Nougat and Xanion socialize while their mothers hunt in the distance. These bottlenose dolphin calves are at the perfect age!
We are half way through the dolphin field season for 2013, and it is time to take stock.
Seawater temperatures were in the 60-degree range during the winter months, in the 70-degree range in the spring months and in the 80-degree range in the summer months. Ah, Nature is so lovely in her rhythmicity.
To monitor the local bottlenose dolphin community, which we do under federal permit, we identify individual dolphins by their unique dorsal fin patterns of notches, rips, or other scars. We document dolphin presence in local waters with extensive use of photography and keep running tabs on dolphin numbers.
Between 2005 and 2013, we identified 312 different dolphins using the waters of John’s Pass, seven of which we added this year. All these dolphins make John’s Pass a “grand central station” agog with marine mammal activity.
From January to July, Capt. John Heidemann and I surveyed our study area for dolphins 51 times. During these surveys, we saw 688 dolphins or saw dolphins 688 times, as you like. In practical terms, this meant that we saw an average of 13 dolphins per trip, give or take eight dolphins. We saw dolphins on every survey; never did we fail to see at least one dolphin.
The only time we saw a single dolphin was a sad exception. It was not a regularly-scheduled survey and we did not survey the entire route. Instead, we raced to the location of a real-world drama: the would-be mother dolphin JJ was trying to help or revive her little dead newborn. So, technically, there were two dolphins there.
JJ’s little dead baby was the first of five babies born to moms using our local waters this summer. That is a low number of births; there could be more births this year, but the odds are against it. To our knowledge, just two of the five dolphin calves born have survived. Apropos of nothing, the names of the mom dolphins whose babies did not survive are JJ, Jelly and J.
It is always interesting to compare one’s above-average activities to one’s average activity. We saw an above-average number of dolphins on half of the surveys, between 14 and 31 dolphins, which has made 2013 a dizzying year thus far.
Here is a list of our dolphin Top Ten (not counting dependent calves): Q and her little girl Qball, Scrapefin, Split, Hi W Ski, NF and her little girl Nougat, Face and her precocious little boy Facet, Bowery Boys BB and DD2, Front Slash, Stick, Valiant and her little boy Vidalia.
With precious few changes, these are the dolphins we see most often across the years, too. Dolphins live here as much as we do.
Not all dolphins we see on surveys can be identified, although they enter the database as “unidentified” dolphins. The most common reason for unidentified dolphins is that we glimpse a dolphin in the distance and head over. By the time we get there, it has vanished.
Free-ranging dolphins vanish with great facility whenever they are so inclined. Unidentified dolphins also arise from faulty photography, attributed to both user error and clouds.
High-speed digital photography is an absolute god-send to field biology but it requires unfettered radiant light to take pictures of moving objects. Without great gobs of bright light, the computer in the camera balks and hesitates as it searches its memory bits. If it does deem to take the picture of the dolphin going by, that picture will be out of focus. Who would have thought that lovely summer days with scattered clouds play havoc with photographic data collection?
That is OK. Bring on the blue skies and puffy clouds. I can deal with fuzzy photography!
Dr. Weaver studies wild dolphins under federal permit 16299, National Oceanic and Atmospheric Administration. Send her an email at firstname.lastname@example.org or visit her website www.goodnaturedstatistics.com. NOAA advises anyone who sees a stranded dolphin in the Gulf of Mexico to call 877-942-5343 or 877-433-8299.