Rarest of the Rare: List of Critically Endangered Species
The list of a dozen animals includes an eclectic collection of birds, mammals, reptiles and amphibians. Some are well known, such as the Sumatran orangutan; while others are more obscure, including vaquita, an ocean porpoise. The list appears in the 2010-1011 edition of State of the Wild -- a Global Portrait.
Threats to each species vary widely. In the case of the vaquita, fishermen's nets are catching them and inadvertently causing them to drown. Meanwhile, the Grenada dove -- the national bird of the small island nation -- has been severely impacted by habitat loss. Other species suffer from illegal trade, as in the case of the ploughshare tortoise.
"The Rarest of the Rare provides a global snapshot of some of the world's most endangered animals," said State of the Wild Kent Redford, director of the Wildlife Conservation Society Institute. "While the news is dire for some species, it also shows that conservation measures can and do protect wildlife if given the chance to work."
The list of endangered species includes:
- Cuban crocodile: Currently restricted to two small areas of Cuba.
- Grenada dove: The national bird of Grenada is threatened by habitat loss.
- Florida bonneted bat: Thought to be extinct in 2002; a small colony has since been discovered.
- Green-eyed frog: Only a few hundred of these small amphibians are left.
- Hirola: Also called Hunter's hartebeest; the hirola is a highly threatened African antelope.
- Ploughshare tortoise: With only 400 left, the ploughshare tortoise is threatened by the illegal pet trade.
- Island gray fox: Living on the California Channel Islands, this is the smallest fox in the United States.
- Sumatran orangutan: This population has declined 80 percent during the past 75 years.
- Vaquita: This small ocean porpoise is drowning in fishing nets.
- White-headed langur: Only 59 of these monkeys remain on a small island off Vietnam.
The 2010 list highlights positive news, with two species on the road to recovery thanks to conservation efforts: Rober's tree frog whose population has grown due to captive breeding in zoos; and Przewalski's horse, which is starting to rebuild numbers after being re-introduced into the wild.
The 2010-2011 State of the Wild includes a special section devoted to the impact of human conflicts on wildlife and wild places. It considers how conservation can contribute to peace-building and reconstruction in post-conflict areas.
Invasive Fish and Mussels Team Up to Transfer Toxic Substances Into Great Lakes Walleyes
The links between zebra mussels, round gobies and contaminated Saginaw Bay walleyes is a disturbing example of unanticipated problems that can occur when non-native species get loose in the Great Lakes, said University of Michigan fishery biologist David Jude, lead author of a paper on the topic published online April 9 in theJournal of Great Lakes Research.
"This zebra mussel-to-goby link in Great Lakes contaminated areas is one of the main conduits of PCB transfer to top aquatic predators such as the walleye, and it plays a substantial role in PCB transfer to birds, mammals and reptiles in the region as well," said Jude, a research scientist at the U-M School of Natural Resources and Environment.
Between 2005 and 2007, Jude's team collected walleyes, round gobies and various other fish species, as well as zebra mussels and zooplankton, in the Tittabawassee River, the Saginaw River and Lake Huron's Saginaw Bay. Then they measured levels of PCBs in all those organisms -- the first such study in the Saginaw Bay region.
"Though the levels of PCBs in Saginaw Bay walleyes have declined sharply in recent years, these toxic substances continue to show up at levels high enough to warrant concern," Jude said.
The highest levels were seen in the largest walleyes, which contained an average of 1,900 nanograms of PCBs per gram -- just under the 2,000 nanogram Environmental Protection Agency threshold for mandatory fish-consumption advisories. A nanogram is a billionth of a gram.
Polychlorinated biphenyls, or PCBs, are manmade chemicals that were once used in hundreds of industrial and commercial applications. But the manufacture of PCBs was banned in the United States in 1979, and EPA now classifies the chemicals as probable human carcinogens.
Beginning in the 1940s, factories, chemical manufacturers and municipal wastewater treatment plants discharged PCBs into the Saginaw River; many of the PCBs settled into river-bottom sediments. The contamination led to advisories against human consumption of selected species and sizes of fish from the Saginaw River, as well as many species of fish in the Bay.
In 2000-01, the mouth of the Saginaw River was dredged to remove accumulated sediments contaminated with PCBs, metals and various hazardous compounds. Since then, the level of PCBs has dropped precipitously in Saginaw Bay walleyes.
In addition to the U-M scientists, Jude's team includes researchers from Grand Valley State University and the University of Saskatchewan. The team compared its results to the findings of a similar study conducted in the same area in 1990, prior to the dredging project.
Jude's team found that the average concentration of PCBs in Saginaw River walleyes dropped 65 percent between 1990 and 2007, a result that is consistent with previous studies that also showed significant declines. Much of the change can likely be attributed to the dredging project, though changes in the food web and other factors may also have played a role, Jude said.
The walleye is the top predator in the Saginaw Bay ecosystem, and the bay's world-class walleye fishery is a key part of the $7 billion-a-year Great Lakes fishery.
Twenty years ago, Saginaw Bay walleyes fed mainly on alewives, another non-native fish species. But alewives have been nearly eliminated from Lake Huron, a decline blamed largely on predation by salmon and the proliferation of invasive zebra and quagga mussels, which have depleted two of the alewives' main food sources.
As alewives declined, the zebra mussel/round goby/walleye link enabled substantial amounts of PCBs to continue moving up the food chain and into Saginaw Bay walleyes.
Walleyes prey on round gobies, which in turn gorge on bottom-dwelling zebra mussels that suck up massive amounts of lake water. Each fingernail-size zebra mussel filters up to a liter of water a day -- taking in any toxic substances present in the water. Some of those contaminants are incorporated into the mussels' tissues and shells, and round gobies eat the little mollusks shell and all.
"Zebra mussels can accumulate relatively high concentrations of PCBs, which can then be transferred to round gobies and eventually to walleyes," Jude said.
The Saginaw Bay/Saginaw River region is designated an International Joint Commission Area of Concern, due to contamination of sediments with persistent inorganic and organic pollutants. It is one of 14 Areas of Concern in Michigan.
Authors of the Journal of Great Lakes Research paper are Jude and Stephen Hensler of the University of Michigan, Richard Rediske and Jim O'Keefe of Grand Valley State University, and John Giesy of the University of Saskatchewan.
Support for the study was provided by the U-M School of Natural Resources and Environment and the U-M Office of the Vice President for Research.
Eating Like a Bird Helps Forests Grow
A new study examines complex interactions in the middle of the pyramid, where birds, bats and lizards consume insects. These predators eat enough insects to indirectly benefit plants and increase their growth, Smithsonian scientists report. "Our findings are relevant to natural communities like grasslands and forests, but also to human food production, as these insect-eating animals also reduce insect pests on crop plants," said Sunshine Van Bael, scientist at the Smithsonian Tropical Research Institute.
Previous theory on food webs suggested that the effects of insect-eaters on plants would be weak, because animals like birds not only feed on herbivores -- which is good for the plants- but may also benefit them by feeding spiders and predatory insects. If a bird eats a lot of spiders, for example, caterpillars could be "released" from spider predation and then consume more plant material. The authors found that previous theory did not hold true; in fact, the birds simply ate the spiders and the caterpillars.
The authors reviewed more than 100 studies of insect predation by birds, bats or lizards from four continents. They found that the identity of the predator didn't make much of a difference. Together, by eating herbivores and their insect predators, they reduced damage to plants by 40 percent, which resulted in a 14 percent increase in plant biomass.
"It's no longer apt to say that one 'eats like a bird'," said Van Bael, "Our study shows that birds, bats and lizards act as one big vacuum cleaner up in the treetops. Everything's on the menu."
Nevertheless, there is still a lack of experimental work on the overlap in diets of the insects that birds, lizards and bats are eating, and the insects that the predatory insects, themselves are eating. "Our study shows that birds, bats and lizards protect plants, underscoring the importance of conservation of these species in the face of global change," summed up lead author Kailen Mooney, professor of ecology and evolutionary biology at the University of California-Irvine.
Co-authors of this study, published online by the journalProceedings of the National Academy of Sciences, also include researchers from the University of Maryland, the University of Missouri -- St. Louis, the University of Toledo, and the Smithsonian´s Migratory Bird Center at the National Zoological Park. The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of beauty and importance of tropical ecosystems.
Undersea Superhighway: Long-Distance Larvae Speed to New Undersea Vent Homes
One such "pioneer species,"Ctenopelta porifera, appears to have traveled over 300 kilometers to settle at the site on the underwater mountain range known as the East Pacific Rise. "Ctenopelta had never been observed before at the…study site, and the nearest known population is 350 km to the north," said Lauren S. Mullineaux, a senior scientist in WHOI's biology department.
The discovery -- in collaboration with the Lamont-Doherty Earth Observatory (LDEO) and the NOAA Pacific Marine Environmental Laboratory (PMEL) -- clashes with the widely accepted assumption that when local adult life is wiped out in a hydrothermal eruption, it is replaced by a pool of tiny creatures from nearby vents. In this case, however, the larvae that re-settled the post-eruption vent area are noticeably different from the species that were destroyed and appeared to have traveled great distances to do so.
"This raises the question of how they can possibly disperse so far," says Mullineaux. The findings have implications, she says, for the wider distribution of undersea life. "If these new pioneers persist and cause a regime shift, that will expand their range and increase the regional diversity," Mullineaux says.
A report on the research by Mullineaux and her colleagues is published in the current (April 12) issue of the Proceedings of the National Academy of Sciences.
The discovery of hydrothermal vents on the bottom of the Pacific Ocean in 1977 revolutionized ideas about where and how life could exist. The seafloor vents gushing warm, mineral-rich fluids and teeming with life raised new question that researchers have been studying ever since, including: How can so much life thrive at the sunless seafloor? What is the nature of organisms at hydrothermal vents? How do animals migrate to other vent sites?
It was this last question that motivated Mullineaux and her team as they began their study of a vent area on the East Pacific Rise "to gather observations of currents, larvae and juvenile colonists…in order to understand what physical processes might facilitate dispersal," Mullineaux says. One of the group's primary challenges was to determine where the organisms around the vent came from.
As the scientists set out on their mission in 2006, "we got a surprise," said Mullineaux. "A seafloor eruption was detected at our study site…resulting in changes in topography and enormous disturbance to ecological communities.
"The eruption was, in essence, a natural experiment."
By the time the researchers arrived at the site, they found a scene quite unlike that usually observed at a hydrothermal vent. Normally, such fissures are teeming with life, supported by the hot chemicals that spew from the vents and provide food through microbial chemosynthesis, a deep-sea version of photosynthesis.
But at this spot on the East Pacific Rise, near 9 degrees North, there was no life. The eruption had wiped it out.
"Although the vents survived, the animals did not, and virtually all of the detectable invertebrate communities were paved over," said Mullineaux. "For us, this was an exciting event. In essence it was a natural clearance experiment that allowed us to explore how this elimination of local source populations affected the supply of larvae and re-colonization."
What they found went against the accepted assumption that most of the organisms to re-populate the area would come from relatively nearby. But instead, the new larval inhabitants came from considerable distance.
"These results show clearly that the species arriving after the eruption are different than those before," says Mullineaux, "with two new pioneer species, Ctenopelta porifera and Lepetodrilus tevnianus, prominent."
To the biologist, the most important finding is that "the processes of the larval stage -- as opposed to those of adult organisms--seem to control colonization," Mullineaux says. "We found that a pioneer colonization event by Ctenopelta radically changed the community structure."
But the question remained, how were these weak-swimming larvae propelled such vast distances to the decimated vent area? The answer may lie in a recently developed model by Mullineaux's colleagues Dennis McGillicuddy and Jim Ledwell of WHOI, Bill Lavelle of PMEL and Andreas Thurnherr of LDEO, all part of the LADDER team--LArval Dispersal on the Deep East Pacific Rise.
Seemingly the only way the emigrating larvae could get to their new home from so far away, Mullineaux says, would be to ride ocean-bottom "jets" traveling up to 10 centimeters a second, such as those identified in the work of McGillicuddy and Thurnherr.
Theoretically, however, even these ridge-crest jets might not quite be able to transport the larvae from 350 km within the time frame of their 30-day lifespan, she said. "Either the larvae are using some other transport or they are living longer than we thought," said Mullineaux.
She speculates that large eddies, or whirlpools of water, several hundred kilometers in diameter, may be propelling the migrating larvae even faster -- delivering them to their new home while they are still alive. Or perhaps, she says, the larvae are able to somehow reduce their metabolism and extend their life.
In any case, the findings present an array of fascinating scientific scenarios, Mullineaux says, that warrant further exploration.
They also may open up new ways of looking at the impacts of human activities on the seafloor, such as seafloor mineral mining, which could alter a vent site in a similar way to an eruption. Depending on the site, such activity could conceivably foster a greater diversity of species at a vent that has just been mined, or it could cause extinction, she said. But such scenarios are still highly speculative, she emphasizes
Cat Brain: A Step Toward the Electronic Equivalent
U-M computer engineer Wei Lu has taken a step toward developing this revolutionary type of machine that could be capable of learning and recognizing, as well as making more complex decisions and performing more tasks simultaneously than conventional computers can.
Lu previously built a "memristor," a device that replaces a traditional transistor and acts like a biological synapse, remembering past voltages it was subjected to. Now, he has demonstrated that this memristor can connect conventional circuits and support a process that is the basis for memory and learning in biological systems.
A paper on the research is published online in Nano Letters and is scheduled to appear in the forthcoming April edition of the journal.
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