Orcas have a terrific cardio vascular system, allowing a fast response to critical situations. Human blood is evenly distributed within the body; killer whales’ blood is directed according to the immediate needs. They are capable of sending the blood flux to vital organs, like when in deep dive for example. The animal not breathing anymore, heart and brain do not suffer from a lack of oxygen.

This is made possible thanks to the secondary venous network called the admirable network. The biggest of this network is situated on the front side of the orca, at an inferior level to the spine axis. The others are close to the brain, the skull and the cervical. They interlink with the main venous network. By doing so, the main organs are constantly irrigated even if the other organs are less irrigated. This is paramount during prolonged dives. These networks act like secondary roads, quiet and under utilised on a normal basis; they are systematically used in case of heavy traffic. Therefore, when there is a need for it, the brain is going to choose to modify the blood flux and increase its presence in the secondary network. Thus the most used organs become the better irrigated.

Orcas have a blood volume superior to the one of the terrestrial mammals of a similar size and weight. Their capacity to stock the oxygen in the blood and the tissues is also bigger. It is the carbon dioxide accumulation that generates the need to resurface in order to breathe; not the lack of oxygen.

It is worth noting that the animal renews 80% of its oxygen during the breathing against about 20% for the terrestrial mammals.