Survival rate in this group of dolphins was estimated at only 86%, down from the 95-96% survival seen in dolphin populations not in contact with Deepwater Horizon oil. In fact, the number of dolphins washing up dead in Barataria Bay from August 2010 through 2011 was the highest ever recorded for that area. One of them, Y12, was a 16-year-old adult male whose emaciated carcass washed up in Louisiana only a few weeks before the pregnant Y35 was last seen. Or rather, they were never seen again alive. Three others were never sighted again in the 15 straight surveys tracking these dolphins. The only two dolphins to give birth to healthy calves had relatively minor lung conditions.ĭolphin Y35 wasn't the only one of the 32 dolphins being monitored in Barataria Bay to disappear in the months following her 2011 examination. At least half of the dolphins with failed pregnancies also suffered from moderate-to-severe lung disease, a symptom associated with exposure to petroleum products. Dolphin calves stick close to their mothers’ sides in the first two or three months after birth, indicating that these pregnant dolphins also had calves that did not survive. The other five dolphins to lose their calves after the Deepwater Horizon oil spill, excluding Y35, survived pregnancy themselves but were seen again and again in the months after their due dates without any young. Given that dolphins have a gestation of over 12 months, this means Y01 had two failed pregnancies in a row. Another pregnant dolphin, Y01, did not successfully give birth in 2012, and was then seen pushing a dead newborn calf in 2013. Veterinarians confirmed with ultrasound that one of these dolphins, Y31, was carrying a dead calf in utero during her 2011 exam. Cynthia Smith/National Marine Mammal Foundation)Īmong the pregnant dolphins being monitored in this study, at least two lost their calves before giving birth. Dolphin Y37 was seen with a live calf in both April and August of 2012. Vessel-based surveys documented that the pregnancy was successful. Dotted line shows the skull biparietal diameter, which is used to estimate gestational age and birth date. Right, an ultrasound image of dolphin Y37 showing an approximately 18-week gestational age fetus in a longitudinal plane, acquired in August of 2011. Researchers found a trend of failed pregnancies in Barataria Bay, Louisiana, dolphins in the years following the Deepwater Horizon oil spill. A fetal heart beat was not detected, Doppler interrogation showed no fetal blood flow, and there was no fetal movement. Left, a reproductive ultrasound image of dolphin Y31 showing an approximately 22-week gestational age, nonviable (dead) fetus in a longitudinal plane, acquired in August of 2011. This unusually low rate of reproductive success-only 20%-stands in contrast to the 83% success rate in the generally healthier dolphins being studied in Florida's Sarasota Bay, an area not affected by Deepwater Horizon oil.

Of the 10 Barataria Bay dolphins confirmed to be pregnant during the 2011 health assessment, only two successfully gave birth to calves that have survived.

His trend of reproductive failure and death in Gulf dolphins over five years of monitoring after the 2010 Deepwater Horizon oil spill is outlined in a November 2015 study led by NOAA and published in the peer-reviewed journal Proceedings of the Royal Society. She and her calf are now both presumed dead, a disturbingly common trend among the bottlenose dolphins that call Barataria Bay their year-round home. It was only 16 days before her expected due date. Less than six months later, researchers spotted Y35 for the last time. This rare condition-known as hypoadrenocorticism-had never been reported before in dolphins, which is why it was not used for Y35 and the other dolphins' health prognoses. Normal levels of these hormones help animals cope with stressful situations. Veterinarians did note, however, that she had alarmingly low levels of important stress hormones responsible for behaviors such as the fight-or-flight response. She wasn't extremely underweight or suffering from moderate-to-severe lung disease, conditions connected to exposure to Deepwater Horizon oil in the heavily impacted Barataria Bay. Based on the ultrasound, she was in the early stages of pregnancy, but unlike many of the other dolphins examined that summer day, Y35 was in pretty good shape.

4, 2015 - In August of 2011, a team of independent and government scientists evaluating the health of bottlenose dolphins in Louisiana's Barataria Bay gave dolphin Y35 a good health outlook.

Dolphin fetus