A Friday Photo: Jazz for the Bears

I came across this photo while doing some research about the National Zoo. It's a picture of jazz quintet playing a concert for a polar bear in (I think) the 1920s. Errr... what? I'd really like to know what precipitated this. Did these dudes just wake up one morning and say, "Hey, let's go down to the zoo and play a set for the bears." "Good idea, I'll see if Gertrude is free to dance for them."? Well, in any case, the bear seems to be enjoying it. Or maybe he's just waiting for his chance to take a swipe at them through the bars.

Source:
Jazz for the Bears
Five men playing musical instruments and woman dancing in front of bears in cage at the National Zoo, Washington, D.C.
Library of Congress
LOT 12357-5 [item] [P&P]