Pseudomys shortridgei is in a critical weight range of small to medium mammals that succumbed to a mass extinction event during the period 1875 to 1925, the result of one or several threatening factors that caused localised, near or complete extinction. A theory that proposes the primary cause as an epizootic, a novel disease that spread from the Western Australian coast, may be the cause of its apparently large population decline or disappearance; in modelling of the hypothetical disease this species was estimated to have had weak immunity that accounted for its large reduction in range.
