Abstract: An improved animal trap in which the animal may be made to expire due to hypercapnia rather than through impact or trauma. The trap includes a generally air-tight enclosure having the shape of a hollow prismoid defined by a relatively long, rectangular, bottom wall, a relatively short rectangular wall of a width equal to that of the bottom wall, a rear wall exending perpendicularly to the bottom wall at one end edge thereof and joined to the top wall at a corresponding end edge thereof, and first and second side walls in the form of a four-sided irregular polygon, there being an obliquely extending door opening at the end of the enclosure opposite to the rear wall. A door member is provided which is pivotally mounted proximate the door opening and is biased to assume a normally closed, sealing relationship with respect to the door opening. The door is adapted to be propped open by means of a latch member.