Photo-identification

Fluke pattern of Patchwork. Note that the yellow color is not pigment, but a coating of diatoms (algae) The ability to recognize individual animals, whether through the use of tags, bands, or naturally-occurring marks, facilitates the study of their demography and behavior.

Of all of the naturally-occurring marks on humpback whales, the pigment pattern on the ventral surface of the flukes is most commonly used to identify individuals. These patterns are present at birth, although they may be hazy in calves and other young whales.  Dorsal fin shape is also helpful, as are persistent scars on any visible part of the body.  In the Southern Hemisphere humpback whales can be matched based on the pigmentation patterns along their flanks.

Matching a fluke photograph to a catalog of individuals takes good observational skills and patience.  We focus on three things, in particular:

1. Pigmentation

Fluke pigmentation ranges from all white in some individuals to all black in other individuals, with the majority of individuals lying somewhere in between. When black pigmentation is present it may be limited to the core, or it may extend outward along the top and/or bottom of the flukes.

2. Distinctive marks or scars

It is helpful to focus on one or more specific marks or scars. 

3. Trailing edge shape

The trailing edge ranges from being perfectly smooth to having noticeable 'hills' and 'valleys'. Sometimes the 'hills' are quite round, but they can also be pointy. The trailing edge is a very useful tool when trying to match whales without distinctive pigment patterns (for example, whales with nearly all-black flukes). The shape of the trailing edge is like a bar code--no two individuals are exactly alike.

The ease of matching depends greatly upon the quality of the photograph (distance and angle from the subject, as well as exposure). In addition, whales do acquire marks (scratches, nicks and notches) during their lifetime which can alter the appearance of the tail.  Finally, a small proportion of whales experience substantial pigmentation changes that can make re-identification difficult. These types of changes generally occur within the first three years of life.

Biopsy sampling

Understanding genetic population structure is critical to the conservation of endangered species.

Cetacean genetic data is generally obtained from skin samples.  Pieces of naturally-sloughed skin can sometimes be collected from the water after a whale has been active (breaching, lobtailing or flippering) at the surface   Unfortunately, sloughed skin can only be collected on an opportunistic basis, may not be attribued to the correct individual when more than one whale is present, and does not always provide enough high quality DNA.   

More commonly, skin samples are by biopsy sampling.  In this procedure, a small tissue sample is obtained by firing a modified arrow from a cross bow (see above).  When the arrow bounces off the whale, it retains tissue in the sampling tip and floats at the surface until it can be retrieved.  PCCS and others have studied the reaction of whales to this procedure and do not believe that it causes significant harm in the long- or short-term.  In fact, we observe the same range of reactions when a whale is missed entirely, indicating to us that most individuals are simply startled by the procedure

Humpback whale genetic analysis is performed by our collaborators at the University of California at Berkeley.  However, we continue to seek other scientific uses of these tissues.  Biopsy samples can now be used to measure contaminant loads, foraging preferences, pregnancy rates and even used to determine the age of an individual.