Post-speleogenetic Biogenic Modification of Gomantong Caves, Sabah, Borneo

The Gomantong cave system of eastern Sabah, Malaysia, is well-known as an important site for harvesting edible bird-nests and, more recently, as a tourist attraction. Although the biology of the Gomantong system has been repeatedly studied, very little attention has been given to the geomorphology. Here, we report on the impact of geobiological modification in the development of the modern aspect of the cave, an important but little recognized feature of tropical caves. Basic modeling of the metabolic outputs from bats and birds (CO2, H2O, heat) reveals that post-speleogenetic biogenic corrosion can erode bedrock by between ~ 3.0 mm/ka (1 m/~300 ka) and ~ 4.6 mm/ka (1 m/~200 ka). Modeling at high densities of bats yields rates of corrosion of ~ 34 mm/ka (or 1 m/~30 ka). Sub-aerial corrosion creates a previously undescribed speleological feature, the apse-flute, which is semicircular in cross-section and ~ 80 cm wide. It is vertical regardless of rock properties, developing in parallel but apparently completely independently, and often unbroken from roof to floor. They end at a blind hemi-spherical top with no extraneous water source. Half-dome ceiling conch pockets are remnants of previous apse-fluting. Sub-cutaneous corrosion creates the floor-level guano notch formed by organic acid dissolution of bedrock in contact with guano. Speleogenetic assessment suggests that as much as 70–95% of the total volume of the modern cave may have been opened by direct subaerial biogenic dissolution and biogenically-induced collapse, and by sub-cutaneous removal of limestone, over a timescale of 1–2 Ma

A Note on the Thermal Ecology and Foraging Behaviour of the Egyptian Fruit Bat, Rousettus Aegyptiacus, at Mt. Elgon, Kenya

The Egyptian fruit bat, Rousettus aegyptiacus, is an abundant and widely distributed African pteropid (Nowak, 1999). The species is unusual amongst pteropids in being an obligate cave-dweller (Kwiecinski & Griffiths, 1999), sometimes reaching colony sizes in the thousands (Kingdon, 1974). In the caves of Mt. Elgon National Park, western Kenya (1° 08′N, 34° 39′E), precision temperature loggers placed in major Rousettus roosts and intervening passages have allowed us to precisely monitor bat emergence and return times. The major caves of Mt. Elgon National Park consist of geophagically modified tunnels and collapse chambers cut into Miocene-aged pyroclastic strata (Lundberg & McFarlane, 2006). These caves can be as much as 200-m deep (e.g. Kitum Cave) and can have volumes exceeding 4 × 104 m3 (e.g. Makingeny Cave). The caves support at least 11 species of bats (Bauer, Weis-Spitzenberger & Weis, 1981). The caves are of interest in the present context because, being located at relatively high altitudes (∼2500 m), the ambient rock temperatures are low and the large biomass of bats produces significant temporal fluctuations that more than doubles roost temperature

Bats and Bell Holes: The Microclimatic Impact of Bat Roosting, Using a Case Study from Runaway Bay Caves, Jamaica

The microclimatic effect of bats roosting in bell holes (blind vertical cylindrical cavities in cave roofs) in Runaway Bay Caves, Jamaica, was measured and the potential impact of their metabolism on dissolution modelled. Rock temperature measurements showed that bell holes with bats get significantly hotter than those without bats during bat roosting periods (by an average of 1.1 °C). The relationship is clearest for bell holes with more than about 300 g aggregate bat body mass and for bell holes that are moderately wide and deep, of W:D ratio between 0.8 and 1.6. Measurement of temperature decay after abandonment showed that rock temperature returns to normal each day during bat foraging periods. Metabolic activity from a typical population of 400 g bat (10 individuals) yields 41 g of CO2, 417.6 kJ of heat, and 35.6 g of H2O in each 18 hour roost period, and could produce a water film of ~ 0.44 mm, that is saturated with CO2 at ~ 5%. The resultant rock dissolution is estimated at ~ 0.005 cm3 CaCO3 per day. The metabolic heat ensures that the focus of dissolution remains vertical regardless of geological controls. A typical bell hole 1 m deep may be formed in some 50,000 years by this mechanism alone. Addition of other erosional mechanisms, such as direct bacterial bio-erosion, or the formation of exfoliative organo-rock complexes, would accelerate the rate of formation. The hypothesis is developed that bell holes are initiated and formed by bat-mediated condensation corrosion and are governed by geographic distribution of clustering bats and their roosting behaviour

The 19th Century Excavation of Kent\u27s Cavern, England

Between 1858 and 1880, William Pengelly developed revolutionary new techniques for the archeological and paleontological excavation of cave deposits. His work at Brixham Cave and Kent’s Cavern, England, yielded tens of thousands of specimens from the mid-Pleistocene to the Holocene, settled the intellectual debate over the co-existence of humans and extinct mammals, and accumulated an unparalleled resource for continued study. Although the Brixham Cave work was thoroughly summarized in print, Pengelly never published the plans of his much more thorough and extensive excavations at Kent’s Cavern. Here we present a reconstructed plan of the Pengelly excavations that we hope will be a valuable resource for future analyses of the archaeological and paleontological collections

A Middle Pleistocene Age and Biogeography for the Extinct Rodent Megalomys Curazensis from Curaçao, Netherlands Antilles

The extinct oryzomyine rodent Megalomys curazensis has been known from abundant but fragmentary remains on the island of Curaçao since 1959. Here we demonstrate an age of 130 000 to 400 000 years before present based on geomorphological context, and propose a biogeographical model for the genus

Subaerial Freshwater Stromatolites in Deer Cave, Sarawak – A Unique Geobiological Cave Formation

A suite of distinctive freshwater subaerial phosphatic stromatolites is developed close to the northeastern entrance of Deer Cave, Gunung Mulu National Park, Sarawak, Borneo, in conditions of very low light but ample supply of nutrients from guano. These stromatolites are not particulate; they are composed of alternating layers of more porous and more dense amorphous hydroxylapatite. This biomineralization occurs as moulds of coccoid (the majority) and filamentous (less abundant) cyanobacteria. Mineralization occurs at a pH of ~ 7.0 in the extracellular sheaths and in micro-domains of varying carbonate content in the surrounding mucus of the biofilm. The most recent surfaces that are not yet strongly mineralized show still-living filamentous, coccoid and rod-shaped forms. Trace element composition shows enrichment in metal ions, especially Mn and Zn. The stromatolites are present as horizontal shelves arranged in series on a steep rock face that is vertically under a guano-laden shelf. The rock face undergoes active dissolution from acidic guano drainage water (e.g., pH of 2.43) and from aggressive rainwater from an overhead discharge. However, the rock surface under the stromatolite is protected while the rest of the cliff face is backcut, creating a hoodoo-like effect. The stromatolites are ~ 15–20 cm deep, ~ 4–7 cm thick, and of variable width, generally ~ 50 cm. Eventually, guano and biological detritus in the descending water film lodge in the lee of the stromatolite lip, causing local acidification and erosion of stromatolite and rock on the underside of the ledge. A dynamic equilibrium is established between upward accretion of the fresh surface and destruction at the base such that the base of the stromatolite does not reflect the date of its inception and the stromatolite climbs up the wall

A Late Quaternary Paleoecological Record From Caves of Southern Jamaica, West Indies

Studies of an unusual and diverse system of caves in coastal southern Jamaica have yielded a paleoclimatic record associated with a fossil vertebrate record that provides useful insights into the poorly documented paleoecology of latest Wisconsinan and Holocene Jamaica. Episodes of significantly increased precipitation during the Holocene have left characteristic deposits of speleothems, and have supported both faunal and archaeological communities that were dependent on these mesic conditions. Deposits of fossil bat guano preserved in the caves provide a δ¹³C record of alternating mesic and xeric climatic episodes that supports the interpretation of the faunal and archaeological record

An Undescribed Gecko (Gekkonidae: Cyrtodactylus) from Deer Cave, Gunung Mulu National Park, Sarawak, with Comments on the Distribution of Bornean Cave Geckos

Geckos of the genus Cyrtodactylus are a speciose group in Southeast Asia, with at least nine species known from the island of Borneo (Das & Ismail, 2001; Das, 2006). Of these species, Cyrtodactylus cavernicolus has the smallest known range and is therefore the most vulnerable, a status that is reflected in the species having been designated a Totally Protected Species in Sarawak. Confirmed records of C. cavernicolus are known only from Niah Cave, located in an isolated limestone block known as the Gunung Subis massif, approximately 13 km² in extent. The Niah Cave Gecko is presumed to be dependent on the bat and swift guano ecosystems of the larger cave passages (c.f. Harrison, 1961), and its core habitat may be limited to Niah Great Cave which has some 1 x 10^5 m² of passages (data from survey by Wilford, 1964). The only published record of the species from outside the Niah massif is a single record from the Melinau Gorge of Gunung Mulu National Park (Hikida, 1990)

A Geographic Information Systems Approach to the 19th Century Excavation of Brixham Cavern, Devon, England

The oldest known spatially-explicit archaeological excavation, conducted in Brixham cave, Devon, in 1858, is reconstructed using geographic information systems technology. Two dimensional plots of individual fossil taxa and flint artefacts demonstrate the utility of the technique for elucidating taphonomy and palaeobiology. The cave served as a den for hibernating brown bears, as a den for hyena and cave lion, and as a reliquary for their prey

An Unusual Lava Cave from Ol Doinyo Lengai, Tanzania

A new type of lava cave is described from the summit crater of Ol Doinyo Lengai, a unique active carbonatite volcano in Tanzania. This and other similar caves on Ol Doinyo Lengai are formed by thermal erosion and aqueous dissolution of otherwise solid spatter cones. Meteoritic water and endogenous condensates act to form speleothems of complex mineralogy up to 3 m in length. We propose the new classification of “polygenetic spatter cone cave”