According to the Headtap Horror By Bobby Boom You Tube Channel:

… in the heart of New York City lies an extraordinary secret that defies
imagination. A protected sanctuary on Roosevelt Island housing the last
surviving population of Wooly Hippos magnificent creatures that once roamed
the Arctic Circle alongside mammoths and woolly rhinoceros…

…The
Roosevelt Island woolly hippo Reserve
established in 1952 but kept secret for
decades spans a carefully concealed
section of the Island’s Northern tip. Here behind carefully designed barriers
that appear to be natural rock
formations, a population of 23 woolly
hippos thrive in complete secrecy. Their
existence is known only to a select
group of scientists, caretakers and a
handful of local residents who have
learned to recognize the distinctive
sound of their calls echoing across the
East river at dawn…

Believe it

or not.