Simon Laughlin's book wins a Prose Award
From Department of Zoology. Published on Feb 09, 2016.
Killer flies: how brain size affects hunting strategy in the insect world
By sc604 from University of Cambridge - Department of Zoology. Published on Feb 09, 2016.
As in economics, there is a law of diminishing returns in neuroscience – doubling the investment going in doesn’t equal double the performance coming out. With a bigger brain comes more available resources that can be allocated to certain tasks, but everything has a cost, and evolution weighs the costs against the benefits in order to make the most efficient system.
“Larger brains are specialised for high performance, so there’s a definite advantage to being bigger and better,” says Professor Simon Laughlin of the Department of Zoology, whose research looks at the cellular costs associated with various neural tasks. “But since most animals actually have very small brains, there must also be advantages to being small.” Indeed, there is strong selection pressure to have the minimum performance required in order to survive and it’s not biologically necessary to be the best, only to be better than the nearest competitor.
So does size matter? Do small insects with relatively few neurons have the same capabilities as much larger animals? “When an animal is limited, is it because their neural system just can’t cope? Or is it because they’re actually optimised for their particular environment?” asks Dr Paloma Gonzalez-Bellido from Cambridge’s Department of Physiology, Development and Neuroscience.
With funding from the US Air Force, Gonzalez-Bellido is studying the hunting behaviours of various flying insects – from tiny killer flies, slightly larger robber flies to large dragonflies – to determine how their visual systems influence their attack strategy, and what sorts of trade-offs they have to make in order to be successful.
Dragonflies are among the largest flying insects, and hunt smaller insects such as mosquitoes while patrolling their territories. They have changed remarkably little in the 300 million years since they evolved – most likely because they are so well optimised for their particular environmental niche.
“Other researchers have found that dragonflies are capable of doing complex things like internally predicting what their body is going to do and compensating for that – for instance, if they’re chasing a target and turn their wings, another signal will be sent to turn their head, so that the target stays in the same spot in their visual field,” says Gonzalez-Bellido. “But are smaller animals, such as tiny flies, capable of achieving similarly complex and accurate feats?”
Gonzalez-Bellido also studies the killer fly, or Coenosia attenuata. These quick and ruthless flies are about four millimetres long, and will go after anything they think they can catch – picky eaters they are not. However, the decision to go after their next meal is not as simple as taking off after whatever tasty-looking morsels happen to fly by. As soon as a killer fly takes off after its potential prey, it exposes itself and runs the risk of becoming a meal for another killer fly.
To help these predacious and cannibalistic flies eat (and prevent them from being eaten), they need to fly fast and to see fast. Insects see at speeds much higher than most other animals, but even for insects, killer flies and dragonflies see incredibly fast, at rates as high as 360 hertz (Hz) – as a comparison, humans see at around 60 Hz.
“For prey animals, the most important thing is to get out of the way quickly – it doesn’t matter whether they know exactly what’s coming, just that it doesn’t catch them,” says Gonzalez-Bellido. “Predators need to be both fast and accurate in their movements if they’re going to be successful – but for very small predators such as insects, there are trade-offs that need to be made.”
By making the ‘pixels’ on their photoreceptors (the light-sensitive cells in the retina) as narrow as possible, killer flies trade sensitivity for resolution. In bright light, they see better than their similar-sized prey, the common fruit fly. However, the cap on sensitivity and resolution imposed upon killer flies by their tiny eyes means that they can only see and attack things that fly close by.
While dragonflies, with their larger eyes and better resolution, can take their time and use their brain power to calculate whether a prey is suitable for an attack, killer flies attack before they’ve had a chance to determine whether it’s something they can actually catch, subdue or eat – or they risk missing their prey altogether. Once a killer fly gets relatively close to its potential prey, it has to decide whether to keep going or turn back – this is one of the trade-offs resulting from evolving such a tiny visual system.
In the early 2000s, Laughlin determined the energy efficiency of single neurons, by estimating the numbers of ATP molecules – the molecules that deliver energy in cells – used per bit of information coded. To do this he compared photoreceptors in various insects. Laughlin and his colleagues found that photoreceptors are like cars – the higher the performance, the more energy they require, and costs rise out of proportion with performance. “For any system, whether it’s in a tiny insect or a large mammal, you don’t want something which is over-engineered, because it’s going to cost more,” says Laughlin. “So what’s the root of inefficiency, and how did nature evolve efficient nerve cells from the bottom up?”
Researchers in the Department of Engineering are taking the reverse approach to answer questions about how the brain works so efficiently by looking at systems from the top down. “If you reverse engineer an animal’s behavioural strategy by asking how an animal would solve a task under specific constraints and then work out the optimal solution, you’ll find it’s often the case that animals are pretty close to optimal,” says Dr Guillaume Hennequin, who looks at how neurons work together to produce behaviour.
Hennequin studies how brain circuits are wired in such a way that they become optimised for a task: how primates such as monkeys are able to estimate the direction of a moving object, for example. “How brain circuits generate optimal interpretations of ambiguous information received from imperfect sensors is still not known,” he says. “Coping with uncertainty is one of the core challenges that brains must confront.”
Different animals come up with their own solutions. Both dragonflies and killer flies have systems that are optimal, but optimal in their own ways. It’s beneficial for killer flies to be so small, since this gives them high manoeuvrability, enabling them to catch prey that turns at speed. Dragonflies are much bigger, and can do things that killer flies can’t, but their size means they can’t turn or stop on a dime, like a killer fly can.
“By answering some of the questions around efficiency in brain circuits, large or small, we may be able to understand fundamental principles about how brains work and how they evolved,” says Laughlin.
Inset images: top to bottom: robber fly, dragon fly, killer fly; credit: Sam Fabian.
Cambridge researchers are studying what makes a brain efficient and how that affects behaviour in insects.
Wolf species have ‘howling dialects’
By fpjl2 from University of Cambridge - Department of Zoology. Published on Feb 08, 2016.
The largest ever study of howling in the ‘canid’ family of species – which includes wolves, jackals and domestic dogs – has shown that the various species and subspecies have distinguishing repertoires of howling, or “vocal fingerprints”: different types of howls are used with varying regularity depending on the canid species.
Researchers used computer algorithms for the first time to analyse howling, distilling over 2,000 different howls into 21 howl types based on pitch and fluctuation, and then matching up patterns of howling.
They found that the frequency with which types of howls are used – from flat to highly modulated – corresponded to the species of canid, whether dog or coyote, as well as to the subspecies of wolf.
For example, the howling repertoire of the timber wolf is heavy with low, flat howls but doesn’t feature the high, looping vocal that is the most frequently used in the range of howls deployed by critically-endangered red wolves.
Lead researcher Dr Arik Kershenbaum from the University of Cambridge describes these distinctive howl repertoires as resembling vocal dialects, with each species having its own identifiable use of the various howl types. He says the findings could be used to track and manage wild wolf populations better, and help mitigate conflict with farmers.
The origins of language development in humans are mysterious, as the vocalisations of our closest existing biological relatives such as chimpanzees are relatively simple. Kershenbaum and colleagues believe that studying the sounds of other intelligent species that use vocal communication for cooperative behaviour – such as wolves and dolphins – may provide clues to the earliest evolution of our own use of language.
“Wolves may not be close to us taxonomically, but ecologically their behaviour in a social structure is remarkably close to that of humans. That’s why we domesticated dogs – they are very similar to us,” said Kershenbaum, from Cambridge’s Department of Zoology.
“Understanding the communication of existing social species is essential to uncovering the evolutionary trajectories that led to more complex communication in the past, eventually leading to our own linguistic ability” he said.
The research was conducted by a team of scientists from the UK, US, Spain and India, and is published in the journal Behavioural Processes.
The researchers made use of howls recorded from both captive and wild animals, from Australia and India, to Europe and the United States, creating a database of 6,000 howls that was whittled down to 2,000 for the study. This included combing YouTube for domestic dog howls.
These were then fed into machine learning algorithms to classify the howls into discrete types. Studies on howling in the past have had to rely on subjective human comparisons by looking at soundwave patterns, but the new algorithms allowed the howl types to be compared objectively, revealing that the various species have characteristically different repertoires of howl type usage.
While the howling repertoires of most of the 13 species analysed were very distinct, some bore close similarities to each other that may influence interbreeding and, in at least one case, threaten the survival of a species.
Red wolves, hunted to the brink of extinction in the mid-20th century, were the focus of a reintroduction programme instigated by the US government, which has recently been halted due to a lack of success.
Part of the problem was red wolves breeding with coyotes, and the resultant hybridisation diluted attempts to maintain this rare wolf species. The researchers found significant overlap between the howling vocabulary of the red wolf and the coyote – with both favouring highly modulated, whining howls such as the one classed by researchers as ‘type three’.
“The survival of red wolves in the wild is threatened by interbreeding with coyotes, and we found that the howling behaviour of the two species is very similar. This may be one reason why they are so likely to mate with each other, and perhaps we can take advantage of the subtle differences in howling behaviour we have now discovered to keep the populations apart,” said Kershenbaum.
Other conservation uses for the new findings may involve refining the use of playbacks to recreate more accurate howling behaviours that imitate territorial markings, thereby encouraging wolf packs to steer clear of farms and livestock.
However, we know very little about the meaning of different howl types and what they are actually communicating, says Kershenbaum, because – as with dolphins, that other highly vocal, smart and social species which he studies – wolves are extremely difficult to study in the wild.
“You don’t observe natural wolf behaviour in zoos, only in the wild, and you need to know where the animals are when howling before you can really begin to try and discern meanings. But, as with dolphin pods, physically following a wild wolf pack is virtually impossible,” explained Kershenbaum.
“We are currently working on research in Yellowstone National Park in the US using multiple recording devices and triangulation technology to try and pick up howl sounds and location. In this way we might be able to tell whether certain calls relate to distance communication or pack warnings, for example,” he said.
For Kershenbaum, wolves and dolphins show remarkable parallels with each other in social behaviour, intelligence and vocal communication – all comparisons that extend to humans.
“As well as being intelligent and cooperative species, wolves and dolphins have remarkably similar vocal characteristics. If you slow a dolphin whistle down about 30 times it sounds just like a wolf howl, something I often do in my lectures,” he said.
“The presence of complex referential communication in species that must communicate to survive was probably a crucial step in the evolution of language. I think we can shed a lot of light on early evolution of our own use of language by studying the vocalisation of animals that are socially and behaviourally similar to us, if not necessarily taxonomically closely related.”
Largest quantitative study of howling, and first to use machine learning, defines different howl types and finds that wolves use these types more or less depending on their species, resembling a howling dialect. Researchers say findings could help conservation efforts and shed light on the earliest evolution of our own use of language.
How 'more food per field' could help save our wild spaces
By fpjl2 from University of Cambridge - Department of Zoology. Published on Jan 28, 2016.
Agricultural expansion is a leading cause of wild species loss and greenhouse gas emissions. However, as farming practices and technologies continue to be refined, more food can be produced per unit of land – meaning less area is needed for agriculture and more land can be 'spared' for natural habitats.
While this may sound like good news for nature, conservation scientists warn that, without the right policies, higher farm yields could be used to maximise short-term profits and stimulate greater demand, resulting in less wilderness and more unnecessary consumption and waste.
Now, leading conservationists writing in the journal Science are calling on policymakers to harness the potential of higher-yield farming to spare land for conservation, instead of solely producing more food and profit. By minimising the footprint of farming in this way, vital land could be spared for maintaining and restoring the rapidly dwindling natural world.
The authors describe a series of "land-sparing mechanisms" that link yield increases with habitat protection, such as land-use zoning and smart subsidy schemes, along with real-world examples that show how they can work – from India to Latin America.
They write that replicating these mechanisms elsewhere depends on "the political will to deliver strong environmental governance".
"Reconciling agriculture and conservation is one of this century's greatest challenges," said Dr Ben Phalan from Cambridge University's Department of Zoology.
"To help meet that challenge, we need to move on from thinking about higher yields simply as a means to produce more food, and to use them to free up land for conserving biodiversity and ecosystem services," said Phalan, who authored the policy paper with colleagues from Cambridge, the RSPB and Brazil.
Previous research from Cambridge and elsewhere has shown sparing land for nature by producing more food per field is the "least worst option" for both biodiversity and greenhouse gas emissions, says co-author Andrew Balmford, Cambridge professor of conservation science.
"Sparing tracts of land as natural habitat is much better for the vast majority of species than a halfway house of lower-yielding but 'wildlife-friendly' farming, and we have recently shown that in the UK land spared through high-yield farming could even sequester enough greenhouse gases to mitigate the UK's agricultural emissions," said Balmford.
However, Phalan says that policies to encourage higher farm yields need to avoid the 'rebound effect'. First identified by William Jevons in 1865 – when he noticed more efficient engines increased rather than reduced coal use, as engines were put into more widespread use – the rebound effect for higher yields could see food prices drop, encouraging greater consumption, more food waste and even more conversion of habitats to farmland.
Higher yields may also increase the cost of conservation if they allow farmers to earn more per field. "If a hectare of farmland is producing higher profits, farmers will charge more to give it up for conservation," said Phalan. He says that conservation efforts can be undermined by unintended consequences. "Halting agricultural intensification or expansion in one area may just shift pressure to farm in others. Increasing farm yields can help counter this 'leakage'."
The land-sparing approaches advocated by the researchers are designed to address both rebound effects and leakage. Examples from around the world show how these approaches can work, although researchers caution that further work is needed to improve and test each of them.
Designating "land-use zones" for both conservation and farming would safeguard habitats, while incentivising higher yields to compensate for limits on the extent of farmland. Researchers say that restrictions should target export commodities rather than staple foods.
In Costa Rica, for example, the clearance rate of mature forests halved after the government zoned forests as off-limits for agricultural expansion. Food production for export shifted from cattle farming toward high-yielding pineapple and banana crops.
Economic incentives can be tailored to increase yields and prevent destruction of wildlife, with payments conditional on conservation. Himalayan herders are rewarded for setting aside pastures for wild sheep – a food source for snow leopards – and insuring against loss of their livestock. This has dramatically improved yields and eliminated killing of the endangered cats for livestock protection.
To encourage land sparing in developing countries, help with enhancing yields should focus on smallholder farmers growing staple crops. Researchers say that technical advice on water management and multiple cropping should be balanced with advice on reducing any side-effects: by using natural pest control and other agro-ecological methods, for example, instead of pesticides.
Policies and practices to minimise pollution are essential. "If yields are increased using large quantities of fertilisers and pesticides, they can pollute the air and rivers. It is even possible that the effects of this pollution could cancel out the benefits of sparing natural habitats," said Phalan.
Improved farming practices can have a knock-on economic as well as environmental impact. In the Philippines, introducing irrigation helped lowland rice farmers produce two crops per year rather than one. The higher labour demands were met by employing upland farmers, who invested their new income in fertiliser, boosting their own yields and reducing farmland expansion.
Deforestation rates in the uplands halved, while larger and poorer households were those most likely to benefit.
Combinations of these mechanisms and more will make saving land from agriculture and sparing it for nature more likely, write the researchers. They point to Brazil as an example of multiple policy interventions working together:
"Zoning of protected areas and forest conservation on private land, combined with subsidising farmers to increase yields on degraded pastures rather than create new ones, has seen deforestation of the Brazilian Amazon decline steeply since 2004 - although it's too early to say if this success will be sustained," said co-author Dr Bernardo Strassburg of Brazil's International Institute for Sustainability.
Phalan says that, while these examples show land sparing can be achieved, making sure that higher-yield farming benefits nature at scales that matter will require commitment from senior levels of government.
"Making space for nature is largely a question of societal and political priorities," said Phalan. "The challenge is less whether it's possible to reconcile farming and conservation, than whether those with power are willing to make it a priority."
Increased farm yields could help to spare land from agriculture for natural habitats that benefit wildlife and store greenhouse gases, but only if the right policies are in place. Conservation scientists call on policymakers to learn from working examples across the globe and find better ways to protect habitats while producing food on less land.
Defending larvae from microbial attack
From Department of Zoology. Published on Jan 28, 2016.
Lizards camouflage themselves by choosing rocks that best match the colour of their backs
By jeh98 from University of Cambridge - Department of Zoology. Published on Jan 25, 2016.
Resting out in the open on rocks can be a risky business for Aegean wall lizards. Out in these habitats they have nowhere to hide and their backs, which show varying shades of green and brown between individuals, are dangerously exposed to birds hunting in the skies above.
New research by Kate Marshall from the University of Cambridge’s Department of Zoology and Dr Martin Stevens from the University of Exeter’s Centre for Ecology and Conservation, published today in Scientific Reports, shows that individual lizards are able to choose their resting spot wisely and select a rock in their natural environment that will make their backs less conspicuous to avian predators.
“This suggests that wild individual lizards can choose to rest on the rock they will most resemble, which enhances their own degree of camouflage against visually-oriented predatory birds,” says Marshall. “This is the first result of its kind in wild animals, and in lizards specifically.”
“One intriguing puzzle remains: how do the lizards ‘know’ how camouflaged their own backs are to a bird against a particular rock?” She adds.
Other types of lizard, such as chameleons and geckos, are able to rapidly change colour in a matter of seconds or minutes to better match their background environment and avoid being spotted by approaching predators. Aegean wall lizards, which are widespread across the South Balkans and many Greek islands, are unable to do this. Instead, this new research shows that they enhance their level of camouflage to hunting birds by choosing to rest on rocks that are more similar in colour to that of their own backs.
Birds see the world differently from you or I: for example, they are able to see ultraviolet light whereas we cannot, which means they perceive colour (and camouflage) in a very different way. Marshall and her colleagues used visual modelling to test how conspicuous individual lizards would be to a bird’s eye against the backgrounds they had chosen to sit on.
Marshall and her field assistant and co-author, Kate Philpot, found that on each island individuals showed better colour matching against their own chosen rock backgrounds than against other lizards’ rock backgrounds, as perceived by avian predators such as the crows and raptors abundant in their study sites.
“This strongly suggests that lizards rest on backgrounds that heighten their own camouflage to reduce the risk of being attacked by birds, and that individual behaviours have an important role in enhancing camouflage across different microhabitats,” says Marshall. “Our findings appear to be the first demonstration of this occurring in wild populations as viewed by likely predators.”
The researchers also found that lizards’ resting site choices that heightened individual camouflage were more evident on islands with higher numbers of predatory bird species, suggesting that this behavioural defence is more likely to evolve in riskier environments. It was also more apparent in female lizards, probably because males have a conflicting need to stand out against the rocks to attract mates.
“As for the puzzle over how the lizards ‘know’ how camouflaged their own backs are against a particular rock - one theory is that it is under genetic control, while another possibility is that it develops in early life through learning from other lizards and from experience,” says Marshall.
“Although we don’t know what the exact mechanism is yet, we hope to uncover some clues in future research. It would also be interesting to look at whether lizards can adjust their choice of rock not just for camouflage but also to aid thermoregulation (basking site choices) and sexual signalling,” she adds.
“Our study shows that there is much more to camouflage than just an animal’s appearance - how individuals behave and what backgrounds they choose to sit on can have a major bearing on how effective their camouflage will be. This is something that needs much more research in future,” says Stevens.
This research shows that individual animals’ behaviours can increase their chances of survival by allowing flexible, real-time adjustments to the many different microhabitats encountered in the wild. Marshall suggests that it also emphasises the importance of considering broader environmental contexts, such as predation risk, as well as the perceptual abilities of natural observers like predators in studies of animal behaviour.
Marshall, K et al. ‘Microhabitat choice in island lizards enhances camouflage against avian predators’ Scientific Reports 25 January 2016.
Inset images: Aegean wall lizards resting on rocks (Kate Marshall).
New research shows wild Aegean wall lizards found on Greek islands choose to sit on rocks that better match their individual colouring. This improves camouflage and so reduces the risk of being attacked by birds when they sit out in the open, raising the intriguing question of how the lizards know what colour they are.
Neighbourhood watch and more: how reed warblers watch out when there’s a cuckoo about
By amb206 from University of Cambridge - Department of Zoology. Published on Jan 22, 2016.
It’s a risky business being a reed warbler. Not only do these tiny birds embark on an annual migration of some 5,000 km from their West African winter quarters to breeding grounds in the north, but they are also ‘hosts’ to the cuckoo, a species that lays its eggs in other birds’ nests and takes no further part in raising its offspring. When the cuckoo chick hatches, it pushes the reed warbler eggs and young out of the nest. As sole occupant, it tricks its warbler ‘parents’ into supplying its voracious appetite until it fledges.
Cuckoos are expert tricksters: their eggs mimic those of their hosts in pattern though they are a little bigger. If the reed warbler detects an alien egg in its nest, or spots a cuckoo nearby, it may eject the odd-looking egg. But cuckoos are so swift in laying their eggs (only one is laid per nest and the process is over in as little as 10 seconds), and so clever at disguising their eggs, that warblers are often uncertain whether an odd egg in the clutch is a cuckoo egg or one of their own.
Research into the relationship between cuckoos and reed warblers has to date concentrated on the behaviour of individual birds and their interactions with cuckoos, described as parasites. A new study published today (22 January 2016) in Scientific Reports looks at wider interactions between neighbouring communities of reed warblers, their strategies for coping with cuckoos, and, in particular, how warblers assess levels of risk by gathering information from a variety of sources.
After two years of observation of warblers that spend the breeding season at Wicken Fen in Cambridgeshire, authors Rose Thorogood and Nicholas Davies (Department of Zoology) reveal that a kind of “neighbourhood watch” exists out in the reed beds, keeping birds up-to-date with the latest threats. Using a series of controlled experiments, involving model cuckoos and broadcasts of reed warbler alarm calls, the researchers revealed that reed warblers factored information gathered from close surveillance of the neighbourhood into their decision-making when assessing whether or not to eject an egg.
When reed warblers spot a cuckoo, they may mob it and emit alarm calls that carry up to 40 metres. These alarm calls attract neighbours, who come to investigate the cause of the commotion. But the sound of neighbourly mobbing of a cuckoo alone is insufficient to prompt warblers to eject a suspect egg from their own nests. They also need clues that suggest a more close-up and personal threat.
“We found that warbler pairs ejected an odd egg only when there was strong evidence that it might not be one of their own. For action to be taken, the clues had to add up. The warblers needed to be alerted by their neighbours’ behaviour that there was a cuckoo at large in the neighbourhood and they needed to be aware of a more local and imminent threat, by seeing a cuckoo near their own nest. ” said Thorogood.
“Neither personal encounters nor social encounters alone were sufficient to stimulate egg rejection. Instead, information was combined from both these sources. This is fascinating because we have assumed previously that animals favour one type of information over the other – for example, experiments show that some fish species will ignore where their shoal mates forage if they already have information about the location of food themselves, even when it is less profitable. Here we show that combining information is the best way to take the most appropriate course of action.”
The use of multiple sources of information has important consequences for cuckoos too. With their neighbourhood abuzz with information, cuckoos need to be wary of alarming potential hosts.
“Because the information warfare between cuckoos and their hosts extends well beyond individual interactions, there’s pressure on cuckoos to be increasingly secretive, not only to avoid alerting their target host pair, but also other host pairs in the local neighbourhood” said Thorogood.
Cuckoo numbers have declined by as much as 60% in the past 30 years for reasons that remain unclear. At Wicken Fen, where several hundred warblers arrive to breed each May, between 10% and 20% of reed warblers nests were used by cuckoos. Today only 2% of warbler nests at Wicken host cuckoos. This rapid drop in cuckoo numbers, which contrasts with a stable warbler population, has enabled Thorogood and Davies to track how the warblers have dropped their defences in concert with the dramatic decrease in cuckoo threat.
Davies has been researching cuckoos and their hosts at Wicken Fen since the 1980s. He said: “Reed warblers are much less likely to eject an egg from their nest today than they were in the 1980s. This makes complete sense. They have matched their behaviour to the changing level of risk. Most reed warblers have just one or two summers in which to breed. So every opportunity to mate, construct a nest and raise a clutch of eggs is precious. If a pair of warblers mistakenly identifies one of their own eggs as a cuckoo egg and chucks it out, or deserts the nest, the loss is great. Our work shows how they match their defences to the risk of parasitism.”
A study of reed warbler behaviour reveals for the first time that in assessing the risks posed by cuckoos the birds combine information from multiple sources. An ‘information highway’ provides one set of clues and personal encounters another. Only when both add up, do the birds take defensive action.
Why Spider-Man can’t exist: Geckos are ‘size limit’ for sticking to walls
By jeh98 from University of Cambridge - Department of Zoology. Published on Jan 18, 2016.
A new study, published today in PNAS, shows that in climbing animals ranging in size from mites to geckos, the percentage of body surface covered by adhesive footpads increases as body size increases, setting a limit to the size of animal using this strategy because larger animals would require impossibly big feet.
Dr David Labonte and his colleagues in the University of Cambridge’s Department of Zoology found that tiny mites use approximately 200 times less of their body surface area for adhesive pads than geckos, nature's largest adhesion-based climbers. And humans? We’d need as much as 40% of our total body surface, or roughly 80% of our front, to be covered in sticky footpads if we wanted to do a convincing Spider-Man impression.
Once an animal is so big that a substantial fraction of its body surface would need to be sticky footpads, the necessary morphological changes would make the evolution of this trait impractical, suggests Labonte.
“If a human, for example, wanted to climb up a wall the way a gecko does, we’d need impractically large sticky feet – and shoes in European size 145 or US size 114,”says Walter Federle, senior author also from Cambridge’s Department of Zoology.
“As animals increase in size, the amount of body surface area per volume decreases – an ant has a lot of surface area and very little volume, and an elephant is mostly volume with not much surface area” explains Labonte.
“This poses a problem for larger climbing animals because, when they are bigger and heavier, they need more sticking power, but they have comparatively less body surface available for sticky footpads. This implies that there is a maximum size for animals climbing with sticky footpads – and that turns out to be about the size of a gecko.”
The researchers compared the weight and footpad size of 225 climbing animal species including insects, frogs, spiders, lizards and even a mammal.
“We covered a range of more than seven orders of magnitude in body weight, which is roughly the same weight difference as between a cockroach and Big Ben” says Labonte.
“Although we were looking at vastly different animals – a spider and a gecko are about as different as a human is to an ant – their sticky feet are remarkably similar,” says Labonte.
“Adhesive pads of climbing animals are a prime example of convergent evolution – where multiple species have independently, through very different evolutionary histories, arrived at the same solution to a problem. When this happens, it’s a clear sign that it must be a very good solution.”
There is one other possible solution to the problem of how to stick when you’re a large animal, and that’s to make your sticky footpads even stickier.
“We noticed that within some groups of closely related species pad size was not increasing fast enough to match body size yet these animals could still stick to walls,” says Christofer Clemente, a co-author from the University of the Sunshine Coast.
“We found that tree frogs have switched to this second option of making pads stickier rather than bigger. It’s remarkable that we see two different evolutionary solutions to the problem of getting big and sticking to walls,” says Clemente.
“Across all species the problem is solved by evolving relatively bigger pads, but this does not seem possible within closely related species, probably since the required morphological changes would be too large. Instead within these closely related groups, the pads get stickier in larger animals, but the underlying mechanisms are still unclear. This is a great example of evolutionary constraint and innovation.”
The researchers say that these insights into the size limits of sticky footpads could have profound implications for developing large-scale bio-inspired adhesives, which are currently only effective on very small areas.
“Our study emphasises the importance of scaling for animal adhesion, and scaling is also essential for improving the performance of adhesives over much larger areas. There is a lot of interesting work still to be done looking into the strategies that animals use to make their footpads stickier - these would likely have very useful applications in the development of large-scale, powerful yet controllable adhesives,” says Labonte.
This study was supported by research grants from the UK Biotechnology and Biological Sciences Research Council (BB/I008667/1), the Human Frontier Science Programme (RGP0034/2012), the Denman Baynes Senior Research Fellowship, and a Discovery Early Career Research Fellowship (DE120101503).
Labonte, D et al "Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing." PNAS 18 January 2016. DOI: 10.1073/pnas.1519459113
Inset images: Vallgatan 21D, Gothenburg, Sweden (photo by Gudbjörn Valgeirsson, footprints added by Cedric Bousquet, University of Cambridge); How sticky footpad area changes with size (David Labonte); Diversity of sticky footpads (David Labonte).
Latest research reveals why geckos are the largest animals able to scale smooth vertical walls – even larger climbers would require unmanageably large sticky footpads. Scientists estimate that a human would need adhesive pads covering 40% of their body surface in order to walk up a wall like Spider-Man, and believe their insights have implications for the feasibility of large-scale, gecko-like adhesives.
Genetic ‘paint box’ shuffled between butterfly species to create new wing patterns
By fpjl2 from University of Cambridge - Department of Zoology. Published on Jan 15, 2016.
New research on butterfly genomes has revealed that the genetic components that produce different splotches of colour on wings can be mixed up between species by interbreeding to create new patterns, like a "genetic paint box".
Research on Amazonian Heliconius butterflies has shown that two of the most common colour patterns, found in combination on the wings of many Heliconius species – the dennis red patch on the base of the forewing, and the ray red streaks that fan out across the hindwing – are controlled by separate genetic switches that arose in completely different species.
A team of researchers has traced the merging of these two wing pattern elements to interbreeding between butterfly species that occurred almost two million years ago.
It has been known for some time that exchange of genes between species can be important for evolution: humans have exchanged genes with our now extinct relatives which may help survival at high altitudes, and Darwin's Finches have exchanged a gene that influences beak shape. In butterflies, the swapping of wing pattern elements allows different species to share common warning signs that ward off predators – a phenomenon known as mimicry.
However, the new study, published today in the journal PLOS Biology, is the first to show such mixing of genetic material can produce entirely new wing patterns, by generating new combinations of genes.
"We found that different colour patches on the wings are controlled by different genetic switches that can be turned on and off independently. As these switches were shared between species they got jumbled up into different combinations, making new wing patterns," said senior author Professor Chris Jiggins, from Cambridge University's Department of Zoology.
The researchers sequenced the genomes from 142 individual butterflies across 17 Heliconius species and compared the DNA data, focusing on the regions associated with the two red colour patterns of dennis and ray on the forewing and hindwing. "In each butterfly genome, we narrowed down around 300 million base pairs of DNA to just a few thousand," said Jiggins.
They found that the genetic switches for these distinct wing splotches operated independently, despite being located next to each other in the genome. The sequencing revealed that the switch for each colour splotch had evolved just once, and in separate species, but had been repeatedly shared across all the Heliconius species at occasional points of interbreeding dating back almost two million years.
"By identifying the genetic switches associated with bits of wing pattern, when they evolved and how they diverged, we can actually map onto the species tree how these little regions of colour have jumped between species - and we can see they are jumping about all over the place," said Jiggins.
The key to this evolutionary butterfly painting is the independence of each genetic switch. "The gene that these switches are controlling is identical in all these butterflies, it is coding for the same protein each time. That can't change as the gene is doing other important things," said lead author Dr Richard Wallbank, also from Cambridge's Department of Zoology.
"It is the switches that are independent, which is much more subtle and powerful, allowing evolutionary tinkering with the wing pattern without affecting parts of the genetic software that control the brain or eyes.
"This modularity means switching on a tiny piece of the gene's DNA produces one piece of pattern or another on the wings – like a genetic paint box," Wallbank said.
Wallbank RWR, Baxter SW, Pardo-Diaz C, Hanly JJ, Martin SH, Mallet J, et al. (2016) Evolutionary Novelty in a Butterfly Wing Pattern through Enhancer Shuffling. PLoS Biol 14(1): e1002353. doi:10.1371/journal.pbio.1002353
Research finds independent genetic switches control different splotches of colour and pattern on Heliconius butterfly wings, and that these switches have been shared between species over millions of years, becoming “jumbled up” to create new and diverse wing displays.
Boosting farm yields to restore habitats could create greenhouse gas ‘sink’
By fpjl2 from University of Cambridge - Department of Zoology. Published on Jan 04, 2016.
New research into the potential for sparing land from food production to balance greenhouse gas emissions has shown that emissions from the UK farming industry could be largely offset by 2050. This could be achieved if the UK increased agricultural yields and coupled this with expanding the areas of natural forests and wetlands to match its European neighbours.
The new study suggests that by upping forest cover from 12% to 30% of UK land over the next 35 years – close to that of France and Germany, but still less than the European average – and restoring 700,000 hectares of wet peatland, these habitats would act as a carbon ‘sink’: sucking in and storing carbon.
This could be enough to meet government targets of 80% greenhouse gas reduction by 2050 for the farming industry. Agriculture currently produces around 10% of all the UK’s damaging greenhouse gas emissions.
The new woodlands and wetlands would be more than just a carbon sink, say researchers. They would help support declining UK wildlife – including many species of conservation concern – provide more areas for nature recreation, and help to reduce flooding.
However, to make space for habitat restoration, and to meet rising levels of food demand, land sparing would depend on increases in farm yields, so that food needs can be met from less farmland.
The new study, published today in the journal Nature Climate Change, is the first to show that land sparing has the technical potential to significantly reduce greenhouse gas emissions at a national scale.
“Land is a source of greenhouse gases if it is used to farm fertiliser-hungry crops or methane-producing cattle, or it can be a sink for greenhouse gases – through sequestration. If we increase woodland and wetland, those lands will be storing carbon in trees, photosynthesising it in reeds, and shunting it down into soils,” said senior author Prof Andrew Balmford, from Cambridge University’s Department of Zoology.
“We estimate that by actively increasing farm yields, the UK can reduce the amount of land that is a source of greenhouse gases, increase the ‘sink’, and sequester enough carbon to hit national emission reduction targets for the agriculture industry by 2050,” he said.
The study originated from a workshop run as part of the new Cambridge Conservation Initiative, which convened leading experts and asked them to “look into their crystal balls”, says Balmford. “We wanted to know what food yield increases they reckoned were achievable in the 2050 timescale across crop and livestock sectors,” he said.
This included researchers from the Universities of California, Bangor, Aberdeen, East Anglia, the Royal Society for the Protection of Birds, Forestry Commission, Rothamsted Research, ADAS UK Ltd and Scotland’s Rural College (SRUC).
The potential they identified included improving farm management and optimising breeding programmes to produce plants that are better at capturing soil nutrients, sunlight and water, and to produce more efficient animals that produce less methane.
The researchers then used these and other data to produce a series of modelled scenarios that projected long-term farm yields. Scenarios ranged from yield declines through to sustained yield growth that averaged 1.3% per year until 2050.
If yields rise, the area of farmland required for food production can decline – allowing countryside to be spared. By converting spared land back to natural habitats of woodland and wetland, which would have been a large portion of the UK’s native land cover in the past, a carbon sink is created that the research suggests could come close to cancelling out agricultural emissions in just a few decades.
Dr Toby Bruce, co-author from Rothamsted Research, said: "The current findings show the value of land sparing for reducing greenhouse gases. To allow this productivity needs to increase on the remaining land, for example, by minimising crop losses to pests, weeds and diseases or by improving crop nutrition.”
Importantly, says Balmford, the research team did not allow themselves the “get-out-of-jail-free card” of increasing food imports. Overall food consumption looks set to rise substantially – some 38% – in the UK by 2050, and the researchers locked into their future models the contribution that UK production makes to its food supply.
“We made sure we met expected production requirements in all our figures, and then explored the consequences of different ways of achieving them,” he said.
However, it is not all or nothing, say the researchers, who conducted lots of sensitivity analyses around different ways of using spared land, and different levels of yield growth, consumer waste, and meat consumption – which has a disproportionate environmental footprint
“Reducing meat consumption appears to offer greater mitigation potential than reducing food waste, but more importantly, our results highlight the benefits of combining measures,” said Balmford.
“For example, coupling even moderate yield growth with land sparing and reductions in meat consumption has the technical potential to surpass an 80% reduction in net emissions,” he said.
Added Balmford: “We need to turn our minds to figuring out policy mechanisms that can deliver sustainable high yield farming that doesn’t come at the expense of animal welfare, soil and water quality, as well as safeguarding and restoring habitats.
“The right incentives need to be provided to landowners to spare land. Subsidies under the EU’s Common Agricultural Policy could be redirected so that landowners get paid properly for taking land out of food production and putting it into climate regulation.
“If we are serious about saving the planet for anything more than food production then the focus has to be on increasing yields and sparing land for the climate. We need to look objectively and dispassionately at every option we have for achieving that.”
New study using UK data is first to show that raising farm yields and allowing ‘spared’ land to be reclaimed for woodlands and wetlands could offset greenhouse gas produced by farming industry to meet national target of 80% emissions reduction by 2050.
Professor Jenny Clack awarded the Palaeontological Association's Lapworth Medal
From Department of Zoology. Published on Dec 18, 2015.
Feeding food waste to pigs could save vast swathes of threatened forest and savannah
By jeh98 from University of Cambridge - Department of Zoology. Published on Dec 10, 2015.
A new study shows that if the European Union lifted the pigswill ban imposed following 2001’s foot-and-mouth disease epidemic, and harnessed technologies developed in East Asian countries for ‘heat-treating’ our food waste to safely turn it into pig feed, around 1.8 million hectares of land could be saved from being stripped for grain and soybean-based pig feed production – including over quarter of a million hectares of Brazilian forest and savannah.
While swill-feeding was banned across the EU in 2002 following the foot-and-mouth outbreak – triggered by a UK farmer illegally feeding uncooked food waste to pigs – other countries, such as Japan, responded by creating a highly regulated system for safely recycling heat-treated food waste as animal feed.
Researchers describe the EU ban as a “knee-jerk reaction” that no longer makes sense when East Asian countries have demonstrated that food waste can be safely recycled. The models in the latest study show that pigswill reintroduction would not only decrease the amount of land the EU pork industry requires by 21.5%, but also cut in half the ever-increasing feed costs faced by European pig farmers.
Researchers describe swill as a feed which is commonly used in other parts of the world, one that could save a huge amount of global resources, and provide an environmentally sound recycling solution to the estimated 102.5 million tonnes of food wasted in the EU each year. Over 35% of food waste is now recycled into animal feed in Japan, where swill-fed “Eco-pork” is marketed as a premium product.
“Following the foot-and-mouth disease outbreak, different countries looked at the same situation, the same evidence, and came to opposite conclusions for policy,” said Erasmus zu Ermgassen from the University of Cambridge’s Department of Zoology, who led the study, published today in the journal Food Policy. “In many countries in East Asia we have a working model for the safe use of food waste as pig feed. It is a highly regulated and closely monitored system that recycles food waste and produces low-cost pig feed with a low environmental impact.”
The researchers examined data about the current land use of EU pork, the availability of food waste in the EU, and the quality and quantity of pork produced in feed trials that compared pigswill to grain-based diets, to produce a model of how much land could be saved if the pigswill ban was lifted.
Some 21.5 million tonnes of pork, around 34kg of pork per person, are produced in the EU each year. Livestock production occupies approximately 75% of agricultural land worldwide – with most of this used to produce animal feed. For EU pork, much of the environmental burden stems from the farming of soybean meal, which takes up in excess of 1.2 million hectares of land across South America.
As swill is much cheaper than grain and soybean-based pig feed, reintroducing swill feeding could reduce costs faced by EU pig farmers by 50%, say the researchers.
Most objection to swill feeding in the EU stems from concerns about safety, and the sentiment that feeding human food waste to pigs is unnatural. But zu Ermgassen argues that those concerns are largely based on incorrect assumptions.
“Pigs are omnivorous animals; in the wild they would eat anything they could forage for, from vegetable matter to other animal carcasses, and they have been fed food waste since they were domesticated by humans 10,000 years ago. Swill actually provides a more traditional diet for pigs than the grain-based feed currently used in modern EU systems,” said zu Ermgassen.
“A recent survey found that 25% of smallholder farmers in the UK admit to illegally feeding uncooked food waste to their pigs, so the fact is that the current ban is not particularly safe from a disease-outbreak perspective. Feeding uncooked food waste is dangerous because pigs can catch diseases from raw meat, but a system supporting the regulated use of heat-treated swill does not have the same risks,” he said.
With the demand for meat and dairy products forecast to increase 60% by 2050, reducing the environmental footprint of current systems of meat production will become increasingly critical.
zu Ermgassen points out that economic and environmental concern is driving a reassessment of EU animal feed bans that were put in place in the 2000s, as well as attempts to recycle food waste more effectively. The EU is currently looking into repealing bans on using waste pig and poultry products as fish feed and reintroducing insects as pig and poultry feed.
“The reintroduction of swill feeding in the EU would require backing from pig producers, the public, and policy makers, but it has substantial potential to improve the environmental and economic sustainability of EU pork production. It is time to reassess whether the EU’s blanket ban on the use of food waste as feed is the right thing for the pig industry,” he said.
Erasmus zu Ermgassen’s research is funded by the Biotechnology and Biological Sciences Research Council.
Erasmus K.H.J. zu Ermgassen, et al. "Reducing the land use of EU pork production: where there’s swill, there’s a way" Food Policy Vol 58 (January 2016). DOI:10.1016/j.foodpol.2015.11.001.
Inset image: "Save Kitchen Waste to Feed the Pigs!" poster from the Imperial War Museums © IWM (Art.IWM PST 14743).
New research suggests that feeding our food waste, or swill, to pigs (currently banned under EU law) could save 1.8 million hectares of global agricultural land – an area roughly half the size of Germany, including hundreds of thousands of acres of South America’s biodiverse forests and savannahs – and provide a use for the 100 million tonnes of food wasted in the EU each year.
Nancy Lane awarded Doctorate of Science by Heriot-Watt University
From Department of Zoology. Published on Nov 23, 2015.
‘Fourth strand’ of European ancestry originated with hunter-gatherers isolated by Ice Age
By fpjl2 from University of Cambridge - Department of Zoology. Published on Nov 16, 2015.
The first sequencing of ancient genomes extracted from human remains that date back to the Late Upper Palaeolithic period over 13,000 years ago has revealed a previously unknown “fourth strand” of ancient European ancestry.
This new lineage stems from populations of hunter-gatherers that split from western hunter-gatherers shortly after the ‘out of Africa’ expansion some 45,000 years ago and went on to settle in the Caucasus region, where southern Russia meets Georgia today.
Here these hunter-gatherers largely remained for millennia, becoming increasingly isolated as the Ice Age culminated in the last ‘Glacial Maximum’ some 25,000 years ago, which they weathered in the relative shelter of the Caucasus mountains until eventual thawing allowed movement and brought them into contact with other populations, likely from further east.
This led to a genetic mixture that resulted in the Yamnaya culture: horse-borne Steppe herders that swept into Western Europe around 5,000 years ago, arguably heralding the start of the Bronze Age and bringing with them metallurgy and animal herding skills, along with the Caucasus hunter-gatherer strand of ancestral DNA – now present in almost all populations from the European continent.
The research was conducted by an international team led by scientists from Cambridge University, Trinity College Dublin and University College Dublin. The findings are published today in the journal Nature Communications.
“The question of where the Yamnaya come from has been something of a mystery up to now,” said one of the lead senior authors Dr Andrea Manica, from Cambridge’s Department of Zoology.
“We can now answer that as we’ve found that their genetic make-up is a mix of Eastern European hunter-gatherers and a population from this pocket of Caucasus hunter-gatherers who weathered much of the last Ice Age in apparent isolation. This Caucasus pocket is the fourth major strand of ancient European ancestry, one that we were unaware of until now,” he said
Professor Daniel Bradley, leader of the Trinity team, said: “This is a major new piece in the human ancestry jigsaw, the influence of which is now present within almost all populations from the European continent and many beyond.”
Previously, ancient Eurasian genomes had revealed three ancestral populations that contributed to contemporary Europeans in varying degrees, says Manica.
Following the ‘out of Africa’ expansion, some hunter-gatherer populations migrated north-west, eventually colonising much of Europe from Spain to Hungary, while other populations settled around the eastern Mediterranean and Levant, where they would develop agriculture around 10,000 years ago. These early farmers then expanded into and colonised Europe.
Lastly, at the start of the Bronze Age around 5,000 years ago, there was a wave of migration from central Eurasia into Western Europe – the Yamnaya.
However, the sequencing of ancient DNA recovered from two separate burials in Western Georgia – one over 13,000 years old, the other almost 10,000 years old – has enabled scientists to reveal that the Yamnaya owed half their ancestry to previously unknown and genetically distinct hunter-gatherer sources: the fourth strand.
By reading the DNA, the researchers were able to show that the lineage of this fourth Caucasus hunter-gatherer strand diverged from the western hunter-gatherers just after the expansion of anatomically modern humans into Europe from Africa.
The Caucasus hunter-gatherer genome showed a continued mixture with the ancestors of the early farmers in the Levant area, which Manica says makes sense given the relative proximity. This ends, however, around 25,000 years ago – just before the time of the last glacial maximum, or peak Ice Age.
At this point, Caucasus hunter-gatherer populations shrink as the genes homogenise, a sign of breeding between those with increasingly similar DNA. This doesn’t change for thousands of years as these populations remain in apparent isolation in the shelter of the mountains – possibly cut off from other major ancestral populations for as long as 15,000 years – until migrations began again as the Glacial Maximum recedes, and the Yamnaya culture ultimately emerges.
“We knew that the Yamnaya had this big genetic component that we couldn’t place, and we can now see it was this ancient lineage hiding in the Caucasus during the last Ice Age,” said Manica.
While the Caucasus hunter-gatherer ancestry would eventually be carried west by the Yamnaya, the researchers found it also had a significant influence further east. A similar population must have migrated into South Asia at some point, says Eppie Jones, a PhD student from Trinity College who is the first author of the paper.
“India is a complete mix of Asian and European genetic components. The Caucasus hunter-gatherer ancestry is the best match we’ve found for the European genetic component found right across modern Indian populations,” Jones said. Researchers say this strand of ancestry may have flowed into the region with the bringers of Indo-Aryan languages.
The widespread nature of the Caucasus hunter-gatherer ancestry following its long isolation makes sense geographically, says Professor Ron Pinhasi, a lead senior author from University College Dublin. “The Caucasus region sits almost at a crossroads of the Eurasian landmass, with arguably the most sensible migration routes both west and east in the vicinity.”
He added: “The sequencing of genomes from this key region will have a major impact on the fields of palaeogeneomics and human evolution in Eurasia, as it bridges a major geographic gap in our knowledge.”
David Lordkipanidze, Director of the Georgian National Museum and co-author of the paper, said: “This is the first sequence from Georgia – I am sure soon we will get more palaeogenetic information from our rich collections of fossils.”
Inset image: the view from the Satsurblia cave in Western Georgia, where a human right temporal bone dating from over 13,000 years ago was discovered. DNA extracted from this bone was used in the new research.
E.R. Jones et. al. ‘Upper Palaeolithic genomes reveal deep roots of modern Eurasians.’ Nature Communications (2015). DOI: 10.1038/ncomms9912
Populations of hunter-gatherers weathered Ice Age in apparent isolation in Caucasus mountain region for millennia, later mixing with other ancestral populations, from which emerged the Yamnaya culture that would bring this Caucasus hunter-gatherer lineage to Western Europe.
Pevensey giant whale remembered 150 years on
From Department of Zoology. Published on Nov 16, 2015.
Changes in DNA are NOT random - a Naked Scientists podcast featuring Professor Bill Amos
From Department of Zoology. Published on Nov 05, 2015.
Tom Evans awarded the John Ray Science Prize 2015
From Department of Zoology. Published on Sep 01, 2015.
Claire Feniuk successful at 2015 International Conference on Conservation Biology in Montpellier
From Department of Zoology. Published on Aug 13, 2015.
Hugh Cott - master of camouflage
From Department of Zoology. Published on Aug 11, 2015.
Isabel Palacios helps African universities reap fruits of fly research
From Department of Zoology. Published on Jul 10, 2015.
Why insects are marvels of engineering
From Department of Zoology. Published on Jul 03, 2015.
Emeritus Professor Sir Pat Bateson awarded the ZSL Frink Medal 2014
From Department of Zoology. Published on Jun 25, 2015.
Richard Preece and Roz Wade on 'Wildlife Wednesday'
From Department of Zoology. Published on Jun 18, 2015.
Prof. Simon Laughlin publishes new book on brain design
From Department of Zoology. Published on Jun 15, 2015.
Nick Davies appears on 'Springwatch'
From Department of Zoology. Published on Jun 12, 2015.
Janet Moore Prize for Supervising in Zoology
From Department of Zoology. Published on Jun 12, 2015.
All Museum creatures great and small
From Department of Zoology. Published on Jun 09, 2015.
Henry Disney paper chosen as Science Editor's Choice
From Department of Zoology. Published on May 18, 2015.
Legs give moths a flying start
From Department of Zoology. Published on May 01, 2015.
The Arup Building is renamed The David Attenborough Building
From Department of Zoology. Published on Apr 22, 2015.
Wendy Gu wins first place in BSCB BSDB Student Poster prize competition
From Department of Zoology. Published on Apr 15, 2015.
Red Noses in Zoology
From Department of Zoology. Published on Mar 25, 2015.
Zoology student success in 2015 Graduate School Life Sciences Poster and Image Competitions
From Department of Zoology. Published on Mar 25, 2015.
MPhil student wins bursary
From Department of Zoology. Published on Mar 09, 2015.
Nick Davies’ new book, Cuckoo: Cheating By Nature
From Department of Zoology. Published on Mar 06, 2015.
Museum of Zoology plans boosted
From Department of Zoology. Published on Mar 02, 2015.
Congratulations to Nick Crumpton and Robert Brocklehurst
From Department of Zoology. Published on Feb 26, 2015.
Museum of Zoology on BBC Look East
From Department of Zoology. Published on Feb 20, 2015.