Zoologist Jordi Casamitjana meets up close and personally some of the animals belonging to so-called “invasive species” commonly living in cities among us.

There is no day I do not hear them. Even in the dark winter months.

I would be walking in my local park in London, and I would hear their high-pitched intermittent squeaky squawks moving from one part of the sky to another. Seeing them is far more difficult. They fly fast and they perch high. A few decades ago, it would have been impossible to see them, because they had not arrived yet. A few decades ago, I had not arrived yet either. I was still in Barcelona. In fact, I met them there for the first time, in 1981. I was sitting by the big aquarium tank at the Faculty of Biology when someone came in, asking where the zoology department was. Apparently, some strange bird had been spotted somewhere in the city. A green parrot, he said. I, and all my fellow students, dismissed it straight away as a possible ex-pet escapee. But when more of such sightings were reported, our curiosity picked.

We went to where the last sighting was, and after a while, I heard a screech. I followed it with my eyes, and finally, I saw a green bird flying. Indeed, she or he had the profile of a parrot — a very long tail, a relatively short wingspan, and a rounded head with a short beak. Well, a small parrot, in fact. A parakeet. Today, seven species of tropical parakeets can be easily found all over Barcelona. When I grew up there, I did not see any until I went to university. Now, you cannot miss them. For a tourist, sighting them among the many palm trees would make them think they are witnessing a bit of local fauna. They are not. They are as alien to Barcelona as they are to London. They are immigrants that came from the South and the East. They are aliens. As a matter of fact, they are a kind of non-human Illegal aliens. What governments and species-obsessed conservationists contemptibly call “invasive species” — on account of their success in breeding and expanding in a new environment, sometimes altering the ecosystem to the decrement of some local species.  

Like many others, they are caught in between worlds. They are wild animals, and yet they do not belong to the “local wildlife”. They are wildlife but yet they live in cities. They are common, and yet they used to be rare. They are exotic but yet they now feel familiar. They are enjoyed by animal lovers but yet they are despised by some conservationists. They brighten the monotonous existence of some citizens but may ruin the day of others. They are the urban invaders…and I love them. Because they feel family to me.

The Alien Invasion

Harlequin Ladybird (c) Jordi Casamitjana

Biologically speaking, the idea of “invasive species” is fundamentally flawed. It assumes that ecosystems are static, with a fixed set of species, and if any other come to live in them, they are unwelcomed and classed as “alien species”.  The truth is that balanced habitats and ecosystems achieve their balance dynamically, not statically. There are always new species coming in, either from the outside by migration, or from the inside by evolution. And there are always species leaving or becoming extinct. We live on a very dynamic planet that even in the past had different continents than the ones we see today. The British islands were under the ice for a while — there were not even Islands once. Africa and South America used to touch each other. Just a few thousand years ago, North America was full of camels. India used to be in contact with Antarctica. The Sahara used to be a forest. Not even the permafrost is permanent.  

Either big catastrophic changes (such as big meteorites falling from the sky or major droughts drying rivers and lakes) or gradual changes (such as erosion and glaciations) have created new bridges and paths between habitats allowing species to move between them. Some make it, some don’t. Some barely survive, and some thrive. And is the careful balance between the newcomers and the residents which enrich the biodiversity that fuels stability on the face of an impermanent world. Like in any country, we are all immigrants or descendants of immigrants (humans, or otherwise).

And you know that the anthropocentric “invasive species” concept is wrong when you see what people do with it. They use it as an excuse for systematically killing sentient beings, eradicating local populations.  In the name of an old fashion view of conservation, animals considered “alien invaders” are persecuted and exterminated. And if the numbers are too high and cannot be controlled, then they are culturally vilified and commonly mistreated as “pests”. There are even laws that force people to report them when found, and not only don’t punish those who killed them (with approved methods) but punish those who save them.

I agree that people introducing species in habitats where they never evolved is not a good idea. This sort of forced migration is far from a natural one and can shake ecosystems excessively and threaten some native animals. It can cause local harm and the ecosystem may need a longer time to recover and find stability again. This is certainly a good argument against keeping “exotic” animals in zoos or as pets, as they not only suffer the captive conditions they are forced into but if they escape or are released can cause havoc to the local populations. 

We should do as much as is practicable to prevent these human-made “radical” exosystemic invasions, but, above all, we need to see what Nature does with them. If, after a while, the “invaders” settle in, and Nature seems to find a role for them in the system (perhaps using an empty ecological niche left vacant by one native species that became extinct or evolved into a different one) then we should let them be. Prevention yes, but persecution no. Nature does not need us to mess with it by suddenly adding drastic biological changes, but it does not need us to intervene either when it has found a solution and is rebalancing itself incorporating the newcomers as “new legitimate members” of the system. It is not up to us to dictate who deserves to be in and out. That’s Nature’s prerogative. We can practice “compassionate conservation”, caring about real individuals more than abstract species, in an egalitarian and non-judgemental way.

And then we have the vegan approach. Ahimsa, the Sanskrit term that means “do no harm”, is the most basic principle of the philosophy of veganism, and killing or persecuting in any way another sentient being, is contrary to this principle. Being anti-speciesist (not discriminating against individuals for the species they belong to) is an essential principle of veganism too, and persecuting animals for belonging to invasive non-native species is a speciesist act. And although there is debate regarding how much we should intervene with Nature to prevent the suffering that occurs naturally there, most vegans agree that wild animals also matter but we should let them be doing what is natural to them when they live in the wild. 

These are the ecological and ethical arguments against the persecution of the so-called invasive species. There is a geographical one too. The urban environments we have created are not part of the wild anymore. They are a different paradigm. For me, anyone who dares to make it there, human or otherwise, has the right to stay, as it is no longer a natural system, but an artificial setting in which typical ecological rules do not apply. In cities, we all survive how we can, and after a while, we all realise that we survive better when we leave the others in peace. In urban environments, immigrants are a more explicit and essential component of their biological structure. In these environments, everyone is an alien trying to make it. I should know. I am an urban human. I am a human immigrant born in a city but living in another. And if London accepted me, who I am to deny the same acceptance to members of other cultures, races or species? 

I am a Londoner now, and I have many friends here, of many shapes and colours. I’ll introduce you to some.

My Green Friends the Parakeets

Maggie the London Parrakeet (c) Jordi Casamitjana

In the Summer of 2020, when the first pandemic wave seemed to be over, I spent a long time lying on my local park’s grass reading books. Every now and then, I would break my reading concentration to look at whatever creature crossed my line of sight. 

If I heard parakeets vocalising, I would try to spot them. It’s like my private game, as it’s not that easy. Because their calls are high pitched, they bounce around a lot, so when you think they are on your right, they may be flying on your left with their voices bouncing on nearby buildings. Once they land on a tree, though, they often shut up — especially around their nest, to avoid drawing attention to potential predators.

But one afternoon in August, the flying parakeet I was looking at not only did not shut up after landing but made a very exciting squawk. That allowed me to locate exactly where she or he was — unusually, on a relatively low tree branch, about two metres from the ground.  I decided that my book could wait, so I stood up and, slowly, headed towards the tree. 

Compared with other local birds such as tits and finches, parakeets are not very shy, but they are not exhibitionist either — like the robins — so they tend to fly away if they feel anyone is watching them. Therefore, I quickly took my camera out from my belt pouch so I would not spook them with my hands’ movements when I would be closer. When I got to the apple tree, the parakeet did not move. I got even closer, and nothing. Eventually, at about three or four meters, she looked at me and said hello — or the equivalent in the Indian parrot language — and resumed eating what it seemed to be a very delicious apple. I thought I made a new friend.

I said she, because I could tell she was a female. In the UK, most feral parakeets are ring-necked parakeets (Psittacula krameria) and although males have a dark ring around the neck, females don’t. She didn’t and was a fully grown adult, so she was a female. Let’s call her Chhaya.

Chhaya had definitively been born in London, as her parents, grandparents, great grandparents, and so on. How far back? Quite a lot, actually. There are plenty of urban legends about how the London parakeet population first came to be (Jimi Hendrix releasing them in 1968, Humphrey Bogart and Katharine Hepburn letting them escape in 1951 while filming The African Queen, etc.) but the truth is that they have been flying free in the UK in big numbers at least since the 1930s, from multiple escapes and releases from different locations. The earliest recorded sightings were in Dulwich in 1893 and Brixton in 1894, but it wasn’t until the late 20th century that the first large colony was established at Kingston-upon-Thames. It took them decades to spread to the rest of London and probably arrived at my local park in the mid-1990s — about the same time I arrived. Before all that, they live in their native homes, in sub-Sahara Africa and the Indian subcontinent —their range there extends into the cold foothills of the Himalayas, and therefore English winters are not really a big deal for them. Clearly, Nature in the British Islands and most of Europe has welcomed them, and Londoners too.

Through the year, Chhaya would know which tree in the park would have edible fruits, so she would know where to go every day, and always find something. And being social, if her companions would find something nice first, they would call out so others can come and eat it too — which is what Chhaya did when she found the apples. Therefore, she did not mind when I came to watch her — she had invited me, actually. 

There are tropical Indian trees in the park, but she had no preference for them. English apples would do just fine. I enjoyed her trust, and I felt blessed for being allowed to be so close while she was having her lunch. In that relaxed atmosphere, I wondered if she had a foreign accent, as I do. Then I realised how silly the idea was. She had been born here, unlike me. She is probably a Cockney, I thought. She kind of looks like one. Let’s call her Maggie. It suits her better.

My Grey Friends the Squirrels

Elijah the London grey squirrel (c) Jordi Casamitjana

The very first day I entered Saint James’ Park in London — my favourite— I was greeted by very forwards squirrels who seem to be in charge of public relations there. Tourists love them and give them food (which they bought with the expectation of finding them), so squirrels approach anyone with a camera or a half-unfolded map, hoping for a treat. They approached me too, and I became fascinated by their inquisitive eyes and human-like hands — as never saw them in Barcelona.

Almost 30 years later, I still very much enjoy their presence, as they remind me how lucky I am to be allowed to live here. I remember one particular encounter in June 2020, as I was re-learning to be “outside” again and to master social distancing. My local park was my safe training space, so I walk all its length every day (I am lucky as it is a big park, over 50 hectares). I always see squirrels jumping in the trees and hopping on the grass from one tree to another, but that day I saw one that drew my attention. He was not running. He was on the grass, just sitting and looking at me from the distance. Normally, when you stop and look at squirrels in my local park (which doesn’t have many tourists) they notice it and they move to safety. But this one did not move. Slowly, I got a bit closer, and I sat on the grass about 15 yards away — always checking it was clear of insects and other creatures — with my back against a Lime tree. The squirrel remained on the spot, sitting in such a fashion that looked like a miniature office clerk asking me “How can I be of service?”— but with a Californian accent. Let’s call him Elijah.  

There are native squirrels in the British Islands, but Elijah doesn’t belong to them. The red squirrel (Sciurus vulgaris) is the native European squirrel that inhabits all of Europe and northern Asia. But although it used to be all over Great Britain, these days you can only find it in Scotland and Cumbria. In the rest of England and Wales, it has now been mostly displaced by the Eastern grey squirrel (Sciurus carolinensis) originally from the eastern US states (hence his other name Californian squirrel). Elijah is one of them — like all the other squirrels in London — so he has grey fur and doesn’t have hairy tufts at the end of his ears.  They were imported to the UK from the 1890s onwards, and it seems that Herbrand Russell, the 11th Duke of Bedford who died in 1940, released and gifted many grey squirrels around the UK (including Regent’s Park in London), from his home at Woburn Park, in Bedfordshire. Today in the UK, there are between two and three million greys and between 150 and 200 thousand reds.

Because of pushing away local populations of “native” red squirrels, various countries and regions in Europe have declared war to the grey squirrel — but most of them lost. Nature seems to have accepted them, and the reds can still thrive in some of the most northern regions where the abundance of coniferous trees made them less grey-friendly. But when there is war, allies turn up. Many people love the grey squirrels’ hold of our big cities (the reds would never make it big in the cities anyway) and there are even groups that exist to protect them from government’s culls and people’s aggression. 

Urban squirrels is an animal protection organisation based in London which protects grey squirrels by campaigning against their culling and rehabilitating injured individuals. Unfortunately, they recently lost the legal right to do the latter. In December 2018, rescue centres that deal with “alien” species received an email from Natural England (the licensing body) stating that their licences to keep and release these animals were going to be revoked at the end of March 2019, under the new Invasive Alien Species Order (Enforcement and Permitting) 2019. A campaign started to make rescue exempted from this legislation, and because of it, the government announced that licences to keep will still be issued in future. But rescue centres are still not allowed to release the animals they take in, so they cannot continue their full rehabilitation work.

This organisation has gathered many good arguments to defend grey squirrels. For instance, the specifically British sub-species of the red squirrel, Sciurus vulgaris leucurus, is extinct, but this happened before grey squirrels were introduced (so, the current reds in the islands are also immigrants). Then we have the poxvirus that kills red squirrels whereas the more robust greys carry the virus without becoming ill themselves. However, although the greys may have originally helped to spread the epidemy, currently the vast majority of the reds do not get the pox from the greys, but from fellow reds (who are starting to develop immunity). It is true that squirrels — both grey and red, by the way — are opportunistic feeders that might take a bird’s egg from an unattended nest, but a 2010 government-funded study showed they are unlikely to be responsible for the reduction of bird populations. And the accusations that grey squirrels destroy many trees is false. On the contrary, they regenerate forests by spreading nuts, which often need a squirrel to bury them to germinate properly.  

I now understand what Elijah’s transfixed behaviour was about. In their role as nut collectors and dispersers, grey squirrels are very aware that if they bury a nut and someone sees them, the nut may be stollen. To prevent this, they sometimes make “fake” burials as decoys. So, they must be very aware of who is looking, and what are their intentions. And I probably behaved differently enough than the average park visitor to confuse Elijah about my intentions. “Is this guy a nut burier? Is he a nut thief? Is he nuts?” I guess ethologists like myself unusually watch non-human animals, moving slower and avoiding eye contact (a trick of the trade) to prevent disturbance. Something that Elijah was probably not accustomed to. Not even in his cosmopolitan city. 

My Feathery Friends the Pigeons

Saoirse the London pigeon (c) Jordi Casamitjana

In Spring 2021 we all had grown accustomed to the wavy nature of our existence under the virus, and we learn how to be “normal” again, even if still restricted in some ways. I resumed some of my long walks around London, and on 30th April I decided to eat my lunch at Potter Fields Park, by the City Hall, close to the river Thames. Something quite amazing happened to me there.

I was eating a nice vegan black-bean burrito when, as is customary, a local flock of pigeons flew towards where I was sitting to ask me whether I would like to share some of my food. I tend not to do it when I am sitting on the grass, as otherwise, I may end up surrounded by hundreds of pigeons when the news of my generosity spread out. I normally tell them that I will save some of the bits they can eat and leave them around when I leave. Many pigeons get it quite quickly and move to the next potential source of food, while others prefer to hang around for a while just in case.

When I was watching them, I saw something unpleasant. A female pigeon landed a few metres from where I was sitting, and I noticed that she was severely disabled. One of her feet was gone, replaced by a deformed stump. Limping about, she got closer to me, and then it happened.  A frisky male approached her and started courting her — puffing his chest and bobbing his head making the distinctive display cooing call we all are familiar with. Normally, if the female is not interested, she moves away, but in this case, her disability did not allow her to do it fast enough. He was very insistent, and she clearly did not like him. She was being harassed. I felt sad for her as she seemed overwhelmed by this pushy guy.  Heading towards me as if looking for assistance, I was suddenly brought into the scene. 

I normally don’t intervene with the love affairs of other species, but this time I felt I had to do something. Therefore, I politely — but firmly — talked to the gentleman suitor telling him that the lady clearly did not like his advances, and he should give her a break. Somehow embarrassed, he got the message and flew off in shame. And then it happened. Relieved, she limped closer to me, uttered something in pigeon, and laid down on the grass to have a rest, merely one metre from where I was. 

I was touched. She decided to hang out with me for a while for safety. We spend a few minutes together sunbathing in peace, and I took great close-up pictures of her beautiful face. No other pigeons bothered her while she was with me. She looked content, and I felt like a horse-less knight. Let’s call her Saoirse.

These days, domestic pigeons (Columba livia domestica) are a common sight in most cities, but where did they originally come from? They are domestic versions of the rock dove (Columba livia), native from the Mediterranean region, the Sahara, the Arabian Peninsula, South Asia, but also, interestingly, the west coast of Scotland and Ireland. Wild rock doves are pale grey with two black bars on each wing, whereas domestic and feral pigeons vary in colour and pattern. 

The domestication of pigeons probably occurred as early as 10,000 years ago, and since then they have been spreading all over the world. Feral pigeons, also called city doves, city pigeons, or street pigeons, are descendants from the domestic pigeons that have returned to the wild — and particularly thrived in cities that look closer to their original rocky homes. Saoirse is one of them, and for many generations before hers, pigeons have been landscaping London’s streets. Although they are considered invasive species (in the US they are labelled an invasive species by the USDA) because they are not technically native, and some people do not like how they adorn concrete and cars with their faeces, I think that, by now, we should all accept they are the ultimate urbanites whose right to citizenship has been earned (remember how much they helped humans in the early wars).

But life in a city can be tough. Unfortunately, Saoirse disability is quite common. People used to believe that it was caused by their faeces, which are corrosive enough to damage buildings (so they could damage their feet too). However, in 2018, researchers from the Centre for Ecology and Conservation Science in Paris conducted a study on 1,250 pigeons across 46 sites and came up with a new theory. They found that pigeons were more likely to have mutilated feet in areas with the densest human population, where the air and noise pollution was high, and, interestingly, with a high number of hairdressers. They concluded that the high movement of traffic and people would spread human hair and plastic threads, and then the pigeons’ legs would get tangled. When they try to remove them with their beaks, they accidentally pull them tighter restricting the blood flow. 

Living among polluting people is difficult, but they don’t blame us. Saoirse and her colleagues just go along with their lives, and if they see friendly humans, they like to hang out with them — as we also do. I am thankful for that. 

We are African Invaders 

Terrapin in London (c) Jordi Casamitjana

I have many more immigrant friends in London, but I have no time to introduce them to you all. The wet red-eared terrapins, the colourful harlequin ladybirds, the shifty signal crayfish, the polite Canada geese, etc. And quite a few humans too.

I live in an area of London with a high proportion of immigrants from Africa. But you know what? we all do. If you live in a place with other humans, you are living close to people from Africa, as Homo sapiens sapiens is an African sub-species of an African species. Since Homo erectus left Africa around 1.9 million years ago, most of us have become immigrants. When we have stayed in one place long enough, we have slightly changed colours and shapes to adapt better to the new environment, but we remain African. We acquired most of our genetic, physical and psychological traits when we evolved in Africa. We are, without any doubt, an African primate that has become an invasive species in all the remaining continents. Spider monkeys in a New York Zoo are less alien than the human keeper that keeps them locked up — even if he is white with a Brooklyn accent and a US passport. Scarlet macaws in a pet shop in Mexico City are less alien than the shop attendant who gives them food — even if she is a Latina with Aztec ancestry. 

Unless we still live in Eastern sub-Saharan Africa, we are all Africa immigrants or descendants of African immigrants, and if we are decent people, we will welcome other immigrants where they come to live in our cities with us. No matter where they come from, and no matter which species they belong to. Is hard enough trying to survive in a new environment. We do not need to be hated by those who just happened to arrive a few years earlier than us.

Let’s welcome the newcomers, not shun them. Let’s celebrate the survivors, not persecute them. 

Let’s befriend our urban brothers and sisters who also made it, like us. 

That’s the vegan thing to do.

“Originally from Catalonia, but resident in the UK for several decades, Jordi is a vegan zoologist and author, who has been involved in different aspects of animal protection for many years. In addition to scientific research, he has worked mostly as an undercover investigator, animal welfare consultant, and animal protection campaigner. He has been an ethical vegan since 2002, and in 2020 he secured the legal protection of all ethical vegans in Great Britain from discrimination in a landmark employment tribunal case that was discussed all over the world. He is also the author of the book, ‘Ethical Vegan: a personal and political journey to change the world’.