Abstract

The Aquarium du Québec reports the successful births of two walrus calves from two primiparous females (10 and 12 y.o.) during the same month. Natural fertilizations, from a 10-year-old bull, likely occurred at the beginning of March. First signs of pregnancy included marked increase in food intake, marked weight gain and nipple swelling. Pregnancies were confirmed by ultrasound in January. Partial visualization of the fetuses was possible by ultrasound up to the end of the pregnancies. Calves were born within a week of the estimated delivery dates, based on limited data available on prenatal ultrasonography in this species. Based on our fetal measurements the "estimated age of the fetus in weeks" = 1.6 x "dorsoventral depth of the thoracic cavity in cm (in January–February)" + 22. Premonitory signs of incoming parturition included a sudden decrease in food intake two days before the beginning of the labor. Births occurred on May 7 and 23, 6.5 and 1.5 hours after the rupture of the amniotic sacs, and 20 and 14 minutes after the back flippers of the calves appeared. Active labor lasted 96 and 30 minutes. Placentas were expulsed 1 and 19 hours after the birth, and the calves successfully nursed within 7 and 10 hours. Postnatal complications included skin abscesses in one calf (successfully treated with antibiotics), self-limiting idiopathic multifocal histiocytic dermatitis in both calves, and an episode of lethargy and anorexia in one of the mothers. Solid food was progressively introduced starting at 8 months of age.

Acknowledgement

We would like to thank the staff of the Aquarium du Québec who was involved in the care of the dams and calves. Special thanks go to the marine mammal trainers, animal health technicians, and members of the veterinary team that was assembled for these events. We also thank the estimated colleagues from other institutions that generously shared their knowledge and experiences on walrus reproduction.

* Presenting author