Yes we worked on Labor Day

Sightings in areas with High Traffic
Crazy as it seems, collecting data on days when a lot of people are on the water (Labor Day in the US is a major holiday) can be really important. Because we are trying to document how dolphins are being affected by boat traffic in the Lower Florida Keys, today was a great day to see what was happening. Today we found two groups in areas with heavy boat traffic. However, in both of these cases, the dolphins traveled on the edges of the channels, helping them to avoid the potential for being hit by vessels.

In the area with unpredictable boat traffic (see previous blog post) no dolphins were sighted prior to the arrival of tour boats (7:30am) or later in the day when these vessels were in the area (counts made today of 8 parasails, 5 jet skis, and two ski boats within the area while surveying).

In areas without heavy traffic, two other groups were encountered.

How do we know who is in a group of dolphins?
For some species of dolphins, individuals can be readily identified using nicks along the edges of the dorsal fin. These nicks are obtained generally early on, probably when juveniles, from fighting with others in the population. After a certain point, the addition of new nicks decreases significantly. Because dolphins do not re-grow lost tissue on their fins, these nicks can be used to identify individuals, similar to the way we can identify individual humans using fingerprints.

We immediately recognized Danger Pear in our first group using the pattern on nicks on his dorsal fin. Danger Pear is missing the top piece of his fin and has two smaller nicks on the top half. 

Danger Pear

In our fourth group sighting for the day, we noted another male, Columbia, who has a very distinctive dorsal fin. Columbia has been noted in the Key West population since 2000, and can often be found with another large male, Maple Leaf. Today Columbia was in a group with four other dolphins who were extremely active and social, splashing and leaping, but Columbia did not participate in the activity, staying about 30 meters ahead of the rest of the group, moving slowly.

Columbia

Not all dolphins in a group will participate in social activity. Columbia, who refrained from this today, still seemed to be exerting some control over what the group did, as they continued to move wherever Columbia did as he meandered through the region through the mid morning.