By Maureen Jouglain
The rescue operation of the beluga trapped in the Nepisiguit River, New Brunswick, raised the question: how can a marine species survive out of its environment? For the occasion, Whales Online met with Dr. Émilie L. Couture. A member of the Université de Montréal’s Department of Veterinary Medicine, she assisted the young beluga during its relocation to the St. Lawrence.
First and foremost, belugas are mammals. Now, what is the difference between a fish and a marine mammal? Whereas a fish absorbs dissolved oxygen in the water by creating a current flowing through its gills, a beluga, like other mammals, breathes oxygen from the air and must surface to breathe. There is therefore no risk of suffocation when it is kept out of water. Although it does not need to be immersed to breathe, specific adaptations to the marine environment nonetheless give it several disadvantages with respect to life on land.
The first challenge to overcome is the difference in density between water and air. A cetacean’s weight is usually supported by water. Out of water, the thick layer of blubber is no longer sustained and can damage the organs and muscles. In order to relieve pressure on the body, the beluga can be transported on a stretcher. In the case of travel by aircraft of truck, the adult beluga will be placed in a water-filled compartment. If it is smaller, however, it can be placed on a memory mattress, as was the case for the Bathurst beluga. This pressure management is essential on one hand for the animal’s comfort, but also to ensure that it has no difficulty breathing. When a whale is stranded, the cause of its death is often related to this pressure. The crushed muscles release a protein called myoglobin, which reaches the kidneys and then becomes highly toxic.
The second key factor to control is temperature. As a mammal with Arctic origins, the beluga is acclimated to very cold waters. Although it lives in a frigid environment, it is an endothermic species, meaning it is warm-blooded and must produce its own heat. It therefore has a thick layer of blubber that allows it to maintain its internal body temperature at about 35-36°C in water that is often close to 4°C. Exposed to higher air temperatures, this excess heat will tend to accumulate. The weather and time of day are therefore factors to take into account, although “the urgency of the situation often leaves little latitude for this kind of control,” explains Dr. Émilie L. Couture. Moreover, the composition of its skin – which contains neither keratin (proteins notably offering UV protection) nor sudoriferous (sweat) glands – makes it all the more susceptible to increases in internal temperature. To address these problems, a beluga in the open air must be constantly sprayed with water and covered with damp sheets. Heat loss mainly occurs in the blood vessels under the skin of the fins, so these areas should be hydrated as a top priority.
The fact that a beluga can survive an onshore incident does not mean that it is adapted for it, so the duration of exposure must always be minimized.
Pour en savoir plus
- Jean-Pierre Sylvestre (2005), Le béluga, (ISBN : 2-7619-1995-5), pp 36-40.