Wild City： Comeback of Wildlife ｜ Full Nature Documentary

The lockdowns of 2020 and 2021 opened up a gap in all of our lives that no one had ever imagined possible. Before the menace of a terrifying virus, cities came to a standstill. Nearly three billion people had to suddenly lock themselves away in their homes. From one day to the next, the streets were emptied, leaving behind a disturbing silence. But not for everyone. Very often, wild animals filmed in urban environments are used to humans who have fed and raised them since birth like their natural parents would have done. So we get beautiful and spectacular pictures which are not always realistic. But in 2020, reality would go beyond fiction. City dwellers from around the world filmed what were once unimaginable scenes with mobile phones. Peacocks, goats, deer, wild boars, foxes, weasels, and many other wild creatures walked down the roads as if they were alone in the world. More interested than disturbed by this universe where humans seem to have suddenly disappeared. Once more, birdsong can be heard in the middle of town. Lockdowns and the return of silence put us suddenly in front of a disturbing reality. We live night and day in a maddening cacophony of sound. Ports also stopped. Astonished by this silence, many marine animals came to see what was happening. Naturally curious and playful, dolphins arrived to scout. In the port of Set, a shark explored in a meter of water. A family of manatee and Indian file made a show in a Florida port. In New Zealand, a humpbacked whale came to inspect the keys of the port of Wellington. But what was it like in the open sea? The Mediterranean Sea is one of the busiest seas on the planet. Noise pollution is at its worst. Lockdown imposed a silence that hadn't been heard for a long time. Researchers from the University of Toulon seized this historical occasion to launch a study project baptized Quiet Sea. Installed on a catamaran, the team piloted two electric marine drones, perfectly silent, inspired by the traditional Polynesian canoe. The two asymmetric hulls assure exceptional stability, which reduces pitching and rolling strongly. So, sound distortion on the submarine listening instruments on board is greatly reduced. The two drones can patrol a zone for hours without any human intervention. Hervé Gloutin, acoustic researcher, analyzes the recordings made. That's the noise of the environment there. This packet is the noise of fish. Organisms around the drone. And there's no other noise added. Anthropic, etc. Among the animals that people the Mediterranean, the great sperm whale is a giant, 18 meters long. It's the only cetacean with teeth in its jaw. It spends a large part of its life below the water and comes up periodically to the surface to fill up with oxygen. Water offers such high resistance to the penetration of light that at a few dozen meters depth, it emerges us in darkness. However, sounds benefit from the density of water to propagate very far and very quickly, allowing an intense exchange of vital information for the cetaceans and the balance of ecosystems. While it was long believed that marine animals were silent, we now know that they are noisy and incorrigibly talkative. Fish make noises either by their swim bladder or by moving their fins. That grinds or it burps. Or it belches. In this unusual silence, the sperm whale flatulence sounds like underwater eruptions. The great sperm whale uses its nostrils to produce sound signals like a series of clicks, for which it then waits for the echo that the environment sends back. It's by this process, known as echolocation and like sonar, that the cetacean spots its prey. Each sperm whale has its own acoustic signature. In a group discussing, each individual can be identified. For the first time in the world, a few weeks before the Quiet Sea operation, the acoustic coordinates of several sperm whales hunting in a group were recorded in the great deeps offshore from Monaco. The ecosystems are very rich and the prey numerous in this zone carved with deep submarine canyons. The recordings made show that, even at 500 metres distance from each other, the actions and movements of the sperm whales were concerted and synchronised, which implies they communicate between each other. What are they saying? Are they giving instructions? Orders? Are those on watch, on the flanks, describing to the others what they perceive in the depths, movement of the prey that the herd is pursuing? Nothing is yet known. Sole certitude, the recordings have confirmed that the sperm whales have a strong collaborative intelligence based on the communication of sound. However, in ordinary times this is heard. A noise mainly due to blades, boat motors and sonar. This accumulation of sound sometimes exceeds 160 decibels, the limit beyond which the human ear is in danger. Nowadays, these animals are separated by an uncrossable barrier of acoustic disturbances and which prevents them from meeting or simply communicating. Sound pollution is also the reason why many marine animals, like the great dolphins, rarely approach the coasts. However, surprise, during the period of lockdown, amazed witnesses filmed with their phones large dolphins right beside the coasts, like here in Turkey, in the port of Bosphorus. In Spain, in the little Galician port of Ogrove, researchers from the Bottlenose Dolphin Research Institute are studying these cetaceans. Bruno Díaz-López, its director, has equipped the port with sound captors to record the dolphins that arrived during lockdown. Now the dolphins are wandering about in groups around the port. During lockdown, we saw that sometimes the dolphins went to feed in unusual places. In the absence of man, some even risked going into mollusc farms. It's coming out there. Bruno asks himself if the dolphins have benefited from the end of port activity to modify their behavior. There's one. Ford's staying at about 60 meters. This individual is, I think it's Ford, yes. He's staying in this zone where we've seen him for a long time and frequently during lockdown. First indispensable step, identify the individuals. Each dolphin fin is specific. The scratches, the cuts due to the dangers which the animal has affronted during its life are like fingerprints. Once the dolphin is identified, researchers give it a name and especially record its vocalizations. During lockdown, because there was less sound disturbance, the dolphins communicated better. They didn't have to increase the amplitude of their sound emissions. In normal times, dolphins are forced to shout to be heard because of the intense noise of boats. The port of Agrobe is very active at all hours of the day and night. During lockdown, the constant coming and going stopped. Hydrophones recorded many dolphin vocalizations. Their vocal repertory is rich with 14 distinct signals used for communication. Each signal is defined by a particular acoustic structure and a determined length. Some large dolphins hit the surface of the water with their tails to make large splashing sounds. But is this a kind of communication or perhaps an invitation to play? No one knows. These studies will allow us to better understand the behavior of large dolphins and their hunting zones in the absence of noise. They point to the measures to be taken to define safer transit corridors for large dolphins and to limit the port's and its surrounding areas' noise pollution. Because of the halt in maritime activity, the general sound level fell by 5 decibels and even 12 decibels in some Mediterranean zones. At the same time, the water grew clearer. Ordinarily, large dolphins are rare in the Calanques of Marseille, which are crowded in winter and summer. But with lockdown, the dolphins are there in numbers, busy with rarely observed activity. The hydrophones on board the Quiet Sea Operations drones have recorded curious signals. After two months of lockdown, we've got animals in the Calanques who are playing with the echoes from the surface, the floor, and the sides, like we might enjoy ourselves in a cathedral or cave to listen to the echoes. They're enjoying it, and they're astonished. A signal arrives at the antenna directly. The direct signal is reflected to the surface, which is there. But that signal also went to the floor and returned from the floor. We know these are curious and playful animals, and this is just a demonstration of what a mammal does naturally to amuse itself. Supplementary proof that surrounding stress considerably diminished during lockdown, scientists from Quiet Sea were surprised to see large dolphins with young seeking contact and playing with their boat. Unfortunately, since the return of crowds to the Calanques, not so many dolphins come. In the Gulf of Mexico, the pandemic halted the petrol exploitation offshore, which usually causes an important and continuous flow of petrol and gas tankers. As a result, pollution of the seawater due to hydrocarbon leaks from boats dropped by half, and noise pollution was largely reduced. Common blue whales, magnificent cetaceans about 20 meters long and weighing 40 to 50 tons, which usually cruise the open sea, came close to the coasts. Freed from the interference from the noise of boats, their communications became two to six times longer. Further north, the immense Canadian Gulf of Saint-Laurent is the industrial outflow from the Great Lakes region. It's an intense hub of traffic where commercial shipping from around the world crosses paths. When the traffic was interrupted, people from Montreal were astonished to see a humpbacked whale come up the Saint-Laurent river, making impressive leaps which made it famous. Social networks shared these pictures millions of times. What's a humpbacked whale doing here? Montreal is 400 kilometers from the ocean. When it crosses the city, the Saint-Laurent doesn't carry a drop of salt water and a cetacean will find nothing to eat. This will remain a mystery because the whale died shortly afterward from unknown causes. Further downstream in the Saint-Laurent estuary, where salt and fresh water mix, a population of some hundreds of beluga whales has lived for a long time. These small cetaceans, four to five meters long, weighing up to a ton and a half, usually live in the cold waters of the Arctic. Nicknamed sea canaries, beluga are amongst the noisiest mammals on the planet. Like all great talkers, they don't like being interrupted and the usual cacophony found in the estuary disturbs them a lot. Robert Michaud, research director of GREM, study group for marine mammals, knows these endearing creatures perfectly well. 60 to 80 belugas. They're fine animals. One there is a bit big. This population here, if it was healthy, should have doubled since we started studying them at the start of the 1980s. For several years, the scientific community has been worried about the rapid decline of the Saint-Laurent beluga population. The mortality of females and young is rising, while Arctic populations have been spared. Is it possible that we're too noisy and that the noise interferes with communication between mothers and their young? Do the mothers spend more time looking for their young and the young their mothers? That could impose additional energy costs on them, which they can't afford. Researchers are working to identify the cause of this regression. Researcher Valeria Vergara is especially interested in communication between the mother and her single calf. She has identified a key element. That's a contact call. A reply. There you go, another. In the case of the contact call, we now suspect that mother-calf contact or acoustic contact might be getting compromised by vessel noise and that in some circumstances, this might make a reunion by mothers and calves that have become separated a lot more difficult. And this can be dire for little calves. The large merchant ships that take the Saint-Laurent produce noise that can reach 180 decibels. The many pleasure and excursion craft are also very noisy. In 2010 and 2012, the years when the newborn death rate was highest were those when there were the most pleasure craft. To understand the effects of noise on the relations between a mother and her calf, Robert Michaud and Valeria Vergara go to the fjord of Saguenay. This affluent of the Saint-Laurent is a crash for the belugas. Valeria drops a hydrophone into the fjord waters while Robert overflies it with a drone. The two researchers have come to evaluate the effect of boat noise on the contact call, the cry for help which maintains the relation between the mother and her young calf. Synchronization of the hydrophone and the aerial pictures show that the sound space is saturated by the noise of a ferry crossing the opening of the fjord of Saguenay. This is a necessary passage for the belugas coming in and out of the nursery. Valeria has an analogy. It's like deciding to go into a dark tunnel where you can't see or hear anything. This sensory hole identified by the researchers comes from the fact that the young beluga emit their calls on frequencies close to those of the deafening noise made by the ferries. As a result, communication between the mother and the child is interrupted. When it has lost contact with its mother, the isolated and stressed young beluga is in great danger. Its need for socialization pushes it to go into ports where it hears a noise and to have contact with humans. But without its mother, it is condemned. In 2020 and 2021, during the pandemic, pleasure craft remained tied up. These years were exceptionally serene for the belugas of Saint-Laurent. Robert Michaud and his team took advantage of this to make a number of sound recordings. Last April, our reflex was to put hydrophones in the water. Post-pandemic follow-up will be fascinating and interesting for us all. We all have intuitions and I think we all have wishes that a peaceful summer could have improved relations between the mothers and their young. We just offered a publication which shows that during the passage of a boat, contact call distance is reduced by 50%. The beluga has become one of the best indicators of the state of health of the marine world. Once, miners took a canary with them down the mines. Its death warned them of the presence of methane and explosive gas. The withering of the colonies of sea canaries warns us that the marine environment is not well. From the end of lockdown, beachings began again to be notified from the Quebec Emergency Network of Marine Mammals. Rapid intervention is vital. Pulled off the rocks where it has washed up, the animal is cared for and comforted. It is put back in the water when it has regained its strength. We'll have to turn it to the front of the boat. Get ready. One, two, three, let go. Marine animals are subject to many sound disturbances. Ship sonar, especially military submersibles, examine the undersea space by echolocation like sperm whales. They interfere with the whale's system of communication, as well as of other cetaceans and particularly belugas. Undersea drilling, seismic campaigns on the ocean floor in search of hydrocarbons and also wind farms at sea disturb the lives of marine fauna. In water, sound propagates further and four times faster than in the air. Animal life is therefore particularly affected by the racket of human submarine activity. It mixes up their references and causes stress, which puts many species under pressure. Particularly violent noise can seriously affect the hearing of cetaceans, pushing them up to the surface without decompressing. This can cause an embolism and sometimes their beaching. By imposing a pause unknown in modern history on human activity, the COVID-19 epidemic has at least offered to scientists an unhoped for field of experimentation. While noise pollution of marine environments has been known and observed for a long time, the full extent was far from understood. On Earth, silence suddenly fell on urban areas and the great transport networks, which revealed the incessant racket we suffer. With lockdown, cities took on an apocalyptic air, but not for everyone. The many animals living in our towns came out of their hiding places. It's estimated that 35,000 wild boar are hiding in Berlin and there are 15,000 coyotes in the parks and gardens of Chicago. Hiding in all large cities are deer, squirrels, geese, hunting birds and other wild animals. They've learnt so well to fool humans that city folk aren't even aware they are there. Cities were built on their territory. Lots of animals fled, but others learnt the art of camouflage and getting by and stayed where they were born. Food is abundant, hunting forbidden and in green areas pesticides are now forbidden. These stowaways with fur and feathers took advantage of empty streets and deserted squares to go out and enjoy themselves, muzzle or beak in the wind. In large urban areas, sound pollution fell sharply, so much that city dwellers, who couldn't believe their ears, heard the birds sing. Thierry Aubin, specialist in bioacoustics at the University of South Paris, has recorded for years the song of tits and red breasts in the parks of Paris and its surrounds. So, there we're diffusing the song of a strange red breast on the territory of another red breast. It's answering, not at all happy, because that's an intruder on its territory. The great tits, which in a forest sing at a certain level of frequency, quite bass, well, in town they sing higher to rise over the deep note of the cars. This effort wouldn't have an effect if females didn't prefer coupling with males with deeper voices, which characterize the best reproducers. So, noise pollution goes against natural selection. In nature, the average noise is around 60 to 65 decibels. In towns, it could be much more, 70 to 75 decibels. The fact there was a lockdown dropped the level by an average of 20 decibels, which is enormous. Like the red breast, the white-crowned sparrow sings to mark its territory. To sing, it perches in a well-exposed place, like near the Golden Gate Bridge in San Francisco. Traffic on the bridge reduced to nothing during lockdown. A blessing for the white-crowned sparrows. According to ornithologists, these little sparrows took advantage of the break to reduce their sound volume by four decibels, which saved them a lot of effort. They also made, again, deeper tones, which pleased so much the females, and they also sang for longer and more brilliantly. During the winter lockdowns, humans stayed more often at home. Wildlife took off strongly in the forests, and didn't hesitate to dance on their hooves in many villages, sometimes creating epic shows. According to recent work in bioacoustics, half of the sounds of nature have disappeared over the last 50 years. Sensitive to the value of these sound landscapes, the Natural Park of Haidoura launched a listening program for biodiversity in the Rizou Forest. Thanks to a dozen recorders, the noises of the forest have been archived 24 hours a day, seven days a week, over 15 years. Capuchiles, red crossbills, pied woodpeckers, pygmy owls, tufted titmouse, woodcock, Eurasian jays, wood pigeons, ravens. Briefly, all the wildlife with feathers and fur lives its winter life without imagining that the forest is a recording studio. Frederic Sebb, specialist in acoustics at the CNRS and his team, regularly pick up the sound recordings. It's exactly like a musical score with all of the sound landscape, all the different species that are found here. For example, here we have a tree creeper in the highest frequencies, and after that it surely tits. And what is really impressive is that here you have this little black bar, and that is the noise of planes. Rizou Forest is in fact sited 40 kilometres from Grenoble airport, and plane noise is present on 85% of the recordings. Those are the recordings made during lockdown, and there's no more black bar. In Spain, research is being made on the disturbances caused by the coming and going of planes near to Madrid airport. Evolutionary ecologist Diego Ril, from the National Museum of Natural Science of Madrid, is setting up microphones and feeding stations near runways to study how birds adapt the time of their song to the noise of planes. The species which sing late in the day, like the chaffinch, are severely cut up by the planes. On the other hand, the tits that sing very early in the morning scarcely change their singing times, because they don't have to fight aircraft noise. Cameras set up close to the feeding stations record the behaviour of the birds. See how it's eating calmly, but when there's aircraft noise, it stops eating, it starts observing, looking from left to right. It stays vigilant until the plane has completely passed over the birds. The powerful and aggressive reactor noise causes stress in the birds. Stress causes them to spend a lot of time watching for possible danger, and reduces the time they have to find food. Their attention is distracted by the planes, which stops them from detecting the presence of winged predators, like sparrowhawks or peregrine falcons. The usual deafening and ceaseless air traffic suddenly stopped during the lockdowns. With the Madrid airport shut down, the birds rapidly went back to their natural behaviour. The same behaviour was seen in the city. A study showed that during lockdown, in the absence of human noise, the birds came back to sing in the city at normal times, with a more natural song frequency. Unable to substantially change their voices' low frequencies, turtle doves usually abandon noisy places like motorways and airports. But during the short calm of lockdown, they quickly returned close to the runways. In a German airport, the return of long-billed curlews was even seen. These are threatened migrating birds, who used the almost complete stop of air traffic to explore the carpet of long grass, left wild, and which houses a rich and varied fauna. The effect of noise pollution on birds was particularly visible at Marseille airport. During lockdown, pink flamingos rushed to the salt pools that are alongside the runways. There were 40,000 paddling in the salty water, whereas in normal times there are only 15,000. In India, flamingos swarmed at the feet of the buildings where the inhabitants were locked down. In the USA, they invaded the industrial zones fixed in lugubrious silence. It seems that the silence had, for some species, unexpected consequences. In the salt pools of Marseille, the number of births was multiplied by 10. 16,000 chicks were counted, a figure only seen three times in 30 years. But why so many births? In species that nest on French beaches, like the plover, births increased by 40%. This spectacular rise is probably due to the fact that the hatchings weren't disturbed by walkers and their dogs. Everywhere on the planet, a rage to copulate took over wild animals, which were a lot less stressed. This fever even hit zoos, closed and without public. And so in the zoological garden of Hong Kong, a couple of pandas that hadn't shown the slightest affection for each other for 10 years, coupled for the first time. In a nature free from human noises, the growth of amphibians can be perceived from further off by their fellows and helps reproduction. Male green frogs and tree frogs have particularly powerful voices. At the time of reproduction, the males croak with all their force to attract females by swelling their vocal sacks, which amplifies their songs. Thierry Langagne, specialist in noise and light pollution at the CNRS, has found a second criteria as important as the first. Here we have a green male tree frog. You can see very clearly the colour of his vocal sack here, which is orange. And this is a very important criteria for the females when they choose a partner, because they don't couple by chance on the pond. They couple with males of better quality. Tree frogs usually live in trees where they hunt insects. They only go to the ponds to reproduce. The vocalizations of the males then mix in a great polyphonic chorus of amphibians who sing at night until the morning. The males call. The females are sensitive to their voices and go closer to the voice which seems the most seductive to them. Then the colour of the vocal sack, which they can distinguish in the shadows, confirms the correct choice of partner. Thierry captures tree frogs alive in isolated places with no noise pollution. Returning to his CNRS laboratory at Lyon, Thierry makes up two groups of male tree frogs. The first is submitted to the usual sound of a pond in nature. The second group is exposed to the same noise to which is added the noise of road traffic at 75 decibels as if the pond was beside a fairly busy highway. Here we have a male with a very clear sack because he's had noise pollution for 10 days, while this one has a sack with much more orange because he was in the control group that didn't. This means that the females on the basis of the colour of the vocal sack can no longer detect which are the super males with which they should couple and so we expect a quite rapid deterioration in genetic quality which could lead to a collapse of populations in time. The group which suffered from noise pollution show a stress 57% higher than that of the control group. Thierry is convinced that the negative impact of noise doesn't just concern atrassians, sperm whales and birds. And so for man, as for the tree frogs, exposure to a high level of noise pollution means a strong increase in stress which will have effects on cardiovascular illness, sleep quality and cognitive capacity. Therefore these effects can be very worrying for humans in a time when the world becomes more and more noisy. When we see the negative effects of noise on animals, it seems urgent to worry about the effect on humans. The struggle against noise pollution has only just begun. The noise of cars on roads is being reduced by new surfaces. Anti-sound walls are more often installed to reduce noise by half. Designed obviously for us, animals also benefit. A system of a bubble curtain has been developed which limits the propagation of sound waves in water. In Brittany, these bubble curtains have been put in place to protect the sites of Saint-Jacques shellfish exposed to the noise of underwater works. This same system has been deployed on Reunion Island during the gigantic work of the construction of the coast road. These curtains reduce noise pollution by 25 decibels. The vibrations of propellers in boats is being reduced. More aerodynamic hulls are being constructed which leave less of a wake. And finally, the decline of internal combustion engines has truly begun. The return of wild animals during the period of the pandemic allowed us to glimpse a world stripped of the noise pollution which gets on our nerves. The extraordinary distribution of these videos on social networks shows our fascination for the wild and our vital need to renew our ties with nature and silence.