Semi-Annual Dolphin Report

Dolphin Explorer LLC is the proprietor of the 10,000 Island Dolphin Study Project. Begun in 2006, the current team studies the abundance, social behavior, well-being, travel range, genealogy and more of the local bottlenose dolphin population in and around Marco Island. The study continues….

Over the past few years, the dolphin study team on board the Dolphin Explorer has expanded the results of their survey findings and now share this information with agencies around the world. This includes several universities, zoological societies, research facilities and private organizations as far away as Australia.

Here are a few of the results regarding the study and its findings for the first 6 months of 2021.

From January 1 through June 30, 2021, the study team experienced 225 excursions with a total of 2,553 individual dolphin sightings of 104 unique dolphins.  On some days there were two excursions so sightings would include both morning and afternoon hours.

The ecosystem consists of mangrove islands, sandbars, and oyster beds. The introduction of seawalls, docks and canals have provided additional feeding opportunities for the dolphins, with the introduction of human expansion since the 1950s. The overall ecosystem is very shallow in general. The dolphin diet is primarily fish.

A total of six calves were born in the Fall of 2020 and in January of 2021 and all are surviving and doing well. They are all now between six and eight months of age. The primary birthing months as observed by the team are September through November with exceptions to include August, December, and January. “Babysitting” activity was noted on several occasions. Adult females with more than one offspring were able to enjoy some rest when an older sibling of the calf watched the youngster for a short period of time. This was noted on a few excursions and the behavior was observed regarding several adult females and their offspring.

There was a unique observance in early June when an adult female, mother of a nine-month-old calf, was seen on four separate sightings without the calf by her side. This is typically an indication that a calf did not survive. However, about a week after seeing the female on her own, the team noticed the calf back by its mother’s side. Where the calf went and which dolphins it kept company with is a mystery. There have been numerous sightings of mom and calf together since then.

The adult female population appears to be fine. At least two of our females may have reached physical maturity over the past year. There were notations of these two being consistently followed by a pair of males, possibly for the purpose of mating. There is speculation that one or both of these young females may be pregnant. Special observation will continue to see if either, or both, gives birth this fall.

“Sub-adults” are dolphins that have left the care of a mother but not yet reached physical and sexual maturity. Maturity will occur typically between the ages of seven and 12 years of age, with females maturing earlier than males. Our sub-adult population is thriving. The team has noticed several sightings where three or more of these dolphins will travel and feed together on a regular basis.

General notes: In our geographic survey area the calves will stay with the mother for a minimum of 32 to 36 months and sometimes stay four years or longer. We have nine calves born in 2018 that may go out on their own, as sub-adults, very soon. This presents the possibility that the mothers of these calves could possibly give birth this fall. Also, there are several females that did not give birth in 2020 and one female with a calf turning four years old this fall. The team could, potentially, see 10 or more new births in the coming months.

The above information was collected on a daily basis, as sightings occurred, and information was hand written on a daily survey sheet, then transferred to a unique database where records could be stored.

Dolphin recognition is conducted by markings on each dolphin dorsal fin - the fin seen when a dolphin comes to the surface and breathes. Markings occur primarily when one dolphin nips and bites at another’s dorsal fin. Using photographic identification, the changes of these markings can be noted, and the database updated, so as not to lose track of any specific dolphin.

The team will continue to monitor dolphin habits, travel range and genealogy and will report to many facilities on a quarterly basis. Any need for dolphin assistance or rescue will be immediately reported to the proper agencies with appropriate actions taken as quickly as possible. The Dolphin Explorer study team is devoted to the well-being of all wildlife in our region and looks forward to continuing its educational services to its clientele and to the scientific community worldwide.

Bob is the Head Naturalist on board the dolphin study vessel, Dolphin Explorer. He is the author of two books and a two-time award-winning columnist for Coastal Breeze News. He is also an owner of Wild Florida Ecotours, conducting eco and shelling tours, and fishing charters, from Port of the Islands. Bob loves his wife very much!