Report 1999

Article Index



The Vietnam ‘99 team visited two biologically quite different regions. In general, biological landscapes are shaped by mean annual temperature (insolation) and mean annual precipitation. Global variations in these factors result in large regions (biomes) that share similar attributes. Broadly speaking, biomes are arranged latitudinally, with those characterised by high rainfall and/or high temperatures tending to be centered around the equator. However, due to the effect of altitude on temperature and rainfall, biomes typically associated with higher latitudes may appear on mountains and high plateaus in otherwise equatorial climes. The predominant biome in central Vietnam is rainforest, while northern Vietnam is characterised by subtropical and some tropical forest, and at higher altitudes by scrub forest and grasslands.

A second factor affecting the fauna and flora of northern Vietnam is a consequence of geological history. The large landmass of Europe and Asia never divided, and the climate therefore retained a relatively uniform character throughout the geological ages. The different biomes on this large continent are strongly affected by large east-west running mountain ranges, such as the Alps and the Himalayas. These constitute both climatic and topographic barriers to dispersal between cold-adapted and warm-adapted species. The influence of the Himalayas means the north of Vietnam forms the southern limit of the Palearctic, comprising northern Asia and Europe. Central Vietnam, by contrast, falls into the Oriental region and groups with Thailand and Malaysia.

Correspondingly, much of the surface (and cave) wildlife observed in the higher altitude regions of Cao Bang province in the north was reminiscent of that in Britain and Europe, while central Vietnam was thoroughly tropical. As regards birds, for example, great tits, collared crows, sparrows and magpies abounded in the north, while central Vietnam was dominated by more exotic species, such as bulbuls, drongos, pittas, barbets,etc. In terms of invertebrates, most expedition members were probably relieved to find large, tropical, ‘creepy-crawlies’ were absent from the north. However, for someone who likes bugs, Quang Binh province provided a more rewarding environment.

The lack of time and the scarcity of accessible literature available for a detailed study of Vietnamese cave fauna means that the following account is necessarily sketchy.

Phylum Mollusca

Class Gastropoda

Abandoned and/or partly fossilised snail shells were found in a few caves in Cao Bang province. Live molluscs, although possibly present, were not spotted in any of the caves visited. Shells of large freshwater snails, resembling those of the European genus Natica, were seen in Nguom Sap, and shells of snails and freshwater clams were found in Na Lung.

Phylum Arthropoda

Subphylum Chelicerata:

(No antennae, two body parts, marine origin)

Class Arachnida

Order Scorpiones (Scorpions)

Only one scorpion was spotted (on a caver’s wetsuit) in Hang Khe Rhy. The scorpion was described as white, with a relatively small pedipalp (pincer) to body length ratio.

Order Araneae (Spiders)

As with many other cave-dwelling animals, sighting of spiders tends to be biased towards larger and more mobile species, whereas smaller and nearly sessile web-builders are often overlooked. Of the non-web making cursorial spiders in the family Sparassidae, the hirsute, stripey-brown giant crab spider (possibly Heteropoda robusta) was among the most abundant and most striking. Typically not found deep inside caves, this spider tended to be most common near entrances and in short remnant caves. Giant crab spiders hunt crickets, cockroaches and other cave-dwelling invertebrates, have the ability to move rapidly, even across water, and also frequently jump when frightened. Although most individuals were of moderate size (1-2 cm body length, <10 cm diameter including legs e.g. in Nguom Sap and Phong Nha Kho) a specimen from Ben Dap cave, near Son Trach village, reached remarkable proportions (3-4 cm across body, >20 cm diameter including legs). The other sparassidid frequently observed was the much smaller, and less obviously hairy, uniformly pale-brown ‘huntsman’ (likely Heteropoda venatoria, a common house spider throughout the tropics), seen e.g. in Nguom Sap, Lung Sam, Phong Nha Kho, Hang Khe Rhy.

Web-builders abounded, however, these were difficult to identify in the short time available. Spiders in the family Pholcidae are leggy with a narrow grey-black body, make untidy three-dimensional webs, and are adapted to dark and humid environments. Spiders from this family are frequently found in houses and cellars throughout the world. Of these, we saw two morphotypes in northern and central Vietnamese caves. A number of other spiders that construct orbwebs, some with spiral stabilimenta (Aranaeiae, Tetragnathidae) were also sighted. Mygalopmorph spiders are a primitive group with chelicerae that work in a downwards strike, rather than in a pincer-like lateral move as those of modern spiders. They often make thick sheet webs and live in burrows or small solution pockets. Mygalomorphs were not observed in northern caves, however, several individuals of a small-sized black species, identified as a mygalomorph by its recently moulted skin (including chelicerae), was sighted in rock crevices near the downstream entrance of Hang En (Quang Binh Province).

Order Opiliones (Harvestmen)

Harvestmen were common in caves from both northern and central regions. White, presumably cave adapted, morphotypes were seen in Hang Khe Rhy.

Order Uropygidae (Whip scorpions)

Not to be confused with their cousins, the dorsoventrally flattened, crab-like, ‘tailless whip scorpions’ (Amblipygidae), Uropygids are usually black and have stout, ovoid, bodies with strongly developed pincers (pedipalps). These are used to grasp and tear apart their invertebrate prey. The first pair of legs is often modified into thin, tactile, antennae-like appendages. A thin, segmented flagellum (the ‘whip’) protrudes from the last body segment. When frightened, Uropygids may spray a repellent fluid, consisting mainly of acetic acid, from their anal glands. The strong smell of this vinegar has earned them the vernacular name of ‘vinegarroon’.

None were spotted in northern caves, however, they were very abundant in the Hang En downstream entrance. Uropygids were also seen in the drier parts of Hang Khe Rhy near the downstream entrance.

Subphylum Crustacea

(Branched appendages, marine origin)

Class Malacostraca

Order Isopoda, Suborder Oniscoidea (Woodlice)

Crustaceans that have become amphibious or terrestrial. Dorso-ventrally flattened. Several terrestrial woodlice were spotted in the Hang Vom entrance and collected to be sent to Dr. David Bilton, University of Plymouth.

Order Decapoda (Shrimps, lobsters, crabs), Infraorder caridea (freshwater shrimps)

Large (>10cm length) shrimps were common in northern and central Vietnamese caves.

Superfamily Potamoidea (Freshwater crabs)

Crabs were particularly common in the Lung Sam streamway (Cao Bang).

Subphylum Uniramia

(unbranched appendages, evolved on land)

Class Chilopoda (Centipedes)

Carnivorous. Typically poisonous. One pair of legs per segment, fast, powerful gait, and easily distinguished from millipedes (two pairs of legs per segment, slow moving).

Order Scolopendromorpha

Very poisonous. To be avoided at all costs... Dorso-ventrally flattened, heavy-bodied,with 21-23 pairs of short, stout legs of equal length and two thick poison claws (maxillipeds) at head end. Two last legs may be elongated and can be used for pinching. Many species have ventral repugnatorial glands that can cause a nasty rash/discoloration should the animal crawl over human skin. Typically brown in colour, but can be turquoise, red, yellow and green in the tropics.

We did not see many scolopendromorphs underground. Several were spotted in the underground camps of Hang Khe Rhy. The most spectacular individual was seen crossing the rocks at the foot of the climb to Phong Nha Koh (Quang Binh) after a rain shower. The dimensions of this individual rivaled those of the largest known centipede, (Scolopendra gigantea), a neotropical species that grows to 30 cm in length.

Order Scutigeromorpha

Poisonous, best left alone. Long-legged (15 pairs in adult) with hind legs longer than front legs. Body clear off the ground, very fast moving. Two last legs held above body. Typically beige to dark brown with lighter-coloured, often blue, tergites (plates) on back.

Scutigeros were relatively common across northern and central Vietnam. A large number of medium-sized (10-15 cm long) scutigeros was observed in Nguom Dam cave, clustered near the choked top entrance. An adult (15 pairs of legs) of a small (3 cm long) species was collected from Nguom Sap. Scutigeros were also reported from Hang Khe Rhy (Quang Binh) and Hang En.

The remaining two centipede orders, geophilomorphs and lithobiomorphs, were not spotted, presumably this was due to their more cryptic habit.


Class Insecta (Insects; six legs, antennae, three body parts)

Subclass Pterygota (Winged or secondarily wingless insects)

Order Odonata

Dragonflies. Visually oriented aerial predators, and an unlikely insect to find in a cave environment. No adults were seen, but empty, hatched exuvia of dragonfly nymphs were stuck to logs, flood debris, and cave walls in upstream Hang En.

Order Orthoptera

Crickets, katydids, grasshoppers. Camel crickets in the family Rhaphidophoridae were ubiquitous. Almost every cave contained crickets. We may have found several species. Crickets differed in size and colouration, and a preliminary genetic analysis revealed several distinct genotypes.

Order Blattodea

Cockroaches. Winged cockroaches were seen in Na Lung, the through trip, Hang Khe Rhy. Although there are wingless cockroach species, such as hissing cockroaches, females of some cockroach species have vestgial wings (e.g. Blatta orientalis), and it is possible that the wingless morphotypes spotted, for example, in Nguom Sap were females of an otherwise winged species.

Order Diptera

Flies. Attracted in swarms by our carbide lamps, small dipterans, caddis flies, stone flies and mayflies were ubiquitous in cave entrances in Quang Binh. Larvae of flies in the family Mycetophilidae are pale, thin, and vermiform and live in a nest made of horizontal and vertical slime threads. Sticky vertical threads dangle in the draught and trap passing insects. Mycetophilids can be quite common, but are difficult to spot. We saw threads containing larvae in Lung Sam.

Order Dermaptera

Earwigs were common in the Hang En and Hang Khe Rhy downstream entrances. Several morphotypes were seen, differing in size, mobility and colouration. A black and yellow morphotype was seen flying round our carbide lights in Hang Khe Rhy. Red and yellow, and all black individuals were spotted in Hang En.

Order Lepidoptera

Moths and butterflies. Many small, possibly Taenaeid, moths were attracted to our carbide lights in the cave entrances of Hang Khe Rhy and Hang En. Day-flying moths, possibly in the family Zygaenidae were seen in the entrances of northern caves (e.g. Lung Sam).

Order Coleoptera

Beetles, presumably saprophytic or carnivorous, were found crawling in the rich guano in the downstream Hang En entrance.

Phylum Chordata (Chordates)

Subphylum Vertebrata (Vertebrates)

Class Pisces (Fish)

White, fish of no detailed description were seen in several caves in north (Nguom Sap, 2 morphotypes; Lung Sam, long and slender fish; Na Nguom) and in central Vietnam (Hang Khe Rhy).

Barbled catfish, typically small in size (<20cm), were also common and spotted in northern caves (Lung Sam, Na Nguom I).

An eel of considerable size (reputedly 1.5 m and arm-thick) was stepped on by a caver in Hang Khe Rhy.

Class Reptilia (Reptiles)

Order Squamata

Infraorder ophidia (Snakes)

One unidentified morphotype with a small, brownish head and mottled grey-green markings on the body was sighted in or near several cave entrances in Cao Bang. It is likely that this is not a cave adapted snake, but a troxophile that makes use of the shelter provided by cave entrances. The largest individual was about 4 m long. The characteristically small head and the abundance of this snake permits its tentative placement in the genus Elaphe (rat snakes). Elaphids tend to prey on rodents and other small vertebrates and kill by constriction.

Class Aves (Birds)

Order Apodiformes, Family Apodidae

Swifts were the commonest cave-dwelling birds, seen and heard in caves throughout central Vietnam (Hang Khe Rhy, Hang En, Hang Vom). A (very) few swiftlets were heard echo locating in the Hang En downstream entrance.

Class Mammalian (Mammals)

Order Chiropteran (Bats)

Not surprisingly, quite a few bats were observed. In the short time available, and due to the relatively low bat density that precluded close examination of the inevitable casualties on the cave floor, it was impossible to classify them even remotely. Large morphotypes were sighted in Nguom Sap. Smaller types were found in Na Lung, Nguom Dam in the north. In central Vietnam, bats were also observed in Pong Nha Kho (very few). A very audible, but sadly not visible, bat colony inhabits the roof of the Phong Nha resurgence showcave. Bat colonies (two different morphotypes) were heard/seen in the roof of Hang Khe Rhy.

Order Carnivora (Carnivores)

Family felidae (Cats) or viverridae (civets, genets etc)

The ‘Cave Cat’. This was a mysterious and unidentified mammal, possibly not a cat at all, but a viverrid. It was described as cat-like, but also resembling a chinchilla, with large eyes, small ears and teeth, and a bushy tail. The creature was sighted in a cave in Ha Lang, perched on a stalagmite. Another potential sighting occurred in a local market, where a caged specimen was for sale. At least five small cat species are known in Indochina/Western China. Only two of the five species are likely to be found in caves, the first being the endangered jungle cat Felis chaus, a long legged, sandy coloured species that dens in burrows, the other being Felis bengalensis, a cat that inhabits montane and lowland forests. This cat is known to den in caves and under rock overhangs. There are a number of viverrids (civets, palm civets, otter civets, binturongs and linsangs) in Vietnam, however, these are predominantly arboreal and perhaps less likely to be encountered in caves. A potential candidate for the animal seen may be the oriental civet, Viverra zibetha, or its endangered cousin Viverra megaspila. Finally, the description also matches a number of members of the family Sciuridae in the rodent order. Eurasian tree and ground squirrels, (e.g. Callosciurus sp.) can reach the size of a small cat, have small ears, large eyes, bushy tails and rodent facial features, thus resembling a chinchilla. A candidate here may be Prevost’s squirrel (Callosciurus prevosti), or the shrew-faced long-nosed squirrel (Rhinosciurus sp.).

Anette Becher


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