Donald A. McFarlane

Stable carbon and hydrogen isotopes from bat guano in the Grand Canyon, USA, reveal Younger Dryas and 8.2 ka events

We inferred climate change through the Pleistocene-Holocene transition from δ 13 C and δD values of bat guano deposited from 14.5 to 6.5 ka (calendar ka) in Bat Cave, Grand Canyon, Arizona. The δ 13 C and δD values generally covaried, indicating that regional late Pleistocene climate was relatively cool and wet, and early Holocene climate gradually became warmer with increased summer precipitation until ca. 9 ka, at which time the onset of modern North American Monsoon–like conditions occurred. During the Younger Dryas event, δ 13 C values decreased, whereas δD values increased, indicating a cool and possibly drier period. We also observed a distinct isotopic anomaly during the 8.2 ka event, at which time both δ 13 C and δD values decreased. The δ 13 C values abruptly increased at 8.0 ka, suggesting a rapid change in atmospheric circulation and greater infl uence from convective storms originating from the south. Deposits of bat guano represent a largely untapped source of paleoenvironmental information that can provide continuous and long-term continental archives of environmental change.

Pre-Wisconsinan mammals from Jamaica and models of late Quaternary extinction in the greater Antilles

Abstract The vertebrate fauna recovered from indurated conglomerates at Wallingford Roadside Cave (central Jamaica) is shown to be in excess of 100,000 yr old according to uranium series and electron spin resonance dating. The Wallingford local fauna is therefore pre-Wisconsinan in age, and Roadside Cave is now the oldest radiometrically dated locality in the West Indies containing identifiable species of land mammals. In the absence of a good radiometric record for Quaternary paleontological sites in the Caribbean, there is no satisfactory basis for determining whether most extinct Antillean mammals died out in a “blitzkrieg”-like event immediately following initial human colonization in the mid-Holocene. Fossils of Clidomys (Heptaxodontidae, Caviomorpha), the giant Wallingford rodent, have never been found in situ in sediments of demonstrably Holocene age, and its extinction may antedate the middle Holocene. This is also a possibility for the primate Xenothrix mcgregori, although its remains have been found in loose cave earth. A major, climate-driven bout of terrestrial vertebrate extinction at about 14,000–12,000 yr B.P. has been hypothesized for the West Indies by G. Pregill and S. L. Olson (Annual Review of Ecology and Systematics 12, 75–98, 1981), but at present there is nothing to connect the disappearance of Clidomys with this event either. Quaternary extinctions in the Caribbean may prove to be of critical significance for evaluating the reality of New World blitzkrieg, but not until an effort is mounted to constrain them rigorously using modern radiometric approaches.

Reciprocal altruism between male vampire bats, Desmodus rotundus

We conducted a 7-month behavioural study of a captive colony of vampire bats and documented that reciprocal altruism between adult males of low relatedness did occur, was relatively common, and was associated with a very low-intensity, non-linear dominance relationship between males. The experimental group consisted of two male and four female adult vampire bats of four independent maternal lines. We calculated relatedness between members of the colony from genealogies (Krebs & Davies 1978) using data extending back three generations. We determined maternal contributions directly, and determined paternal contributions probabilistically using the number of available potential sires at the times of conception. Relatedness between the two males (32L and 35R) was 0.26 (x41 s~=O.l5 & 0.06 for the whole colony). The males were 51 and 42 months of age, respectively, at the conclusion of the study. Bats were housed in a 0.4-m3 plywood roost box designed to simulate a hollow tree and provide a variety of roosting options in all three dimensions. We subjected the colony to experimental manipulations (unpublished data) intended to promote blood-sharing behaviour and test the extent of reciprocity and effects of ‘cheating’ (i.e. nonreciprocation).

Pleistocene depositional history in a periglacial terrane: A 500 k.y. record from Kents Cavern, Devon, United Kingdom

The signifi cance of the stratigraphic record in Kents Cavern, Devon, United Kingdom, to the interpretation of the British Quaternary is confi rmed on the basis of a thorough reexamination of the deposits in concert with 2 new Al-Be cosmogenic and 34 new thermal ionization mass spectrometry U-Th dates. The deposits show evidence of complex reworking in response to periglaciation, and the main fl owstone deposit is a multilayered complex spanning marine isotope stage (MIS) 11‐3. The lowermost unit of fl sands is Cromerian or older. The second deposit, a muddy breccia of surfi cial periglacial solifl uction material containing Acheulian artifacts, entered the cave during MIS 12 from highlevel openings to the west. Cave bears denned in the cave during MIS 11, the Hoxnian interglacial; their bones are capped by an MIS 11 calcite fl owstone layer. From MIS 11 onward, each interglacial period and the warmer interstadial periods (MIS 11, 10b, 9, 7, 6b, 5, and 3) produced calcite fl owstone deposition in the cave; MIS 9 was particularly active. Each glacial or stadial period (MIS 10c, 10a, 8, 6c, 6a, 4, and 2) caused periglacial activity in the cave, during which the thinner layers of calcite were fractured by frost heave and redistributed by solifl uction. This sequence was interrupted during MIS 3‐2 with the

Ammonia Volatilization in a Mexican Bat Cave Ecosystem

Direct measurements of gaseous ammonia in the atmosphere of a dry bat cave containing several million insectivorous bats revealed a peak concentration of 1779 ppm (0.96 mg/dm3). Observations indicate that the origin of the gaseous ammonia is rapid microbial decomposition of bat urea, not chitinous guano. Modelling of ammonia distribution and diffusion indicates that ammonia production at the Cueva del Tigre is ∼257 g NH3/day, equivalent to the decomposition of ∼454 g urea/day. Ammonia production is also characterized by significant isotopic fractionation favoring isotopically light (δ15N depleted) ammonia.

Terrestrial LiDAR-based automated counting of swiftlet nests in the caves of Gomantong, Sabah, Borneo.

High resolution terrestrial laser scanning (TLS) within the Simud Hitam Cave, Gomantong, has proven successful at discriminating the nests of black-nest swiftlets from roosting bats in high, inaccessible locations. TLS data were imported into ArcGIS software, allowing for semi-automated counting of nests based on resolved geometry and laser return intensity. Nest resolution and counting accuracy was better than 2%. Spatial analysis of nest locations has established a maximum packing density of 268 nests/m2 in optimum locations, which correspond to roof slopes of >20 degrees. Co-occurring Rhinolophid bats roost adjacent to, but not within nest locations, preferring roof surfaces close to horizontal.

A Note on the Occurrence of a Crayback Stalagmite at Niah Caves, Borneo

Joyce Lundberg1 and Donald A. McFarlane2 Figure 1. Location of Niah Caves, Sarawak, Malaysia

Cryogenic fracturing of calcite flowstone in caves: theoretical considerations and field observations in Kents Cavern, Devon, UK.

2WM. Keck Science Center, The Claremont Colleges, 925 North Mills Avenue, Claremont CA 91711 USA (dmcfarla@jsd.claremont.edu) Lundberg J. and McFarlane D. 2012. Cryogenic fracturing of calcite flowstone in caves: theoretical considerations and field observations in Kents Cavern, Devon, UK. International Journal of Speleology, 41(2), 307-316. Tampa, FL (USA). ISSN 0392-6672. http://dx.doi.org/10.5038/1827-806X.41.2.16

A Comparison of Methods for the Probabilistic Determination of Vertebrate Extinction Chronologies

Much effort has been directed toward determining the extinction dates of late Quaternary megafaunal mammals, usually in the context of testing models of anthropogenic “overkill” or terminal Pleistocene climatic change. These studies have typically relied on searching for the youngest reliable date (e.g., Long and Martin, 1974), or on matching the mode of a sequence of dates to the time of presumed anthropogenic impact (e.g., Martin, 1986). Little attention appears to have been paid to the determination of vertebrate extinctions dates by probabilistic methods, although a number of authors have treated the related problem of determining invertebrate fossil taxon ranges in biostratigraphical analysis (e.g., Hay, 1972; Strauss and Sadler, 1989; Gilinsky and Good, 1991), and Badgley (1990) has addressed the importance of statistical evaluation of the relationship between sample size and apparent extinctions in the Eocene vertebrate record. Here, I use Monte Carlo simulation to compare the performance of two published probabilistic techniques and a third technique developed here that is based on median stratigraphic gap length in estimating the 95% confidence interval relative to a known extinction date. When applied to a sample of the published record of radiocarbon dates, these techniques indicate that the current database is inadequate to constrain the “late Pleistocene” megafaunal extinction event(s) to the narrow chronological window required by the “blitzkrieg” anthropogenic overkill model (but see Alroy, this volume; Martin and Steadman, this volume). Although this result is not disconfirmatory of the blitzkrieg model, it does argue for the necessity of continuing to improve the data base of published radiocarbon dates.

Estimating Colony Size of the Wrinkle-Lipped Bat, Chaerephon plicatus (Chiroptera: Molossidae) at Gomantong, Sabah, by Quantitative Image Analysis

The Gomantong cave system, Kinabatangan, Sabah (Malaysia) hosts one of the largest bat colonies known from north Borneo. The nightly exodus of Chaerophon plicatus from this site is an economically valuable tourist attraction, and must impose significant controls on the regional ecology. Monitoring ecosystem health requires monitoring bat population size, but no quantitative assessments for the Gomantong colony are available in the literature. Traditional censusing techniques (based on packing density and roost area or on roost exodus counts) yield notoriously unreliable results. Here we have applied innovative image analysis and counting techniques to videographic, photographic and terrestrial laser scanning data obtained in July 2012. The colony exits in a consistent stream along a narrow exit trajectory. The laser scanning of the large cave entrance allowed precise measurement of bat position. Video data provided 0.02-second time resolution. Average flight speed was calculated (10.38 ± 0.85 m/sec), bat exit rate was estimated at three minute intervals (peaking at 14,000 bats/minute) and then summed over the 40 minutes of bat flight. The resultant colony size estimate of 275,625–276,939 (95% confidence interval) individuals of C. plicatus in Gomantong Caves in 2012 demonstrates that the technique is viable, provides a realistic basis for ecosystem management, and can be repeated to monitor ecosystem change. The estimated insect consumption by the colony of this size is 927 ± 191 metric tons of insects per year over an estimated 270 km2 area, a very important component in maintaining ecosystem stability in the Gomantong Forest Reserve and the Kinabatangan Wildlife Sanctuary, as well as pest control over the large agricultural tracts of the region.