The future of data storage lies in DNA microcapsules

Storing data in DNA sounds like science fiction, yet it lies in the near future. Professor Tom de Greef expects the first DNA data center to be up and running within five to ten years. Data won't be stored as zeros and ones in a hard drive but in the base pairs that make up DNA: AT and CG. Such a data center would take the form of a lab, many times smaller than the ones today. De Greef can already picture it all. In one part of the building, new files will be encoded via DNA synthesis. Another part will contain large fields of capsules, each capsule packed with a file. A robotic arm will remove a capsule, read its contents and place it back.

We're talking about synthetic DNA. In the lab, bases are stuck together in a certain order to form synthetically produced strands of DNA. Files and photos that are currently stored in data centers can then be stored in DNA. For now, the technique is suitable only for archival storage. This is because the reading of stored data is very expensive, so you want to consult the DNA files as little as possible.

Large, energy-guzzling data centers made obsolete

Data storage in DNA offers many advantages. A DNA file can be stored much more compactly, for instance, and the lifespan of the data is also many times longer. But perhaps most importantly, this new technology renders large, energy-guzzling data centers obsolete. And this is desperately needed, warns De Greef, "because in three years, we will generate so much data worldwide that we won't be able to store half of it."

Together with PhD student Bas Bögels, Microsoft and a group of university partners, De Greef has developed a new technique to make the innovation of data storage with synthetic DNA scalable. The results have been published today in the journal Nature Nanotechnology. De Greef works at the Department of Biomedical Engineering and the Institute for Complex Molecular Systems (ICMS) at TU Eindhoven and serves as a visiting professor at Radboud University.

Scalable

The idea of using strands of DNA for data storage emerged in the 1980s but was far too difficult and expensive at the time. It became technically possible three decades later, when DNA synthesis started to take off. George Church, a geneticist at Harvard Medical School, elaborated on the idea in 2011. Since then, synthesis and the reading of data have become exponentially cheaper, finally bringing the technology to the market.

In recent years, De Greef and his group have looked mainly into reading the stored data. For the time being, this is the biggest problem facing this new technique. The PCR method currently used for this, called 'random access', is highly error-prone. You can therefore only read one file at a time and, in addition, the data quality deteriorates too much each time you read a file. Not exactly scalable.

Here's how it works: PCR (Polymerase Chain Reaction) creates millions of copies of the piece of DNA that you need by adding a primer with the desired DNA code. Corona tests in the lab, for example, are based on this: even a minuscule amount of coronavirus material from your nose is detectable when copied so many times. But if you want to read multiple files simultaneously, you need multiple primer pairs doing their work at the same time. This creates many errors in the copying process.

Every capsule contains one file

This is where the capsules come into play. De Greef's group developed a microcapsule of proteins and a polymer and then anchored one file per capsule. De Greef: "These capsules have thermal properties that we can use to our advantage." Above 50 degrees Celsius, the capsules seal themselves, allowing the PCR process to take place separately in each capsule. Not much room for error then. De Greef calls this 'thermo-confined PCR'. In the lab, it has so far managed to read 25 files simultaneously without significant error.

If you then lower the temperature again, the copies detach from the capsule and the anchored original remains, meaning that the quality of your original file does not deteriorate. De Greef: "We currently stand at a loss of 0.3 percent after three reads, compared to 35 percent with the existing method."

Searchable with fluorescence

And that's not all. De Greef has also made the data library even easier to search. Each file is given a fluorescent label and each capsule its own color. A device can then recognize the colors and separate them from one another. This brings us back to the imaginary robotic arm at the beginning of this story, which will neatly select the desired file from the pool of capsules in the future.

Read more at Science Daily

What would the Earth look like to an alien civilization located light years away?

What would the Earth look like to an alien civilization located light years away? A team of researchers from Mauritius and Manchester University has used crowd-sourced data to simulate radio leakage from mobile towers and predict what an alien civilization might detect from various nearby stars, including Barnard's star, six light years away from Earth. Ramiro Saide, currently an intern at the SETI Institute's Hat Creek Radio Observatory and M.Phils. student at the University of Mauritius, generated models displaying the radio power that these civilizations would receive as the Earth rotates and the towers rise and set. Saide believes that unless an alien civilization is much more advanced than ours, they would have difficulty detecting the current levels of mobile tower radio leakage from Earth. However, the team suggests that some technical civilizations are likely to have much more sensitive receiving systems than we do, and the detectability of our mobile systems will increase substantially as we move to much more powerful broadband systems.

Saide is also excited by the fact that his simulations show that the Earth's mobile radio signature includes a substantial contribution from developing countries, including Africa. According to team leader Professor Mike Garrett (University of Manchester, Jodrell Bank Centre for Astrophysics), "the results highlight Africa's success in bypassing the landline stage of development and moving directly into the digital age." Garrett is pleased with the results. "I've heard many colleagues suggest that the Earth has become increasingly radio quiet in recent years -- a claim that I always contested -- although it's true we have fewer powerful TV and radio transmitters today, the proliferation of mobile communication systems around the world is profound. While each system represents relatively low radio powers individually, the integrated spectrum of billions of these devices is substantial."

Dr. Nalini Heeralall-Issur, Saide's supervisor in Mauritius, thinks Saide might be right. "Every day we learn more about the characteristics of exoplanets via space missions like Kepler and TESS, with further insights from the JWST -- I believe that there's every chance advanced civilizations are out there, and some may be capable of observing the human-made radio leakage coming from planet Earth."

The team is eager to extend their research to include other contributors to the Earth's radio leakage signature. The next step is to include powerful civilian and military radars, new digital broadcast systems, Wi-Fi networks, individual mobile handsets and the swarm of satellite constellations now being launched into low Earth orbit, such as Elon Musk's Starlink system. According to Garrett, "Current estimates suggest we will have more than one hundred thousand satellites in low Earth orbit and beyond before the end of the decade. The Earth is already anomalously bright in the radio part of the spectrum; if the trend continues, we could become readily detectable by any advanced civilization with the right technology."

Read more at Science Daily

Without more data, a black hole's origins can be 'spun' in any direction

Clues to a black hole's origins can be found in the way it spins. This is especially true for binaries, in which two black holes circle close together before merging. The spin and tilt of the respective black holes just before they merge can reveal whether the invisible giants arose from a quiet galactic disk or a more dynamic cluster of stars.

Astronomers are hoping to tease out which of these origin stories is more likely by analyzing the 69 confirmed binaries detected to date. But a new study finds that for now, the current catalog of binaries is not enough to reveal anything fundamental about how black holes form.

In a study appearing in the journal Astronomy and Astrophysics Letters, MIT physicists show that when all the known binaries and their spins are worked into models of black hole formation, the conclusions can look very different, depending on the particular model used to interpret the data.

A black hole's origins can therefore be "spun" in different ways, depending on a model's assumptions of how the universe works.

"When you change the model and make it more flexible or make different assumptions, you get a different answer about how black holes formed in the universe," says study co-author Sylvia Biscoveanu, an MIT graduate student working in the LIGO Laboratory. "We show that people need to be careful because we are not yet at the stage with our data where we can believe what the model tells us."

The study's co-authors include Colm Talbot, an MIT postdoc; and Salvatore Vitale, an associate professor of physics and a member of the Kavli Institute of Astrophysics and Space Research at MIT.

A tale of two origins

Black holes in binary systems are thought to arise via one of two paths. The first is through "field binary evolution," in which two stars evolve together and eventually explode in supernovae, leaving behind two black holes that continue circling in a binary system. In this scenario, the black holes should have relatively aligned spins, as they would have had time -- first as stars, then black holes -- to pull and tug each other into similar orientations. If a binary's black holes have roughly the same spin, scientists believe they must have evolved in a relatively quiet environment, such as a galactic disk.

Black hole binaries can also form through "dynamical assembly," where two black holes evolve separately, each with its own distinct tilt and spin. By some extreme astrophysical processes, the black holes are eventually brought together, close enough to form a binary system. Such a dynamical pairing would likely occur not in a quiet galactic disk, but in a more dense environment, such as a globular cluster, where the interaction of thousands of stars can knock two black holes together. If a binary's black holes have randomly oriented spins, they likely formed in a globular cluster.

But what fraction of binaries form through one channel versus the other? The answer, astronomers believe, should lie in data, and particularly, measurements of black hole spins.

To date, astronomers have derived the spins of black holes in 69 binaries, which have been discovered by a network of gravitational-wave detectors including LIGO in the U.S., and its Italian counterpart Virgo. Each detector listens for signs of gravitational waves -- very subtle reverberations through space-time that are left over from extreme, astrophysical events such as the merging of massive black holes.

With each binary detection, astronomers have estimated the respective black hole's properties, including their mass and spin. They have worked the spin measurements into a generally accepted model of black hole formation, and found signs that binaries could have both a preferred, aligned spin, as well as random spins. That is, the universe could produce binaries in both galactic disks and globular clusters.

"But we wanted to know, do we have enough data to make this distinction?" Biscoveanu says. "And it turns out, things are messy and uncertain, and it's harder than it looks."

Spinning the data

In their new study, the MIT team tested whether the same data would yield the same conclusions when worked into slightly different theoretical models of how black holes form.

The team first reproduced LIGO's spin measurements in a widely used model of black hole formation. This model assumes that a fraction of binaries in the universe prefer to produce black holes with aligned spins, where the rest of the binaries have random spins. They found that the data appeared to agree with this model's assumptions and showed a peak where the model predicted there should be more black holes with similar spins.

They then tweaked the model slightly, altering its assumptions such that it predicted a slightly different orientation of preferred black hole spins. When they worked the same data into this tweaked model, they found the data shifted to line up with the new predictions. The data also made similar shifts in 10 other models, each with a different assumption of how black holes prefer to spin.

"Our paper shows that your result depends entirely on how you model your astrophysics, rather than the data itself," Biscoveanu says.

"We need more data than we thought, if we want to make a claim that is independent of the astrophysical assumptions we make," Vitale adds.

Just how much more data will astronomers need? Vitale estimates that once the LIGO network starts back up in early 2023, the instruments will detect one new black hole binary every few days. Over the next year, that could add up to hundreds more measurements to add to the data.

Read more at Science Daily

Biblical military campaigns reconstructed using geomagnetic field data

A joint study by Tel-Aviv University and the Hebrew University, involving 20 researchers from different countries and disciplines, has accurately dated 21 destruction layers at 17 archaeological sites in Israel by reconstructing the direction and/or intensity of the Earth's magnetic field recorded in burnt remnants. The new data verify the Biblical accounts of the Egyptian, Aramean, Assyrian, and Babylonian military campaigns against the Kingdoms of Israel and Judah.

Findings indicate, for example, that the army of Hazael, King of Aram-Damascus, was responsible for the destruction of several cities -- Tel Rehov, Tel Zayit, and Horvat Tevet, in addition to Gath of the Philistines, whose destruction is noted in the Hebrew Bible. At the same time, the study refutes the prevailing theory that Hazael was the conqueror who destroyed Tel Beth-Shean. Other geomagnetic findings reveal that the cities in the Negev were destroyed by the Edomites, who took advantage of the destruction of Jerusalem and the Kingdom of Judah by the Babylonians.

The groundbreaking interdisciplinary study was published in the Proceedings of the National Academy of Sciences (PNAS) and is based on the doctoral thesis of Yoav Vaknin, supervised by Prof. Erez Ben-Yosef and Prof. Oded Lipschits of TAU's Institute of Archaeology and Prof. Ron Shaar from the Institute of Earth Sciences at the Hebrew University.

The researchers explain that geophysicists, attempting to understand the mechanism of earth's magnetic field, track changes in this field throughout history. To this end they use archaeological findings containing magnetic minerals which, when heated or burned, record the magnetic field at the time of the fire. Thus, in a 2020 study, researchers reconstructed the magnetic field as it was on the 9th of the month of Av, 586 BCE, the Hebrew date of the destruction of the First Temple and the City of Jerusalem by Nebuchadnezzar and his Babylonian army. Now, using archaeological findings unearthed over several decades at 17 sites throughout Israel, alongside historical information from ancient inscriptions and Biblical accounts, the researchers were able to reconstruct the magnetic fields recorded in 21 destruction layers. They used the data to develop a reliable new scientific tool for archaeological dating.

Yoav Vaknin explains: "Based on the similarity or difference in intensity and direction of the magnetic field, we can either corroborate or disprove hypotheses claiming that specific sites were burned during the same military campaign. Moreover, we have constructed a variation curve of field intensity over time which can serve as a scientific dating tool, similar to the radiocarbon dating method."

One example given by the researchers is the destruction of Gath of the Philistines (identified today as Tel Tzafit in the Judean foothills) by Hazael, King of Aram-Damascus. Various dating methods have placed this event at around 830 BCE, but were unable to verify that Hazael was also responsible for the destruction of Tel Rehov, Tel Zayit and Horvat Tevet. Now the new study, identifying full statistical synchronization between the magnetic fields recorded at all of these four sites at the time of destruction, makes a very strong case for their destruction during the same campaign. A destruction level at Tel Beth-Shean, on the other hand, recording a totally different magnetic field, refutes the prevailing hypothesis that it too was destroyed by Hazael. Instead, the magnetic data from Beth-Shean indicate that this city, along with two other sites in northern Israel, was probably destroyed 70-100 years earlier, a date which could correspond with the military campaign of the Egyptian Pharaoh Shoshenq. Shoshenq's campaign is described in the Hebrew Bible and in an inscription on a wall of the Temple of Amun in Karnak, Egypt, which mentions Beth-Shean as one of his conquests.

One of the most interesting findings revealed by the new dating method has to do with the end of the Kingdom of Judah. Prof. Erez Ben Yosef: "The last days of the Kingdom of Judah are widely debated. Some researchers, relying on archaeological evidence, argue that Judah was not completely destroyed by the Babylonians. While Jerusalem and frontier cities in the Judean foothills ceased to exist, other towns in the Negev, the southern Judean Mountains and the southern Judean foothills remained almost unaffected. Now, the magnetic results support this hypothesis, indicating that the Babylonians were not solely responsible for Judah's ultimate demise. Several decades after they had destroyed Jerusalem and the First Temple, sites in the Negev, which had survived the Babylonian campaign, were destroyed -- probably by the Edomites who took advantage of the fall of Jerusalem. This betrayal and participation in the destruction of the surviving cities may explain why the Hebrew Bible expresses so much hatred for the Edomites -- for example, in the prophecy of Obadiah."

Prof. Oded Lipschits adds: "The new dating tool is unique because it is based on geomagnetic data from sites, whose exact destruction dates are known from historical sources. By combining precise historical information with advanced, comprehensive archaeological research, we were able to base the magnetic method on reliably anchored chronology."

Read more at Science Daily

Isotope data strengthens suspicions of ivory stockpile theft

In January 2019, a seizure of 3.3 tons of ivory in Uganda turned up something surprising: markings on some of the tusks suggested that they may have been taken from a stockpile of ivory kept, it was thought, strictly under lock and key by the government of Burundi.

A new study from University of Utah distinguished professor Thure Cerling and colleagues, published in Proceedings of the National Academy of Sciences, uses carbon isotope science to show that the marked tusks were more than 30 years old and somehow had found their way from the guarded government stockpile into the hands of illegal ivory traders. The results suggest that governments that maintain ivory stockpiles may want to take a closer look at their inventory.

Ivory's isotope signatures

Cerling is a pioneer in the use of isotopes to answer questions about physical and biological processes. "Isotopes" of a given element refer to atoms of the element that vary in their number of neutrons, and thus vary oh-so-slightly in mass. A carbon-14 isotope has one more neutron than carbon-13, for example.

Some isotopes are stable and some are unstable. Unstable isotopes decay into other isotopes or elements through radioactive decay. Since the rate of decay is known for unstable isotopes, we can use the amounts present in a sample to determine ages. That's how carbon dating works -- it uses the rate of decay of unstable carbon-14 to determine the age of organic matter.

Around a decade ago, Cerling attended a presentation at the U by Sam Wasser of the University of Washington, who was studying the genetics of wildlife and using those tools to investigate the date and place of wildlife poaching. Cerling, recognizing that his expertise in isotope science might be able to add useful information, began an ongoing collaboration with Wasser.

In 2016, Cerling, Wasser and colleagues published a study that addressed a key question in the ivory trade: how old is the ivory seized by governments? Some traders have claimed their ivory is old, taken before 1976, and thus exempt from sales bans. And with the average size of ivory seizures more than 2.5 tons, researchers, governments and conservationists wonder how much of the ivory is recent and how much is coming from criminal stockpiles -- or is stolen from one of several ivory stockpiles held by the governments of some countries in Africa.

"Governments keep their stockpiles for multiple reasons," Wasser says. "They hope to sell the ivory for revenue, sometimes to support conservation efforts. However, they can only sell ivory from elephants that died of natural causes or were culled because they were problem animals. They can't sell seized ivory because they don't know it came from the country."

With the combination of Cerling's isotope data and Wasser's genetic data, the 2016 study found that more than 90% of seized ivory was from elephants that had been killed less than three years before. It was a sobering result, showing active and well-developed poaching and export networks. The study seemed to show that little ivory from government stockpiles had ended up on the black market.

Marked tusks

But the 2019 seizure of ivory in Uganda showed something concerning. Some of the tusks sported markings that looked suspiciously like the markings that CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, uses to inventory stockpiled ivory.

Due to the markings seen on some samples of the ivory," Cerling says, "it was thought that quite a few samples in this shipment could be related to material held in a government stockpile in Burundi. We were asked to date samples from this, and three other recent ivory seizures, to see if some samples could possibly be from older stockpiles."

To determine the ivory's age, the researchers collected small samples from the tusks and analyzed them for the amount of carbon-14 isotopes in each sample. They were looking specifically for the amount of "bomb carbon" in the tusks. Between 1945 and 1963, nuclear weapons testing doubled the amount of carbon-14 in the atmosphere, so anything living that's consumed carbon since then -- including you -- has a measurable carbon-14 signature. The amount of carbon-14 in a sample of ivory that hasn't yet radioactively decayed can tell scientists when the ivory stopped growing, or when the elephant died.

The method takes some calibration, using samples from organisms living in the same area. Some of the samples came from schoolchildren in Kenya, through a program called "Kids and Goats for Elephants." Because most families in rural Kenya keep goats the program, run by Cerling and Paula Kahumbu of WildlifeDirect engages children in collecting hair samples from goats for isotopic analysis. The isotope data is useful for many applications, including fighting elephant poaching and, in this case, calibrating the bomb carbon decay rate for more accurate dating of ivory.

A consequential result

The researchers analyzed ivory from four seizures in Angola, Hong Kong, Singapore and Uganda. Genetic data ensured that they weren't sampling two tusks from the same individual. The results of analysis from the Angola, Hong Kong and Singapore seizures were as expected -- the samples were mostly around three years after the death of the elephant, with no tusks having been taken more than 10 years previous.

But the Uganda seizure, with the inventory markings on the tusks, showed something very different. Nine of the 11 tusks tested had been taken more than 30 years before, with the dates of death ranging between 1985 and 1988. Those dates are consistent with the age of ivory in the stockpile of the government of Burundi, which was inventoried and stored in sealed containers in 1989.

"My suspicions were affirmed," Wasser says. "The bigger surprise was how near to 1989 the elephants were killed." At the time Burundi assembled its stockpile, a condition of joining CITES, which assists governments in managing ivory reserves, was that the ivory to be stockpiled was old. The results suggest that that wasn't the case, Wasser says, which would have violated conditions for Burundi to join CITES.

Read more at Science Daily

Getting data to do more for biodiversity

Michigan State University ecologists have developed a mathematical framework that could help monitor and preserve biodiversity without breaking the bank.

This framework or model takes low-cost data about relatively abundant species in a community and uses it to generate valuable insights on their harder-to-find neighbors. The journal Conservation Biology published the research as an Early View article on Aug. 25.

"One of the biggest challenges in monitoring biodiversity is that the species you're most concerned about tend to be lowest in abundance or they're the hardest species to observe during data collection," said Matthew Farr, the lead author on the new report. "This model can be really helpful for those rare and elusive species."

Farr, now a postdoctoral researcher at the University of Washington, helped develop the model as a doctoral student in Elise Zipkin's Quantitative Ecology Lab in the College of Natural Science at MSU.

"There are a lot of species in the world and many of them are data deficient," said Zipkin, an associate professor of integrative biology and director of MSU's Ecology, Evolution and Behavior Program, or EEB. "We're developing approaches to more quickly estimate what's going on with biodiversity, which species are in trouble and where, spatially, do we need to focus our conservation efforts."

After validating the model with an assist from forest-dwelling antelope in Africa, the researchers say it could be applied to a variety of other animals that meet certain criteria.

"The model doesn't work for all types of species. It's not a panacea," Zipkin said. "But when it does work for a community, we can learn a lot more about member species without much data."

The 'magic' of the model

For its newest model, Zipkin's team focused on what's called detection-nondetection data that tracks whether or not a given animal is detected in a given habitat.

"It's basically the cheapest data and the easiest to collect," Zipkin said. "You go to a spot, wait and see what animals are there and only need to record which species are seen."

Researchers gather this data visually in person or with low-cost, motion-detecting camera traps that snap photos when triggered by an animal. Researchers then analyze the photos to record detection-nondetection data over time.

There are trade-offs, though. Although relatively cheap and easy to collect, detection-nondetection data doesn't provide as much information as researchers and conservationists want. Historically, that has required intensive observational approaches such as tagging and tracking animals.

"That lets us calculate all sorts of things about the animals and their communities, but that data is expensive and hard to get," Zipkin said. "For certain species, it's impossible."

The MSU team realized that, for the right animals, they could use an understanding of animal behavior and statistics to close the information gap by squeezing more insight out of detection-nondetection data.

"For some species, these are the best data you can get," Farr said. "Now we can get more out of it."

That may sound like magic -- some of Zipkin's colleagues have even said so -- ?but there's nothing supernatural about the model. Like much of science, it's the result of hard work, collaboration and building on previous efforts in the field.

The story of the new model has its roots in 2003 with researchers J. Andrew Royle and James D. Nichols. The duo devised a mathematical link between the abundance of a species and the probability of detecting it.

At the time, Royle was a researcher with the U.S. Fish and Wildlife Service and Nichols was with the U.S. Geological Survey. Both are MSU alumni: Royle graduated with his bachelor's degree in 1990 and Nichols earned his doctorate in 1976.

"It's interesting," said Farr, whose current adviser, Sarah Converse, also graduated with a bachelor's degree from Michigan State before becoming an associate professor at the University of Washington. "Wherever you go in this field, people have some connection to Michigan State."

After publishing the Royle-Nichols model, Royle joined the USGS, where he'd work with Zipkin before she joined MSU in 2014. In 2016, Zipkin's team evolved the Royle-Nichols model to estimate things like the survival and reproduction rates for a single species using the barred owl as a case study.

Working in Zipkin's lab with support from the National Science Foundation, Farr took the next step by linking the population dynamics of different species within the same communities.

"The model lets information from more common species inform what's happening with the rare and elusive species," said Farr. "The model relies on the commonalities between species, but still allows for variations."

To develop the model, the team had to make some assumptions, like that the target species were territorial and did not travel much. The researchers then had to find real species that fit those assumptions to validate their model.

"We knew it would work for certain types of communities, but did those communities exist in real life?" Zipkin said.

"That's one of the biggest challenges in model development," Farr said. "You develop the model in a vacuum with simulations running under perfect conditions. You need to show what it can do in a real-world situation."

"That's when Tim O'Brien reached out and said, 'I have your animals,'" Zipkin said.

The duiker data

Timothy O'Brien is a retired ecologist in Kenya who worked with the Wildlife Conservation Society, a nongovernmental organization or NGO, and an expert in camera traps. As part of what's known as the Tropical Ecology Assessment and Monitoring program, or TEAM, he's helped standardize how camera traps are used to make their data as powerful as possible.

He was familiar with Zipkin's 2016 work and learned that she was expanding the model to include multiple species over multiple seasons. He suspected that forest-dwelling antelopes, notably those known as duiker, would provide the perfect test case.

Not only did duiker behavior match the assumptions of the model, but O'Brien had been helping monitor the animals for years using camera traps. Duikers presented an interesting and important conservation case.

"The duiker that live in rainforests, they are the most sought-after bushmeat in Africa," O'Brien said. "If duiker populations are in decline, it's usually because of people hunting for bushmeat."

Bushmeat is meat from any wild animal and it's an important source of food and income for many communities. But the hunting is loosely regulated and is financially incentivized by markets that sell bushmeat. The combination can be devastating for duiker populations.

With MSU's model and TEAM's duiker data, the team assessed the population dynamics of a total of 12 antelope species -- some more abundant than others -- in six national parks in Africa, where duikers are protected. The data covered time periods ranging from four to 11 years.

"We didn't see the level of population decline in duiker you expect to see when hunting is an issue," O'Brien said. "I would say the parks are fulfilling their function as far as duiker are concerned."

Overall, the duiker populations were mostly stable, but the researchers did detect population declines in about 20% of the combinations of species and parks that they examined. Again, the declines weren't so substantial to suggest that the duiker were being overhunted in the parks, but the researchers still want to understand what's happening in those cases.

"We found that's what causing the changes was more the differences between the parks than between the species," Zipkin said. "We haven't pinpointed the exact causes yet, but our results could help us do that."

"Matt and Elise have taken this model to a whole new plane," O'Brien said. "I've really enjoyed the collaboration."

Read more at Science Daily