Tuesday, February 21, 2017

Who Can Swim Further: A Race to the Depths and Back (A Guest Post)

By Jefferson Le

The blue whale (Balaenoptera musculus) is the largest mammal on the planet. Image by
NMFS Northeast Fisheries Science Center (NOAA) available at Wikimedia Commons.
Helloooooo! My name is Bailey and I am a 25 meter long blue whale, the largest living mammal on Earth! My friend Finley, a 21 meter long fin whale comes in second for largest in size. We had an interesting adventure recently where we were followed by humans. While Finley and I were foraging for food, I overheard the humans talking about investigating our diving behavior when we hunt and not hunt. With that, I will tell you what these foreigners did to investigate our behavior and also what happens when we dive.

A chart of whales of different sizes. Image by Smithsonian Institute.
To record our dives, the humans travelled to Mexican waters to attach recorders onto our mid-backs using a crossbow. Now, it didn’t hurt much due to my thick blubber. These devices recorded depth of how far we dived, time of dives, and our location. These recorders eventually came off between 5 to 13 hours later. Finley and I were not the only test subjects. Other members of our species were also tagged. After all the data on the devices were collected, the humans finally left our waters and did statistical analyses on our diving behavior.

The fin whale (Balaenoptera physalus) rarely exposes its fluke when it prepares to dive
to the abyss. Image by Aqqa Rosing-Asvid at Wikimedia Commons.
Now, before we talk about what the humans found, I want to share with you the whale secret to a great dive. In case that you ever find yourself in the ocean or your local pool, you can try it! The nose for Finley and I are called blowholes, which are found on top of our heads. This tract is separated from our digestive tract so we do not have to worry about having food go down our blowhole. When I am about to dive, instead of gulping in lots of oxygen, I exhale out as much as I can. This causes my lungs to collapse and flexible walls in my chest allow even more compression. Also, tiny structures in my lungs called alveoli collapse which halts any gas exchange. All of the decrease in lung space decreases buoyancy so I can descend down to the depths.

As I descend, my heart rate lessens to reduce energy used during the dive. The oxygen that I had obtained before the dive is stored in my blood and muscle tissue. Since the deep depths are really cold, blood flow is temporarily halted at the thinner areas of my body, like flippers, and some organs to keep the main body going. When I ascend back up, I gradually increase space in my lungs and my alveoli regain full function to allow gas exchange. If you were to ascend too quickly, you could get shallow water blackout or even worse, the “bends” (where nitrogen bubbles in your blood) and I heard it is painful. After ascending is complete, I can release my blowhole open and take in fresh oxygen again.

I was secretly told what the results to the humans’ experiments were. They found out that fin and blue whales dove deeper when hunting on shallow dives when not hunting. It makes sense! Why spend so much energy diving when not hunting? Also, they noted that our lunge feeding frequency was different. Lunge feeding is where we propel ourselves towards our prey with our mouth open and grab as much food as we can into our mouth. Blue whales lunged about 2.5 times more than fin whales! That’s a point for the blue! However, the record dive depth came from a fin whale. Hmm… I wonder if Finley broke that record.

Did you find my secret and what the humans found interesting? I surely did. I never thought about how I dive and how I behave as it is practically in my blood! Well, the next time you are at a deep pool, try those secrets I spilled to you. It might be fun! Then again, you might be thinking, how does a whale communicate with a human and understand scientific data? That is a secret you may never know…

Literature Cited:

Croll DA, Acevedo-Gutiérrez A, Tershy BR, & Urbán-Ramírez J (2001). The diving behavior of blue and fin whales: is dive duration shorter than expected based on oxygen stores? Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, 129 (4), 797-809 PMID: 11440866

Hill, R. W., G. A., Wyse, M. Anderson. (2008). Animal Physiology. 2:641-660

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