I recall a short story I read in High School. We read it in English class so it was likely published in an anthology intended for use in schools. (This was in Scotland in the 1970's if that helps.)
The story begins, I think, with a robot being programmed to collect, from a certain planet, an example of every type of fauna which falls within a certain weight range. (The planet does not have a 'human-niche' type civilization, just wildlife, as it were.)
After the robot is programmed and set to work some disaster or other befalls the spaceship carrying the entities who programmed the robot and no-one ever goes back for it. It just stays there, collecting....
Skip forward many years and the main human character enters the story. I can't recall how or why he is on the planet, but he is. He can't contact his mothership and somehow we know some of his vital stats, including his weight. He is in the collectable range......
He discovers this 'storage area' of fauna samples all standing in suspended animation and the robot appears and tries to 'collect' him too.
Our hero flees the scene and outwits and dodges the robot for an extended period, we are in great suspense because we know he is within the specified range for collection.
Eventually the relentless pursuit over many hours, possibly days, wears him down, the way a human can run down an antelope, and the robot catches him. It picks him up with its robotty appendages, turns him round a bit then puts him back down and placidly trundles away.
How has he escaped? He was in target range for collection! Readers are wracked with consternation.
Our hero finally manages to make contact with his mothership and tells them all about it, when they ask if he is okay he says something like, 'yeah, but I must have lost at least five pounds...' putting him just outside the target range for the trundling collector.
I've searched for this on and off over the years with no success. Would love to know what else, if anything, the author had published.