This is a save game demonstrating that bug 0006015 is still present in 40.06.
For the full bug report, see: http://www.bay12games.com/dwarves/mantisbt/view.php?id=6015

Upon loading the save game you'll find yourself in a player created, abandoned fort, as an adventurer.
This adventurer has slept/rested repeatedly at the site, causing it to be offloaded and reloaded repeatedly, likely doubling the animal populations at the site each time.

The loaded game will suffer from severe lag, and leather is visible on the surface. No leather was ever created at the site, and it likely comes from animal people accumulating in the caves.

This can likely be reproduced in any player created abandoned fortress by going to the site with an adventurer and sleeping and waiting repeatedly.