to fend off a raccoon invasion.

The masked critters were everywhere,

pooping on porches, stopping traffic,

and infesting attics, and they're not

just taking over Toronto.

Reports of raccoon vandalism have plagued cities

like Portland, Chicago, and New York City,

and as raccoon-ridden cities know,

we can't seem to stop them.

Between the 1930s and 1980s, the US raccoon population

increased twentyfold, and it's still going strong.

From 2014 to 2015, raccoon complaints

in Brooklyn nearly doubled,

so how are these masked bandits making it in big cities?

Well, for starters, they can digest just about anything

from fish and acorns in the forest

to dog food and pizza on the street,

and just like humans, raccoons usually prefer the pizza,

which is why they flock from woodland

to city in the first place.

In Brooklyn, for example, captured raccoons sometimes

get relocated to Prospect Park and nearby forests,

but wildlife biologists report they often head right back

to the dumpster-packed city streets.

It's just about impossible to stop them,

as Toronto discovered after it spend millions

on raccoon-proof waste bins.

Unlike traditional bins, the lids had special gravity locks,

which open when a garbage truck arm

turns the bin upside down.

The idea was that if you cut off their major food source,

they would skip town, but that didn't happen.

In fact, one year later, a wildlife-control business

reported that raccoon-related work had doubled.

Finally, a clever raccoon was caught on camera

jailbreaking the new bin.

How did she outwit an entire city?

Well, study after study has revealed that raccoons

are considerably smarter than your average medium-sized

critter. Turns out raccoon brains have more neurons packed

into their brains than other animals of the same size.

In fact, they have the same neuron density as primates,

who are notoriously smart, and their clever brains help

explain why raccoons can open complex locks,

solve puzzles with ease, and even come up with solutions

to problems that scientists didn't think of.

Add to that their ultrasensitive hands,

er, paws, which have four times as many sensory receptors

as their feet. This helps them to feel subtle textures

like special trashcan lids in Toronto

and even open locks without looking.

And unfortunately for us,

driving them away is a fool's errand.

Studies show that after mass removal,

populations tend to rebound

to their previous levels in a year.

After all, females can start giving birth

at just 1 year old and can have as many as eight kits

in a single year.

This quick breeding is also why experts say mass cullings

aren't a long-term solution.

And while they're awfully cute,

the damage they can cause is not.

When raccoons nest in buildings,

they can destroy insulation,

chew up wires, and tear holes through walls,

and it can cost you hundreds or even thousands

of dollars to repair that kind of damage.

One raccoon was even caught

destroying over $3,000 worth of artwork,

and just removing them can cost $300 to $500 a pop.

Plus, the poop they leave behind can contain roundworms

and other parasites, which can enter your lungs

when you breathe or get tracked into your home by your pets.

Even worse, raccoons can transmit diseases

like canine distemper and, in rare cases, rabies.

So it's understandable that cities are trying

to find some way, any way, to manage them.

Can't do a thing about it, just chase them off.

They come back.

Narrator: If nothing else, it's a lesson learned.

We may have built the cities,

but we don't necessarily rule them.