To answer your question: Physics namely a lack of negative intrapleural pressure.

When mammals breathe they do so by contracting their diaphragm muscle. The diaphragm is not directly attached to the lungs. The lungs are surrounded by a layer of slimy tissue called the pleura. There is also a layer of pleura on the inside of the diaphragm, the ribs and surroungding the heart. The pleura is waterproof and airtight, think of saran wrap. The pressure inbetween the layers of pleura is lower than outside air. When the diaphragm and other breathing muscles (internal intercostals, sternocleidomastoids, etc) contract they pull the ribs and diaphragm away from the lungs. Since the pleureal pressure is less than outside air and also less than inside the lungs, the pleural layers "stick" together and the external pleural layer pulls the internal pleural layer with it expanding the lungs causing negative pressure in the lungs relative to the external air and air comes in.

When the pleural seal is broken, the diaphragm and other breathing muscles can contract all they want and it's not gonna do a damn thing because the pleural space has lost its pressure gradient relative to the external air and the air in the lungs. With the pleural space interrupted on both sides as in a true double lung shot, it is impossible for a deer or any other animal to breathe. This means they will be able to go as far as the oxygen they currently have in their blood will take them and no further. Realistically this means death in seconds, not minutes and definitely not hours.

If a deer is "double-lunged" and live for minutes or even hours afterwards, both lungs were no punctured.




To address the first part, a human can survive a second collapsed lung if and only if they have a chest tube or some other similar type device working to re-expand the 1st collapsed lung. I love deer and I know how to put chest tubes in, but I have never seen a deer with a chest tube in nor can I envision a scenario where I would even think about putting a chest tube in a deer. As such, deer CANNOT survive having bilateral collapsed lungs.