Tiger Ray Birth at John G Shedd Aquarium
The John G Shedd Aquarium has had Tiger Rays, Potamotrygon menchacai, in its collection since 1999. In June 2000, The Shedd opened a new Amazon exhibit. At that time a pair of tiger rays was moved onto exhibit, where they have resided ever since. At the time of their acquisition, they appeared to be immature.
The exhibit is approximately 3500 gallons, and is on a system that has a volume of around 10,000 gallons. The system receives weekly water changes using RO water. The pH of the system runs between 7.2 and 7.4. The temperature runs between 80°F and 82°F. The temperature was elevated 5 months prior to mating behavior from 78°F in an attempt to see if we could trigger interest in mating. At this time, we do not think that this was a factor that contributed to our success as the temperature had been elevated for 5 months before we saw breeding activity. The stingray diet consists of a gel carnivore diet, krill, smelt, shrimp and earthworms. Typically, the rays are fed 4x/week.
In early December, 2004 we observed chew marks on the margins of the disc of our largest female. Around the same time her appetite appeared to increase. In January, we began to suspect that she was pregnant. Eight weeks after mating we dropped the water level on the exhibit, and preformed an ultrasound procedure in the corner of the exhibit. This was done on the suspected female, and confirmed that she was pregnant. Only one pup was observed at this time. We repeated the ultrasound 11 weeks later, and again saw a single pup. During the time of the pregnancy the female’s appetite increased by quite a bit, and we started feeding the rays daily.
On April 25, 2005, the female gave birth to 2 female pups, a first for the Shedd Aquarium. Gestation time was about 20 weeks.
The size of the female who gave birth is approximately 60 cm disc width and 94 cm total length. The male who we believe to be the father is approximately 50 cm disc width, 86cm total length. We believe size needed to reach maturity was a factor, as the smaller pair that has been in the same exhibit and conditions has not shown signs of reproductive activity.
AZA Communiqué Jul 2005 (pdf-file)