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Welcome to synurbia

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Matt Walker Matt Walker | 14:58 UK time, Wednesday, 3 August 2011

European badger (Image: Andrew Parkinson / NPL)

Are badgers at the forefront of synurbization? (image: Andrew Parkinson / NPL)

Some animals are synurbic, and some aren’t.

Badgers are. As are wood pigeons. Tigers most definitely aren’t.

It is, by definition, impossible for a whale to be synurbic, but perhaps not a frog.

What on earth am I going on about?

I’m talking about those animals and plants that like living where we do.

This is a phenomenon most of us are aware of, even if not explicitly. We feed garden birds, and enjoy catching a furtive, shadowy glimpse of an urban fox or hedgehog.

But the concept of synurbic species, and the process of synurbization, is being taken increasingly seriously by scientists, as too is the whole concept of urban ecology.

Because they address the intriguing question of whether wildlife is finding ways to live alongside people, and our urban sprawl.

More intriguingly, they also examine whether some species are going further: and are positively adapting to life in towns and cities, becoming more successful as they do.

That could lead to the rise of synurbia – where wildlife comes in from the country, and learns to live all around us. That’s interesting in itself. But it is something we can all look out for. Are animals and plants encroaching on your back yard? Are you increasingly living in synurbia?

To add another definition into the mix: some species are synanthropes. These are those species particularly associated with humans and places of human habitation
(The prefix “syn” comes from the Ancient Greek for “together with”.)

I’ve taken the definition above from a new research paper published by Robert Francis and Michael Chadwick, both of whom study at King College London, UK.

Rock pigeons (image: Laurent Geslin / NPL)

Rock pigeons have become town birds (image: Laurent Geslin / NPL)

Published in the journal Applied Geography, the paper details Francis and Chadwick’s thoughts about the concept of synurbic species. I want to share their thoughts with you – but also as a way to ask you to think about the concept of synurbia.

Examples of synanthropes include tapeworms and lice, agricultural weeds and pest species, as well as pigeons and rats (ecologists exclude domestic species from this discussion).

These species do well around people, living off us, our crop fields or waste. Some, say Francis and Chadwick, have thrived, as humans have expanded their reach around the world.

However, many of these species also do well in other ecosystems; in the wild and in rural areas not yet urbanised.

Synurbic species however, go a step further. They should be defined as species which live at greater densities in urban areas than rural ones, say Francis and Chadwick.

And to understand them better, the researchers say, we need objective measures of how many individuals of a species are living in towns and cities as compared to the country.

Recent studies have shown that blackbirds, wood pigeons and mockingbirds among other birds, badgers, some insects and plants all live at greater densities in many towns than outside of them.

This week, entomologists announced a study into whether UK cities are becoming a haven for insect pollinators.

Most interestingly, Francis and Chadwick also spell out in their paper how some species can become synurbic. Understanding that will help ecologists understand how human impacts affect wildlife, and which species have an opportunity to adapt to city-living. It will also allow researchers to deal with a less-regarded category of synurbic species – pests, such as rats.

Much of the work done so far has focused on birds: some species, such as light-vented bulbuls have learnt to make nests out of man-made materials; others such as monk parakeets have adapted to nest in telegraph poles. Birds have changed their egg laying habits, songs and even escape flights, with the northern mockingbird learning how to recognise individual people, and flee from them differently.

Common blackbird (image: Markus Varesvuo)

Common blackbirds live at greater densities in urban areas (image: Markus Varesvuo)

Fewer studies have been done on mammals, though eastern grey squirrels and northern racoons have responded well to urban environments, while stone martens often prefer to den in buildings than more natural sites.

Foxes now live in densities up to 30 times greater in urban areas than in the country, as shown by studies in Zurich, Switzerland and Bristol, London.

As for invertebrates, numbers of dust mites and bed bugs are likely much higher in urban environments, though surprisingly few studies have been done to show this. Invasive mosquitoes have taken to city life, reproducing in bird baths, guttering and disused tyres, say Francis and Chadwick, as have sandflies. Bumblebees change the way they forage in towns and cities.

But it may be plants that have best embraced synurbization. Walls make great habitat for cliff-dwelling species and several plant species in the UK, including ferns such as maidenhair spleenwort, are more abundant on urban walls than in their original cliff habitat.

Other plants respond to urban habitats by hybridising – creating new types such as the Railway yard-knotweed, which is a hybrid of Japanese knotweed (Fallopia japonica) and the Chinese fleecevine (Fallopia baldschuanica), which is mostly found in London.

Whether these species are actually adapting, in evolutionary terms, to urban life is harder to show.

Some are certainly making behavioural changes; town-living European foxes have reduced territories, forage in packs, eat our leftovers and tolerate people far more.

But that doesn’t mean their “evolutionary fitness” is increasing. Foxes may naturally have a range of territory sizes, for example, and may simply use smaller territories more in towns, and larger ones in the country. They do as needs must, rather than urban foxes on the whole are evolving to have permanently smaller territories.

There is however, tantalising evidence that some species are evolving to live around us.

Urban house finches have evolved different bill shapes and bite with different forces to their rural cousins, so they can eat different seeds found in towns, studies have shown.  Blowflies in towns and the country have different life histories – and these seem to persist down the generations in flies reared in the lab – suggesting the urban flies are evolving away from their country cousins.

Bumblebee (image: Kim Taylor / NPL)

Bumblebees seem to be adapting (image: Kim Taylor / NPL)

Separating out genuine adaptation from more plastic responses will need some strict comparative studies to be done. But done they should be, as the difference is important.

If species can only adapt to city life in the short term, the future for them is bleak as global urban sprawl continues, eating into more of the wilderness. But if they can quickly evolve to exploit this new environment, we may all one day be living in Synurbia.

If you think it’s happening already, let me know.


  • Comment number 1.

    Matt, I think this's possibly the most important piece you've written.

    At first sight it seems like it's merely observing a few critters out there've taken to using humans as a source of la Dolce Vita, but a little bit of thought and you realise now, more than ever, humans and every life form that happens to fall under their sway better start forgetting la Dolce Vita and start getting ready for la Vita Nuova.

    It's not just that cities are expanding and gobbling up more and more of the land, to a degree where I firmly predict sooner or later, say, Liverpool and Manchester will eventually overlap with each other and form a mega city on a par with Greater London, but for some reason - I don't know, types of crops, pesticides, farmer poverty? - more and more country based critters are migrating into the city.

    I'll give you an example of what I mean, ever since I was a kid in the Sixties, I've been an ardent visitor to parks who, even as a young kid, was struck by how much plant life could spread out from those parks and insert itself into even the most arid urban environments.

    I'd notice not just weeds but seedlings of various trees sprouting out of ruts in the tarmac of roads, out of cracks in house bricks, even, somehow, flourishing in rooftop gutters, sprouting out from under roof tiles, basically just about anywhere you bothered to look.

    But what I didn't see was a corresponding variety of park type or country based animals making similar insertions - in fact the only animals I was familiar with from early on was cats, dogs and rats.

    At one time you could spot piebald rats almost everywhere you looked, now you're lucky to spot them in alleyways.

    However, all of a sudden I've started to occasionally spot near Edge Hill Railway station and surrounding environs - including once in my own garden - a type of rat I've never seen before, which resembles a very fierce looking flattened red squirrel; but other people, including my brother've also seen them, and they're all struck by the same thing, how intensely orange and identical their colouring is.

    Similarly, until relatively recently, I used to mediate or do Tai Chi at a nearbye place called the Botanic Gardens, a tiny little walled off section inside Wavertree Park, (I was forced to quit in the end because various chaps'd started turning it into a 'dating' centre and kept refusing to take no for an answer), but one thing I noticed during the times the Gardens were quiet was there was a rabbit colony there.

    At first I was convinced they were the offspring of abandoned domestic rabbits, but not only were they all of the same identical darkish exotic non domestic patterning, but after months of observing them emerging from hiding, I never once saw what you might call an 'adult', to the degree I became half convinced I might be observing some sort of pygmy species.

    My point being, I've been living around and visiting places like Edge Hill Station and Wavertree Park since I was an infant, fifty odd years ago, but I've only noticed the intense red 'rats' for the first time in the last year, and the 'pygmy' rabbits since the '90s, which tends to lead me to suspect something's changing out there which's not only 'encouraging' animals to adapt and take a stand in the city in a way they never previously did, but almost seems to make them prefer the city to what's on offer out in the country.

  • Comment number 2.

    Hi Matt

    I've been exploring this idea about wildlife evolving to live with humans for some time. Recently i have also started a blog about it. I love the term Synurbic, but have come up with a more simple device to discuss the effect humans have on all wildlife everywhere, quite simply it is "Accidental Nature". The blog is here https://accidentalnature.blogspot.com

    Evolutionary biology that studies the edge between humans and wildlife is by far the most exciting thing in natural science at the moment. Thanks for a great blog post. I will link to it if you don't mind.

    Richard Taylor-Jones

  • Comment number 3.

    We have recently discovered that there is a badger regularly visiting our garden. We llive very close to a main ring road in a large city. The garden is by no meas big, it's actually quite small. The badger is having a great time digging up the lawn!! Proof enough for us that these animals are making themselves at home in the cities.

  • Comment number 4.

    Hi Matt, totally off topic I know, so please accept my apology.... Firstly, how can I stop the magpies from eating all the baby frogs in my garden? and, why are magpies and grey squirrels always the first on the scene when there is food in the garden? are they like 'mystic meg' or is there another reason, like, they spend a lot more energy hunting out that food, making more frequent rounds in their territory. if so then given the number of these particular animals, is this the secret of their success?

  • Comment number 5.

    Animals have to be opportunists. Go for a walk in woodland where there are houses nearby, and you will see far more birds around the houses than elsewhere - in winter it will be warmer, there will be more food, either in feeders or in rubbish. We have taken away so much natural habitat, those that can still fit in with us will, and may flourish partly because competitors/predators can't. The ones that concern me are the ones that can't adapt quickly enough - glow worms, for example. Yes, I'm sure evolution is happening in front of us. I'm also sure a little of it is to do with the introduction of pets being released into the wild, such as rabbits where cross-breeding will be successful.

  • Comment number 6.

    Interesting piece but it suggests a distinction between plants and animals living in the artificial urban environment as opposed to the “natural” countryside. But the countryside is also an environment that has been shaped by human activity, and continues to be. I was very struck recently when staying in a village in Essex how the village was full of the sound of birdsong, but the sound quickly faded when you walked out into the fields. I realised that the removal of hedgerows to create huge fields meant the countryside would seem like a desert to birds, and the village gardens an oasis.

  • Comment number 7.

    Evolution in action - those that are best adapted or able to adapt to new conditions thrive (such as urban foxes).

    But part of the evolutionary mix is human intervention to support wildlife - building ponds and insect towers, and putting up bird feeders, for example.

    We aren't the first species to have made dramatic changes to the environment - stromatolites (bacteria) billions of years ago, and over a period of many millions of years, eventually filled the atmosphere with oxygen (and also caused the vast layers of iron ore deposits at the bottom of the seas).

    But we are the first species to be able to consciously intervene and help or hinder life (including our own).

  • Comment number 8.

    [ Walls make great habitat for cliff-dwelling species and several plant species in the UK, including ferns such as maidenhair spleenwort, are more abundant on urban walls than in their original cliff habitat. ]

    In the tropics, semi-epiphytic or epiphytic plant species like Ficus (Fig) & Asplenium australasicum (Bird's Nest Fern) are often found self-sown not just on urban dwellings & infrastructure, but also on park & wayside trees that have been planted by humans.

    A fauna species that has literally embraced synurbization across most of the human world would be Columba livia (Rock Dove) -- typically referred to as the common feral pigeon. As its official common name implies, its wild ancestors & counterparts feed & breed on sea-cliffs & rock ledges. So it doesn't require a great evolutionary leap for adventurous specimens to colonize built-up cities full of artificial cliffs & rock faces. It also helps that these seed/grain-eating birds do not mind scavenging bread, popcorn & other bits of organic detritus discarded by humans.

    [ I’m talking about those animals and plants that like living where we do. ]

    I'm not sure if all of the urban-adapted species (or at least the fauna) actually like or enjoy living in the same spaces as humans. As I see it, the phenomenon of synurbization is more defined by a lack of choice. On a human-dominated planet with rapidly-dwindling wilderness, those species that don't (happily or grudgingly) adapt to human habits would quickly or gradually go extinct, depending on their respective hardiness. Likewise for humans who don't really like humans or human culture.

  • Comment number 9.

    Hyraxes: why Israel's 'rock rabbits' have become pests (BBC Nature - 05 Aug 11)

    Just came across this highly-relevant report that was published 2 days after Matt's article. Excerpts as follows ...

    [[ "It turns out that it's the piles of boulders [created by clearing sites for building] that attract the hyraxes," said Mr [Arik] Kershenbaum.

    They make their homes in the underground caverns and crevices created by these man-made rubble piles. "We confirmed that they're attracted to the boulder piles rather than heading specifically for people's gardens," said Mr Kershenbaum.

    Although hyraxes are generally quite popular with suburban wildlife-watchers, some people have called for a cull. But early research indicates that simply filling in the boulder piles would drive hyraxes out of the villages and back to the cliffs, just as it says in the Bible. ]]

  • Comment number 10.

    Very interesting article!

    It is only to be expected that certain species should be able to adapt to a new environment--never mind if it is man-made or not--and that these populations, now isolated from species unable to survive in the new environment, with a new set of evolutionary pressures, would begin to evolve both behaviorally and physiologically. But I would not attribute the success of "synathropes" to short-term adaptations; rather, most seem more suited to the features of urban and suburban living--more fit by nature of pre-existing needs and the lack of non-human predators. Examples from this side of the bond would be the American robin (which can now forage in lawns, rather than open fields), house sparrows and house finches, rabbits, squirrels (we have to put special locks on our trash cans to keep these buggers out), peregrine falcons (which are now more plentiful in New York City, where they nest and hunt from skyscrapers, than in the surrounding Hudson regions), raccoons, coyotes, and crows.

    It cannot be a mistake that most "synathropes" are foragers, which are simply opportunists. I think we must be careful to separate species which are evolving under active pressures in a new environment (those animals cited in the above article), and animals whose natural behaviors are becoming more apparent as they become more comfortable in a human landscape when looking to best protect those with the tenacity to live beside us.

  • Comment number 11.

    Great article and discussion!
    In Canada, foragers such as coyotes, deer and raccoons have famously adapted to urban or suburban life. Who could forget the moose in Edmonton and Banff? Or the bears entering West Vancouver supermarkets? Vancouver's Canada geese are increasingly nesting on highrise office balconies. In Burnaby (a suburb of Vancouver), the Great Blue herons have added, along their regular flight route from lake to ocean, dips for very expensive fish in koi ponds that have come as a byproduct of two decades of East Asian migration to the suburb.

    But why exclude domestic animals from consideration? While the long established syndom[estic] habits of dogs and cats (and mitochondia, I might add) might make it hard to tease out what has happened, there are two locations where current adaption is taking place: China, where farmed dogs (or those kept and raised in the home for food) are now being adopted as pets, and Russia, where a 50 year longitudinal study of fox domestication has recorded this adaptation in detail. https://en.wikipedia.org/wiki/Domesticated_silver_fox

  • Comment number 12.

    I have often wondered about corvids in London.

    I grew up in the countryside with a full complement of UK corvids (but ravens). Jackdaws in small groups, rooks in large groups, crows alone or in pairs, and magpies (for sorrow, for secrets, and more) would be common sights. Occasionally, on a walk in the Wytham Woods one would hear a jay or catch the briefest of glimpses.

    In central London one rarely sees jackdaws or rooks, but crows seem to gather in large flocks. Kennington Park is often covered in 20 or 30 crows -- and while they tend to space themselves out as much as they can and don't seem to enjoy each other's company too much, one could never imagine seeing so many together in the countryside where I grew up.

    And jays? Jays sit on the for sale signs along our street. One sits on the fence in our garden staring into the flat. Not the secretive and elusive countryside bird, the city jay.

    Magpies are magpies are magpies it seems, and their behaviour in the city (eating baby frogs) is the same as that in the country it seems.

    I miss jackdaws, my favourites. And I wonder why they haven't penetrated London, as I see them in other cities.

    Another recent observation of crows. The crows and squirrels of Kennington seem to be at the start of a war. I recently saw a crow harassing a squirrel to the point that it seemed the crow was trying to kill the squirrel. But on another occasion, I saw a crow pecking at something in the ground (perhaps some of a squirrel's stash) and the squirrel was persistently trying to shoe the crow away, leaping down from the trunk of a tree onto the crow then leaping back up.

    So, yes, perhaps changes in behaviour. Adaptation perhaps, evolutionary advantage, who knows?

  • Comment number 13.

    Like all species density, it comes down to food

    Scavengers can find enormous quantities of discarded food in human environs, so the territory required to support one family is correspondingly smaller

    And while you may claim that tigers are not synurbic, in South Africa, leopards ARE!
    They are natural scavengers, able to feed off of discarded restaurant refuse, and well adapted to a crepuscular urban lifestyle

  • Comment number 14.


    Cover your pond with plastic mesh, as if you were stopping toddlers falling in, but it doesn't have to be so tough.

    As for being first to the food, it could simply means that they live closest to the food, but both species are rather intelligent, and could easily have learned to associate your movements around the feeders with the presence of food.

    You could test this by pretending to put food out - go through the exact motions, miming pouring seed etc, then retreat indoors and watch to see what arrives first, and how quickly.


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