Showing posts with label amphibian conservation. Show all posts
Showing posts with label amphibian conservation. Show all posts

Sunday, December 11, 2011

A New Bush Viper & The Strategy to Save it from Extinction

Atheris ceratophora, a species related to
A. matildae. Photo Credit Al Cortex.

Fourteen species of the arboreal viper genus Atheris (subfamily Viperinae), sometimes called bush vipers, are distributed over much of central Africa but seem to reach their greatest diversity in east Africa's sky island complex. The Atheris ancestor originated in Africa's Oligocene and they all use an ambush foraging strategey to capture food. Bush viper have frequently evolved in patches of forest on a mountain top and have stayed put, so most recognized species have limited distributions. Because they depend on forests, many of these snakes are threatened by habitat destruction, but they are also threatened by collectors who feed the wildlife market of developed countries.

This week the journal Zootaxa published the description of a spectacular new species of Atheris, Matilda’s Horned Viper, Atheris matildae which was discovered during a biological survey in southern Tanzania. Superficially It resembles the Usambara bush viper, Atheris ceratophora, but it is larger, has distinct scalation and a genetic divergence of 3.18% in one mitochondrial gene, suggesting the two species separated about 2.2 million years. 

Atheris matildae was discovered in a remote montane forest fragment in southwest Tanzania, a remnant of a more widespread forested landscape that was interspersed with plateau grasslands and other naturally isolated forest islands. The Menegon et al. (2011) suggest that A. matildae is a range-restricted forest species, limited to an area smaller than 100 km2 in an area of declining habitat quailty. 

Wildlife trade is estimated to be US$159 billion a year business and  reptiles play a large part in the exotic wildlife trade that is having a devastating effect on wild populations. So much so, that in many parts of Africa it is the single biggest threat to the existence of many wild species. The colourful, Atheris are popular pet snakes in many countries, however, their natural habitat is seriously threatened and the numbers of wild caught animals destined for the pet trade continues to be unsustainable.

Newly discovered bush viper species can bring a high price and this can have a very damaging impact on the population. In the case of Matilda’s Horned Viper, a sudden rush to collect as many specimens as possible could actually extirpate the species in the wild. To avoid the unsustainable collection of such a rare snake, the authors of the species have agreed with the editor of Zootaxa – where the species description is published – to keep the locality as vague as possible, with the possibility of more specific information provided by the authors on request, scientific purposes only. The authors suggest this practice should be taken into consideration by taxonomists every time a new, rare species of potential commercial interest is described.

While collection from the wild is mostly unsustainable and has reached a level whereby it represents perhaps the biggest threat to Tanzania’s amphibians and reptiles, the authors have propsed a conservation strategy to save the new snake and provide a new conservation opportunity. The authors have initiated a breeding program for the new viper in Tanzania. This will act as an ‘insurance population’ to protect the new species from overexploitation, and begin the conservation of its threatened habitat so that this unique animal can persist in the wild. The first few dozens of babies will n\be placed into the market to produce a commercial population that won't depend upon the wild population. This is an attempt to flood the market with specimens of the new species in order to lower the price and to encourage the captive breeding in the most highly demanding countries, and raise funds to establish an in situ community based forest conservation, programme, including environmental education and wildlife management. The authors will also ask CITES to list the wild population of the species in the Appendix 1 and the captive population in the Appendix 2. Find out more about this strategy at: http://www.atherismatildae.org/

Citation
Menegon, M. T. R.B. Davenport and K M. Howell. 2011. Description of a new and critically endangered species of Atheris (Serpentes: Viperidae) from the Southern Highlands of Tanzania, with an overview of the country’s tree viper fauna. Zootaxa 3120: 43–54.

Sunday, December 4, 2011

Indigo Snake Survival Demographics

The Indigo Snake, Drymarchon couperi JCM

The Eastern Indigo snake, Drymarchon couperi has been federally listed as threatened since 1978. It is one of the largest North American colubrids (if not the largest) reaching 2.63 m and has been the focus of intensive research and conservation efforts throughout its range in the southeastern United States. Indigo snakes frequently encounter humans because they  actively forage for food during the day. They prey on a wide range of vertebrates and have been reported to act as scavengers.  Breeding occurs from October to March when the snakes are using sandhill habitats. Gestation lasts 100–150 days and a single clutch of 4–12 relatively large eggs are normally laid in May or June, and they hatch about 90 days later. Drymarchon couperi exhibits male-biased sexual size and require 3 to 4 years of growth before they reach sexual maturity. Indigos often the use xeric sand ridge communities (or sandhills), especially during the fall-winter breeding season and frequently inhabit burrows of the gopher tortoise, Gopherus polyphemus for protection from environmental extremes, fires, and predators.

Hyslop et al. (2011) examined indigo snake demographic data collected over 11 years of capture-mark-recapture (CMR)  studies as well as  2.5 years of radiotelemetry data from snakes in southeastern Georgia, to estimate apparent survival, capture and transition probabilities, and evaluate the factors that influencing these parameters. They estimated the annual survival probability is 0.700 (±0.030 SE), a number  comparable to a knonw fate analysis (radiotelemetry) done at the same site. Body size positively influenced survival, regardless of sex, with larger snakes having a greater chance of surviving a year. Their model averaged estimate of annual adult survival was 0.738 ± 0.030 and 0.515 ± 0.189 for subadults. Population growth rate ranged from 0.96 to 1.03 depending on the value of the probability of transitioning from subadult to adult stage. Their results suggest that protecting adult snakes and their habitats will result in the highest likelihood of long-term population stability and growth. This is excellent news for a species that has been greatly reduced in numbers over the last 50 years. Now, if we can just keep its habitat intact.

Citation
Hyslop N, Stevenson D, Macey J, Carlile L, Jenkins C, et al. 2011. Survival and population growth of a long-lived threatened snake species, Drymarchon couperi  (Eastern Indigo Snake). Population Ecology: 1-12.

Thursday, September 22, 2011

Diverse Ecosystems May Reduce Threat From Bd

The Western Toad, Anaxyrus boreas.

Photo Credit: Ivan Phillipsen, OSU

The following is a press release from Oregon State University.

CORVALLIS, Ore. – Researchers at Oregon State University have shown for the first time that loss of biodiversity may be contributing to a fungal infection that is killing amphibians around the world – a finding that provides more evidence for why biodiversity is important to many ecosystems.

The research, being published this week in Proceedings of the National Academy of Sciences, used laboratory studies of amphibians to show that increased species richness decreased both the prevalence and severity of infection caused by the deadly chytrid fungus, Batrachochytrium dendrobatidis.

“With greater diversity of species, you get a dilution effect that can reduce the severity of disease,” said Catherine Searle, an OSU zoologist and lead author on the study. “Some species are poor hosts, some may not get infected at all, and this tends to slow disease transmission.

“This has been shown in other systems like Lyme disease which infects humans, mice and deer,” she said. “No one has really considered the dilution effect much in amphibians, which are experiencing population declines throughout the world. It’s an underappreciated value of biodiversity.”

It’s generally accepted, the researchers said, that a high diversity of species can protect ecosystem function, help to recycle nutrients, filter air and water, and also protect the storehouse of plant or animal species that may form the basis of medicines, compounds or natural products of value to humans.

Protection against the spread of disease should more often be added to that list, they said.

“Emerging infectious diseases are on the rise in many ecosystems,” said Andrew Blaustein, a co-author on this study, professor of zoology at OSU and leading researcher on the causes of amphibian declines.

“Protection of biodiversity may help reduce diseases,” he said. “It’s another strong argument for why diverse ecosystems are so important in general. And it’s very clear that biodiversity is much easier to protect than it is to restore, once it’s lost.”

The fungus, B. dendrobatidis, can lead to death from cardiac arrest when it reaches high levels in its amphibian hosts. It is not always fatal at lower levels of infection, but is now causing problems around the world. One research team has called the impact of the chytrid fungus on amphibians “the most spectacular loss of vertebrate biodiversity due to disease in recorded history.”

Amphibians face threats from multiple causes, including habitat destruction, pollution, increases in ultraviolet light due to ozone depletion, invasive species, and infectious disease.

The dilution effect can occur in plants and animals, but also in human diseases. In a different report published last year in Nature, researchers noted an increased risk of West Nile encephalitis in the U.S. in areas with low bird diversity. And in more diverse communities, the infection of humans by schistosomiasis – which infects 200 million people worldwide – can be reduced by 25-99 percent.


Citation
Catherine L. Searle, Lindsay M. Biga, Joseph W. Spatafora, Andrew R. Blaustein. A dilution effect in the emerging amphibian pathogen Batrachochytrium dendrobatidis. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1108490108

Sunday, May 29, 2011

Modern EU Agriculture Jeopardises Biodiversity in New Member States

A new study from Romania highlights the importance of traditional agriculture in protecting amphibians.

Traditional agricultural practices can make a major contribution to preserving biodiversity in the EU’s new member states in Central and Eastern Europe. By contrast, the construction of roads and the intensification of agriculture currently encouraged by EU farming subsidies pose a threat to amphibians. The rich natural environment still extant in many accession countries is under threat, according to scientists writing in the journal Biological Conservation.

The researchers from Romania, Germany and the Netherlands investigated amphibians for their study in the Romanian province of Transylvania. They spent nine years studying the populations of various species of newts, frogs and toads in 54 ponds and related their performance to nearby land use.

All in all, the scientists found 10 amphibian species in the surveyed ponds, including EU-wide protected species like the Great Crested Newt and the Yellow Bellied Toad. Statistical evaluation revealed that roads had the biggest impact on their populations. Other factors like the size of ponds, building development, farmland, pasture, woodland and marshlands proved to be far less important. "Roads have a direct negative effect on many species of amphibians, which can get run over by cars. But roads also have an indirect impact, for example by the destruction and isolation of the critical habitats for amphibians such as breeding, summering and overwintering habitats" explained Dr Tibor Hartel from Babeş-Bolyai University, Cluj-Napoca (Romania).

The study area was the "Saxon area" of Southern Transylvania along the Târnava Mare basin in Romania. The agriculture is still largely traditional in this region, sometimes with little changes through the centuries. The landscape is dominated by pasture and deciduous forest, while the arable lands are small sized and scattered across the native grassland vegetation. Mankind’s negative impact on biological diversity is statistically still far lower in Eastern Europe than in the West - but this traditional cultural landscape and hence its unique biodiversity could soon disappear if agriculture were to be intensified. "We believe that the comparatively extensive agriculture in the study region with little machinery and hardly any chemicals provides conditions which are still suitable for many amphibian species," explains Dr Oliver Schweiger from UFZ.
The findings could have important consequences for protective measures for amphibians in regions of Central and Eastern Europe, where farming has remained largely traditional. Preserving traditional, extensive land management could be the key factor in protecting these species. However, that could be a tough challenge, for many regions, joining the EU will lead to more intensive land use and infrastructure expansion. And that in turn will result in the fragmentation of the landscape and the general deterioration of the remaining habitats. Researchers are now calling for a balance to be struck between the legitimate desire for improved infrastructure and higher agricultural yields on the one hand and the beneficial effects of extensive land use on the other. In their view, this challenge should be regarded as an opportunity for Eastern Europe not to repeat the mistakes made in the West.

Photos: The common toad, Bufo bufo. And an agricultural pond Photo credits: Tibor Hartel/Babes-Bolyai-Universität Cluj-Napoca.

Saturday, March 19, 2011

Crawfish Frogs Are Infected with Bd During Breeding Activities


Crawfish Frog, Lithobates areolatus
 Photo Credit: Stanley Trauth
Amphibian populations around the world have been decimated by the chytrid fungus, Batrachochytrium dendrobatidis (Bd), but not all species or individuals in all regions are equally susceptible. Vanessa Kinney and colleagues (2011) report the first case of Bd in Crawfish Frogs (Lithobates areolatus). But, more importantly, describe the nature and the course of this disease in Crawfish Frogs which has an unusual natural history. They investigated whether there is a life history pattern or a seasonal pattern to infection by this fungus, and if it is possible to determine when and where the infection is being acquired and shed. Given the concern for the conservation of Crawfish Frogs, they examined the potential of Bd to cause fatalities in this species and to determine if they are carriers of the fungus, as are other large North American ranids. Crawfish Frogs are a typical North American pond-breeding species that have explosive spring breeding aggregations in seasonal and semi-permanent wetlands. However, when they are not breeding Crawfish Frogs are solitary, isolated from other individuals in burrows dug by crayfish. The burrows penetrate the water table, providing a permanent aquatic habitat when the frogs are not breeding. Over the course of two years Kinney et al. sampled for the presence of Bd in Crawfish Frog adults. Sampling was conducted seasonally, as animals moved from post-winter emergence through breeding migrations, then back into upland burrow habitats. During the study, 53% of Crawfish Frog breeding adults tested positive for Bd in at least one sample; 27% entered breeding wetlands Bd positive; 46% exited wetlands Bd positive. Five emigrating Crawfish Frogs (12%) developed chytridiomycosis and died. In contrast, all 25 adult frogs sampled while occupying upland crayfish burrows during the summer tested Bd negative. One percent of postmetamorphic juveniles sampled were Bd positive. Zoospore equivalents/swab ranged from 0.8 to 24,436; five out of eight frogs with zoospore equivalents near or more than 10,000 died. The data suggest Crawfish Frogs acquire Bd during breeding activities. A Bd-positive female entered a breeding pond on 8 April, 2010 with a low infection intensity (20 zoospore equivalents) and exited 15 days later with a high infection intensity (8,607 zoospore equivalents). A similar situation occurred on 19 April 2010, when a Bd-positive subadult Crawfish Frog entered the breeding pond with 119 zoospore equivalents and exited 5 days later with 23,006 zoospore equivalents. Overall, 46% (42/91) of samples from Crawfish Frogs exiting breeding wetlands on our study site were Bd positive. Thus, infection rates in Crawfish Frog populations increased from near zero during the summer to over 25% following overwintering; rates nearly double again during and after breeding—when mortality occurs—before the infection wanes during the summer. Bd-negative postmetamorphic juveniles may not be exposed again to this pathogen until they take up residence in crayfish burrows, or until their first breeding, some years later.

Citation
Kinney VC, Heemeyer JL, Pessier AP, Lannoo MJ (2011) Seasonal Pattern of Batrachochytrium dendrobatidis Infection and Mortality in Lithobates areolatus: Affirmation of Vredenburg's “10,000 Zoospore Rule”. PLoS ONE 6(3): e16708. doi:10.1371/journal.pone.0016708