Realistically, what are the chances that a baby alligator flushed into a major metropolitan sewer system could survive for any reasonable length of time?
Alligators are air breathing reptiles, so survival would be zero in a “sealed pipe” system. But if the OP refers to the kind of scary, wet, and dreary systems we all know from movies and TV, air would be available.
Alligators can survive with little sunlight, can feed on a variety of things including garbage, and are unaffected by “sewage” although chemical pollutants can (depending on the specific chemical) be problematic.
However, alligators can only briefly survive sub-freezing temperatures. Any sewer system in states that have an actual winter could not harbor alligators long term. An individual dumped into such a sewer might survive until winter.
There have been a few cases of exotic animals being found during the summer in the Toronto area, like the pirahna they found in Professor’s Lake in Brampton a few years ago, but they would not have survived the winter.
In Florida, the case is quite the opposite: any number of large snakes, primates and other exotic animals have been released into the Everglades, and lots of them are thriving.
Some of the local wildlife and fisheries people are pretty certain there’s now a breeding population of Burmese pythons, among other things.
Yes, breeding Burmese pythons are confirmed. Florida has taken new regulatory steps for 5 large snake species. In point of fact, Florida is home to a plethora of non-native species, including (at last count) at least 48 species of reptiles. linky
But are you saying that Florida is a sewer? Them’s fightin’ words, son!
Have you smelled the Everglades lately? 
There are bound to be local “hot spots” in any large city’s sewer system where an alligator could survive over winter. If nothing else, a significant portion of wastewater will be “room temperature” or above, and I have never heard of an entire city’s wastewater management system freezing.
The Master Speaks:
Are there alligators living in the sewers of New York?
Words from the Master (although he avoids a direct answer) here.
Significant amounts of wastewater may be at “room temp” when introduced to the system, but it won’t long remain at that temp in winter time. Alligators are simply not adapted to survive in a temperature regime that cycles well below optimum, and frequently dips to or below the “critical thermal minimum” for months at a time.
This citesuggests that baby alligators (subject of the OP) are probably unable to survive even brief iceing.
I’m not sure I agree with this. The alligator’s range stretches all the way up to the Carolinas, where temperatures may remain below freezing for weeks at a time.
This isn’t GD and I do not want to start a pissing contest. So may I politely suggest reading the cite? It refers specifically to South Carolina.
I did read it. The fact that they are there in the first place indicates that they (alligators) generally survive these temperature extremes, even if individuals do not.
That suggests that while individuals may die off during freezing periods in NYC sewers or wherever, it doesn’t mean there isn’t a viable population.
*For the record, I don’t think there is - I just don’t think it’s because of the cold.
Wouldn’t the water be at above room temperature, considering that what we put into it tends to be quite warm? At first anyway.
I’m not sure that signifies; AFAIK, human waste is a pretty miniscule fraction of the stuff that comes into a water treatment plant. Obviously, in a highly residential area, it may be most of what’s in the main, but in general terms, human waste is dwarfed by industrial outflow.
Fair enough. I’ll happily concede that alligators flushed into South Carolina sewer systems might survive long term, the evidence being that alligators live wild in South Carolina under ambient temperature regimes.
Can we also conclude that alligators flushed into, say, the NYC or the Chicago or the Boston sewer systems will not survive, the evidence being that there are no wild populations of alligators living in the swamps and rivers of New York, Illinois, or Massachusetts and subject to their ambient temperature regimes ?
Gladly. The OP specifies “metropolitan” only. Plenty of such areas within the gators’ natural range.
The alligator’s native range extends into extreme southeastern North Carolina, the area southwest of Wilmington. Subfreezing weather there is rare and when it does happen is rarely more than a day (or more properly a night).
Im fairly certain that there are microclimates permitting crocodilians to survive beyond the “official” ranges in particular niche habitats. During the 1980s I observed, over two summers, what I’m fairly certain was a feral caiman, at “Sandy Pond,” two barrier-dune lagoon formations at the extreme eastern edge of Lake Ontario. Both times I was standing at one point or another on the barrier sandspit side of the northern lagoon, looking across open water dotted with small clumps of aquatic plants. I observed, in the water, what appeared to be a ~80-cm crocodilian swimming towards the far shore of the lagoon. Since I had (and have) no credentials, had only a visual sighting at a distance, and far from any normal range, I didn’t report it to anyone. However, the circumstances would be ideal for a far-north-of-normal-range survival, including overwinter: a point at a far extreme of a State Wildlife Management Area (=game preserve) in the mixed water channels-muddy shores-dry land regime, teeming with “trash fish” and a regular stop for waterfowl, and with warm springs feeding the lagoons that normally keep them at least partly open water year round… I wouldn’t be surprised if (presuming there were some way to get a definitive answer 20 years later) I were proven to be mistaken, but I can make a fairly good case for having observed an aberrant feral sighting.
Polycarp, if by “over two summers” you meant that this sighted animal had survived a single winter, and crediting your suggestion of the presence of “warm springs feeding the lagoons” then I have little reason to disbelieve. Crocodilians, either as escapees or deliberate releases are seen in many, many places. You quite correctly I believe characterize it as “an aberrant feral sighting”.
I doubt though that it would survive long term, even given warm springs.
I’m so glad I’m not the only person who thinks about this. A point that I frequently have to make to DH when he suggests allowing our children to swim in any non-man-made bit of water here in the Mid-west is this; Just because a snake/crocodile/shark/unusually large lamphrey couldn’t survive a winter out here doesn’t mean that they are not in the water RIGHT NOW!
Besides, isn’t it possible that someone might keep a pet croc in a public watering hole over the summer and then in a private heated area for the cold months?
Lampreys of unusual size?
I don’t believe they exist.