First Born Dolphin Calves Survival Rate

Recently, Marine Biologist James Livacarri and I were discussing information that we mutually found very interesting, a book titled “Bottlenose Dolphin” by Randall Wells, a renowned dolphin specialist working for the Chicago Zoological Society and stationed at Mote Marine Laboratories in Sarasota, Florida. Wells is a foremost authority on this species and is respected widely for his research.

Mote Laboratories has been studying the Bottlenose Dolphin population in Sarasota Bay and surrounding areas since the 1970s. A lot of information shared on the Dolphin Explorer is cited from this magnificent research team. Dr. Wells’ book, published in 2004, offered information regarding first-time moms and the survival rate of their young. Dr. Wells states, “first-time mother dolphins have on only one occasion raised a calf in the nearly thirty years in which dolphins have been studied there.” So, basically, only one calf from the 1970s until the early 2000s that was first born of an adult female made it to its third birthday. Dr. Wells goes on to cite excellent reasons why this might be.

There is a possibility that these first-time mothers have accumulated toxicants in their systems over a period of five to twelve years, a period that applies to the beginning of sexual maturity for female dolphins in Sarasota Bay (this may vary from one area to another). A “toxicant” is a human-made chemical that may act as a poisonous agent, for example a pesticide. A “toxin” is a substance poisonous to them that is naturally produced, which may be caused by algae.

There is a potential that these moms have accumulated an enormous amount of toxicants in their systems over the years and are passing it on to their calves through their milk, severe enough that the calves cannot survive. The following calves birthed by these females tend to survive better, possibly because mom has not had the number of years to accumulate a lethal dose of milk for these young.

Sarasota Bay is in a well-developed community, with many subdivisions that allow manmade chemicals to travel down the rivers, streams and estuaries to the bay where the dolphins live. It is a large, thriving city with enormous opportunities for toxicants to become a problem for area marine life.

So, in the first 30 years of Mote Marine’s study, only one firstborn calf survived. Let’s look at Marco Island’s bottlenose dolphin population. The 10,000 Islands Dolphin Study Project on board the Dolphin Explorer vessel has been collecting data for 17 years, since 2006. Many of the females documented during the early years of the study had calves by their side, but it is not, and never will be, known if these calves were first born to the mothers.

However, we have seen females born from 2006 through 2010 that have produced young for the first time, and at least five of them have survived more than three years, long enough to leave their mother’s care and go out on their own. They are Sintas, a female born in 2006, and her first-born, Fireball, born in 2015 and now coming up on eight years old. Destiny was born in 2008, and her first calf Irma was born in 2017. Irma is now 5+ years old. Nadine is a female born in 2009, and her first calf, Pigeon, was born in 2018 and is now out on its own. Jing Jing was born in January 2010, had her first calf Jordan in 2017, and he is doing well in the area. Last, female Kaya was born in 2010, giving birth to a young male named Ariel in 2018. Ariel is thriving in the north Marco waters.

So, why is there such a difference in the survival rate between Sarasota Bay and Marco Island?

As mentioned previously, Sarasota is a big city with an expansion like few others along the southwest Florida coastline. Marco Island, on the other hand, is a 24-square-mile island with very little industry. Toxicants in this area will be greatly reduced compared to Sarasota Bay. Also, we are surrounded by water, and we have the largest mangrove forest to potentially filter any toxicants right in our backyard, called Rookery Bay and the 10,000 Islands.

“Phytoremediation” is the use of green plants and trees, microorganisms and proper soil techniques to remove or render toxic environmental contaminants harmless. Mangrove trees and their filtering system fit the bill for protecting an environment. Our Marco dolphins feed along the mangrove islands very often. The more mangroves there are, the better chance we have less toxicants in our waters.

Two different ecosystems, two different results in the number of live births for first-time dolphin mothers. With a limited data period of 17 years, our team has witnessed five first born calves surviving in our area. Sarasota Bay documented one in their first 30 years of study. Where many dolphin-populated areas have a survival rate, in general, of young reaching three years old to be around 60%, our area is over 80%. 

Fortunately, Marco Island has little room for further growth and this may bode well for our amazing dolphin population!