In the early Twentieth Century it was thought California had lost its sea otter population to the fur trade; indeed even when a small population was discovered in the 1930’s it wasn’t thought likely that they would be able to resurrect a stable population. Flash forward some eighty years and we may just be witnessing one of those rare success stories as it appears there are now too many sea otters in California’s waters.
After a population of fifty sea otters was rediscovered in 1938, they became the subject of intensive conservation programmes in an aid to save a species “on the edge”. The path wasn’t plain sailing and in recent years as numbers peaked around 3,000 individuals many claimed that the recovery was being hampered by a variety of factors.
As population growth curtailed, one key theory was that a lack of genetic diversity as a result of their near extinction was slowing recovery efforts. However Tim Tinker of the United States Geological Survey has dismissed this theory as a “flawed assumption” with his research which he presented at the Society for Marine Mammalogy’s biennial conference. Sea otters are no longer reproducing as rapidly because they have reached the carrying capacity for their environment. This essentially means that the area in Monterey, California where sea otters live cannot support any more individuals. Their population can no longer grow as there isn’t enough food for a larger population.
Whilst Tinkers research may ease any concerns of struggling sea otters still battling extinction, he is quick to note that it is only in the central part of their range that carrying capacity has been met. Those populations in the Northern and Southern areas still face a multitude of threats and are actually in decline by 1-2% every year.
This is thought to be the result of a surge in predator attacks. For some reason sharks have started to bite and kill the sea otters, although they do not eat them. Whilst this increase is cause for concern for researchers, there are also worries about additional threats emerging.
The current El Niño cycle is being billed as the largest in 20 years and could wreck havoc amongst sea otter populations as it brings in marine parasites which have the potential to cause neurological conditions in sea otters. Alternatively a less dramatic threat could be the lack of breeding females. Max Tarjan, a doctoral candidate at the University of California, Santa Cruz has reported that 80% of male otters never mate or sire pups; something which could dramatically impact upon future population dynamics.
Regardless of any potential threats, it is rare that a species can recover from near extinction to being overpopulated. Thus Californian sea otters are a species which needs to be celebrated whilst looking to the future to ensure the current population is maintained.
Featured Image by otterproject.org
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