Maternal Instincts

Hi ho everyone! I know it's been forever since I last posted, and you're probably missing your weekly-ish fix of fascinating marine science and news. I've been enjoying an incredible field course through my university that has been eating up all my time. I might do a post about it at some point because we've spent some time doing ocean education. Anyway Depth and Taxa is back just in time for mother's day, so this week we'll be looking at some of the best moms the ocean has to offer.

All moms are willing to give up everything for their kids, but our first ocean mother takes this to a bit of a literal extreme. We've talked about how giant Pacific octopus (Enteroctopus dolfleini) are the largest in the world before, but there's a lot more to these incredible creatures than their size. After mating with one or more partners, female giant Pacific octopus lope off to find themselves a den. Sturdy shelters are an important part of octopuses' entire lives since they have no shell to protect them like other mollusks, but this will be a special space. The den the mother to be is looking for will be her nursery. Once she's found the perfect spot, she'll start braiding together 80-100 thousand eggs with her bare suckers. 

  "Oh you knitted those socks yourself? That's cute."

Couretsy: Ratha Grimes via Flickr

The mother octopus sticks these ropes of eggs to the ceiling where they'll spend the next five to seven months developing. In all that time mom never leaves the den. She sits in her nest, brushing her arms over the eggs to keep them clean, and pushing water from her siphon over them to keep them oxygenated. From the day she lays to the day the babies hatch she never eats a thing. All that devotion and starvation takes a severe toll on mother octopuses' and usually their last act is to push their adorable octolings out into the world with a blast water. 

It's certainly a beautiful story of motherly commitment, but why does it have to be so sad? Why can't mom stick around and raise her young. Well no one knows for sure, but it might have something to do with the fact that adult octopus compete to the point of occasionally eating one another.

 "One look at you and I can't disguise. I've got hungry eyes."

Courtesy: John Turnbull via Flickr

To find an ocean mom that keeps mothering long after her kids are capable of surviving on their own; we need to return to the more familiar world of mammals. 

Orcas, also called killer whales (Orcinus orca), are found across more of the world than most other mammals. In order to become so successful they've had to come up with some incredible strategies for survival. One of those strategies is recognizing that "mother knows best". Orca groups, called pods, are led by matriarchs who care for their children their entire lives. These mother-leaders remember where the best hunting grounds are, what areas to avoid, and where to go when food is scarce. Keep in mind that orcas can live as long as humans. A whale named Granny from the Salish Sea in the Northeast Pacific, is estimated to be 103 years old, far, far beyond reproductive age. A theory called the "grandmother hypothesis" suggests that the life experience of these mature females is so important that, evolutionarily, they contribute to the reproductive success of their pod even after they go stop reproducing. Of all the animals in the world only humans, pilot whales, and orcas are known to go through menopause, and their wonderful mothering may be why.

Courtesy: Mike Charest via Flickr

So who else is left? What other mother can compete with these two incredible species? Well the answer is simple, mine. My mom has been a big part of my life for as long as I've had it, and I want to dedicate this post to her this mother's day. Mom has always respected my goals and encouraged me to pursue the sea since I first responded "oceanographer!" when I was asked what I wanted to be when I grew up. 

The only thing that's changed in 21 years is that my brother 

doesn't fit in a dolphin anymore.

Mom and I always have wonderfully deep conversations about education and science, and she's been the number one supporter for the blog. I know that, like a giant Pacific octopus, my mom would give up everything to give her family a head start on life. But she'll also be around for years to come, to give me and my brother guidance, just like an orca matriarch. So since I know she's reading this, I just want to say thank you, thank you for everything, and Happy Mother's Day.

References:

No author, "Orcas of the Salish Sea, Part 1 & 2", The Orca Network. 

Accessed via: http://www.orcanetwork.org/Main/index.php categories_file=Natural%20History%20of%20Orcas%20-%20Part%201

Weiler, Nicholas, "Menopausal Killer Whales are Family Leaders", Science News, March 5th 2015. 

Accessed via: http://news.sciencemag.org/biology/2015/03/menopausal-killer-whales-are-family-leaders

Anderson, Roland C., Mather, Jennifer A., & Wood, James B., "Octopus: The Ocean's Intelligent Invertebrate",  Timber Press, May 21st 2010.

The Notorious B.I.G.

"Where does everyone keep getting that number!" I shouted irritably one day while doing some research for the Seattle Aquarium. I was profiling the giant Pacific octopus (Enteroctopus dofleini) and the number that kept coming up was 272Kg/600Lbs. Don't get me wrong, giant Pacific's are well named. They're the largest octopus species in the world, and they can be massive. The largest animal I ever encountered was an octopus named Roland who weighed over 90 pounds and he had an arm span above ten feet.

Giant Pacific octopus also grow incredibly fast. They're short lived, only lasting 3-5 years in the wild, and they go from the size of a grain of rice to broader than a man's height in that time. It's been estimated that they average a gain of 1-2% of their body weight every day. They literally grow exponentially. A well-fed octopus gets bigger today than it got yesterday, and will get bigger tomorrow than it got today.

What had me so flustered about that 600 pound claim is that most giant Pacific octopus never get any bigger than 70 pounds, and the reliable accounts of extremely large animals only weighed around 120 pounds. I found article after article that referenced that size, in both the popular press and the peer-reviewed literature. Six hundred pounds is so far off from what's normally their maximum that I began thinking fish stories might not always be about fish. Many articles even acknowledged that any account above 120ish pounds was probably unreliable.

"I swear it was like two people across!" (Person in this example is defined 
as one elementary aged child) 

Courtesy LAZLO ILYES via Flickr

     Of course it's not not unheard of for a population of animals to shrink over time due to human influence. For example, the dusky grouper (Epinephalus marginatus) from the Mediterranean, is thought to be much smaller than before modern fishing pressure. In ancient Roman murals dusky grouper are portrayed as almost as large as a man, now they rarely get bigger than around 50cm (about 19 inches). Giant Pacific octopus on the other hand haven't really been a targeted catch thanks in part to their chewy texture. It could be that pollution has affected the health of these species, but the reports of truly giant octopus were claimed to be from Alaska where human impact is less significant.

Alright, so where did this number come from? Well lucky for our quest to discover the origins of the "super giant Pacific octopus, TM" , science has a spectacular convention of citation. At the end of every peer reviewed article the authors are expected to cite previous research that informs their experiment and is the basis of their prior knowledge. You can think of it as a built-in BS alarm.

Statistical analypus thinks you should have used an eight tailed test.
Courtesy canopic via Flickr

So I took the opportunity to put on my detective cap and dig around some scholarly research! I have friends I swear, they're humans and everything. Anyway after a little leg work (keyboard work?) I managed to track down the source of the 600 pound octopus in the room. It turns out that in 1975 William High wrote a summary of knowledge about giant Pacific octopus for the National Marine Fisheries Service's annual report. This article was cited by almost every paper I had been looking through, so I suspected it was what I needed. Thankfully the good folks at NOAA keep an online archive of these reports.

In High's summary he discusses how large these animals can get and even he doesn't totally buy the hype at first. He states: "Much larger ones (octopus bigger than 100 pounds) have been reported, but like the Loch Ness Monster, these usually elude the careful photographer or scientist." which is basically the scientific paper equivalent of "cool story bro." But then just a few lines later he goes on to say: "In the late 1950's I interviewed a Canadian commercial diver Jock MacLean... He reported capturing an immense creature weighing 600 pounds and measuring 32 feet from arm tip to top. MacLeans photographs, unfortunately, were of poor quality. Smaller animals, to 400 pounds, were occasionally taken..." Seriously!? Poor quality photos and the testimony of a guy whose job it was to go and get narc'd all the time are all we're going on. You'll have to forgive me if I remain skeptical.

"No you can't be real! The scientific literature doesn't substantiate 
your existence!" -The ship's naturalist
 "Denys de Montfort Poulpe Colossal" by Pierre Denys de Montfort († 1820)
 - Ellis, R. 1994. Monsters of the Sea. Robert Hale Ltd. Licensed under Public domain via Wikimedia Commons  

Sadly it looks like the reports of "super giant Pacific octopus ™" have been exaggerated, even among those who try hardest to avoid hyperbole. Although I can't help but wonder; why is a giant octopus such a universal story? From the legends of the kraken to the creature that supposedly lives under the narrows bridge in Tacoma, Washington; monstrous octopus just capture our imagination. Maybe long ago there were octopus large enough to destroy a ship, or maybe having no frame of reference in the vastness of the ocean led to exaggeration. Either way the real giant Pacific octopus is a huge, magnificent creature that deserves our respect.

References:

Cosgrove, James, & McDaniel, Neil, "Super Suckers: The Giant Pacific Octopus and Other Cephalopods of the Pacfic Coast.", Harbour Publishing, March 2009

High, William, "The Giant Pacific Octopus", Marine Fisheries Review, Vol. 38 No. 9, Sept. 1976
Accessed via: http://spo.nmfs.noaa.gov/mfr389/mfr3893.pdf

Guidetti, Paolo, & Fiorenza, Micheli, "Ancient Art Serving Marine Conservation", Frontiers in Ecology and the Enironment, 9: 374-375, DOI 10.1890/11.WB.020