Stellar's sea cow

Bringing back the Steller’s Sea Cow: a Stellar Idea?

By Zach Sheldon, Sterling Pino-DeGale, Will Kennerley, Sarah Schneider
 
Imagine, it’s a chilly day off the coast of Bering Island in the Commander Islands of far Eastern Russia and you and your crew have been shipwrecked. Cold and hungry, you are in desperate need of a way to return back to shore since your lifeboat can only hold so many people. You gaze off into the distance and notice a large object floating off in the sea. You quickly grab the attention of your crew and begin rowing towards what looks like an overturned boat. As you’re rowing, you notice the object has started to move toward you! You try to row away, but your oars become entangled in the kelp forest below. Stranded in the water, you fear what lurks beneath the surface. Suddenly, a head the size of a large boulder appears and you begin to fear for your life. The creature that emerges gives the appearance of a whale but is much more concerned with eating the kelp entangling your oar than it is the people floating in the water.

Hopefully now you have a better idea of what Georg Steller possibly felt on that day back in 1741 when he discovered the sea cow that would later become the salvation for his ship wrecked and disease-ridden crew. This massive animal would later be named for him, and then hunted pretty quickly to extinction.

The Steller’s sea cow (Hydrodamalis gigas) was a 20 foot long aquatic mammal that could weigh up to 12 tons. This is equivalent to approximately 24 cows, or two adult male African elephants.  Like elephants, sea cows lived in herds but were non-migratory, staying pretty much around the islands where they were discovered, a last vestige of their once sizable distribution that had been declining since the end of the last glacial period.

Though they did not migrate, Steller’s sea cows were forced to move to areas dense in kelp for foraging as opposed to traditional algae found on the seafloor due to the development of chemical defenses by the algae to fight herbivory. While the kelp promoted a larger body size and higher birth weight, it was also met with some competition. Sea urchins, a population whose magnitude was controlled by the declining sea otter population due to the fur trade, fed on the same kelp found in shallow waters that the sea cows did. The abundance of sea urchins ultimately minimized the amount of available kelp for the sea cow to forage on, giving rise to starvation.

Along with competition, the kelp gave the sea cows a buoyancy which denied them their ability to fully submerge underwater. This allowed mariners to hunt them with little to no effort and spread the word of this resource to others. Since their fecundity remained relatively low, the sea cows were unable to replenish their declining population quickly. As more and more people gained knowledge of this ecological goldmine, the Steller’s sea cow began to see a quick demise from its first discovery in 1741, with the last one being seen in 1768, less than thirty years later.


While not much is known of the sea cow, we can look to its closest living relative the dugong (Dugong dugon); a large marine mammal which feeds on seagrass and lives in herds, majestically roaming bays and channels. We can infer that the seacow would have similar reproductive methods to the dugong which has a 13-15 month gestation period and must nurse their calves for 14-18 months following conception.
From a management standpoint, special attention would have to be directed at the Steller’s sea cow during reproductive cycles in order to ensure reproductive success. Wildlife managers would have to figure out a way to provide ample amounts of kelp to this species while leaving other trophic cascades undisturbed or lightly affected if reintroduction of this species were to occur. Laws would need to be passed that would inhibit the hunting of the sea cows, and regulations would need to be made that limit the amount of sea cows allowed for take. If we compare this species to the dugong, we would have to assume that daily access to a freshwater source for drinking would need to be provided as dugongs require this in contrast with their saltwater habitats. Many dugong populations are facing decline solely for this reason which may make the reintroduction of this species problematic. The introduction of a larger species that would out-compete for resources can potentially limit current conservation efforts, but may also make future conservation efforts absolutely necessary since the potential to wipe out remaining dugong species is a possibility.

In addition to the lack of ecological resources, many obstacles still remain in the way of potential Steller sea cow de-extinction and reintroduction. The costs involved in cloning sea cows and reintroducing a self-sustaining population in remotest Russia are staggering, and the sheer size of the animals involved would make their release and reintroduction a logistical nightmare. Perhaps more than this, the ecological niche once held by the sea cow may not still exist. The once-mighty kelp forests of Steller’s day are now largely diminished due to overpopulation of grazing sea urchins caused by local population declines of predatory sea otters; therefore, the vast quantities of kelp required by such a massive animal may not still be available.

From a biological standpoint, organisms birthed through surrogate species often lack necessary passive immunity normally obtained from their mothers during birth. Lacking the proper sea cow immunity may predispose the reintroduced herd to any infections they may face. The fecundity and birth rate of sea cows in general is also dismally low, making the establishment of a self-sustaining reintroduced population especially challenging, taking many years to fully know how the population would fare.

Considering the sizable challenges involved, any attempt at reintroduction would face a low probability of success. When taking into account the impressive costs required for the project and the overall scarcity of funds available for conservation, the justification of a de-extinction and reintroduction project may be difficult when so many existing species, even within the proposed reintroduction area, could benefit from the money and conservation efforts. The official recommendation, therefore, is to simply learn from past management mistakes made with this species and keep them as a relict of the past, deciding against the proposed plan to recreate and reintroduce the fantastic Steller’s sea cow.


For additional information, check out these additional sources: The International Union for the Conservation of Nature, Princeton University, Scientific American, The Sixth Extinction, Austrailian Department of Sustainability and Environment, EDGE, BRITANNICA

Anderson, Paul K. "COMPETITION, PREDATION, AND THE EVOLUTION AND EXTINCTION OF STELLER’S SEA COW, HYDRODAMALIS GIGAS." Marine Mammal Science 11.3 (1995): 391-94. Wiley Online Library. Blackwell Publishing Ltd, 26 Aug. 2006. Web. 30 Apr. 2013.