Ashley Pearson at Año Nuevo State Reserve, CA-- If you went to Año Nuevo every day for a week, do you think you could start to tell individual seals from one another?  Although we can tell some seals apart using physical attributes, genetically speaking, northern elephant seals are all almost identical!  Northern e seals are so similar genetically, that it is hard to identify who fathered a pup – even with a  paternity test!

    Why are all Northern E Seals so genetically similar??  In the late part of the 19th century northern E seals were hunted almost to extinction for their blubber.  For a while people actually thought that they were extinct! Luckily, hunters stuck to hunting on land and missed a few e seals who were out at sea.  You see, at any given time, there is a large percentage of the E Seal population out at sea! For example, when females are giving birth and adult males are protecting them, juveniles and subadult males are off shore still hunting. When juveniles come into molt in early spring, all adults have already left for sea!

Adults and pups scatter the beaches during breeding season while juveniles and yearlings are out at sea.  Photo:  Ashley Pearson

Pods, or groups, of weaners and juveniles relax on land after the breeding season ends; the adults are all swimming in the ocean on a short foraging trip!  Photo:  Ashley Pearson

So, even if entire harems were hunted, there were always e seals thousands of miles away, surviving. After years of hunting though, even those animals at sea started to get picked off one by one. It is thought that the number of E seals that remained at that time could have been as low as 8!  Out of this small group of E seals grew the entire population of northern e seals that are thriving today; this is called a genetic bottleneck. 

Graphic:  Ashley Pearson

There’s a catch. Because the group was so small, biologists think that there must have been a lot of inbreeding, leading to very little genetic variation in the current population.  Researchers at UCSC and NOAA fisheries are currently examining northern e seal DNA to better understand how a species with so much inbreeding is able to survive so well.

Two men at a "blubber stove,"  November 3, 1911.  Photo:  Bancroft Library, Berkeley, CA; more pictures like this.

Artic Oil Works, established in 1883, where blubber from seals and whales was made into oil (Carlsson, foundsf.org).  Photo:  Bancroft Library, Berkeley, CA

What does this mean for the e seals? So far, not much! They’ve been very successful at reaching near historic population levels, however they don’t have the protection that other species have in genetic diversity. For example, human influenza. During the influenza outbreak, some humans were not as susceptible to the disease, because of their DNA. This is how people survived despite the very dangerous disease (read more at Wikipedia). If elephant seals get a disease, they will not have this genetic safety net to protect them.

 Lots of seals everywhere, thats what we like to see!  Photo:  Ashley Pearson.