In the second book of the Silo series, Shift, Jimmy "Solo" mentions two kind of animals:

  • Flies flying over his poop.
  • Fishes in the flooded bottom of the silo.

Considering we are in a sealed environment, animals can't spontaneously appear. How were they introduced in these places?

1 Answer 1


In reference to fish, we learn in book 5 that they have fish farms. It's certainly possible that some eggs made their way from one location to another, possibly so some nefarious person could have their own source of fish, possibly just out of idle curiosity (e.g. would they survive?), possibly by accident (carried on a person's clothes/boots, etc)

When the wind blew past her boots and across the bodies, strips of clothing waved like kelp in the down deep’s fish farms.

Wool 5 - The Stranded

With reference to flies, we learn in book 4 that they have self-sustaining "dirt farms" which are positively overflowing with rotting fruit and vegetation, a perfect breeding ground for flies.

The smell was definitely coming from the dirt farms. And Juliette could hear that whirring again, louder now. She stopped the door and propped her thermos against the railing and checked inside.   The smell of vegetation was overpowering. Ahead, in the dim green glow, she could see bushy arms reaching over the railings and into the pathway. She vaulted the security gate and explored the edge, one hand on the wall while her eyes adjusted again.

There was definitely a pump running somewhere. She could also hear water dripping, either from a leak or a functioning tap. Juliette felt chills from the leaves brushing her arms. The smell of rot was distinguishable now: it was the odor of fruit and vegetables decaying in the soil and withering on the vine. She heard the buzz of flies, the sounds of life.

Wool 4 - The Unraveling

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