JUDY WOODRUFF: It's not a sight you
see every day, a herd of elephants,

leaving their home turf, making their way
through Southwestern China, most recently

stopping in a city of millions. But
that is what's happening right now.

William Brangham looks
at their mysterious trek,

and why they might have hit
the road in the first place.

WILLIAM BRANGHAM: It's been an
epic and highly unusual journey
so far, more than 300 miles over

the last year, across deserts,
through forests, crossing busy
city streets, navigating ditches.

This herd of 15 Asian elephants is
captivating China. Every step of

their trek documented on state-run
media, and seemingly everywhere
on Chinese social media.

The world can't seem to get
enough of this trip, a trip to --
well, nobody quite knows where.

They stop for naps, though the adults seem
more tuckered out than their offspring.

They eat corn in the fields, even
try to break into power plants.

But why are they on this
journey? I asked conservation
biologist Peter Leimgruber that

very question at the Smithsonian's
National Zoo in Washington, D.C.

PETER LEIMGRUBER, Smithsonian's
National Zoo: We don't have a
clear answer, but I think that

we have some guesses or ideas.

Usually, these elephants

move when they are being disturbed by
people, or when they lose their habitat,

or when they're trying to find
food. So they might move out of
the forest into the agriculture and

find some food there. But they
usually don't move distances
that are as long as this.

WILLIAM BRANGHAM: Is that
right? So, this - - the length
of their journey is unusual?

PETER LEIMGRUBER: That's the most
unusual piece. So, it's very common

for them to move into agriculture,
but it's very unusual for elephants

to move in a straight line distance
for hundreds of miles or kilometers.

WILLIAM BRANGHAM: Leimgruber has
studied Asian elephants for decades,

and took us in for a closer look.

So, the differences between
an Asian elephant and

the larger elephants people will see
in Africa, what are the differences?

PETER LEIMGRUBER: Oh, there
are lots, so, first of all,
the size. So these are between

three and five tons, and an
African elephant would be
between five and seven tons,

so it's quite a bit bigger.
The head is shaped differently.

WILLIAM BRANGHAM: Still seems pretty big.

(LAUGHTER)
PETER LEIMGRUBER: Yes, it's very big, yes.

(LAUGHTER)
PETER LEIMGRUBER: Yes. Yes. Yes. Yes. Yes.

WILLIAM BRANGHAM: These elephants
are endangered. There are only
around 30,000 to 50,000 left, down

from 100,000 at the beginning of
the 20th century, and a lot of
that is because of human expansion.

PETER LEIMGRUBER: We can show
with our research that this
expansion of human activity is

further and further restricting the
movements of individual animals,

as well as entire populations of animals.

And there's a limit, right?
So, if you keep restricting
their movement, eventually,

these populations, they just
have to decline. There's just
not enough space for them to

move enough and find enough food and
do all the things they need to do.

WILLIAM BRANGHAM: For the
wandering herd in China,

authorities are working carefully to
keep both people and elephants safe.

They're trying to guide this group away
from cities, and back to a safer home.

For the "PBS NewsHour" in Washington,
D.C., I'm William Brangham.

JUDY WOODRUFF: And we
just hope they stay safe.

Thank you, William.