This page contains a Flash digital edition of a book.
BE INSPIRATION │ KNOWLEDGE


ANTARCTIC BLUE WHALES The Antarctic blue whale is the largest of the baleen whales and is


believed to be the largest animal to have ever lived, reaching up to 100 feet in length and weighing over 160 metric tons. Due to its massive size, this species was targeted by the commercial whaling industry and hunted to near extinction. During the 20th century, over 350,000 Antarctic blue whales were killed, reducing the population to less than 400 individuals scattered around the Southern Ocean. Despite this exploitation, the Antarctic blue whale remains a relatively unstudied species, partially due to the difficulty in studying an animal known to inhabit such an extensive territory. There are few barriers limiting mobility throughout the world’s ocean basins, and the majority of knowledge about the life history of this species comes from catches during the commercial whaling era.


In our recently published study, we described the genetic diversity of the contemporary population of Antarctic blue whales. As with most baleen whales, the Antarctic blue whale is thought to migrate annually from summer feeding grounds in polar waters to winter breeding areas in or near tropical waters. Unlike other baleen whales, however, the breeding areas of the Antarctic blue whale remain unknown. Given this limitation, we studied the genetic diversity of the population on its Southern Ocean feeding grounds using genetic samples provided by the International Whaling Commission (IWC). Between 1990 and 2009, the IWC collected biopsy samples from 218 living whales during vessel surveys intended to estimate abundance in the Southern Ocean.


Despite their history of intense exploitation, we discovered a relatively high level of genetic diversity among the contemporary Antarctic blue whale population. We identified 52 maternal lineages represented by variation in the maternally inherited mtDNA that survived the population bottleneck. This is the point at which the population declined to its lowest numbers, estimated to have occurred in 1972. Among the remnant population we also found the first evidence of population structure. Antarctic blue whales appear to show a maternal fidelity to regions within the feeding grounds of the Southern Ocean, most likely as a result of an early experience as a calf with its mother. Despite the evidence of maternal fidelity to feeding grounds, we also documented large-scale movements of Antarctic blue whales throughout the Southern Ocean.


Through microsatellite genotyping, a type of DNA fingerprinting, we identified 166 individual whales among the 218 biopsy samples


Several whales were sampled on more than one occasion in different locations, documenting individual movement in parts of the Southern Ocean. In one case, we identified a female Antarctic blue whale that traveled approximately 6,650 km, almost halfway around the Southern Ocean over an interval of four years. This was the first record of individual movement of an Antarctic blue whale since the end of the commercial whaling era.


The high genetic diversity is a good sign for the long-term potential for recovery of the Antarctic blue whale, but it is important to monitor genetic changes in the population over the next few decades. The population bottleneck was recent, only 40 years ago. Given their longevity (maybe up to 90 years), many Antarctic blue whales that survived the bottleneck might still be alive today. This long life span, with overlapping generations, probably helped the Antarctic blue whale escape a larger loss of genetic diversity during the intense but relatively brief population bottleneck. However, the surviving genetic diversity could still be lost in the next several generations as these older whales die.


The current abundance of Antarctic blue whales is estimated to have increased to about 2,200 whales, from the minimum of 400 in 1972. However, the population still remains at less than 1% of the estimated pre-exploitation abundance of 250,000 whales. Even at this rate of increase, and with continued protection from hunting, a recovery is likely to require most of this century.


Photo: Paul Ensor


This research was conducted by Angie Sremba who is currently enrolled as a PhD student at Oregon State University in the Cetacean Conservation and Genetics Laboratory under the supervision of Dr. C. Scott Baker, with funding from the Mamie Markham Research Award at Hatfield Marine Science Center.


Funding to help further this research can be donated to the Marine Mammal Institute Cetacean Conservation and Genetics Laboratory.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121