Week 9: The Seals are Doing Fine

Apr 26, 2019

Dang my titles are only getting better

My first day back in Santa Cruz was basically a bunch of computer work. I finished off my spreadsheet of the (corrected) weaner weights I had at that time, and started graphing my stuff. Honestly it looks like there is a slight relationship between the movement of the mother seals and the weight of the babies, in that the more positive the mothers’ reactions are (the more they move towards the car at its first and second approaches), the heavier the babies tend to be. However it’s only a slight correlation, soooo… Anyway, I also decided to start using the postive and negative values of the seals’ reactions in my own analysis (previously I had wanted to use magnitude), but it seemed like oversimplifying the data to use magnitude and not direction (shoutout to all my physics fans out there). Prety boring stuff to talk about now, but it’ll turn out cool in the end because I have a lot of data and my graphing skills on Desmos have improved. I also got a few new seal videos to grade, so I added those seals to my list of pup masses/seal responses (which was nice because one of the seals I received a video for was one with like six pups that I couldn’t use before so that was fun). Other than that, not an eventful day.

On my second day, I worked on some data entry for the lab, and also got to sit in on another procedure on a seal, one that was much more technical and gentle than the previous one at the lab. It was a translocation like the one the week prior, but this one had more instruments and different goals. First off, I guess I should say that often multiple experiments are run on a single seal on any one translocation. For example, there were the long-term dive data collection instruments on the last seal, in addition to the thermal sensors. This week’s seal had all the sensors for the thermal experiment, plus a depth-time recorder, plus an ARGOS tag for location, plus a ton of other equipment. That other equipment was part of another experiment, one which was dedicated to tracking the seal’s heartrate when it was under threat. Have I mentioned that elephant seals are really really heckin cool?? Cuz they are. When they hear or otherwise detect a predator around them when they’re swimming, for example a great white or a killer whale (especially killer whales since those are common in their feeding grounds), their bodies do a couple of things. First, they begin sinking as deep and as fast as they can. Second, they drop their heart rates. Now by drop their heart rates, I don’t mean like “ooh it went down to 40 bpm”.


A seal’s diving heart rate is around 25 bpm already. When they hear a predator, their heart rate drops to 2-3 bpm. 2 to 3 beats PER MINUTE. Absolute legends. In doing so, they conserve energy and oxygen to be able to stay underwater deeper and for longer, because they’re safer at 1000 meters than at the surface. Third, they start circulating blood through their flippers, something that isn’t usually done on long dives to conserve body heat, because flippers exchange heat comparatively quickly. So why do they turn on that blood flow? Because they want to cool down, because the cooler they are, the less energy they use. So in response to a predator, the seals drop their heart rate, cool off quickly, and plummet as deep as they can go.

The other equipment on this seal? A speaker and a sound recorder, to record any natural stimuli that might cause a seal to dive, and to play a killer whale call at pre-determined intervals. Essentially the device was meant to trigger a fear response. In addition to that, there was an EKG wire implanted in a huge (quarter-sized diameter) blood vessel running down her spine (I mentioned that vessel before, that’s where sedatives are injected once the seal is down already). As one could imagine, that’s a relatively major procedure, and it hurts the seal considerably more than a small incision. Normally, we operate on seals that are very sedated and relaxed with tranquilizers and Valium. This seal needed to be completely down, because any slight movements could hurt it a lot, and even very sedated seals move a bit. So out came the funniest anesthesia mask you’ve seen, a giant cup-shaped thing with a foam seal that fit over the seal’s whole head. There was a closed loop of gas, with anesthesia in one cannister and oxygen in another. The whole loop was controlled by a human anesthesiologist from San Diego (I never asked how he wound up there). Once the seal was completely down, a tube was inserted down its throat and a bag was used to inflate its lungs at a constant rate to keep it breathing. The bag was manually squeezed and opened by a researcher there. While the seal was down, all the instruments were attached, secured, and covered by a waterproof sheet. Then the seal was monitored as it recovered from anesthesia, and eventually loaded back into a cage when it could breathe on its own. It was cool and really interesting to watch the procedure unfold, though I was unable to watch the whole thing as it took several (read: five/six) hours.

Anyway, that’s all for now 🙂

One Reply to “Week 9: The Seals are Doing Fine”

  1. Helena Vervoort says:

    I knew seals had the ability to slow down their heart rate but I never heard it was that low! Would be nice if we could do that too. Make that scuba tank last a bit longer…

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