How long do they live? Sei whales can live to at least 74 years old [1], which isn’t bad, but they possibly love much longer than this.

Where are they found? They enjoy all of the ocean except for polar and some tropical regions [2], which I can’t really blame them, I mean I live in Florida to avoid snow (that came with an education trade off though). See figure 1.

Figure 1. Range of Sei whales.

What do they eat? Sei whales are baleen feeders and skim the water in search of small fish, krill, and tiny creatures [2]. I’ve mentioned krill in many of these entries, so check out figure 2 for what krill look like.

Figure 2. Krill.

What do they look like? They can grow to be almost 50 feet long and weigh over 44,000 pounds [2]. In other words they are huge. See figures 3 and 4.

Figure 3. Sei whale
Figure 4. Female Sei whale with calf.

How do they reproduce? Sei whales are viviparous and reach sexual maturity around 10 years of age. Females usually give birth to 1 calf per year [2], but little is known about reproductive senescence in this species.

How do scientists know how old they are? By analyzing the waxy ear plugs of dead whales.

So what are we lacking? The humanity to live peacefully with the rest of the species in this world. Mitochondrial genome information can be found on the NCBI, but nothing about the nuclear genome of Balaenoptera borealis yet. Age validation studies and reproductive senescence data would be really useful too.

Conservation status: Sei whale conservation came too little, too late. They are an endangered species as listed by the IUCN Red List, but some folks still enjoy harpooning them (looking at you Japan). The Sei whale population has decreased by nearly 80% over the last three decades [3] because humans have yet to grasp the whole concept of just because we can does not mean we should.

  1. Carey, J., and D. Judge. “Longevity records: Life spans of mammals, birds, amphibians, reptiles, and fish.” On-line).
  2. Animal Sei whale.  Accessed 11/3/2016 
  3. Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Balaenoptera borealis. The IUCN Red List of Threatened Species 2008: e.T2475A9445100.  Accessed 11/3/2016