Life can be scary for endangered loggerhead sea turtles immediately after they hatch. After climbing out of their underground nest, the baby turtles must quickly traverse a variety of terrains for several hundred feet to reach the ocean.
While these turtles’ limbs are adapted for a life at sea, their flippers enable excellent mobility over dune grass, rigid obstacles and sand of varying compaction and moisture content. A new field study conducted by researchers at the Georgia Institute of Technology is the first to show how these hatchlings use their limbs to move quickly on loose sand and hard ground to reach the ocean. This research may help engineers build robots that can travel across complex environments.
“Locomotion on sand is challenging because sand surfaces can flow during limb interaction and slipping can result, causing both instability and decreased locomotor performance, but these turtles are able to adapt,” said Daniel Goldman, an assistant professor in the Georgia Tech School of Physics. “On hard-packed sand at the water’s edge, these turtles push forward by digging a claw on their flipper into the ground so that they don’t slip, and on loose sand they advance by pushing off against a solid region of sand that forms behind their flippers.”
Details of the study were published online on February 10, 2010 in the journal Biology Letters. This research was supported by the Burroughs Wellcome Fund, National Science Foundation, and the Army Research Laboratory.
Click here to watch a video of a loggerhead sea turtle on the beach running from its nest to the water.
In collaboration with the Georgia Sea Turtle Center, biology graduate student Nicole Mazouchova studied the movement of sea turtle hatchlings of the species Caretta caretta at Jekyll Island on the coast of Georgia. She and research technician Andrei Savu worked from a mobile laboratory that contained a nearly three-foot-long trackway filled with dry Jekyll Island sand.
The trackway contained tiny holes in the bottom through which air could be blown. The air pulses elevated the granules and caused them to settle into a loosely packed solid state, allowing the researchers to closely control the density of the sand.
In addition to challenging hatchlings to traverse loosely packed sand in the trackway, the researchers also studied the turtles’ movement on hard surfaces -- a sandpaper-covered board placed on top of the sand. Two high-speed cameras recorded the movements of the hatchlings along the trackway, and showed how the turtles altered their locomotion to move on different surfaces.
“We assumed that the turtles would perform best on rigid ground because it would not give way under their flippers, but our experiments showed that while the turtles’ average speed on sand was reduced by 28 percent relative to hard ground, their maximal speeds were the same for both surfaces,” noted Goldman.
Click here to watch a video showing how a loggerhead sea turtle hatchling moves on granular media.
The researchers’ investigations showed that on the rigid sandpaper surface, the turtles anchored a claw located on their wrists into the sandpaper and propelled themselves forward. During the thrusting process, one of the turtle’s shoulders rotated toward its body and its wrist did not bend, keeping the limb fully extended.
In contrast, on loosely packed sand, pressure from the thin edge of one of the turtle’s flippers caused the limb to penetrate into the sand. The turtle’s shoulder then rotated as the flipper penetrated until the flipper was perpendicular to the surface and the turtle’s body lifted from the surface.
“The turtles dug into the loosely packed sand, lifted their bellies off the ground, lurched forward, stopped, and did it again,” explained Goldman.
To extend their biological observations, Goldman and physics graduate student Nick Gravish designed an artificial flipper system in the laboratory. The flipper consisted of a thin aluminum plate that was inserted into and dragged along the trackway filled with Jekyll Island sand. Calibrated strain gauges mounted on the flipper provided force measurements during the dragging procedure.
“Our model revealed that a major challenge for rapid locomotion of hatchling sea turtles on sand is the balance between high speed, which requires large inertial forces, and the potential for failure through fluidization of the sand,” explained Goldman. “We believe that the turtles modulate the amount of force they use to push into the sand so that it remains below the force required for the ground to break apart and become fluidlike.”
Goldman and his team plan to conduct further field studies and laboratory experiments to determine if and how the turtles control their limb movements on granular media to avoid sand fluidization. They are also developing robots that move along granular media like the sea turtle hatchings.
“These research results are valuable for roboticists who want to know the minimum number of appendage features necessary to move effectively on land and whether they can just design a robot with a flat mitt and a claw like these turtles have,” noted Goldman.
This material is based on work supported by the Burroughs Wellcome Fund Career Award at the Scientific Interface. Work related to physics was supported by the Army Research Laboratory (ARL) MAST CTA under Cooperative Agreement Number W911NF-08-2-0004 and the National Science Foundation (NSF) under Award Number CMMI-0825480. Any opinions, views, findings, conclusions or recommendations expressed in this document are those of the researcher and should not be interpreted as representing the official policies, either expressed or implied, of ARL, NSF, or the U.S. Government.
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Showing posts with label georgia tech. Show all posts
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Tuesday, March 2, 2010
Wednesday, June 10, 2009
Georgia Tech Study Reveals How Snakes Slither on Flat Terrain
Snakes use both friction generated by their scales and redistribution of their weight to slither along flat surfaces, researchers at New York University (NYU) and the Georgia Institute of Technology have found. Their findings, which appear in the latest issue of the journal Proceedings of the National Academy of Sciences, run counter to previous studies that have shown snakes move by pushing laterally against rocks and branches.
“We found that snakes’ belly scales are oriented so that snakes resist sliding toward their tails and flanks,” said the paper’s lead author, David Hu, a former postdoctoral researcher at NYU’s Courant Institute of Mathematical Sciences and now an assistant professor in Georgia Tech’s George W. Woodruff School of Mechanical Engineering. “These scales give the snakes a preferred direction of motion, which makes snake movement a lot like that of wheels, cross-country skis, or ice skates. In all these examples, sliding forwards takes less work than does sliding sideways.”
The study’s other co-authors were Jasmine Nirody and Terri Scott, both undergraduate researchers at NYU, and Michael Shelley, a professor of mathematics and neural science and the Lilian and George Lyttle Professor of Applied Mathematics at Courant.
The study centered on the frictional anisotropy—or resistance to sliding in certain directions—of a snake’s belly scales. While previous investigators had suggested that the frictional anisotropy of these scales might play a role in locomotion over flat surfaces, the details of this process had not been understood.
To explore this matter, the researchers first developed a theoretical model of a snake’s movement. The model determined the speed of a snake’s center of mass as a function of the speed and size of its body waves, taking into account the laws of friction and the scales’ frictional anisotropy. The model suggested that a snake’s motion arises by the interaction of surface friction and its internal body forces.
To confirm movement as predicted by the model, the researchers then measured the sliding resistance of snake scales and monitored the movement of snakes through a series of experiments on flat and inclined surfaces. They employed video and time-lapse photography to gauge their movements.
The results showed a close relationship between what the model predicted and the snakes’ actual movements. The theoretical predictions of the model were generally consistent with the snakes’ actual body speeds on both flat and inclined surfaces.
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“We found that snakes’ belly scales are oriented so that snakes resist sliding toward their tails and flanks,” said the paper’s lead author, David Hu, a former postdoctoral researcher at NYU’s Courant Institute of Mathematical Sciences and now an assistant professor in Georgia Tech’s George W. Woodruff School of Mechanical Engineering. “These scales give the snakes a preferred direction of motion, which makes snake movement a lot like that of wheels, cross-country skis, or ice skates. In all these examples, sliding forwards takes less work than does sliding sideways.”
The study’s other co-authors were Jasmine Nirody and Terri Scott, both undergraduate researchers at NYU, and Michael Shelley, a professor of mathematics and neural science and the Lilian and George Lyttle Professor of Applied Mathematics at Courant.
The study centered on the frictional anisotropy—or resistance to sliding in certain directions—of a snake’s belly scales. While previous investigators had suggested that the frictional anisotropy of these scales might play a role in locomotion over flat surfaces, the details of this process had not been understood.
To explore this matter, the researchers first developed a theoretical model of a snake’s movement. The model determined the speed of a snake’s center of mass as a function of the speed and size of its body waves, taking into account the laws of friction and the scales’ frictional anisotropy. The model suggested that a snake’s motion arises by the interaction of surface friction and its internal body forces.
To confirm movement as predicted by the model, the researchers then measured the sliding resistance of snake scales and monitored the movement of snakes through a series of experiments on flat and inclined surfaces. They employed video and time-lapse photography to gauge their movements.
The results showed a close relationship between what the model predicted and the snakes’ actual movements. The theoretical predictions of the model were generally consistent with the snakes’ actual body speeds on both flat and inclined surfaces.
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Wednesday, February 11, 2009
Georgia Tech Biologists Find Gene Network That Gave Rise to First Tooth
Scientists at the Georgia Institute of Technology have identified a set of genes that they believe was responsible for forming the first teeth in vertebrates. This gene network is believed to have been responsible for the formation of teeth in the throat of the first jawless fish half a billion years ago and are still responsible for the development of teeth in the jaws of all animals today. The research appears online in the journal PLoS Biology beginning February 10.
“We have identified a core set of genes that probably made the first tooth in these ancient vertebrates and still governs the formation of teeth in modern vertebrates including humans. So it’s likely that every tooth made throughout the evolution of vertebrates has used this core set of genes,” said Gareth Fraser, postdoctoral fellow in Georgia Tech’s School of Biology.
The first vertebrates to have teeth were a group of eel-like jawless fish known as the conodonts that had teeth not in their mouth, but lining the throat. They’re long since extinct, but Fraser, along with J. Todd Streelman, assistant professor in Georgia Tech’s School of Biology, investigated the teeth in a group of fish known for their rapid rate of evolution, the cichlids of Africa’s Lake Malawi. The cichlids have teeth in both their oral jaws, like humans, and deep in their throats on a pharyngeal jaw. A co-author of the paper, Darrin Hulsey, first identified a surprising positive correlation between the number of teeth in the oral jaw and throat in these fish.
“Originally, I thought there wouldn’t be a correlation due to the developmental differences and the evolutionary distinction between the two jaw regions, but it turns out there is,” explained Fraser. “So fish that have fewer oral teeth also have fewer pharyngeal teeth. This shows that on some level there’s a genetic control that governs the number of teeth in both regions.”
The team investigated what this control might be by using a technique localizing gene expression in the cells during tooth development, known as insitu hybridization, and found that a common genetic network governs teeth in both locations.
“So seemingly, regardless of where you grow a tooth, whether it’s in the jaw or the pharynx, you use the same core set of genes to do it,” said Streelman. “We also think it’s probable that this network is not just acting in teeth, but also in other similarly patterned structures like hair and feathers.”
In another finding in the same paper, Fraser and colleagues found that a set of genes known as Hox genes, which control where limbs and organs should form during development, are expressed in the teeth and jaws found in the pharynx. It has long been known that Hox genes are not expressed in the oral jaw, and it’s widely believed that this lack of expression is responsible for the evolution of the oral jaws. Fraser hypothesized that these Hox genes should be “switched off” during the formation of the pharyngeal jaw as is the case for the oral jaw. The study shows that this isn’t the case.
“The prevailing theory suggests that the loss of Hox genes in the oral region during the transition from jawless to jawed vertebrates facilitated the evolution and diversity of oral jaws. Our data suggest that loss of Hox genes is not an absolute requirement to make a toothed, functional jaw,” said Streelman.
The authors of the study were Gareth J. Fraser, C. Darrin Hulsey, Ryan F. Bloomquist, Kristine Uyesugi, Nancy R. Manley and J. Todd Streelman.
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“We have identified a core set of genes that probably made the first tooth in these ancient vertebrates and still governs the formation of teeth in modern vertebrates including humans. So it’s likely that every tooth made throughout the evolution of vertebrates has used this core set of genes,” said Gareth Fraser, postdoctoral fellow in Georgia Tech’s School of Biology.
The first vertebrates to have teeth were a group of eel-like jawless fish known as the conodonts that had teeth not in their mouth, but lining the throat. They’re long since extinct, but Fraser, along with J. Todd Streelman, assistant professor in Georgia Tech’s School of Biology, investigated the teeth in a group of fish known for their rapid rate of evolution, the cichlids of Africa’s Lake Malawi. The cichlids have teeth in both their oral jaws, like humans, and deep in their throats on a pharyngeal jaw. A co-author of the paper, Darrin Hulsey, first identified a surprising positive correlation between the number of teeth in the oral jaw and throat in these fish.
“Originally, I thought there wouldn’t be a correlation due to the developmental differences and the evolutionary distinction between the two jaw regions, but it turns out there is,” explained Fraser. “So fish that have fewer oral teeth also have fewer pharyngeal teeth. This shows that on some level there’s a genetic control that governs the number of teeth in both regions.”
The team investigated what this control might be by using a technique localizing gene expression in the cells during tooth development, known as insitu hybridization, and found that a common genetic network governs teeth in both locations.
“So seemingly, regardless of where you grow a tooth, whether it’s in the jaw or the pharynx, you use the same core set of genes to do it,” said Streelman. “We also think it’s probable that this network is not just acting in teeth, but also in other similarly patterned structures like hair and feathers.”
In another finding in the same paper, Fraser and colleagues found that a set of genes known as Hox genes, which control where limbs and organs should form during development, are expressed in the teeth and jaws found in the pharynx. It has long been known that Hox genes are not expressed in the oral jaw, and it’s widely believed that this lack of expression is responsible for the evolution of the oral jaws. Fraser hypothesized that these Hox genes should be “switched off” during the formation of the pharyngeal jaw as is the case for the oral jaw. The study shows that this isn’t the case.
“The prevailing theory suggests that the loss of Hox genes in the oral region during the transition from jawless to jawed vertebrates facilitated the evolution and diversity of oral jaws. Our data suggest that loss of Hox genes is not an absolute requirement to make a toothed, functional jaw,” said Streelman.
The authors of the study were Gareth J. Fraser, C. Darrin Hulsey, Ryan F. Bloomquist, Kristine Uyesugi, Nancy R. Manley and J. Todd Streelman.
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Wednesday, November 12, 2008
Ga. Tech Facilitates Virtual Aquarium Visit at SC08
AAG Note: A virtual interaction with the Georgia Aquarium? Cool.
The Georgia Institute of Technology will command a significant presence at next week’s SC08, the international conference on high-performance computing, networking, storage and analysis scheduled for Nov. 15-21, 2008, at the Austin Convention Center in Austin, Texas.
Georgia Tech will co-chair a workshop, participate in panel discussions, present technical papers and host 16 booth presentations and video interviews on emerging high-performance computing projects and application areas. A highlight of Tech’s interactive booth display will be a virtual field trip to the Georgia Aquarium. Utilizing a high bandwidth (1Gbps) channel connecting the Aquarium to the SC08 show floor, visitors to the Georgia Tech booth will be able to interact with researchers, fish and other marine creatures live.
“At Georgia Tech, we believe a strong and expansive high-performance computing research community drives the bigger scientific discoveries and better engineering capabilities at the heart of human progress,” said Dr. Mark Allen, senior vice provost for Research and Innovation at Georgia Tech. “Through this premier industry event, researchers, academics and industry professionals have the opportunity to discuss and demonstrate new innovations and breakthroughs in high-impact areas such as biomedicine, nanoscience, astrophysics and exascale computing.
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The Georgia Institute of Technology will command a significant presence at next week’s SC08, the international conference on high-performance computing, networking, storage and analysis scheduled for Nov. 15-21, 2008, at the Austin Convention Center in Austin, Texas.
Georgia Tech will co-chair a workshop, participate in panel discussions, present technical papers and host 16 booth presentations and video interviews on emerging high-performance computing projects and application areas. A highlight of Tech’s interactive booth display will be a virtual field trip to the Georgia Aquarium. Utilizing a high bandwidth (1Gbps) channel connecting the Aquarium to the SC08 show floor, visitors to the Georgia Tech booth will be able to interact with researchers, fish and other marine creatures live.
“At Georgia Tech, we believe a strong and expansive high-performance computing research community drives the bigger scientific discoveries and better engineering capabilities at the heart of human progress,” said Dr. Mark Allen, senior vice provost for Research and Innovation at Georgia Tech. “Through this premier industry event, researchers, academics and industry professionals have the opportunity to discuss and demonstrate new innovations and breakthroughs in high-impact areas such as biomedicine, nanoscience, astrophysics and exascale computing.
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Saturday, October 25, 2008
Robotic Technology Inspired by Service Dogs
Service dogs, invaluable companions providing assistance to physically impaired individuals, are an elite and desired breed. Their presence in a home can make everyday tasks that are difficult - if not impossible - achievable, enhancing the quality of life for the disabled.
Yet with a cost averaging $16,000 per dog – not to mention the two years of training required to hone these skills – the demand for these canines’ exceeds their availability.
But what if these duties could be accomplished with an electronic companion that provides the same efficiency at a fraction of the cost?
Researchers at the Georgia Institute of Technology have engineered a biologically inspired robot that mirrors the actions of sought-after service dogs. Users verbally command the robot to complete a task and the robot responds once a basic laser pointer illuminates the location of the desired action.
For instance, if a person needs an item fetched, that individual would normally command a service dog to do so and then gesture with their hands toward the location. The service robot mimics the process, with the hand gesture replaced by aiming the laser pointer at the desired item.
Employing this technology, users can accomplish basic yet challenging missions such as opening doors, drawers and retrieving medication.
“It’s a road to get robots out there helping people sooner,” said Professor Charlie Kemp, Georgia Tech Department of Biomedical Engineering. “Service dogs have a great history of helping people, but there’s a multi-year waiting list. It’s a very expensive thing to have. We think robots will eventually help to meet those needs.”
Kemp presented his findings this week at the second IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics – BioRob 2008 – in Scottsdale, Ariz.
This technology was achieved with four-legged authenticity.
Kemp and graduate student Hai Nguyen worked closely with the team of trainers at Georgia Canines for Independence (GCI) in Acworth, Ga. to research the command categories and interaction that is core to the relationship between individuals and service dogs.
Betty, a Golden Retriever, was studied to understand her movements and relationship with commands. Key to the success is Betty’s ability to work with a towel attached to a drawer or door handle, which allows her to use her mouth for such actions as opening and closing. The robot was then successfully programmed to use the towel in a similar manner.
Her handlers were thrilled at the potential benefits of the technology.
“The waiting list for dogs can be five to seven years,” said Ramona Nichols, executive director of Georgia Canines for Independence. “It’s neat to see science happening but with a bigger cause; applying the knowledge and experience we have and really making a difference. I’m so impressed. It’s going to revolutionize our industry in helping people with disabilities.”
In total, the robot was able to replicate 10 tasks and commands taught to service dogs at GCI – including opening drawers and doors - with impressive efficiency. Other successes included opening a microwave oven, delivering an object and placing an item on a table.
“As robotic researchers we shouldn’t just be looking at the human as an example,” Kemp said. “Dogs are very capable at what they do. They have helped thousands of people throughout the years. I believe we’re going to be able to achieve the capabilities of a service dog sooner than those of a human caregiver.”
While the robot may not be able to mirror the personality and furry companionship of a canine, it does have other benefits.
“The robot won’t require the same care and maintenance,” Kemp said. “It also won’t be distracted by a steak.”
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Yet with a cost averaging $16,000 per dog – not to mention the two years of training required to hone these skills – the demand for these canines’ exceeds their availability.
But what if these duties could be accomplished with an electronic companion that provides the same efficiency at a fraction of the cost?
Researchers at the Georgia Institute of Technology have engineered a biologically inspired robot that mirrors the actions of sought-after service dogs. Users verbally command the robot to complete a task and the robot responds once a basic laser pointer illuminates the location of the desired action.
For instance, if a person needs an item fetched, that individual would normally command a service dog to do so and then gesture with their hands toward the location. The service robot mimics the process, with the hand gesture replaced by aiming the laser pointer at the desired item.
Employing this technology, users can accomplish basic yet challenging missions such as opening doors, drawers and retrieving medication.
“It’s a road to get robots out there helping people sooner,” said Professor Charlie Kemp, Georgia Tech Department of Biomedical Engineering. “Service dogs have a great history of helping people, but there’s a multi-year waiting list. It’s a very expensive thing to have. We think robots will eventually help to meet those needs.”
Kemp presented his findings this week at the second IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics – BioRob 2008 – in Scottsdale, Ariz.
This technology was achieved with four-legged authenticity.
Kemp and graduate student Hai Nguyen worked closely with the team of trainers at Georgia Canines for Independence (GCI) in Acworth, Ga. to research the command categories and interaction that is core to the relationship between individuals and service dogs.
Betty, a Golden Retriever, was studied to understand her movements and relationship with commands. Key to the success is Betty’s ability to work with a towel attached to a drawer or door handle, which allows her to use her mouth for such actions as opening and closing. The robot was then successfully programmed to use the towel in a similar manner.
Her handlers were thrilled at the potential benefits of the technology.
“The waiting list for dogs can be five to seven years,” said Ramona Nichols, executive director of Georgia Canines for Independence. “It’s neat to see science happening but with a bigger cause; applying the knowledge and experience we have and really making a difference. I’m so impressed. It’s going to revolutionize our industry in helping people with disabilities.”
In total, the robot was able to replicate 10 tasks and commands taught to service dogs at GCI – including opening drawers and doors - with impressive efficiency. Other successes included opening a microwave oven, delivering an object and placing an item on a table.
“As robotic researchers we shouldn’t just be looking at the human as an example,” Kemp said. “Dogs are very capable at what they do. They have helped thousands of people throughout the years. I believe we’re going to be able to achieve the capabilities of a service dog sooner than those of a human caregiver.”
While the robot may not be able to mirror the personality and furry companionship of a canine, it does have other benefits.
“The robot won’t require the same care and maintenance,” Kemp said. “It also won’t be distracted by a steak.”
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Thursday, October 9, 2008
Diversity of Plant-Eating Fish May be Key to Coral Reef Recovery
For endangered coral reefs, not all plant-eating fish are created equal.
A report scheduled to be published this week in the early edition of the journal Proceedings of the National Academy of Sciences suggests that maintaining the proper balance of herbivorous fishes may be critical to restoring coral reefs, which are declining dramatically worldwide. The conclusion results from a long-term study that found significant recovery in sections of coral reefs on which fish of two complementary species were caged.
Coral reefs depend on fish to eat the seaweeds with which the corals compete, and without such cleaning, the reefs decline as corals are replaced by seaweeds. Different fish consume different seaweeds because of the differing chemical and physical properties of the plants.
“Of the many different fish that are part of coral ecosystems, there may be a small number of species that are really critical for keeping big seaweeds from over-growing and killing corals,” explained Mark Hay, the Harry and Linda Teasley Professor of Biology at the Georgia Institute of Technology. “Our study shows that in addition to having enough herbivores, coral ecosystems also need the right mix of species to overcome the different defensive tactics of the seaweeds.”
By knowing which fish are most critical to maintaining coral health, resource managers could focus on protecting and enhancing the highest-impact species. In situations where local peoples depend on fishing, they might better sustain the reefs on which they depend by harvesting only less critical species.
“This could offer one more approach to resource managers,” Hay added. “If ecosystems were managed for critical mixes of herbivorous species, we might see more rapid recovery of the reefs.”
Believed to be the first study to demonstrate the importance of herbivore diversity in enhancing the growth of coral reefs, the research was conducted at the National Undersea Research Center in Key Largo, Florida. It was supported by the National Oceanic and Atmospheric Administration, the National Science Foundation and the Teasley Endowment at Georgia Tech.
Working 60 feet below the surface near the underwater laboratory Aquarius, Hay and co-author Deron E. Burkpile – who is now at Florida International University in North Miami – constructed 32 cages on a coral reef. Each cage was about two meters square and one meter tall and was sealed so that larger fish could neither enter nor leave.
The number and type of fish placed into each four-square-meter cage varied. Some cages had two fish that were able to eat hard, calcified plants; some had two fish able to eat soft, but chemically-defended plants; some had one of both types, and some had no fish at all. The cages were observed for a period of ten months starting in November 2003, and the change in coral cover and seaweed growth was measured.
“For the cages in which we mixed the two species of herbivores, the fish were able to remove much more of the upright seaweeds, and the corals in those areas increased in cover by more than 20 percent during ten months,” Hay said. “That is a dramatic rate of increase for a Caribbean reef.”
Though the percentage growth was impressive, the actual growth in size of each coral was small, Hay noted. Prior to the experiment, the coral reef areas studied had just four to five percent coverage of live coral. After ten months, the corals caged with the two species showed six to seven percent coverage. Corals caged with just one type of fish or no fish lost as much as 30 percent of their cover during the time period.
Hay and Burkepile attempted to repeat their experiment with a different species of fish, but the underwater cages were wiped away by Hurricane Dennis in July 2005 after only seven months of study.
The researchers studied the effects of the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus) in the first experiment, and the redband parrotfish and princess parrotfish (Scarus taeniopterus) in the second. The two fish per cage was at the “high end” of fish density found on present-day Caribbean reefs, but historic densities might have been much higher before extensive fishing of the Caribbean, Hay said.
Just two decades ago, coral coverage in the Caribbean was commonly 40 to 60 percent. Scientists blame many factors – disease, overfishing, pollution, excessive nutrients and global climate change – for the rapid decline, which has also been seen to differing degrees among coral reefs worldwide.
“Some people would argue that coral reefs really don’t exist as functional ecosystems in the Caribbean anymore,” Hay said. “The best reefs we have today are poor cousins to what was only average 20 years ago.”
For the future, Hay would like to expand the experiments to study the effects of additional species, and repeat the studies in different areas, such as the Fiji Islands, where residents are concerned about sustainability of the coral reefs. Though dependent on local fish for their protein, he said the Fiji Islanders may be able to change their fishing habits if researchers can determine which fish must be protected to help the reefs.
“The data we are seeing in Fiji suggests that diversity may be even more important there than it was in the Caribbean,” he said. “There are a lot of different species doing a lot of very different things. These consumers are very important, and in areas where they are over-fished, the reefs are crashing.”
The study provides more proof of how important biodiversity can be to maintaining healthy ecosystems.
“Species diversity is critically important, but we are losing critical components of the Earth’s ecosystem at an alarming rate,” Hay said. “There has been little work on the role of diversity among consumers and the effect that has on communities. This study will help add to our knowledge in this critical area.”
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A report scheduled to be published this week in the early edition of the journal Proceedings of the National Academy of Sciences suggests that maintaining the proper balance of herbivorous fishes may be critical to restoring coral reefs, which are declining dramatically worldwide. The conclusion results from a long-term study that found significant recovery in sections of coral reefs on which fish of two complementary species were caged.
Coral reefs depend on fish to eat the seaweeds with which the corals compete, and without such cleaning, the reefs decline as corals are replaced by seaweeds. Different fish consume different seaweeds because of the differing chemical and physical properties of the plants.
“Of the many different fish that are part of coral ecosystems, there may be a small number of species that are really critical for keeping big seaweeds from over-growing and killing corals,” explained Mark Hay, the Harry and Linda Teasley Professor of Biology at the Georgia Institute of Technology. “Our study shows that in addition to having enough herbivores, coral ecosystems also need the right mix of species to overcome the different defensive tactics of the seaweeds.”
By knowing which fish are most critical to maintaining coral health, resource managers could focus on protecting and enhancing the highest-impact species. In situations where local peoples depend on fishing, they might better sustain the reefs on which they depend by harvesting only less critical species.
“This could offer one more approach to resource managers,” Hay added. “If ecosystems were managed for critical mixes of herbivorous species, we might see more rapid recovery of the reefs.”
Believed to be the first study to demonstrate the importance of herbivore diversity in enhancing the growth of coral reefs, the research was conducted at the National Undersea Research Center in Key Largo, Florida. It was supported by the National Oceanic and Atmospheric Administration, the National Science Foundation and the Teasley Endowment at Georgia Tech.
Working 60 feet below the surface near the underwater laboratory Aquarius, Hay and co-author Deron E. Burkpile – who is now at Florida International University in North Miami – constructed 32 cages on a coral reef. Each cage was about two meters square and one meter tall and was sealed so that larger fish could neither enter nor leave.
The number and type of fish placed into each four-square-meter cage varied. Some cages had two fish that were able to eat hard, calcified plants; some had two fish able to eat soft, but chemically-defended plants; some had one of both types, and some had no fish at all. The cages were observed for a period of ten months starting in November 2003, and the change in coral cover and seaweed growth was measured.
“For the cages in which we mixed the two species of herbivores, the fish were able to remove much more of the upright seaweeds, and the corals in those areas increased in cover by more than 20 percent during ten months,” Hay said. “That is a dramatic rate of increase for a Caribbean reef.”
Though the percentage growth was impressive, the actual growth in size of each coral was small, Hay noted. Prior to the experiment, the coral reef areas studied had just four to five percent coverage of live coral. After ten months, the corals caged with the two species showed six to seven percent coverage. Corals caged with just one type of fish or no fish lost as much as 30 percent of their cover during the time period.
Hay and Burkepile attempted to repeat their experiment with a different species of fish, but the underwater cages were wiped away by Hurricane Dennis in July 2005 after only seven months of study.
The researchers studied the effects of the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus) in the first experiment, and the redband parrotfish and princess parrotfish (Scarus taeniopterus) in the second. The two fish per cage was at the “high end” of fish density found on present-day Caribbean reefs, but historic densities might have been much higher before extensive fishing of the Caribbean, Hay said.
Just two decades ago, coral coverage in the Caribbean was commonly 40 to 60 percent. Scientists blame many factors – disease, overfishing, pollution, excessive nutrients and global climate change – for the rapid decline, which has also been seen to differing degrees among coral reefs worldwide.
“Some people would argue that coral reefs really don’t exist as functional ecosystems in the Caribbean anymore,” Hay said. “The best reefs we have today are poor cousins to what was only average 20 years ago.”
For the future, Hay would like to expand the experiments to study the effects of additional species, and repeat the studies in different areas, such as the Fiji Islands, where residents are concerned about sustainability of the coral reefs. Though dependent on local fish for their protein, he said the Fiji Islanders may be able to change their fishing habits if researchers can determine which fish must be protected to help the reefs.
“The data we are seeing in Fiji suggests that diversity may be even more important there than it was in the Caribbean,” he said. “There are a lot of different species doing a lot of very different things. These consumers are very important, and in areas where they are over-fished, the reefs are crashing.”
The study provides more proof of how important biodiversity can be to maintaining healthy ecosystems.
“Species diversity is critically important, but we are losing critical components of the Earth’s ecosystem at an alarming rate,” Hay said. “There has been little work on the role of diversity among consumers and the effect that has on communities. This study will help add to our knowledge in this critical area.”
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Wednesday, July 30, 2008
The Wild Side of Georgia Tech
In a community where greater enrollment is often the goal, several members of the Tech community are concerned with keeping their numbers at a status quo.
Construction project manager Steven Johnson and utilities analyst Susan Wardrope work to keep feral cats on campus at a sustainable level, all while preventing more from moving in. Together with a network of campus participants, the group works on its own time—and in most cases, its own dime—to alter, monitor and feed these felines.
A part of Auxiliary Services during his “day” job, Johnson instills the practice of Trap, Neuter and Release (TNR), which works to equalize rather than eliminate feral cat populations. When animal control officers capture these cats, euthanasia is the typical result, as they are well past the age of human socialization. In doing this, a vacuum is created wherein other feral cats will just move into the area, continuing the cycle.
However, the central TNR theory is that a controlled community of altered cats aids in maintaining area populations and keeping more feral cats from moving in.
“The best advantages to having them altered is that they start to concentrate around the feeding stations, and they don’t have any urge to mate,” Wardrope said. “They have their food, their sleeping place and their area that they’re familiar with.”
“They defend their territory, keeping other cats from moving into the area, which stabilizes the population,” Johnson said. “An unaltered male will travel up to three miles. An altered cat will only travel about 300 meters.”
The program at Tech started in 1996. “We’d get reports of cats in the area,” said Johnson, who added he discovered students and employees were leaving food for the animals.
He said they counted 19 adult and juvenile cats on East Campus in those early days. In the first full feral cat census for the Institute, Johnson said they easily counted 179 cats in late 1998—32 in one colony that lived in the president’s glade. (Today, Johnson says, that colony is down to three occasional visitors.) Now, as far as Johnson and his group can tell, about 34 cats call Tech home, including only two or three unaltered females—which Johnson says he is still trying to trap.
According to the duo, 30 to 35 cats on campus is very sustainable. Each feeding station has enough of a colony for one dominant male and one dominant female that protect the territory. This “territorial management practice” leads to a fairly accurate understanding of where overlap between the colonies exists.
Johnson and Wardrope work to answer the call—literally—if someone reports a cat on campus. “I’ll go out that night, see if it’s a new cat or one of our own,” Johnson said. “If it’s a new cat, I’ll try to stake it out and see where it’s going—to established food stations or somewhere else.” Sometimes, Johnson said, people who don’t know about the campus program put a food dish outside of a building for any “strays” they see.
If it is determined that a sighted cat is a new “resident,” Johnson traps it—an undertaking that may require several hours of waiting. (“I know all the third-shift police officers by name.”) He keeps the caged animal in his garage overnight and then carries it to the vet the next morning. The cats are neutered or spayed, vaccinated—many for the first time—and dosed with flea control medication. Males are released the following day after surgery. Females are released three days later. For captured kittens, Johnson either finds adoptive families or takes them to no-kill shelters after they are socialized.
“Without a feeding program to localize a colony, you’ll continue to have mangy-looking cats that are more susceptible to diseases and other vectors that they can catch.” But, in what could be seen as a disadvantage in the program, unaltered females tend to have larger litters because of the better nutrition. “When we first started, cats were giving birth to four, where only 50 percent survived. Now they can give birth to a litter of nine, and seven will survive,” he said.
One challenge Johnson and Wardrope have noticed is well-wishers often will leave food out, which aids in diluting established feeding stations. “We leave a note and let them know,” he said. “We’re trying to get the word out that there is a good program—just by going from 179 to 34 cats shows it’s working.”
But Johnson and Wardrope are by no means acting alone. Roughly 30 people are on his e-mail list, Johnson said, and about six handle the campus-wide feeding stations. Johnson himself handles the heavy lifting: tracking the cats’ movements and trapping them.
“We just started doing this out-of-pocket,” Johnson said. Through the e-mail network, however, people donated food and money for surgeries beyond spaying and neutering.
The duo’s efforts have led to collaborations outside the Institute. When Fulton County’s Animal Control units respond to an on-campus call, Johnson receives a courtesy call if it’s a cat issue. This in turn has expanded his TNR efforts, establishing partnerships with Fulton, Cobb, Douglas and DeKalb counties.
“It’s a quid pro quo,” he says. “Fulton County has the Fix ‘Em Free program. When they found out we were running this initiative at Tech, they offered us use of this program. In exchange, when they have reports of a feral colony somewhere, I’m available to go out and talk to people [about TNR].”
In assisting with feral cat colonies in off-campus communities, Johnson explains the Trap, Neuter and Return philosophy, letting people know the usual fate of a feral animal taken to a shelter. “Once people learn about the program, and Steve offers to take [the cats] in to have them altered and vaccinated, they usually have no problem throwing food out for them,” Wardrope said.
“I volunteer to support both the Fulton County Animal Services and Catlanta, a local organization that is basically the feral cat coordinator of the Lifeline Animal Project.” Catlanta recently received a grant to aid in the spaying and neutering of feral cats within the area. It’s a supplement to what Fulton County currently provides, and the group is now in negotiations with DeKalb County to create a similar “Fix ‘Em Free” program.
“We’ll help get them spayed or neutered, all of them are vaccinated for rabies [and] they can receive additional vaccinations, if requested,” Johnson said, adding that almost all counties have a low-cost program that supplements the cost of altering a cat or dog. “I mainly concentrate on the feral cats, and I’ll go out and do the assessment—is it just a backyard colony; or an abandoned cat colony that’s gone feral. Then I’ll report to the agency that’s going to sponsor it—Catlanta [or] Southern Hope.”
And evidence points to TNR reducing the load on animal shelters. Excepting a spike due to foreclosure increases, Johnson said, Fulton County has noticed a marked reduction in the amount of feral cats brought to the shelter.
According to Johnson, Atlanta-area programs have attracted the attention of several national organizations, including the Humane Society of the United States and Alley Cat Allies (which fights for TNR protocols nationwide). “We haven’t gotten our city commissions to enact ordinances yet, but we’re working toward that.”
Some organizations, however, oppose the principles of TNR, including People for the Ethical Treatment of Animals (PETA), The Wildlife Society and the American Bird Conservancy. PETA states on its Web site: “Because of the huge number of feral cats and the severe shortage of good homes, the difficulty of socialization, and the dangers lurking where most feral cats live, it may be necessary—and the most compassionate choice—to euthanize feral cats. ... If you leave them where they are, they will almost certainly die a painful death. A painless injection is far kinder than any fate that feral cats will meet if they are left to survive on their own.”
Johnson doesn’t see it that way.
“In a managed colony, human caretakers have just made portions of [the cats’] lives easier by removing the stress of producing multiple litters,” he said. “By offering a tended food station, caretakers provide a steady supplemental food source, which also permits the cats to be observed for injuries and, when necessary, to be trapped for treatment. A minority of cats specialize in bird hunting as opposed to rodent hunting,” Johnson concedes. “But rodents are still the main natural prey species of outdoor cats. Just because one might kill a chipmunk or Carolina wren does not mean they, as a species living within a habitat, deserve to be exterminated.”
Overall, Johnson and Wardrope are trying to get the feral cat management plan under way in the metro area, and then slowly branch out to the outlying counties. And he’s been reaching out to other University System of Georgia units.
But as for Tech, the next steps for the program include establishing the Library and Information Center’s feeding station and then moving further north on campus to the Howey building and the College of Computing. “We’ve gotten reports from the building manager, as well as from the College of Computing, that they’ve seen cats in the area. We’re trying to identify where would be the best place to establish a feeding station.”
Construction project manager Steven Johnson and utilities analyst Susan Wardrope work to keep feral cats on campus at a sustainable level, all while preventing more from moving in. Together with a network of campus participants, the group works on its own time—and in most cases, its own dime—to alter, monitor and feed these felines.
A part of Auxiliary Services during his “day” job, Johnson instills the practice of Trap, Neuter and Release (TNR), which works to equalize rather than eliminate feral cat populations. When animal control officers capture these cats, euthanasia is the typical result, as they are well past the age of human socialization. In doing this, a vacuum is created wherein other feral cats will just move into the area, continuing the cycle.
However, the central TNR theory is that a controlled community of altered cats aids in maintaining area populations and keeping more feral cats from moving in.
“The best advantages to having them altered is that they start to concentrate around the feeding stations, and they don’t have any urge to mate,” Wardrope said. “They have their food, their sleeping place and their area that they’re familiar with.”
“They defend their territory, keeping other cats from moving into the area, which stabilizes the population,” Johnson said. “An unaltered male will travel up to three miles. An altered cat will only travel about 300 meters.”
The program at Tech started in 1996. “We’d get reports of cats in the area,” said Johnson, who added he discovered students and employees were leaving food for the animals.
He said they counted 19 adult and juvenile cats on East Campus in those early days. In the first full feral cat census for the Institute, Johnson said they easily counted 179 cats in late 1998—32 in one colony that lived in the president’s glade. (Today, Johnson says, that colony is down to three occasional visitors.) Now, as far as Johnson and his group can tell, about 34 cats call Tech home, including only two or three unaltered females—which Johnson says he is still trying to trap.
According to the duo, 30 to 35 cats on campus is very sustainable. Each feeding station has enough of a colony for one dominant male and one dominant female that protect the territory. This “territorial management practice” leads to a fairly accurate understanding of where overlap between the colonies exists.
Johnson and Wardrope work to answer the call—literally—if someone reports a cat on campus. “I’ll go out that night, see if it’s a new cat or one of our own,” Johnson said. “If it’s a new cat, I’ll try to stake it out and see where it’s going—to established food stations or somewhere else.” Sometimes, Johnson said, people who don’t know about the campus program put a food dish outside of a building for any “strays” they see.
If it is determined that a sighted cat is a new “resident,” Johnson traps it—an undertaking that may require several hours of waiting. (“I know all the third-shift police officers by name.”) He keeps the caged animal in his garage overnight and then carries it to the vet the next morning. The cats are neutered or spayed, vaccinated—many for the first time—and dosed with flea control medication. Males are released the following day after surgery. Females are released three days later. For captured kittens, Johnson either finds adoptive families or takes them to no-kill shelters after they are socialized.
“Without a feeding program to localize a colony, you’ll continue to have mangy-looking cats that are more susceptible to diseases and other vectors that they can catch.” But, in what could be seen as a disadvantage in the program, unaltered females tend to have larger litters because of the better nutrition. “When we first started, cats were giving birth to four, where only 50 percent survived. Now they can give birth to a litter of nine, and seven will survive,” he said.
One challenge Johnson and Wardrope have noticed is well-wishers often will leave food out, which aids in diluting established feeding stations. “We leave a note and let them know,” he said. “We’re trying to get the word out that there is a good program—just by going from 179 to 34 cats shows it’s working.”
But Johnson and Wardrope are by no means acting alone. Roughly 30 people are on his e-mail list, Johnson said, and about six handle the campus-wide feeding stations. Johnson himself handles the heavy lifting: tracking the cats’ movements and trapping them.
“We just started doing this out-of-pocket,” Johnson said. Through the e-mail network, however, people donated food and money for surgeries beyond spaying and neutering.
The duo’s efforts have led to collaborations outside the Institute. When Fulton County’s Animal Control units respond to an on-campus call, Johnson receives a courtesy call if it’s a cat issue. This in turn has expanded his TNR efforts, establishing partnerships with Fulton, Cobb, Douglas and DeKalb counties.
“It’s a quid pro quo,” he says. “Fulton County has the Fix ‘Em Free program. When they found out we were running this initiative at Tech, they offered us use of this program. In exchange, when they have reports of a feral colony somewhere, I’m available to go out and talk to people [about TNR].”
In assisting with feral cat colonies in off-campus communities, Johnson explains the Trap, Neuter and Return philosophy, letting people know the usual fate of a feral animal taken to a shelter. “Once people learn about the program, and Steve offers to take [the cats] in to have them altered and vaccinated, they usually have no problem throwing food out for them,” Wardrope said.
“I volunteer to support both the Fulton County Animal Services and Catlanta, a local organization that is basically the feral cat coordinator of the Lifeline Animal Project.” Catlanta recently received a grant to aid in the spaying and neutering of feral cats within the area. It’s a supplement to what Fulton County currently provides, and the group is now in negotiations with DeKalb County to create a similar “Fix ‘Em Free” program.
“We’ll help get them spayed or neutered, all of them are vaccinated for rabies [and] they can receive additional vaccinations, if requested,” Johnson said, adding that almost all counties have a low-cost program that supplements the cost of altering a cat or dog. “I mainly concentrate on the feral cats, and I’ll go out and do the assessment—is it just a backyard colony; or an abandoned cat colony that’s gone feral. Then I’ll report to the agency that’s going to sponsor it—Catlanta [or] Southern Hope.”
And evidence points to TNR reducing the load on animal shelters. Excepting a spike due to foreclosure increases, Johnson said, Fulton County has noticed a marked reduction in the amount of feral cats brought to the shelter.
According to Johnson, Atlanta-area programs have attracted the attention of several national organizations, including the Humane Society of the United States and Alley Cat Allies (which fights for TNR protocols nationwide). “We haven’t gotten our city commissions to enact ordinances yet, but we’re working toward that.”
Some organizations, however, oppose the principles of TNR, including People for the Ethical Treatment of Animals (PETA), The Wildlife Society and the American Bird Conservancy. PETA states on its Web site: “Because of the huge number of feral cats and the severe shortage of good homes, the difficulty of socialization, and the dangers lurking where most feral cats live, it may be necessary—and the most compassionate choice—to euthanize feral cats. ... If you leave them where they are, they will almost certainly die a painful death. A painless injection is far kinder than any fate that feral cats will meet if they are left to survive on their own.”
Johnson doesn’t see it that way.
“In a managed colony, human caretakers have just made portions of [the cats’] lives easier by removing the stress of producing multiple litters,” he said. “By offering a tended food station, caretakers provide a steady supplemental food source, which also permits the cats to be observed for injuries and, when necessary, to be trapped for treatment. A minority of cats specialize in bird hunting as opposed to rodent hunting,” Johnson concedes. “But rodents are still the main natural prey species of outdoor cats. Just because one might kill a chipmunk or Carolina wren does not mean they, as a species living within a habitat, deserve to be exterminated.”
Overall, Johnson and Wardrope are trying to get the feral cat management plan under way in the metro area, and then slowly branch out to the outlying counties. And he’s been reaching out to other University System of Georgia units.
But as for Tech, the next steps for the program include establishing the Library and Information Center’s feeding station and then moving further north on campus to the Howey building and the College of Computing. “We’ve gotten reports from the building manager, as well as from the College of Computing, that they’ve seen cats in the area. We’re trying to identify where would be the best place to establish a feeding station.”
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