Showing posts with label Borneo. Show all posts
Showing posts with label Borneo. Show all posts

Friday, March 30, 2012

Where Common Snakes are Rare and Rare Snakes are Common - On the Abundance of Tropical Snakes

Above: the arboreal cat snake, Boiga jaspidea; below the cryptozoic Gongylosoma baliodeirus. Photographed in the Danum Valley, Sabah, Malaysia.

Hans Breuer's post on Herp Nation's web site, Herping in the Tropics - Ecstasy or Nightmare?, brought back memories from another lifetime. In 1989 I spent a couple of months collecting data and specimens in Sabah's Danum Valley, an area of more than 400 sq km of lowland and hill dipterocarp forest that ranges in elevation from 150 to 1093 m asl. It was one of four trips to the Danum Valley run by the Field Museum to investigate the community ecology of the herpetofauna in Southeast Asia. From those four trips we put together a field guide and key to the snakes of the area (Murphy et al. 1994).

The article contained a bar graph of the 36 species found in Danum over 166 days of field work and how many of each species were collected. The graph is shown below, the photo insert is the species found most often, Pseudorabdion collaris, a small fossorial snake encountered while turning cover or raking leaf litter. 

Snakes are not easy to find in the tropics. The 166 days of field work produced 161 specimens (0.969 snakes per day). This was accomplished with three to four people working in the field a minimum of 6 hours per day (so at least 18 hours of effort per day to produce just less than one snake per day).

This experience is not unusual. William Beebe (1946) published the results of 36 months of field work at Kartabo, Guyana in one square mile of lowland tropical forest. He collected 425 snakes representing 52 species over 1080 days, or 0.39 snakes per day.

Dunn (1949) described a collection of snakes made by H.C. Clark in Panama. Dunn described 10,690 snakes representing collected over 13 years (4745 days)at four locations (the number of species varied between 40 and 60). The result was 2.25 snakes per day but this was a commercial venture involving many people.

Duellman (1978) reported on 1440 days of field work at Santa Cecilia, Ecuador and four nearby localities. His data show 564 specimens of 51 species, or about 0.38 snakes per day.

Today, the best answer as to why tropical snakes are difficult to find and when you do find them, rarely do you find a single species to be particularly abundant, seems to be exactly what Breuer concluded, the vast number number of hiding places in the tropics combined with the cryptic nature of snakes makes common snakes rare and rare snakes common. It also suggests, the diversity of snakes has been greatly under estimated and much remains to be discovered.

Beebe, W. 1946. Field notes on the snakes of Katabo, British Guiana, and Caripito, Venezuela. Zoologica 31, 11-51.

Duellman, WE. 1978. The biology of an equatorial herpetofauna in Amazonian Ecuador. University of Kansas, Miscellaneous Publications (65), 1-352.

Dunn, ER. 1949. Relative abundance of some Panamanian snakes. Ecology 30, 39-57.

Murphy JC, Voris HK, Karns, DK. 1994, A field guide and key to the snakes of the Danum Valley, a Bornean  tropical forest ecosystem. Bulletin of the Chicago Herpetological Society 29(7):133-151.

Friday, August 19, 2011

Further, faster, higher: wildlife responds increasingly rapidly to climate change

New research by scientists in the Department of Biology at the University of York shows that species have responded to climate change up to three times faster than previously appreciated. These results are published in the latest issue of the leading scientific journal Science.

Faster distribution changes. Species have moved towards the poles (further north in the northern hemisphere, to locations where conditions are cooler) at three times the rate previously accepted in the scientific literature, and they have moved to cooler, higher altitudes at twice the rate previously realised.

These changes are equivalent to animals and plants shifting away from the Equator at around 20 cm per hour, for every hour of the day, for every day of the year

Analysing data for over 2000 responses by animal and plant species, the research team estimated that, on average, species have moved to higher elevations at 12.2 metres per decade and, more dramatically, to higher latitudes at 17.6 kilometres per decade.

Project leader Chris Thomas, Professor of Conservation Biology at York, said: “These changes are equivalent to animals and plants shifting away from the Equator at around 20 cm per hour, for every hour of the day, for every day of the year. This has been going on for the last 40 years and is set to continue for at least the rest of this century. ”

The link to climate change. This study for the first time showed that species have moved furthest in regions where the climate has warmed the most, unambiguously linking the changes in where species survive to climate warming over the last 40 years.

First author Dr I-Ching Chen, previously a PhD student at York and now a researcher at the Academia Sinica in Taiwan, said: “This research shows that it is global warming that is causing species to move towards the poles and to higher elevations. We have for the first time shown that the amount by which the distributions of species have changed is correlated with the amount the climate has changed in that region.”

Co-author Dr Ralf Ohlemüller, from Durham University, said: “We were able to calculate how far species might have been expected to move so that the temperatures they experience today are the same as the ones they used to experience, before global warming kicked in. Remarkably, species have on average moved towards the poles as rapidly as expected.”

A diversity of changes. These conclusions hold for the average responses of species, but individual species showed much greater variation. Some species have moved much more slowly than expected, others have not moved, and some have even retreated where they are expected to expand. In contrast, other species have raced ahead, perhaps because they are sensitive to a particular component of climate change (rather than to average warming), or because other changes to the environment have also been driving their responses.

Co-author Dr David Roy, from the Centre for Ecology & Hydrology, illustrates this variation among species: “In Britain, the high brown fritillary butterfly might have been expected to expand northwards into Scotland if climate warming was the only thing affecting it, but it has in fact declined because its habitats have been lost. Meanwhile, the comma butterfly has moved 220 kilometres northwards from central England to Edinburgh, in only two decades.”

Similar variation has taken place in other animal groups. Cetti’s warbler, a small brown bird with a loud voice, moved northwards in Britain by 150 kilometres during the same period when the Cirl bunting retreated southward by 120 kilometres, the latter experiencing a major decline associated with the intensification of agriculture.

How they did the research. The researchers brought together all of the known studies of how species have changed their distributions, and analysed them together in a “meta-analysis”. The changes that were studied include species retreating where conditions are getting too hot (at low altitudes and latitudes), species expanding where conditions are no longer too cold (at high altitude and latitudes), and species staying where they are but with numbers declining in hotter parts and increasing in cooler parts of the range.

They considered studies of latitudinal and elevational range shifts from throughout the world, but most of the available data were from Europe and North America.

Birds, mammals, reptiles, insects, spiders, other invertebrates, and plants featured in the evidence. For example, I-Ching Chen and her colleagues discovered that moths had on average moved 67 metres uphill on Mount Kinabalu in Borneo.

Co-author Jane Hill, Professor of Ecology at York, said: “We have taken the published literature and analysed it to detect what the overall pattern of change is, something that is not possible from an individual study. It’s a summary of the state of world knowledge about how the ranges of species are responding to climate change. Our analysis shows that rates of response to climate change are two or three times faster than previously realised.”

Implications. The current research does not explicitly consider the risks posed to species from climate change, but previous studies suggest that climate change represents a serious extinction risk to at least 10 per cent of the world’s species. Professor Thomas says: “Realisation of how fast species are moving because of climate change indicates that many species may indeed be heading rapidly towards extinction, where climatic conditions are deteriorating. On the other hand, other species are moving to new areas where the climate has become suitable; so there will be some winners as well as many losers.”

Original Article:
I.-C. Chen, J. K. Hill, R. Ohlemuller, D. B. Roy, C. D. Thomas. Rapid Range Shifts of Species Associated with High Levels of Climate Warming. Science, 2011; 333 (6045): 1024 DOI: 10.1126/science.1206432

Sunday, April 17, 2011

Another New Tiny Frog From Borneo

The Borneo microhylid, Microhyla 
berdmorei. This species is larger
than the one described here, females
of this species reach 32 mm JCM
Frogs in the family Microhylidae are mostly small, ground dwelling species that specilize in feeding on ants - there are exceptions, some have adapted to life in the trees, others are burrowers, and some are semi-aquatic; and some have adapted to eating larger prey. The genus Microhyla is widely distributed from the Japan, Taiwan, and southern China, westward to Southeast Asia, and South Asia including Sri Lanka Currently, about 30 species are recognized. The island of Borneo contains five known species of Microhyla (M. berdmorei, M. borneensis, M. perparva, M. petrigena, and M. maculifera). Recently, Das and Haas described M. nepenthicola from Sarawak, emphasizing its small size as the Old World’s smallest frog, and recorded its unique nepenthiphilous breeding habits - depositing the eggs in water that collects in plants - when they described the species. In the description of M. nepenthicola they treated a sympatric, and sometimes syntopic, larger sized species as M. borneensis. Parker (1934) identified a nepenthiphilous larva from Kuching, near the type locality of M. borneensis. During herpetological fieldwork in Sarawak, Masafumi Matsui studied nepenthiphilous larvae and their parental species at various altitudes of Gunung (= Mt.) Serapi, including the type locality of M. nepenthicola (Das & Haas). Some specimens that keyed out to M. borneensis using Inger's (1966) key, except they had a smaller adult body size. At the same locality, specimens of Microhyla sympatric with the small form also keyed out to M. borneensis. However their body size better fits his description than the smaller form. Matsui also found the large form and larvae assigned to M. borneensis in ponds and stream-side pools in Sarawak and Sabah, and the literature led him to consider the small, nepenthiphilous form as true M. borneensis, and idea confirmed examination of the holotype of M. borneensis. This lead Matsui to described Microhyla malang, a new species of microhylid from Gunung Serapi, Matang Range, in the suburbs of Kuching, Sarawak.The name malang is a Malay word meaning "unlucky," and alludes to the long history of taxonomic confusion with its related species, M. borneensis.To date the new species is known from western Sarawak and eastern Sabah, Malaysian Borneo at altitudes of 50 to 555 m above sea level. M. malang is sympatric with M. borneensis around the type locality, in Kubah National Park. Tadpoles were found in ponds and in shallow, muddy pools in drying stream beds. Adult males are in the size range of 18 to 22 mm, making it one of the smallest frogs of the Eastern Hemisphere.

Matsui, M. 2011. Taxonomic revision of one of the Old World's smallest frogs, with description of a new Bornean Microhyla (Amphibia: Microhylidae) Zootaxa 2814:33-49.