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Against the backdrop of man-driven deforestation pushing some species to extinction, my world needs a viable basis for the survival and thriving of tigers after an apocalypse. It would seem counter-intuitive given large predators are often the most vulnerable due to large territory needs and a slow reproductive cycle (making it more difficult to pass on the genes for a better chance at desirable adaptations).

In our version of Earth, poaching and deforestation appear to be serious challenges to the survival of the tiger species. However, the thriving of the tigers cannot come at the expense of killing off all humans.

So, instead of all of humanity suddenly died from a lethal human-only virus, or nanobot gray ooze, I want to maximize the amount of humans in this world so that the emphasis is on what needs to happen to tigers to survive in urban environments indefinitely.

The immutable constants:

  • No forests left (all of earth's land is a metropolis)
  • Tigers have to survive
  • Many humans still exist

Basic world summary:

  • Concentration of human populations (size of societies): sparse
  • Level of technology (must assume there was once modern civilization): answer configurable
  • Some level of plant life (can assume there is some plant-life to keep ecosystem going, but don't think giant forests)

I can accept that there are no givens, but I definitely need to maximize the tiger's chances in a post-deforestation world. This means I'll need an evolutionary narrative, including but not limited to: new adaptations, new hunting strategies and other behavioral modifications.

Question

What evolutionary narrative would satisfy the stated requirement of having tigers survive indefinitely in a post-deforestation world?

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    $\begingroup$ What are potential food sources for the tigers? And where do you need tigers to thrive? $\endgroup$
    – Otkin
    Jul 19, 2021 at 4:09
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    $\begingroup$ Might I suggest lamination? $\endgroup$ Jul 19, 2021 at 4:23
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    $\begingroup$ As the joke goes, don't eat the coffee lady. $\endgroup$
    – SQB
    Jul 19, 2021 at 14:18
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    $\begingroup$ Two words: Sewer tigers. $\endgroup$ Jul 19, 2021 at 20:42
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    $\begingroup$ @Otkin the problem is the words "after an apocalypse" such technologically intensive farming will not survive apocalypse $\endgroup$
    – John
    Jul 20, 2021 at 6:11

9 Answers 9

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If all the world is a metropolis but human population is scarce, it means part of this world is not inhabited by humans.

We have seen that, when human presence fades, nature is quick to take over. Just look at Chernobyl and Pripyat. Even the COVID lockdown was sufficient to allow sight like dolphins in Venice or wolves and deers roaming through mountain villages or even cities.

So many areas of this world of yours are actually ruins with vegetation creeping through remains of buildings, which is an ideal habitat for a predator like a tiger. Imagine how convenient it is for a hunter to be able to wait on a raised floor, something like a balcony, that an herbivore passes below it. Top it with easily available shelters.

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    $\begingroup$ Street lamps are the ideal hiding spot for drop bears, for example. Lots of well-lit prey that can't look up because of the light bulb. $\endgroup$ Jul 21, 2021 at 9:24
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Urban Parks

In the Indian city of Mumbai there is an urban park/green space that supports a small population of leopards. I believe their chief 'prey' are the local feral dog population.

I suppose the same thing could occur with tigers but it would need to be a much, much larger green space to be viable and some larger kind of animal (feral cows/sheep?)would be required as a prey species. Still a pretty bleak future to contemplate though.

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Adapt Or Die:

To make this work, your tigers need a long period of messiness where they can evolve new traits that allow them to survive in an urban environment. Then, they need to have a new survival strategy that allows them to thrive in an environment filled with quirky, highly intelligent hominids. So you need to figure out how they will need to change and what environments would provide them a niche to live in.

  • Domestication: You might not want this idea, but reasonably if tigers are living amongst humans, it's because humans find them useful. The most likely scenario is that tigers are domesticated and trained to carry out security duties like really big, powerful guard dogs. They might also be used for hunting recreationally or eliminating some kind of high-end pest (like giant Sumatran rats).
  • Population control: The number of humans are so overwhelming (and given an altered climate, "too many" people may be a lot less than you think) that they work to kill as many other humans as possible to reduce competition or as some kind of strange environmental ethic. If people have an ethic against killing other humans, this may provide a perverse way to reduce population. So people allow tigers to roam free, killing and eating humans of rival tribes or communities, or simply letting them kill whomever they please. The rich and powerful support this while building tiger-proof compounds. The poor are eaten, and when they complain or try to stop the tigers, they are arrested.
  • Religious reasons: Humans nearly wiped out large predators, but now those that survived are considered sacred. Like cows in India, the tigers are fed and pampered. If a tiger should maul or kill you, or eat your livestock, it's considered a blessing or favorable sign for your family. There may even be elaborate ceremonies where people try to pet or get close to the tigers - imagine if no one is considered a man until they've vaulted over a tiger and not gotten killed. Really problematic tigers might get taken out by priest-hunters, but they are otherwise left unmolested.
  • Mimicry: If you have domestic tigers, then perhaps wild tigers ACT like trained tiger around humans, behaving like they are following someone's orders. Then, they are able to live amongst humans while still being wild. They would scavenge, hunt livestock and rats, but likely avoid eating actual humans. While this SOUNDS more like intelligent behavior, a species can certainly adapt with enough time to have some quite complex behaviors (especially if the wild tigers are descended/interbred with the domestic ones).
  • New lifestyles: If tigers get smaller, have some kind of adaptive appearance, live nocturnal lives, are very quiet, and very careful how they interact with people (if ever), then they will look increasingly like other species that get along with humans (like coyotes). It's tough being big, aggressive and powerful around the apex primates.
  • Get Smart: If tigers are significantly smarter than they are now, then the options expand. They may even be able to achieve a more symbiotic or community-based relationship with humans. If once humans meddled with tiger DNA to make smarter tigers, you might not need millions of years of evolution to justify this.
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Not sure how feasable it is with how humans work

So, I tried really, really hard to think of a way to make this work. One thing is that a highly confined, "urban jungle" environment could create enough complex three-dimensional space for tigers to be able to hunt. The only problem is this would only work in an environment where the cities are mostly depopulated in some fashion. If I'm reading your question right you want a highly populated world covered in metropolises and has tigers still running around in some fashion.

This relates to a broader ecological problem: large predators and humans are really just not compatible in close proximity and large numbers. The way human beings function as a species is we often, deliberately or not, wipe out all of the large apex predators near our dwellings and territory. The reason for this is simple: humans are very bad at melee combat, our offspring and livestock are very vulnerable, and we function best when we can plan ahead or attack predators from range. Keeping a very large space between us and any potential predators is a good idea.

Humans just plain don't tolerate living around apex predators well. Even though apex predators will generally avoid humans as "not worth it", some individuals will end up becoming man-eaters or livestock predators by sheer chance, and humans will end up hunting them down. Over long enough time frames the low reproductive rates of most large carnivores will result in them being whittled down to extinction. This, incidentally, is why we probably don't have saber-tooths anymore.

Even with modern apex predators that live somewhat near humans (e.g., tigers in Siberia, wolves and bears in Yellowstone, lions in Kenya), the modern predators mostly survive because the area isn't very densely populated and they can easily get away from human activity or spend most of their lives not coming into conflict with humans. As human density increases human-wildlife conflicts increases as well. You can see this in historical time how bears and wolves are driven to extinction across much of Europe, and lions are driven to extinction in Greece roughly correlating with the expansion of larger cities (and with lions disappearing first from highly populated regions like the Peloponnese and only later disappearing from more remote regions with more wild spaces like Macedonia and western Thrace).

The other issue you face is what do your tigers eat. The whole reason why tigers became heavily persecuted in India and much of Asia in general was that deer, gaur, and pig populations were overhunted, causing a drop in available food, which caused tigers to experiment with new food sources to survive: i.e., humans and their livestock. The general lack of available prey for tigers other than livestock and people due to local hunting for game is an issue for many conservationists trying to preserve the species in the wild. In a complex, urban environment with high population densities and little wilderness, the most common prey is going to be humans, and a tiger will be forced to eat humans (or, more charitably, their livestock) to survive. Unlike bears, tigers can't survive off of food rubbish from humans (due to being obligate carnivores). This will cause the tigers to frequently come into conflict with humans, and the humans will band together, hunt the tigers down, and drive them to extinction.

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Tiger King to the Rescue

it basically boils down to this:

There are More Tigers in Captivity Than in the Wild source

Some in zoos, but most in private ownership or roadside attractions, so even if every inch of their habitat on earth vanished tomorrow thousands of tigers would survive. Their numbers in captivity may even increase, as people attempt to "save" the species in a more coherent big-science/government way. As you have lots of human survivors in your setting, you presumably have an Apocalypse Event that moves specifically/slowly enough for people to react to it. Some people make... bad decisions in such cases. The Book Dies the Fire by S.M. Sterling (part of his Emberverse series) populates the US with tigers and lions based on their owners/zookeepers simply "throwing open the doors" when the apocalypse comes. The human population goes through a sharp decline due to famine/general shenanigans. The Big Cat population goes through a boom, as the cats prey on humans during the period of chaos directly surrounding the apocalypse. After a few years the Tiger population stabilizes as humans get more wary and the Tigers learn to hunt things like wild boar (which can get huge in the US) as well as other wild animals.

This could easily be your situation, especially if you can get things like wild pigs/boar to exist in your ruined metropolises. The tigers hunt those, and do a sideline in man eating. The lower the tech-level the better in these conditions though. A society that still has automatic rifles may well kill off all the tigers/reduce them below sustainment level during the apocalypse. Or get together and go "look its us or them lets exterminate all large predators" and be able to actually do it post-apocalypse. However if firearms are rare/nonexistent it'll be pretty hard to totally eradicate them. Not impossible, but with enough other existential threats Big Cats that only occasionally catch the unwary may not be worth your civilization's time.

I should point out that "more tigers exist in captivate than in the wild" only takes into account the 5,000-odd in the US. Many of whom are in large groups which would make procreation easy in terms of finding a mate. But if you're looking to have a tiger population in Mumbai or London or Sydney it would work less-well. At the very least, there's no firm numbers on if there's enough that releasing them would lead to the same results. But if you want a US-based post-apocalypse there's plenty of room for Big Cats.

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  • $\begingroup$ Welcome once again, nice answer. $\endgroup$ Jul 19, 2021 at 16:29
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Frame challenge warning...

No forests left - not realistic long-term

Plants are ridiculously good at self-seeding, and can make a home in places where it seems improbable that they'd get enough water or nutrients. In all English cities, you will regularly see self-seeded buddleias growing out of the side of the brickwork of railway bridges. In Detroit in the early 2000s, the centre was so deserted that there were substantial trees growing out of ruined shops, houses and parking lots. And some plants (Japanese knotweed, for example) are notorious for being almost impossible to kill. Roots can spread and thrive almost indefinitely underground, and then burrow to the surface at random intervals.

Unless humanity has literally poisoned every inch of soil, there will still be plant life around. So when $APOCALYPTIC_EVENT occurs, that plant life will slowly but surely regrow. The previous year's plants will form humus to grow the next year's plants, everything blows around, and sooner or later it all spreads out. Meantime the paved surfaces crack without maintenance, providing more footholds for the plants and access to the soil below.

Exactly what form your new green environment takes will depend on what plants manage to self-propagate. They may not be originally-native species (think buddleia or kudzu), but something will grow and thrive.

"urban environments" - not long-term

All urban environments, without exception, only stay urban through continuous maintenance. After $APOCALYPTIC_EVENT with a sparse human population, that maintenance will only happen where people are living and where people have the time, resources and inclination to carry out maintenance. It may temporarily be an urban environment, for a few decades, but it won't take long to become another Chichen Itza or Angkor Wat. You wouldn't describe either of those ruins as "urban" at the time they were discovered.

Tigers surviving - questionable

With the destruction of their habitats pre-$APOCALYPYTIC_EVENT, all animals (even down to domesticated species) could only survive either as pets or in zoos. All large domesticated (or domesticatable) herbivores need land which excludes anyone keeping them as pets. And any other animals large enough to pose an immediate threat to humans even when only playing are not suitable as pets. Dogs, cats, miniature horses, maybe sheep and goats - OK. Tigers - nope.

So we're looking at zoos as a route to survival post-$APOCALYPYTIC_EVENT. Most zoos do not have enough of any species to ensure proper genetic diversity solely from the population within the zoo. This doesn't mean tigers can't survive, but it reduces their chances because they'll be stuck with genetic predispositions to certain problems.

On the other hand, prey probably isn't a problem. There will be escaped prey animals from the zoos too, as well as feral populations of pet animals. (And sparse collections of humans.) And of course insects and birds, which aren't going away. Since plants will exist (see above), a food chain will re-establish itself. Populations may well spike and crash depending on the availability of food, but that's how nature works.

Change of habits - not required

Predators simply need to be able to sneak up on prey. It doesn't matter whether that's sneaking up around a rock, a tree or a wall. They're already equipped to survive in a hostile environment, because that's what nature is.

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  • $\begingroup$ Environment is very important to whether a specific creature is going to be able to sneak up on prey. Polar bears, for example, are incredibly easy to see when not on snowpack or ice. $\endgroup$ Jul 19, 2021 at 22:01
  • $\begingroup$ To some extent, sure. OTOH a polar bear is just as invisible when it's hiding behind a large rock. :) Predators that hunt (as opposed to ambush) generally use cover as a major part of their approach, followed by a swift sprint. They only have to be sufficiently non-obvious during the approach. Polar bears go more dirty yellow when they don't have snow/water to clean their fur, which presumably helps. In the case of tigers, any kind of dappled shade or uneven ground will work with their "dazzle camouflage". $\endgroup$
    – Graham
    Jul 20, 2021 at 9:37
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Your tiger need to eat meat other than humans -> unless they learn to use the street protein dispensers, they need prey species that are roughly in a similar size than they eat now (or more caloric). They would starve eating rabbits or rats, and might not be able to fit in the ranging areas of the rodents.

=> Keep the vegetation in check with sparse humans: This assumes a significant portion of the megacity that is covered with a roof that is turned into a garden, or a significant portion of the roofs are accessible by tigers and their prey.

-> Automated gardening. The humans have set loose a bunch of robots that garden the roofs of the megacity and keep vegetation from being higher than a certain height on top of the megacity. The original planning included keeping herds of grazers to minimize the grass cutting energy expenditure and get some "free" organic fertilizer. (Where does the oxygen come from in your setting?)

=> Infinite roaming tigers:

  • Some the tigers evolved stripes that make them look invisible or look like grazers to the robot-gardeners recognizers, so the robot herders ignore the tigers or mistake them for grazers and keep them in the herds

  • The programming of some robots has degraded and some robots keep the original plan of an infinite maze of French gardens, some others only kept a part of the programming and have a savannah going on in their assigned area (used by tigers as homegrounds while they hunt in the other well kept areas) The no vegetation higher than 2 meters directive is hardcoded in the robots or a different set of robot that do the tree-trimming regularly)

  • The robots were never programmed with regards to tigers (an oversight from the humans as there were no wilds left so no need to program against that) The humans have stopped visiting the roof gardens so there are no or less collision between the tigers and the humans.

  • The tigers that attacked humans were all eliminated at the first offence so only the skittish ones survived.

(You need to add a constraint on your tiger population size otherwise they eat all the preys and die out as well or start attacking the olny proteins left: your humans)

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A predator the size of modern tiger is simply not going to survive in an urban environment.

However, you could have a species of tiger that went through a period of insular dwarfism, and significantly reduced their maximum size. So perhaps the size of a mountain lion, or even a large bobcat.

A tiger the size of a mountain lion, would still need larger prey, like large pets, or livestock (or deer, if there are large parks). This size will be on the outskirt or suburb areas of the urban areas.

A smaller tiger may be able to primarily target the rats that will always exist in urban environments. If the rats have developed into larger sizes, then the smaller tiger's size can be correspondingly larger.

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  • $\begingroup$ Humans are large predators that live in urban areas. They'd make good prey for tigers as well ;). $\endgroup$
    – jwdonahue
    Jul 20, 2021 at 22:55
  • $\begingroup$ Humans, especially modern humans, are a very poor target as the primary prey of a species of large carnivores. Humans are exceptionally good at eliminating large threats. $\endgroup$ Jul 21, 2021 at 14:15
  • $\begingroup$ LOL, you just need get everyone to belong to a Tiger worshiping religion, so they could feel blessed by the gods when they get eaten ;). My point was that humans are large predators that manage to survive fairly well in urban areas. There isn't any reason we can't extend that survival trait to other large predators. Well fed cats don't hunt. We could provide them with a variety of prey animals. $\endgroup$
    – jwdonahue
    Jul 24, 2021 at 0:00
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Humans can build thousands of massive vertical green houses to preserve forests and maintain wild-life. You would need something like a wildlife loving religion to spread throughout humanity, in order to muster the will to expend the resources required.

Better would be for humans to urbanize the oceans, where there's more room to spread out, leaving the land masses mostly alone. Oceans cover twice as much area as land, but you wouldn't be able to cover it all, without collapsing that ecosystem. Your cities would have to be thousands of kilometers from any land masses, to leave the coastal areas as unaffected as possible, and you'd probably only be able to safely cover less than a third of the remaining ocean surface, but it would still be orders of magnitude more urban area than we cover today.

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  • $\begingroup$ covering the oceans would also eliminate most of the earths oxygen production. $\endgroup$
    – John
    Jul 21, 2021 at 16:15
  • $\begingroup$ @John, well if you constructed without mitigation sure. But you could apply some mitigations, such as lighting the underside of your floating territory and placing transparent bio tanks on the roofs, you might even increase oxygen production. If you have a patch work pattern you could provide natural lighting and open waters as well. You could even create artificial floating reefs. Some of the worlds deserts could be greened up with bio tanks as well. $\endgroup$
    – jwdonahue
    Jul 23, 2021 at 23:56
  • $\begingroup$ if you are providing open water then i the whole surface of the planet is not urbanized. also you would have to light the entire underside of the cities, with light of similar intensity to sunlight, which is quite frankly a ridiculous amount of power. $\endgroup$
    – John
    Jul 24, 2021 at 2:40
  • $\begingroup$ It is already known that the entire surface of the planet cannot be urbanized without triggering a run-away thermal event leading to the extinction of all life on the planet. If you analyze the energy required to construct an urban area, and then extrapolate that to cover the entire planet, you'll find that the surface would be white-hot long before you got 100% coverage, and that's ignoring all the other things that humans do in urban areas (other than construction/maintenance of the structures). $\endgroup$
    – jwdonahue
    Jul 24, 2021 at 17:11

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