Here's a way of calculating it, I think. My numbers are all dog rough, but at least they'll do for an order of magnitude estimate.
It looks like the pipe the elephant stands on is about 3 m (10') high.
The image of that pipe is about 1/3 as high as the image of the DC-8 is long.
First generation DC-8s were about 45m (150') long.
This is where I probably make a big mistake, but if the pipe and the fuselage were to occupy the same length on the image, the aircraft would have to be 15 times further away. But the fuselage is apparently three times the size of the pipe, so only 5 times as far away.
The photograph of the elephant seems to have been made from maybe 50m away. So the aircraft would be maybe 250m away, which doesn't seem plausible.
Please correct my mistakes.