A handle from one of these wheel blocks, maybe?? Like the two by the cones? (Is that black not-quite-loop the thing you're asking about?)

or the random other detritus? or the liquid? or...

the think that looks like they used a squirrel to was the plane.

to the left and slightly down from the green thing? Heh, I thought that looked like a fake dead fish. But I could see it as squirrel-like... No idea.

thinks Squirrel died pushing that white, plastic?/metal? object with the jagged edges away from plane's tires just in the nick of time. Hero Squirrel

RIP, selfless squirrel.

Awwww.