Sunday, May 10, 2015

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.


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

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

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