Fortunately, as humpbacks descend on deeper, foraging dives, they arch their back steeply and often raise their flukes or tail into the air. If positioned correctly, you can snap a photo of the ventral side (underside) of their flukes as they are diving. This photo can then be used to identify each animal. A close look at a good fluke photo can reveal specific markings that are unique to each whale. This method was pioneered by Juneau researchers Chuck Jurasz and Virginia Palmer in the 1960's.
• How is it that each fluke is unique?
• What can we learn through photo identification?
How is it that each fluke is unique?
Humpback flukes have much natural variability in their shape and coloration (pigmentation). The two photos below are an example of this variability. In particular, notice the difference in fluke shape between the two whales.
Further, scarring on the flukes is common and tends to be lasting. Though, some scars will disappear and others can be added over time. Interestingly, areas with white pigmentation will scar black, and areas with black pigmentation will scar white. Below, are a couple of examples of scars that become helpful in identification.
Using scars alone for purpose of identification can be misleading. Just remember that a whale can acquire a scar in the time between the first and second photos being taken. Also, scars can change in appearance and severity over time, and look different depending on the lighting. The following two fluke photos are from the same whale, notice how the scars are more apparent in the photo on the left.
In this case, it is necessary to match the fluke using the trailing edge (see labeled fluke below). This process involves a lot of squinting and a fair amount of patience, but it is often the only way to make a positive identification.
Parts of the flukes
This photo outlines the terminology that is used to describe the different features of whale flukes.
What can we learn through photo identification?
Many questions can be answered using photo identification as a tool. Some information that is commonly gathered from fluke photo ID data is outlined below, along with theoretical scenarios to help illustrate the concept.
We can learn about migration destinations of specific whales, and about the maximum transit time for migration. Also, movements within an area can be determined, and habitat preferences can be seen.
Example: If a whale was identified in Alaska on Nov 8 and then re-sighted in the Hawaii islands on Dec 11 of the same year, we can assume that the maximum time this whale spent migrating was 32 days.
Breeding/Foraging Site Fidelity
We can learn the breeding and foraging preferences of individuals, and determine tendencies humpbacks may have to return to the breeding and foraging (feeding) regions where their mothers initially brought them when they were a calf.
Example: If a mother and calf pair were sighted off Maui, Hawaii during winter, then in Lynn Canal, Alaska for the summer feeding months, it would be possible to monitor these areas in future years to see if this calf maintained those site preferences.
Kin/Social Relationships
We can learn if whales form long-term social bonds or associations and/or if they have long-term recognition and preference for association with kin (relatives).
Example: With good fluke IDs of a mother and calf, it would be possible, through continued monitoring, to identify a mother who retained an association with a former calf (her offspring). Or, similarly, two unrelated animals who maintained a long term association.
Age/Longevity
We can learn a minimum age for each whale based on the date of the first fluke photo taken of each animal. And, if the first fluke photo was taken when the whale was a calf, the exact number of years in age is known. We call these ‘known age whales.’
Example: If a whale was photographed in the winter of 1983, you can assume that the whale is at minimum 25 years old in 2008.
Reproductive Success
By documenting mother and calf pairs, we can learn about the reproductive success and frequency in females.
Example: If a female whale is seen frequently (with multiple sightings each year), it is possible to look at the years she has a calf and document the intervals between offspring. This type of information can be important in extrapolating the overall reproductive rate of the population.
Age of First Successful Reproduction
We can learn at which age female whales give birth to their first calf by observing the first year a known age whale has a calf with her. Due to the breeding strategy of humpback whales, it is not possible to observe the father of a calf, and therefore is not possible to use photo ID as a method to learn the age of sexual maturity for male whales.
Example: If a whale is sighted and photographed as a calf in 1995, and then seen later in 2004 with a calf, it can be assumed that the age of first successful reproduction was a maximum of 9 years.
Population Estimates
Photo ID can be used to determine an estimate for the number of whales in a given population using a basic mark-recapture analysis. The principle behind a mark-recapture study can be seen using a simple closed population (meaning no individuals leave or enter, including no births or deaths). A subsample of this population is taken and “marked” then released. The “mark” in this instance is the photograph taken of the flukes as an identifier for each individual whale. A second subsample is later taken after the population has had sufficient time to mix and reorganize. The re-sighted individuals are considered “recaptured”. Using a complex calculation based on the ratio of marked and unmarked whaled “captured” or documented, an estimate of the number of individuals in this population can be determined.
How to take a good photo identification picture
When taking a fluke photo for purposes of photo ID, the photographer needs to be positioned directly behind the animal, so when the whale dives, the underside of the flukes are facing the camera. Perhaps the most challenging aspect is timing. Remember that the trailing edge is an important part of the identification, so the timing of the photograph needs to be such that the flukes are perpendicular the surface of the water, this is the moment where the trailing edge is most defined.
It is also important to use a telephoto lens for photo identification. By law, you cannot approach within 100 yards of a humpback whale (SEE REGULATIONS). So, it is necessary to have a camera and lens that will allow you to capture a photograph of sufficient quality from a distance
As you can probably guess, fluke photos alone are rarely useful. They must be collected along with some associated data. At a minimum, time, date and location (preferably latitude and longitude) should be recorded at the time that the photo is taken. Other important information that can be collected include; associations (which whales were grouped up with which whales), mother and calf identification and behavior (such as breaching and bubble net feeding).
Basic Fluke Matching 101
- Remember that coloration and markings may be more or less pronounced depending on the lighting and angle.
- Also keep in mind that some markings can be acquired in the time between taking each photo
- When possible, use the trailing edge to confirm a fluke match. This tends to remain fairly stable through the whale’s life, and thus, is a reliable tool in identification.
- If you have access to photo editing software, there are some tools that can help “bring out” details and markings on a fluke that may otherwise be difficult to see. First , rotate the image so the fluke in the image is not slanted in the frame. Next, crop the photo so the fluke is the majority of the frame. You can alter the exposure of the photo by increasing and decreasing the gamma and contrast. It is not advisable to use the other exposure options, as those editing options are more dramatic and could make some markings “appear” that are not actually there.
- If possible, use photos that are the same size. This can be done by cropping your photo to a designated size, , such as 2x3.
- Be sure to always keep a copy of the original photo in case you want to go back to it.