Basking Case

What follows is a cautionary tale. A story about acting out in frustration; of letting passions get the better of our collective judgement. A yarn of life, economy, adventure, and...tourists.

Folks living in major coastal towns around the world know the story. As the days lengthen the sun's rays warm the air and the scent of dry grass drifts in the breeze. Locals finally get on the water as the rains and long dark of winter are left behind. But that's when they come: massive, constantly in the way, slowly moving in impassable groups, gorging themselves on an all you can eat buffet. 

Courtesy: Devin Braun via Flickr 

I am, of course, talking about basking sharks (Cetorhinus maximus). 

-"Hey, Kool-Aid"

-"Oh Yeah!" 

Courtesy: jidanchaomian via Flickr

Basking sharks and cruise ship travelers may not seem to have much in common at first, but diving in (Ha! Ocean puns) to their life history reveals some surprising commonalities.

Baskers are the second largest fish species in the world, growing to average lengths of 15-20 feet, but they can get as long as 30. Because they're so big; a single flick of a basking shark's tail moves a lot of water and thus their streamlined bodies are propelled smoothly along with very little effort. This energy efficient movement allows basking sharks to travel great distances through temperate seas. One shark was tagged in late June of 2007 between Ireland and the UK, and had traveled all the way across the Atlantic to south of Greenland by early August. Like other related sharks that make long treks, basking sharks are cruising in search of food. But these massive fish aren't hunting for seals or other large prey; they're cruising along, mouths agape, straining plankton from the water. The filters on their gills are so good at collecting particles, yet remaining unclogged, that they're even inspiring engineers designing industrial and commercial water and air filters.

Basking sharks migrate seasonally across the ocean, and daily up and down in the water column following their favorite food: calanid copepods (pronounced: ko-peh-pods).

Copepods are rich in fats despite their constant failed attempts
at stealing the Krabby Patty secret formula.
Courtesy: DFO via WOrld Register of Marine Species

During the winter these planktonic crustaceans tend to hang out deeper in the water and farther out to sea, so baskers do the same. During the summer, copepod populations explode near shore as lengthening days cause massive blooms of phytoplankton for the copepods to graze on. Basking sharks head shoreward just ahead of this explosion of life to catch the bloom right as it begins and optimize their own feeding. Like most other zooplankton, copepods also participate in the planet's largest migration. During the day they descend to avoid active predators at the surface, and at night they come up to the phytoplankton rich layer that formed while the sun was high. Typically basking sharks do the same daily vertical migration, but occasionally tons of copepod predators called arrow worms will show up at the surface at night. This unexpected pulse of predators drives the majority of the copepods, and consequently the basking sharks, deep when we'd expect them to be shallow.  So not only do basking sharks show up in the inland waters of the far north and south like cruise ships and their passengers, but they also predictably attend to the abundance of the buffet at the times of day it's most well stocked.

Basking sharks' feeding and travel habits aren't the only ways they jive with tourists. As their name implies, basking sharks often hang out in the sun not doing much. Since the sharks already have a pretty bitchin', deep-brown tan they must not be longing to soak up rays. Nope, it's that layer of copepods again. Because there's so much food at the surface, basking sharks don't have to move fast or far during the spring and summer blooms. The sharks are found in aggregations hundreds strong just lolling at the surface with their mouths open like they've fallen asleep sunbathing.

Okay I know there's a shark in this picture somewhere but...
Courtesy: candiche and Noodles and Beef via Flickr

These high concentrations of slow moving basking sharks occur in only a few places in the world. It's likely that these big shivers (the name for a group of sharks) show up in places like southern Chile, but we only know for sure that they happen in the Irish Sea, outside the Bay of Fundy, and historically in the Northwest Straits of the Salish Sea.

Just in case you're not from one of those places or didn't pay attention in geography

Now, you might have noticed that I said "historically" in the Salish Sea. In the past, basking sharks came to the region in droves every year to bathe in the Pacific Northwest sun and chow on the rich abundance of copepods in those waters. But like any pulse of summer tourists visiting a port; they were slow, in the way, and causing problems for traffic.

I'm lookin' at you; Pike Place!
Courtesy: Michael Munch via Flickr

As happens with anyone who deals with influxes of tourists too often; salmon fisher folk in British Columbia largely hated this yearly migration. The sharks were so numerous and slow that they frequently became entangled in salmon gill-nets. Basking sharks also have the same skin-teeth that other sharks possess, so when they thrashed to free themselves they often destroyed more of the net than just where they were caught.

Since much of the BC economy relied on salmon fishing at the time, basking sharks were listed as "Destructive Pests" by Canada's fisheries department in 1949. Six years later the department began an eradication program that, coupled with a commercial fishery for their skin and oil, did exactly as intended. Basking sharks were functionally extinct in the Salish Sea by the late 60s.

The Comox Post with its shark-slicing bow blade
was the pride of the program.
Courtesy: Popular Mechanics via Google Books

However attitudes towards basking sharks (and to a lesser degree cruise tourists) are changing. People better understand the role baskers play in the marine ecosystem as the massive end of a petite food chain. Ironically basking sharks now bring tourists to the Irish Sea and surrounding waters every year to watch their incredible shivers. Having basking sharks and cruise tourists around can greatly enhance the economies of northern port towns in the summer. And Lord knows we can use that extra cash for good beer and faux daylight to get us through the dreary mists of maritime winters.

There's also hope for the Salish Sea's population of basking sharks. They've been granted the protections that being listed as "endangered" under Canada's Species At Risk Act affords them since 2010. Baskers are also occasionally showing up in unexpected parts of the Salish Sea. In 2014 a basking shark gave a family out fishing a unique encounter when it basked about their boat for 15 minutes off of Edmonds, just 16 miles north of Seattle. No word on if the shark was planning to visit Pike Place.

" Excuse me, can you tell me how to get to the gum wall?"
Courtesy: Grace Coale via Q13 Fox

References:

Gore et al., "Transatlantic Migration and Deep Mid-ocean Diving by Basking Shark", Biology Letters: Marine Biology, Vol. 4 pg. 395-398, 2008.

Accessed via: http://rsbl.royalsocietypublishing.org/content/4/4/395

Lorch, Matt, "Close Encounter with Rare 25-foot Basking Shark in Puget Sound: "I didn't really feel scared, just excited", Q13 Fox News, Aug. 13th 2014

Accessed via: http://q13fox.com/2014/08/13/close-encounter-with-rare-25-foot-basking-shark-in-puget-sound-i-didnt-really-feel-scared-just-excited/

Pynn, Larry, "Rare B.C. Photograph of Endangered Basking Shark Shines Light on Change in Federal Attitudes", Vancouver Sun, Nov. 11th, 2013.

Accessed via: 

http://www.vancouversun.com/technology/Rare+photograph+endangered+basking+shark+shines+light+change+federal+attitudes/9152553/story.html

Sanderson et al., "Fish Mouths as Engineering Structures for Cross-step Vortical Filtration", Nature Communications, Vol. 7, Article #11092, 2016.

Accessed via: https://www.nature.com/articles/ncomms11092

Siders et al., "Seasonal Variation in the Spatial Distribution of Basking Sharks (Cetorhinus maximus) in the Lower Bay of Fundy, Canada", PLoS ONE, Vol 8 Issue 12, 2013.

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082074

Sims et al., "Habitat-specific Normal and Reverse Diel Vertical Migrationin the Plankton-feeding Basking Shark", Journal of Animal Ecology, Vol. 74 pg. 755-761, 2005.

Accessed via: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2005.00971.x/full

Ghost Face Killer (Whales)

December's post got the Depth and Taxa crew thinking. We talk an awful lot about fish and invertebrates on this blog. Of our 32 posts only three directly refer to marine mammals. While it's great that we're bringing the less publicly well-loved species into the spotlight; it's sad because the ocean's mammals are astonishing. Whales, dolphins, porpoises, seals, sea lions, walruses, and sirens (the manatee kind, not the Odyssean) all exhibit remarkable adaptations for a class of animals that arguably don't belong underwater. So in the interest of fairness and the spirit of deeper understanding, let's talk about the biggest, the baddest, the black and white-enest of the dolphins; Orcinus orca, the Killer Whale.

They're like the pandas of the sea! If pandas ate exclusively flesh...

and hunted in groups... and had complex social structures... 

They're like the wolves of the sea!

Courtesy: Matthew Allen via Flickr

Okay so the first thing you might be wondering is how we can call them killer whales if they're dolphins? Well the word "whale" is deceptively complicated. See, back when the common conscious was still in its "everything that swims is a fish phase" a whale was just anything really large that you saw or caught in the ocean. More recently whale has mostly been used to mean any large species of cetacean (pronounced: set-ay-shun). If you've ever called something a whale, porpoise, or dolphin; it's a cetacean. Dolphins are a specific family within the cetaceans, so orcas are both whales and dolphins. 

Just like humans, orcas can be found all over the globe; from the tropics to the poles. They live in groups comprised of their relatives and close associates, just like us. They're the apex predator in their environment, just like us... They live 50-60 years but can get over 100... just...like...us... Hm these similarities are starting to get a bit strange.

Okay, this is officially weird now. 

Courtsey: Douglas Muth via Flickr

 

The truth of the matter is, humans and orcas are both extremely successful because of our large, wrinkly brains and penchant for caring about others of our own species. In humans the prime example of this one-two punch of emotional intellectualism is just how much listening to "Hello"  makes us want Adele to find happiness <sniffles>. In orcas it's their ability to form what are called ecotypes.

There are at least ten orca ecotypes between the northern and southern hemisphere, and likely more to be discovered. Each has its own feeding strategy, typical body type, and associated behavior. Usually more than one ecotype is found living in the same place. Take for example the continental shelf of the northeast Pacific. These nutrient rich waters are home to the kind of expansive seafood buffet usually reserved for Red Lobster and questionable casinos. Fish, birds, mammals, and invertebrates are all in ready supply if you're clever enough to harvest them. This smorgasbord has allowed for three different ecotypes to develop in one region.

Courtesy: Dahlheim et Al. (2008), Marine Mammal Science, 24(3)

The most well understood of these three types are the resident killer whales. There are three populations of resident orcas in the northeast pacific; the Alaskan Residents, the Northern Residents, and the Southern Residents. All of these groups live in fairly large pods of usually around 30 individuals. Occasionally the entire Southern Resident Community gets together for a big ol' fashion hootenanny. Seriously, this 85 whale strong "superpod" is as close to a college kegger as any species other than humans get. This is the time when the Southern Residents say hey to friends, hook up with each other, and shout across the room to orcas they know. That last one is only partly a joke. Resident orcas are the chatty Kathy's of the ecotypes. They're highly vocal because their favored prey requires them to be highly coordinated in their hunting.

Resident orcas eat nothing but fish, and about 90% of that fishy diet is salmon. Why? Because salmon meat is just drowning in oil. Those natural fats are great for preserving the whales' blubber layer, which keeps them warm. Salmon is also absolutely dense with chemical energy, and that's essential for maintaining an active body and mind. 

All orca ecotypes employ echolocation clicks to navigate their environment. But in order to effectively corral schools of speedy fish, residents employ a complex vocabulary of whistles. Their calls regularly change pitch, tone, and frequency as they communicate with one another. 

"So anyway I said to him" 'go left', and he went right, so I said: 'no, 

your left', and he said: 'What do you mean I'm left? we're all still here'" 

Courtesy: Tundra Ice via Flickr  

Resident oracs are usually the ecotype that people are most familiar with. This is mostly due to the fact the they remain in a relatively small area throughout their lives. The Southern Residents are probably the most extensively studied and photographed whales in the world. They have legions of fans, and what's not to love about residents. They're rarely far away when you need them, they're gregarious, and they eat food that we don't find particularly cuddly. Transient orcas, also called Bigg's killer whales, are an entirely different story.

Transients are the leather jacket wearing, smoking behind the gym, switchblade carrying, greasers of the ecotypes. Everyone who's ever loved a bad boy or girl can get into the transient orcas. "What makes transients the badasses of the dolphins?" I'm glad you asked.

 Courtesy: Poorly Drawn Lines

Transient orcas are primarily mammal eaters, and they almost never touch fish. This ecotype preys upon seals, dolphins, porpoises, occasional birds, and even baleen whales! With each prey type comes a different hunting strategy. Seals are usually grabbed from below the surface and quickly killed, but in contrast, sea lions are gradually beaten to death with the tails of each pod member. Then this frequently happens:

Hahaha Okay I admit this at least a little funny.

Yup, they play with their food. Take what your average cat does to a mouse, scale them both up about 1000 times, and you have a Biggs' killer whale playing with a sea lion. But wait! It gets even more intense. Transients hunt the giant cetaceans by drowning them. I'll let the BBC and David Attenborough give you the specifics in the video below

Really intense footage, but absolutely incredible.

Although each attack type has different characteristics, what's consistent is that transients are quiet and work with a small crew. They swim in loosely defined small pods, usually no more than 10 individuals, to increase each whale's share of the prey. And since their prey hears very well, transients go into stealth mode once they've identified a target. Only once they've taken down their meal do they resume vocalizing. 

While all of his mammal killing may seem unpleasant, it actually makes a lot of sense. Since resident orcas are busy eating up all the oily fish in the nearshore, transients need another source of fat. And there's few higher quality fats than the blubber of marine mammals. By consuming different foods transients and residents can live side-by-side with little interaction and no conflict.

So if Bigg's killer whales and residents consume all the energy rich prey in the nearshore then the third ecotype must live somewhere else. 

It's on the shore isn't it? I knew this would come back to pandas.

They're like the orcas of the land!

Courtesy: fortherock via Flickr

The final of the northeast Pacific ecotypes lives in the offshore environment along the edge of the continental shelf. In one of the most creative namings ever, these offshore orcas are called... offshore orcas. Offshore's are the least well understood of the three ecotypes for a number of reasons. The main being, that the open ocean is so much bigger than the inland waters where transients and residents are usually found. It's not surprising that most of the encounters with offshores have occurred off of California where the open ocean abuts the continent.

"California whales they're so incredible. Black tail flukes, 

with blowholes on top"

Courtesy: Matthew Allen via Flickr

Genetic studies have found that offshore orcas are probably most closely related to residents. They're also similar to residents in their behavior and  general diet. Offshores appear to be fish eaters and live in very large pods, sometimes more than 100 whales strong. It's not clear if this is similar to the summer superpod that the southern residents get into once a year, or something else entirely. 

Where residents and offshores differ is in how far they'll travel, and exactly what kind of fish they eat. The same group of offshore orcas have been seen at Dutch Harbor in the Aleutian Islands, and Dana Point in California. That's 4,435km if the pod swam in a straight line, which it almost certainly didn't. In contrast the Southern Resident population only leaves the Salish Sea near Washington and British Columbia on occasion.

Courtesy: Dahlheim et Al. (2008), Marine Mammal Science 24(3)

We don't have a great idea of offshore killer whales' diets, but they seem to be less picky than residents. They've been seen attacking schools of baitfish, and beating blue sharks with their tails. They've also been found beached with salmon and halibut in their stomachs. Another piece of evidence has led some scientists to speculate that sharks are a major component of their diet. 

When offshore orcas wash up on beaches their teeth are frequently worn down almost to the gumline. Even young animals, whose teeth can't have eroded from age, show a lot of wear. Sharks have rough, sand-papery skin that could probably buff an orcas teeth down to the jaw if they eat them all the time. Offshores also have fewer tooth marks on their bodies from scrapping with other orcas, suggesting their teeth aren't very pointy for most of their lives.  

We've barely begun to scratch the surface of offshores' life history even though we've known about them since the 80's. In fact there's so much more to learn about all three ecotypes. Their behaviors and life styles are so different that they might even warrant being considered several species of orca. But for now, killer whales are a single group of highly intelligent, adaptable, long-lived, nomadic hunters, just like humans before agriculture and urbanization. Killer whales, they're like the humans of the sea!

Several ton, fish-eating, flippered, black and white, humans.

Courtesy: Putneypics via Flickr

References:

Dahlheim, Shulman-Janiger, Black, Ternullio, Ellefrit, & Balcomb, (2008) "Eastern Temperate North Pacific Offshore Killer Whales (Orcinus orca): Occurence, Movements, and Insights into Feeding Ecology", Marine Mammal Science 24(3): 719-729, doi: 10.1111/j.1748-7692.2008.00206.x

Accessed via: http://www.orcanetwork.org/nathist/offshoresdalheim.pdf

Dahlheim & White, (2010) "Ecological Aspects of Transient Killer Whales (Orcinus orca) as Predatorsin Southeastern Alaska", Wildlife Biology 16:308-322, doi: 10.2981/09-075

Accessed via: http://www.orcanetwork.org/nathist/Dahlheim2010.pdf

Ford MJ, Hempelmann J, Hanson MB, Ayers KL, Baird RW, Emmons CK, et Al., (2015) "Estimation of a Killer Whale (Orcinus orca) Population's Diet Using Sequencing of DNA from Feces", PLoS ONE, 11(1): e0144956, doi:10.1371/journal.pone.0144956

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144956

Riesch & Deecke, (2011), "Whistle Communication in Mammal-eating Killer Whales (Orcinus orca): Further Evidence for Acoustic Divergence Between Ecotypes". Behavioral Ecology sociobiology, 65: 1377-1387, doi: 10.1007/s00265-011-1148-8

"About Killer Whales", Center for Whale Research 

Accessed via: http://www.whaleresearch.com/#!about-orcas/c1qa8

 

Naut Again

Oh wow, there's some wonderful news that's come out of the US East coast recently that hasn't gotten the coverage it deser....

"NAUT SO FAST PUNK!"

Courtesy: DarTar via Wikimedia Commmons

Oh, god no, not this again. How many weeks am I going to have to go without getting interrupted by a cephalopod? What do you want chambered nautilus (Nautilus pompilius), and did you seriously just use your own name as a pun?

"I'll use my name however I want after you and that wannabe 

Greek hero besmirched it. She should be proud to be 

associated with us nautiluses."

Courtesy: Michael Bentley via Flickr

Alright, alright, I didn't mean to offend anyone. I wrote about argonauts last week since they're a cool family in their own right. I guess I didn't think about how little people know about your family too. Tell you what, I'll make this post all about you, if you promise to tell the other cephs to stop interrupting me. I don't want a ram's horn squid butting in next week.

"Alright deal, but I'm gonna stand here and make sure you do us justice"
Courtesy: OCVA via Flickr

Okay well, if we're gonna give this family the credit it deserves we need to talk about world domination. Don't worry, you needn't imagine a future where shelled overlords subjugate earth's other species, because it already happened. Nautiluses are old, very old, in fact their family members are the OG cephalopods. The first nautiluses to appear had straight shells, but around 400 million years ago they developed the familiar spiral we see today. They were so successful that they, and their cousins the ammonites, would go on to dominate the seas for eons. Nautilus even survived the worst extinction of all time which killed 96% of all life in the sea. Not too shabby for an animal that's essentially a fancy snail.

Even though they ruled the oceans for so long, the nautiluses eventually gave up their family's dynasty to live a life of quiet retirement. Today only two genera of nautilus exist, down from the 75 or so at their peak. Modern nautiluses are found only in the Indian and Pacific oceans in the deep waters at the steep edges of coral reefs. Yet they are some of the most fascinating organisms to occupy those spaces.

Of course what stands out most about nautilus is their incredible shells. Nautilus are the only cephalopod left to still have an exterior shell, which means they don't need all the gaudy color and texture changing flashiness of their cousins. Instead of hiding, speeding away, or out-thinking their predators nautilus prefer the simple life scavenging food off the bottom; and cruising through deeper water at times when predators are at rest.

They're kind of like that friend from college who moves to
 Idaho and starts a goat farm because "It's just easier."
Courtesy: Hans Hillewaert via Wikimedia Commons



Now you might notice that the nautilus' shell is pretty burly. There are hardly any animals with shells that thick that even bother swimming. Other heavily shelled mollusks like clams and snails spend most of their time on or in the ground. So what does the nautilus do that makes it able to hover up in the water like that? Are they just incredibly strong? Not really. When you watch a nautilus puff along by forcing water through its siphon, it kind of makes you want to hand it an inhaler and tell it to go sit on the bleachers. So if it's not pure herculean strength that keeps the nautilus afloat what is it? Well my friends, the nautilus succeeds thanks to the magic of good engineering.

I think like a third of our readers just found their spirit animal
Courtesy: Jason Westley Upton via Flickr

Inside the shell are the structures that put the "chambered" in chambered nautilus. The largest chamber is where the nautilus' mantle is housed, but the others are empty of everything except air and a little bit of water. When a new chamber forms the nautilus walls its previous space off and amazingly, drains the water. See if the chambers stayed filled then the nautilus would get dragged to the bottom thanks to the weight of the water inside the shell. Emptying water from the chambers has the same effect as if the nautilus were to tie balloons to its shell. The air inside pushes up towards the surface while the weight of the shell pulls down, and the two forces balance one another out to make the nautilus neither sink nor float.

You might be wondering: If the nautilus seals the chambers how does it get the water out? Well running through the chambers is a really cool organ with a really cool name, a siphuncle (pronounced: sigh-fun-kull). The siphuncle is a tube that uses water's own physical properties to fill and empty the chambers. See water has a tendency to try and balance the concentrations of different minerals dissolved in itself. So if you put a screen that will only let water through between two solutions and you make one much saltier than the other; the water will cross the screen to the salty side until the two sides' ratios of salt to water are equal. This is exactly what the siphuncle does. When the nautilus wants to remove water from the chambers it adds salt ions to the outer layer of the siphuncle and the water just seeps on out of the chamber. When the nautilus wants to add water to the chambers it does the opposite. This system requires basically no energy on the animal's part, so it's a great strategy for staying properly buoyant.

Who says functional machines can't be pretty? Those little struts in the center 
of each chamber hold the siphuncle in place as it runs through the shell.
Courtesy: Jitze Couperus via Flickr

Of course everyone focuses on the shell of the nautilus, so much so that these animals are being impacted by fisher people catching them for their shells. Many scientists and citizens who care a lot about nautilus are doing everything they can to show the international community that nautilus, not only deserve, but need our protection. The easiest way to do your part is to never buy new nautilus shells. Instead look around antique stores, or purchase nautilus fossils, which have the benefit of being infused with beautiful minerals from fossilization.

Aside from their shells, nautilus are also impressive thanks to over 90 tentacles! These tentacles are much simpler than the complex arms of the nautilus' cousins. They have no suckers and instead use a series of grooves to grip surfaces. They're also incredibly sensitive to scent/taste. As a scavenger nautiluses need to be very aware of where food is sitting, and all of those tentacles act like an array of antennas picking up the fishy signal of food rotting on the bottom.

Okay nautilus, was that a satisfying amount of information for you? We can always come back another week and learn more.

"Well that was better than naut. It'll do for now, and naut to worry,
you've naut seen the last of me."
Courtesy: David Remsen via Flickr

Ugh, the puns man, the puns...

References:

Dunstan, A., Ward, P., & Marshall, N., "Vertical Distribution and Migration Patterns of Nautilus pompilius", PLoS ONE 6(2): 16311, Feb. 2011.
Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0016311

Ward, Peter, "Cameral Liquid in Nautilus and Ammonites", Paleobiology, 5(1), 1979, pg. 40-49.
Accessed via: http://www.jstor.org.ezproxy.library.wwu.edu/stable/2400389?seq=1#page_scan_tab_contents

Crook, R., & Basil, J., "A Biphasic Memory Curve in the Chambered Nautilus, Nautilus pompilius L. (Cephalopoda: Nautiloidea)", Journal of Experimental Biology, June 15th 2008.
Accessed via: http://jeb.biologists.org/content/211/12/1992.long

Dunstan et al., "Nautilus pompilius Life History and Demographics at the Osprey Reef Seamount, Coral Sea, Australia" PLoS ONE, 6(2): e16312, Feb. 2011.
Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0016312

A Sea Lion Story

By now it's probably come across your computer screen at least once. The story may have even shown up in your physical paper. More than 1,800 California sea lion (Zalophus californianus) pups have shown up emaciated on the beaches of California since January. Unusual mortality events like this are most troubling to us because it's adorable baby animals that are suffering, so it's a good opportunity to draw awareness to ecosystem scale issues.

D'aww who's a good vector for a better understanding

 of ecology!? You are, yes you are!

Courtesy: Jaina via Flickr

So what do baby sea lions have to do with the ecosystem as a whole? Well ecosystems are all the living and non-living things in an area that interact with one another. This means that every piece in an ecosystem is significant to the others in some way. For example small fish are important to large predators, currents are important to plankton, and temperature is important to everyone. Each piece has direct effects on the others and those effects themselves interact.

On the surface (pun intended) starving sea lion pups seems to have a pretty straightforward cause. You would assume it's because there isn't enough of whatever it is sea lions eat. That's part of the story, but there's more to it. When baby seals and sea lions are first born they lack the thick blubber of their parents. Pups have to drink extremely rich milk to bulk up enough to survive on their own. California sea lion milk averages about 35% fat, that's about the same fat content as whipping cream, and about ten times the fat content of whole milk. Not only does the thick layer of blubber the pups develop help keep them warm it's important as an energy reserve when they first strike out on their own.

Despite what this sea lion seems to be telling you, Cronuts are not 

a viable source of energy reserves.

Courtesy: Makitani via Flickr

The most important prey for lactating mothers are anchovy, sardine, and hake. These fish live in large schools, so they're usually plentiful and they have extremely oily flesh; perfect producing rich milk. In the past there were very large fisheries for these species off of California. Think Cannery Row on Monterey Bay. However, we aren't taking too much of the sea lions' food away anymore because canned, oily fish have declined in popularity.

I can't imagine why...
Courtesy: dr.coop via Flickr

 What's happened is that for the last few years the waters around the Channel Islands, where the sea lions give birth, have been abnormally warm. Each of the fish the sea lions rely on are cold water species, in fact North Pacific anchovy won't go into water warmer than 62 degrees F. Since California's seas have been so warm the food fish have shifted themselves to colder waters. Sardines have been spawning farther offshore and other fish schools have moved north. These migrations have forced mother sea lions to hunt farther afield, and when their moms don't come back for extended periods of time, the pups set out on their own too early.

So where are the dad's in all this? Why don't we see adult males stranding in California? Well they're not there. Male and female sea lions both take on long migrations from British Columbia to California and back every year, but they have different schedules. Females head down to the breeding grounds first to give birth. Then males head down to meet up with the females once they're ready to mate again; about three weeks later. Being further north for longer has actually lead to boom times for male sea lions. At the mouth of the Columbia river between Washington State and Oregon more than ten times the usual number of males have been hanging out. They came in for this year's copious smelt run and are fattening up to make the trip south to the rookeries. Males need a lot of mass and energy reserves to defend territories on beaches which they won't leave and thus don't eat for several weeks.

   "I'll calm when I haven't gone twelve days without food!"
Courtesy: Bridget Samuels via Flickr

So that's the story. Warm water pooling at the surface has pushed forage fish away from the Channel Islands. This means that female California sea lions have to travel farther to find food that makes rich enough milk for their babies. These longer trips mean that many young are leaving the rookeries too early, and are washing up along the shore. All the while, farther north, males are enjoying a greater supply of food than ever. The biological needs of its inhabitants, and the physical characteristics of the ocean come together to tell the complex story of an ecosystem as long as a continent. We're able to discover the changes happening in the environment thanks to this single species.

Scientists aren't sure if the warming is caused by the changes happening to the global climate system, or if this is part of natural variations of the Pacific. Either way marine mammal stranding networks will need support in the near future. If you want to help one of the best things you can do is to remain informed about who's best prepared to help hungry or sick sea lion pups. There's a good list of organizations to contact and a lot of information here.

References:

"California Sea Lion (Zalophus Californianus)", NOAA Fisheries: Office of Protected Resources. Accessed via: http://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/californiasealion.htm

Bernton, Hal, "Boom Times on the Columbia for California Sea Lions", The Seattle Times, March 27th, 2015, Accessed via: http://www.seattletimes.com/seattle-news/boom-times-on-the-columbia-for-california-sea-lions/

"2013-2015 California Sea Lion Unusual Mortality Event in California", National Marine Fisheries Service Health and Stranding Reports,
Accessed via: http://www.nmfs.noaa.gov/pr/health/mmume/californiasealions2013.htm

Redman, Marianne, "The Pinnipeds: Seals, Sea Lions, and Walruses", pg 282, University of California Press, 1990.

Orr et al., 2011, "Intraspecific Comparison of Diet of California Sea Lions (Zalophus californianus) Assessed Using Fecal and Stable Isotope Analyses", Canadian Journal of Zoology, 89:109-122. 

Party Animals

Starting around this time every year, thousands flock to Florida's beaches with only one thing on their minds. They come from all along the Atlantic and the Gulf in droves to spend a few days getting wild with others they've barely met. That's right it's time for Spring B....eginning of loggerhead sea turtle nesting season.

What did you think I was talking about?

Courtesy: Daytona Spring Break via Flickr

Well actually spring break and loggerhead (Caretta caretta) nesting season don't match up perfectly. Thank god, can you imagine what kind of stuff a bunch of drunk bros would get up to with hundreds of sea turtles? Only the very first nesters come in during April, and the breeding season continues through the summer. Around the world's sub-tropical regions loggerheads return to the beaches they were born at to pass on their genes. The Southeast coast of the US hosts more loggerhead sea turtles than most other breeding regions around the world. Florida is especially important to these turtles. Ninety percent of all loggerheads born in the US nest in Florida.

Spring breakers and sea turtles have other things in common besides an intense urge to mate. They both have many stepped journeys that take them to the beaches of the southeast. After birth, young turtles head out to the open ocean and usually spend their first 5-7 years out at sea. It may seem a little odd for baby turtles to head out to the open ocean since there aren't a lot of places to hide, but there are far fewer predators out there. Plus the Atlantic has a unique region called the Sargasso sea which is named for its abundant floating fields of Sargassum (pronounced: sarj-ass-um) algae. Sargassum is perfect for little turtles because it's about the same color as they are and has a lot of spatial complexity for them to hide in. In these floating prairies, young loggerheads can grow fat on a diet of just about anything. Unlike other toddlers they aren't particularly picky and chow down on jellies, squid, shrimp, crabs, clams (even Tridacna), and fish. As they grow loggerheads rely on increasingly hearty prey so, like a college student raiding your fridge when he/she comes home for the summer, the turtles return to more abundant coastal waters to feed.

"Mom! Mom! You need to run to Costco again!"
Courtesy: rosepetal236 via Flickr


But how do the turtles find their way? Human college students have the benefit of Google maps and Expedia, but loggerheads' flippers make it hard to type. Instead sea turtles use the magnetic field of the earth to navigate. To understand how this works we need to know a little bit about the magnetic field itself.

Beneath the planet's mantle, but above the very center is a region called the outer core. The outer core is made of liquid iron mixtures and it moves around in loops thanks to the heat put out by the inner core. The conductive nature of the iron ensures that as the mixture moves around it generates electrical current, which in turn creates a magnetic field. The planet's magnetic field varies in several ways across the surface of the earth. It has an angle relative to the center of the planet that becomes steeper the closer you get to the poles. The magnetic field also varies in its strength changing along seemingly more random lines (It's weakest around South America and strongest around Siberia and the ocean south of Australia). If you can somehow detect these different lines of magnetism (called isolines) you can use them to figure out where you are on the planet, just like you would use lines of latitude and longitude.

"Stop asking me to pull over, I know exactly where we are."
Courtesy: Wendell Reed via Flickr

Amazingly scientists have enough behavioral evidence to confidently say that turtles navigate by detecting the earth's magnetic field, but don't have enough evidence to figure out exactly how they do it. The problem is it's easy to do experiments and scan data to see where turtles are going, but it's really hard to find possibly microscopic structures that sense magnetism. Perhaps the most compelling way animals might detect isolines is by having evenly spaced crystals of magnetite in their bodies. Magnetite is an iron mineral that has magnetic north and south poles, just like man made magnets. If a series of magnetite crystals is laid out in a line then they'll push away from each other when they're turned perpendicular to a magnetic field, but pull towards one another if they're lined up with it. Magnetite has been found in salmon, several species of birds, and sea turtles, all of which are highly migratory. Scientists think these animals might be able to gauge how much the crystals are pulling or pushing on one another to figure out how isolines are oriented.

Orienting themselves by magnetic fields is so important to loggerheads that they familiarize themselves with the unique magnetic coordinates of their home beach as they hatch. Then as the turtles return, if the isolines have shifted which they often do, the turtles will dig nests away from their birth place.

Despite their incredible abilities loggerheads are an endangered species. Their biggest threat is coastal development and negative interactions with humans since they prefer the same beaches we do. So for anyone out there planning a trip to Florida this spring break; remember that loggerhead turtles are there to have a good time too. If we treat each other with respect then humans and turtles can all have as much fun as this kid:

References:

Brothers, J. Roger, & Lohmann, Kenneth J., "Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles", Current Biology, Vol 25 Issue 3, 2015, DOI 10.1016/j.cub.2014.12.035. Accessed via:

http://www.cell.com/current-biology/fulltext/S0960-9822(14)01638-8

Lohmann, Kenneth J. & Johnson, Sonke, "The Neurobiology of Magnetoreception in Vertebrate Animals", Trends in Neuroscience, No. 23, 2000. Accessed via:

http://www.unc.edu/depts/geomag/PDFGeomag/TINSreview.pdf

The Earth's Magnetic Field, University of North Carolina's Oceanweb. Accessed via: http://www.unc.edu/depts/oceanweb/turtles/juvenilemap/EarthMF.html

"Caretta caretta, Loggerhead Sea Turtle"
The Encyclopedia of Life
Accessed via: http://eol.org/pages/1056566/details

A Clam for Ken Kesey

"That's a CLAM!?" This reaction to a particular animal is almost guaranteed when people look at them for the first time. Check it out.

Oh man, who just leaves a tie-dye shirt laying around on a coral reef?
Courtesy: Nick Hobgood via Flickr

Okay first off, that looks nothing like what belongs in my chowder. Second, this animal just goes to prove that the 60's got to everyone. So where does counter-culture clam come from and why's it so psychedelic? Editor's Note: This post is greatly improved when accompanied by Strawberry Alarm Clock's: Incense and Peppermints, or your own favorite psychedelic rock song.

Well what you're looking at is a Tridacna (pronounced: Tri-dack-na) clam. They're more commonly called giant clams, but I don't really like that name because not all of them are giant. In fact one species, Tridacna maxima, has the common name "small giant clam"; that's just silly so were gonna stick with their scientific name for this post. Anyway Tridacna don't look much like their relatives, but all the pieces are still there. They have heavy rippled shells like their cousins the cockles, and the part that you see sticking out is their mantle (the body of a mollusk) and their siphons (The channels clams use to feed and breathe). These combined anatomical parts are what make up the "meat" of the clam that we eat.

Plankton filled water flows into the hole on the right, and strained 
water flows out of the tube on the left.
Courtesy edgeplot via Flickr

Tridacna clams live on coral reefs in the tropical Western Pacific. Once they settle out from the plankton they spend their entire lives in that single spot. They don't dig into the ground, but instead let it all hang out. Truly these bivalves (animals with two shells) have gotten the hippy lifestyle down pat.

In fact it turns out that Tridacna's trippy colors and patterns are essential to its survival. The reason Tridacna don't dig into the sand is that they're part of a self sustaining commune. Just like the stony corals around them; these mollusks host symbiotic algae under their skin. In order for the algae to photosynthesize they need to be exposed to the sun. The hinge of the clam's shell is heavier than the opening, so it can tilt face up and spend the daylight hours with its skin spread out in the light. The algae get protection from consumers, and the clam gets nutrients without having to feed. Having a backup way to get your food is especially helpful on coral reefs because the water around them is usually lacking in plankton. Completely clear water is great for snorklers' ability to see, but not so great for filter feeders' ability to eat.

"Come on baby light my zooxanthellae" -Jim Molluskson
Courtesy: Eric Johnson via the NOAA Photo Library

Now as anyone who's forgotten sun screen on a tropical vacation can attest, the sun at the equator is incredibly strong. Solar radiation in the middle of the day is so intense that photosynthesis can actually decrease as the clam's symbiotic algae try to protect themselves from sun burn. But this is a collective man, and the clam does its part to help the algae function efficiently.

The algal cells under the clam's skin are arranged in stacked towers, which is confusing because that means the cells on top shade out those below them. To counter this Tridacna have their own cool cells called iridiocytes (pronounced: ear-id-ee-oh-sites) which bend light in different directions. The iridiocytes reflect yellow and green light (which aren't used by the algae) away from the stacks, and reflect blue and red light (which are useful) towards them. Essentially the iridiocytes screen out the best light for the algae, soften its intensity, and evenly distribute it across the stacks of cells.

The combination of colorful algae and reflected light come together to create the mind expanding visual experience of looking at a Tridacna's skin. Cameras can't really capture how magnificently colored these animals are, so I really encourage you all to take a trip to your local aquarium and see them for yourselves. But here's another picture to tide you over 'til then.

  Couretsy: Nick Hobgood via Flickr

References:

Holt et al., "Photsymbiotic giant clams are transformers of solar flux", Journal of the Royal Society Interface, Oct. 2014, DOI 10.1098/rsif.2014.0678 Accessed via:

http://rsif.royalsocietypublishing.org/content/11/101/20140678 

Soo, Pamela & Todd, Peter A., "The behaviour of giant clams (Bivalvia: Cardiidae: Tridacninae)", Marine Biology, 2014, DOI 10.1007/s00227-014-2545-0 Accessed via:

http://link.springer.com/article/10.1007/s00227-014-2545-0/fulltext.html