. Many had roots coming in through the ceiling and walls.

There were surprisingly few bats in these lava tubes, though there was evidence that they had been hunted, as there were many wooden poles and nets lying around in various caves.

We saw a variety of invertebrates.
Spiders were always noticeable by their eye shine in our lights. In many caves they were throughout the cave, but in the longest cave they were only seen near the entrance. They are Sparassidae: Heteropodinae (thanks to Peter Jaeger for the ID) -

Web spiders were far fewer in numbers.

I saw 2 types of cricket -

They are probably Rhaphidophoridae , Subfamily Aemodogryllinae .

I only saw a couple of long legged centipedes. They are a different colour from those in Malaysia.
This one was climbing up tree roots -

Whip spiders were particularly common -

One was identified by Michael Seiter as Phrynichus orientalis.

This was a dead one being eaten by millipedes -

 And another live one -

There were also whip scorpions (Uropygi) -

Millipedes were only seen in 2 caves.

Jean-Jacques Geoffroy (France) identified them as belonging to the family Cambalopsidae. The genus could be Glyphiulus or Plusioglyphiulus (or even Trachyiulus or Hypocambala).

Cockroaches were only seen in one cave. That cave was close to houses so they could have come from there. They are Periplaneta Americana

There were surprisingly few frog species. These tiny little guys - Micryletta inornata - were cute and quick to hop away from the camera  -

 This larger one - Polypedates leucomystax - was close to an entrance (thanks to Lee Grismer for frog ID) -

I was looking for scorpions but saw none. The only ones we came across were these large ones found when digging open a cave -

Some mammals use the caves. In several caves I saw rats, with white chests, Niviventer spp. .
I'm think this is one as well -

This might be a rat -

This skull may be a dog

Porcupine also use the caves and the locals put traps at the entrances to catch them. This is a quill -

These droppings could be from porcupine -

A pile of droppings covered in fungus, note the polished rock above the droppings-

In one cave the locals collected the porcupine droppings to use as fertilizer.

Bats were less numerous than expected. All were insect eating bats. As there were signs of the locals trapping them in nets, maybe that accounts for less bats than a year ago when some of the cavers visited (at the same time of the year). Surprisingly the most bats seemed to be in a cave with very bad air. This cave was also particularly warm. And at the entrance we saw quite a few dead bats, Pomona Roundleaf Bat (Hipposideros pomona) -

There are 6 bats flying in this photo -

 

 

Surprisingly I only saw 1 gecko in the caves , Cyrtodactylus -

See more on the lava tubes :

Part 1 Gia Ray area

Part 2 Than Phu area

Shapes of lava tubes

© Liz Price
No reproduction without permission