Usually when they make a donut shaped nest they are pregnant
Rat's Nest - 2013 was released on: USA: 1 October 2013 (internet)
A rats nests name is a rats nest
a nest
A Nest
By gathering twigs, dry grass, etc and fashioning it into a home.
That would be referred to as a 'nest'.
A rat is already a vertebrate, as it has a spine.
The cast of Rat Nest - 2011 includes: Ben Brough as Barry Brough Tim Manning as Edwardo Mandy Nash as Veronica
Investigative Reports - 1991 DEA The Rat's Nest 1-20 was released on: USA: 14 February 1992
Clean Sweep - 2003 Hickory Dickory Dock the Rat's Nest in the Clock was released on: USA: 2003
The home of a rat is typically referred to as a burrow or a nest. Rats are known to create intricate tunnel systems underground to protect themselves and their young from predators. They may also nest in dark, secluded areas within buildings or structures.
It was cold and lonely.