by Jessica Weiss
Observing a Seasonally Resident Dolphin Population
The summer 2010 field season is now in full swing for the researchers of the Outer Banks Center for Dolphin Research. Through our opportunistic and dedicated survey sightings, it appears many of our seasonally resident population have arrived in the Outer Banks. These individuals usually arrive in Roanoke Sound between May and June every year and are sighted in the sound throughout the summer.
Our first sighting occurred on May 22, 2010 with a group of 20 dolphins, not an unusually large group size for Roanoke Sound. Several females were resighted, such as Fatlip, Artemis, 717, and FB413. Resights are important as they let us keep track of how often we see individual dolphins, who they are spending time with, and the areas of the sound that they prefer to use. Based upon the dark-colored newborn bouncing alongside of her, we were also able to determine that a dolphin known as Sinatra is in fact a female.
Scarlet is another female sighted with a newborn this year. In the last several years, Scarlet has been seen with a juvenile dolphin, Vidalia, believed to be an older calf. Since she has been sighted with her newborn this year, Vidalia has been nowhere to be found and has not yet been sighted in Roanoke Sound this summer. However, it is common for juveniles to leave their mothers when a new calf comes along. As we complete the time of the peak birthing season for bottlenose dolphins in North Carolina, a minimum of 12 newborns have been sighted this summer in Roanoke Sound.
Many male pairs exist within the seasonally resident dolphin population and were first sighted near Oregon Inlet on June 23, 2010. Rake and 92, 708 and Sequoia, and Buddha and Mohammed were observed in a tiny channel moving in Roanoke Sound near Oregon Inlet. Another male pair, Onion and Pinchers, were seen on July 1 in the southern region of Roanoke Sound. Male pairs, such as Rake and 92, are frequently sighted together and receive many reproductive benefits from their strong association. Although these male pairs migrate seasonally to different areas of North Carolina, they are still sighted together regardless of where they may be.
The seasonally resident dolphins will likely be seen throughout Roanoke Sound during the summer. Research this summer will continue to focus on resighting individuals and examining their movement patterns throughout the sound. The seasonally resident dolphins usually leave Roanoke Sound during late September or early October every year. Our last sighting of Sequoia, 708, and Scarlet was October 3, 2009. At this time, members of the seasonally resident population begin to migrate south to Beaufort, North Carolina to spend their winter before they return once again to the Outer Banks.
About the author:Jessica Weiss is the Scientific Advisor for the Outer Banks Center for Dolphin Research (OBXCDR).
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