Blue Whale by Tavi Hillesland

Blue Whale (Balaenoptera muscles)

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Blue whales are the largest animals ever known to have lived on Earth. They are a baleen whale, which means that they feed on tiny crustaceans called krill by taking in a big gulp of seawater (their pleated throat and stomach skin expands in order to make room for all of this water) and then forcing it through the fingernail-like layered plates of baleen attached to their upper jaw with their tongue, which can weigh up to as much as an elephant. This effectively strains out the water, leaving behind the thousands of tiny animals that make up their diet. Blue whales live usually individually or in pairs, across all of the oceans. They have huge babies, weighing in at up to about three tons and measuring up to 25 feet long. The period of gestation is very long - up to a year, and the calf consumes only mother’s milk for a nursing period of 6-7 months, while it grows even bigger and learns to be a whale. 

The only predator of blue whales is the killer whale (and it is an occasional predator at that), but the blue whales were also hunted to near extinction by humans before an international ban on whaling was instituted in 1966. They may live for up to and more than 80 years, but because of the relatively recent whaling (which coincided with the increased interest in this species), no individual has not been tracked for its entire lifetime. 

Geographic and Population Changes

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The geographic distribution of blue whale populations did not change as a result of whaling although the density of the populations has decreased. That is to say, blue whales have remained in their entire range, but in significantly lower numbers. In fact, the population in the Antarctic Sea - once the largest population, has been estimated to have been reduced to 0.15% of the original numbers. It is estimated that the current world population is between 10,000 and 25,000, however, a reliable estimate has not really been made. It was estimated, in a statistic released by the International Whaling Commission in 1996, that between 325,000 and 360,000 blue whales were killed in the Antarctic ocean in the first half of the 20th century. The California population, though, is said to have returned to close to the pre-whaling estimate, 97% of the original population, which was one of the smaller groups worldwide. 

Listing Date and Type of Listing

Blue whales are listed under the Endangered Species Act as endangered, and are also protected under the Marine Mammal Protection Act. The IUCN Red List of Threatened Animals lists three populations: Antarctic stock, endangered, North Pacific stock, low risk, conservation dependent, and North Atlantic stock, vulnerable. The recovery plan was created in July of 1998. 

Cause of listing

The goal of listing the blue whale and creating a recovery plan is to “identify a set of actions that will minimize or eliminate effects from human activities that are detrimental to the recovery of blue whale populations.” In order to do that, it must first create a plan to document the current population levels and establish a goal population level for delisting. 

Main Threats to Continued Existence

Hunting by steam whaling boat was the biggest threat to blue whales in history.
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Ship strikes are a potential cause for harm to blue whales
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1. Blue whales were subject to extensive commercial whaling operations in the late 19th and into the middle of the 20th century. Only a few illegal kills have been documented since the implementation of legal protections in the 1950s and 60s. These have included some by the USSR, although it is not documented exactly which species were taken (and how many) in these illegal whaling operations. No aboriginal subsistence hunting of blue whales occurs, either. Whaling is not a current threat, but it does remain the main reason that current populations are at a low level. 
2. Ship strikes: There have been a number of incidents involving large ships and blue whales in which the whales have been harmed or killed by the ships. In some cases, the dorsal fin is amputated by the ships propeller, in others, the ship strikes the whale and causes bone damage. This is especially a problem in the Gulf of Saint Lawrence in the North Atlantic, an area of heavy ship traffic that coincides with an abundance of blue whales. There is no known impact of disturbances from vessels, although considering that whales communicate through echolocation, I think it is likely that they are somewhat affected by vessels, although it may not be significant or cause harm or mortality. 
3. Fishing net/gear entanglement: Blue whales, for the most part, spend their time more offshore than other baleen whale species, thus, they are less affected by fishing operations. That being said, there have been some incidents reported of entanglement, and it is likely that they are underreported due to the fact that people just don’t see blue whales all that often. It can cause damage, especially to the fins of the whales. 

The Recovery Plan

The first action items of the recovery plan are to determine the stock structure of the worldwide population and estimate the population size and monitor population trends, by conducting surveys and maintaining photo-identification catalogs. The next three deal with reducing harm - first, by identifying and protecting habitat essential to the recovery effort. Then, second, steps are listed to “reduce or eliminate human-caused injury and mortality”. The final step in that part of the recovery plan is to “minimize detrimental effects of directed vessel interactions with blue whales”, by investigating the effects of whale watching and implementing protective measures on whale watching activities. The last three items of the recovery plan outline I would categorize as “scientific and administrative items”. They include acquiring scientific information from dead, stranded, and entangled whales, coordinating government actions to implement recovery plans, and establishing criteria for delisting or downlisting. I thought it was particularly interesting how the recovery plan included maintaining photo-identification catalogs, which uses the unique marking and fin patterns of blue whales to gather scientific information about the location and movement of individuals. I also thought that the identification of the areas of the coincidence of concentration of blue whales and high levels of sea traffic was a good example of different sciences and industries working together in wildlife conservation biology. 

Fun facts about blue whales! 

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• A single adult blue whale can consume about 4 tons of krill a day, during certain times of the year

• Blue whales aren’t really blue, they’re more mottled blue-grey, but they appear blue underwater. 

• It’s thought that blue whales can hear each other up to 1,000 miles away. 

• A blue whale heart is the size of a Volkswagen Beetle.

• The spout of a blue whale can shoot 30 feet into the air.

Works Cited

National Marine Fisheries Service. 1998. Recovery plan for the blue whale (Balaenoptera musculus). Prepared by Reeves R.R., P.J. Clapham, R.L. Brownell, Jr., and G.K. Silber for the National Marine Fisheries Service, Silver Spring, MD. 42 pp.

“Blue Whale” animals.nationalgeographic.com

“Blue Whales” NOAA Alaska Fisheries Science Center, afsc.noaa.gov 

“California Blue Whales Bounce Back to Near Historic Numbers” bbc.com

Sears, R. and J. Calambokidis. 2002. Update COSEWIC status report on the Blue Whale Balaenoptera musculus in Canada, in COSEWIC assessment and update status report on the Blue Whale Balaenoptera musculus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-32 pp.