The DNA used in study of whale sex, genetic variability, and relatedness of individuals is obtained through taking small skin samples from the whales. This is usually done by shooting a biopsy dart at the back of the whale with a crossbow. The dart bounces off the whale with a tiny piece of skin attached. Numerous studies have shown this has negligible impact on the animal. This technique was used in the following study.

Preliminary analysis of mitochondrial DNA variation in a southern feeding group of eastern North Pacific gray whales.

T.E. Steeves, J.D. Darling, P.E. Rosel, C.M. Schaeff & R.C. Fleischer

Conservation Genetics 2: 379-384, 2001

Summary:

In the eastern North Pacific the majority of gray whales migrate from calving and breeding areas on the west coast of the Baja California peninsula to feeding grounds in the northern Bering and Chuckchi Seas.  Some gray whales, however, terminate their migration early.  They spend their summers feeding along the coasts of California, Oregon, Washington, British Columbia (BC) and Southeast Alaska.  Long term photo-identification studies in Clayoquot Sound (CS), BC determined that 35-50 individuals returned to the feeding grounds in subsequent years.

The intent of this study was to determine the sex ratio of those returning whales and if there is matrilineal fidelity to CS.  This was accomplished through DNA samples from tissue biopsies of 16 CS whales and 41 whales from other areas of the eastern North Pacific.  The 41 samples were taken from whales migrating to the northern feeding grounds, thus they were considered to be non-resident.

The sex ratio of sampled CS gray whales was 1.7:1 (male:female).  The male bias was not statistically significant.  There was not a significant genetic difference between resident and non-resident gray whales.  The samples also did not indicate a matrilineal fidelity to CS, however, a larger sample size may be necessary.  In other large baleen whales females seem to introduce their calves to feeding areas which the calves then return to in subsequent years.  As CS is part of a southern feeding area, it is possible that calves are returning to other parts of this area, rather than to CS.  Genetic variation results from this study support theories that the number of gray whales surviving intensive whaling in the mid 19^th and early 20^th centuries may have been in the low to mid thousands.  The diversity indicated by the data from this study was inconsistent with a lower population base.

Both male and female adult gray whales exhibit long-term fidelity to the feeding grounds of Clayoquot Sound.  Determining why they return requires continued study using photo-identification and genetic analysis.