I stuffed up the photo, but managed to solve the riddle, which has puzzled me for some time.
I observed this kangaroo licking the concrete base of the chair, which has been mysteriously excavated for some time, not long after it was initially put in the ground. The concrete must have some mineral content in it, which is of some value to the kangaroos, and they are using it like a salt lick, just as cows and sheep do on a farm etc.