He (or she) is actually part of the Barnes Circus parade, which marched down Atlantic Avenue in 1891.
This photo was taken at Nevins Street by Wallace G. Levison, a New Yorker who leaves behind a pretty interesting collection of images of Brooklyn at the turn of the century.
Here’s another shot of an elephant (maybe the same one?) back in line with the rest of the circus on Schermerhorn Street near Nevins.
Elephants don’t always have it good in Brooklyn, as this post explains.