Latest news with #Couzin
The Hindu
30-04-2025
- Science
- The Hindu
New model finds locusts making complex decisions in deadly swarms
In late 2019, a wave of billions of desert locusts flew into western India through Pakistan. Their journey had already spanned several thousand kilometers since they first erupted in the arid plains of East Africa. Locusts are grasshoppers that, in the right conditions, multiply rapidly. They grow larger and change colour in response to their environment. In a process called gregarisation, they transition from solitary creatures to a swarm, congregating in large numbers and travelling together over several leagues at time. Historically, these 'outbreaks' have led to widespread famine and economic devastation, earning them the name 'locust plagues'. The 2019-2022 outbreak was the worst to hit Kenya in 70 years and to hit Ethiopia, Somalia, and India in 25 years. More than 200,000 hectares of crops were destroyed. At this time, researchers in German and North American universities saw an opportunity to study locust swarms and flew to Kenya, hoping to refine a long-standing theory about swarming behaviour. Previous models of locust swarms have treated them like gases in motion. Specifically, they assumed individual locusts aligned with their neighbors like self-propelled particles — a model-object used in theoretical physics. 'Initially, we wanted to replicate what we thought we knew,' Iain Couzin, director of the Max Planck Institute of Animal Behavior and professor at the University of Konstanz, who has studied collective intelligence and locust behavior for over two decades, said. 'But what we didn't expect was to find that we could not replicate our previous findings, and that completely changed our understanding of how locusts form these massive swarms.' In a recent paper , Couzin and his team proposed a revised model to make sense of swarms. According to this model, locusts don't behave like gases. Instead, their movement is based on a cognitive decision-making process based on their perception of nearby motion. The finding marks a major shift in how scientists understand locust behaviour and their ability to make swarm-related predictions. As climate change continues to alter locusts' breeding patterns, this refined understanding may be the key to protecting crops, and livelihoods, before the next swarm arrives. From field to holograms Just before the spread of COVID-19 became a pandemic, some members of the research team (other than Couzin) conducted a study in Kenya's Samburu and Isiolo counties. They examined large, ground-marching bands of young locusts using precise tracking methods, and noticed a pattern. The locusts weren't explicitly aligning with their immediate neighbors, contrary to what the self-propelled particles model predicted. To test their observations, they conducted sensory-deprivation experiments in which they altered the insects' ability to see, smell or sense movement. The results revealed that vision had a major influence in determining how locusts moved within a swarm. Locusts that couldn't see clearly lost their sense of direction while those with intact vision moved with the swarm even without physical contact. 'Those data showed that olfaction wasn't important, tactile cues weren't important, but vision was really, really important,' Couzin said. 'That justified the use of holographic virtual reality to study this phenomenon in more detail.' The scientists placed locusts in a fully immersive virtual-reality environment and tested their response to different visual stimuli. In these experiments, the locusts interacted with computer-generated swarms that varied in density and movement order. Soon, their key finding emerged: coherence of motion rather than crowding controlled their alignment. Even in sparsely populated swarms, the locusts moved together if their visual cues were strong. The team realised locusts weren't behaving like gas particles. Instead, their movement followed a decision-making process based on their perception of nearby motion. To represent this, the researchers developed a new mathematical model based on a neural ring attractor network, a concept in neuroscience. Instead of treating locusts as mindless particles, the approach addressed them as decision-making entities that could integrate multiple visual inputs before choosing a direction. The model suggested locusts may weigh different potential options and make effective decisions. 'However, at the group level, there's no planning at all,' Couzin added. 'The group is an emergent phenomenon.' An emergent phenomenon is a complex pattern arising from simple interactions, without central control. In locust swarms, collective movement emerges from each locust's individual behavior, creating large, coordinated swarms without a leader. This is how flocks of birds and traffic jams work, too. 'This study established how swarms move and how coordinated motion arises,' Sercan Sayin, neurologist and molecular biologist at the University of Konstanz and one of the study's authors, said. 'The initial direction selection and how this is maintained — that's the next question we would like to answer.' 'Wrong way of thinking' Understanding how locusts move has real-world consequences. Yet how these groups emerge or which exact factors determine the direction of their flight remains unclear. Climate change has worsened the problem by increasing rainfall in desert regions, creating ideal breeding conditions. The 2019-2022 outbreak — one of the worst in decades — was fueled by unusually strong monsoons and cyclones in the Arabian Sea. Cyclones Mekunu and Luban had also struck the Arabian Peninsula in 2018. Unusual monsoons and delayed control worsened the crisis, creating a swarm. 'We thought we had a good understanding, and the old models were being used to try to make predictions, but that was the wrong way of thinking,' Couzin said. 'Hopefully, now we've set the record straight and we can start building a team effort to make increasingly accurate predictions. One way to do that, of course, is to start tracking animals in the wild.' 'With the changing climate, the swarms are expected to become larger and more unpredictable, making management more difficult,' he added. 'To really be able to make predictive models or understand this better, we need much more research. We also need to involve climate scientists and vegetation experts.' Monika Mondal is a freelance science and environment journalist.
Times of Oman
02-03-2025
- Science
- Times of Oman
Scientists crack the code for why locusts swarm
Berlin: After months of building, the biggest locust swarm recorded in 70 years swept across 10 countries in East Africa in spring 2020. The damage to crops was estimated at $8.5 billion (€8.1 billion) in a region where 23 million people face severe food insecurity. During these invasions, desert locusts (Schistocerca gregaria) eat their own weight in food every day. The biblical-scale plague ate through 160,000,000 kilograms of food a day — enough to feed 800,000 people for a year. Scientists have been trying to understand how individual locusts gather in swarms for decades. Knowing their behaviour would help with predicting and managing outbreaks. A new model, published today in the journal Science, casts light on the hive mind of locusts. The study describes how individual locusts transition from behaving as solitary animals to giant swarms with collective motion. "Our work provides a new perspective for considering collective motion in animals, and robotics too," lead author Iain Couzin, a neurobiologist at Centre of the Advanced Study of Collective Behaviour, Konstanz, Germany. "One application is a new class of predictive models of how and where swarms move. Future research on this could impact the livelihoods of 1 in 10 people on the planet," Couzin told DW. A new model of swarming, using insect VR Locusts swarms have threatened food security for millennia and have played their part in history — locusts were one of the 10 plagues brought upon Egypt as retold in the Book of Exodus. For decades scientists have been trying to understand how individual locusts move en masse. In 2006, Couzin developed a model explaining how locusts would march together in a line when they swarm. "This model came from particle physics and suggested that individuals bump into each other randomly, then flow together all in the same direction if there is a high density of individuals," said Couzin. Study author Sercan Sayin began probing this model in locusts using a virtual reality (VR) stage set for locusts. Sayin had the insects walk on a ball surrounded by panoramic views on screens. These landscapes reconstructed the world in 3D to make the locusts think they were in a swarm, Sayin said. But he couldn't replicate the 2006 findings that animal density was responsible for locusts forming swarms. Vision cues swarming behaviours Field experiments in Kenya during the huge 2020 swarm showed certain visual cues caused locusts to behave with collective movements when swarming. "Previously we'd thought that bumping into each other caused swarms, but our experiments showed that it's vision that's important," said Couzin. "We found instead that [swarm behaviours] are triggered by the type of sensory information around them, not how many locusts they're surrounded by." Jan Ache, a neurobiologist at the University of Wuerzburg, Germany, who was not involved in the study, said the research expands a mathematical model of swarms which acknowledges the individuality of locusts. "In order for locusts to have collective motion, they need very basic forms of cognitive processing — where insects integrate their own position relative to the position of those around them, then actively follow other locusts," he said. This occurs in individual locusts, but when they come together in crowds it creates the emergent effect of a swarm. How the brain makes decisions Ache said locusts are fascinating to study because they exist in two different states: solitary or swarming. Normally avoidant, the insects switch into marching bands after several hours of crowding. "When they change from one type to the other, the brain is in two different states. In each state, the same neurons drive very different behaviors — like being attracted to or repelled by other locusts," Ache said. Ultimately, the findings are about decisions-making in neuronal systems, Couzin said. "At the basic level, there's competition between groups of neurons in the brain. The brain must come to a consensus and make a decision about movement," Couzin said. In other words, when there's a conflict in the brain, neuronal pathways compete until a decision is made when one pathway "wins" over the other. In their experiments, the visual cues of other locusts in front acted as a target causing the navigation systems to pull the organism in the same direction. "This is very similar to opinion dynamics in humans, where people adopt similar opinions to others and dismiss other opinions," said Couzin. Predicting swarms and crowds? Couzin said the new model has important implications for predicting swarms in the real world. "If we were able to create a model predicting how swarms move, we were using the wrong model before. The implication is new ways to predict how and where swarms move based on a biological understanding of collective motion," said Couzin. It could also help to understand how fish move in schools; birds move in flocks and potentially how mammals move in herds. Couzin is also applying their research in robots, creating collective motion in autonomous vehicles. Couzin said their findings are worth considering in human crowds too, perhaps to help prevent crowd crushes, but "it's too early to make any claims as those experiments haven't been done."
