It’s sea otter awareness week, which seems like a great time to reveal something heroic about this charismatic animal. A recent study from UC Santa Cruz concluded that sea otters are helping to save the ocean—with their appetites.

When you think of sea otters, you may think “cute and cuddly,” but these playful marine mammals are top predators, like great white sharks and tigers, and their hunt for food is helping to maintain ecosystem health along portions of California’s coastline.

The sea otter’s role in ecosystem management begins with one of its preferred foods: crabs. Sea otters eat crabs. Crabs in turn eat sea slugs and small crustaceans. The slugs and crustaceans eat algae off sea plants, keeping them green and healthy. It’s a relatively typical food web but now it’s clear: The healthier the crab-eating otter population is, the healthier the plants tend to be.

Sea plants, like eelgrass, along the west coast are important habitat for fish such as Pacific herring, halibut and salmon. They also protect shorelines from storms and waves, and they soak up carbon dioxide from seawater and the atmosphere.  Thus, a healthy coastal ecosystem has the right mix of otters eating crabs and invertebrates eating algae.

Unfortunately, seagrass meadows have been declining worldwide, partly due to excessive nutrients from agricultural and urban runoff entering coastal waters.  When sewage and agricultural waste like fertilizers spill into the sea, ecosystems suffer. Excessive nitrogen and phosphorus in the water spawns excessive algae growth, which can block sunlight and limit plant growth. Coastal areas that would otherwise be swaying in seagrass and kelp turn brown, murky, and barren of important marine species. But, not when sea otters are around.

Brent Hughes from the University of California, Santa Cruz and his colleagues studied 50 years’ worth of data, comparing areas with or without otters. The team discovered that otters trigger the above ecological chain reaction that protects seagrass meadows and can stave off algal blooms.

“The seagrass is really green and thriving where there are lots of sea otters, even compared to seagrass in more pristine systems without excess nutrients,” Hughes says.

Sea otters were hunted to near extinction in the 19^th and 20^th centuries. Populations on the California coast are slowly recovering now, and one of those places otters have called home since the 1980s is Elkhorn Slough, an estuary in Monterey Bay. Hughes and his colleagues determined that the re-colonization of that estuary by sea otters has been an important factor in the seagrass comeback.

In Tomales Bay, a nearby inlet with far lower levels of incoming nutrients, but no otters, the beds don’t look nearly as good. Hughes told Ed Yong of National Geographic:

The seagrass looks relatively unhealthy: it’s brown, covered in algae, and slumped over. The crabs are four times more abundant and 30 percent bigger than they are in Elkhorn Slough.

The findings in Elkhorn Slough suggest that expansion of the sea otter population in California and re-colonization of other estuaries will likely be good for seagrass habitat—and coastal ecosystems—throughout the state.

“This provides us with another example of how the strong interactions exerted by sea otters on their invertebrate prey can have cascading effects, leading to unexpected but profound changes at the base of the food web,” Hughes says. “It’s also a great reminder that the apex predators that have largely disappeared from so many ecosystems may play vitally important functions.”

The study was published last month in the Proceedings of the National Academy of Sciences.

(Sea otters also play a heroic role in the next Academy planetarium show! Currently in production and set for a fall 2014 opening date, the latest production from our visualization studio will highlight complex relationships in ecosystems—and how humans fit into the picture.)

Jami Smith is a science geek-wannabe and volunteers for Science Today.

Image: Robert Scoles/NOAA

Welcome to Sea Otter Awareness Week! Started 11 years ago to increase the public’s awareness about sea otters, the event “is an annual recognition of the vital role that sea otters play in the nearshore ecosystem,” according to seaotterweek.org.

Tomorrow we will explore that vital role a little more; for today’s article, we checked in with Moe Flannery, from the Academy’s Ornithology and Mammalogy department, to better understand the health of local sea otters.

The US Geological Survey’s Western Ecological Research Center conducts annual population surveys of the southern sea otter (Enhydra lutris nereis), a federally listed threatened species found in California. Flannery says the southern sea otter’s range extends from Pigeon Point near Half Moon Bay down to Point Conception in Santa Barbara County.

This year’s USGS survey was released earlier this month and the news is cautiously optimistic: sea otter numbers are up, due largely to an increase in the number of pups.

In its 2013 report, the USGS estimates the population to be 2,941. For southern sea otters to be considered for removal from threatened species listing, the population estimate would have to exceed 3,090 for three consecutive years, according to the threshold established under the Southern Sea Otter Recovery Plan by the US Fish and Wildlife Service. The USGS has been conducting the population surveys since the 1980s.

“Population growth in central California has faltered recently, so the fact that we’re seeing a slightly positive trend is a basis for cautious optimism,” says Tim Tinker, a USGS biologist who supervises the annual survey. “Certainly, sea otters have made an impressive recovery in California since their rediscovery here in the 1930s.”

“We counted a record number of pups this year, which led to the uptick in the 3-year average,” says USGS biologist Brian Hatfield, coordinator of the annual survey. “A high pup count is always encouraging, although the number of adult otters counted along the mainland was almost identical to last year’s count, so we’ll have to wait and see if the positive trend continues.”

USGS scientists also annually update a database of sea otter strandings—the number of dead, sick or injured sea otters recovered along California’s coast each year. Flannery leads the Academy as one of the organizations that responds to these strandings as part of the national Marine Mammal Stranding Network.

This year’s stranding number was 368. Flannery says that a remarkable number of sea otters wash up with shark bites. “The shark populations have been increasing because elephant seal populations are increasing,” she says. “The sharks appear to take a bite of the sea otters, but don’t consume them. As bony, skinny and furry as sea otters are (with up to one million hairs per square inch!), they’re probably less desirable than fat, blubbery elephant seals.”

Sharks aren’t the only threat to sea otters. Mainland diseases, such as toxoplasmosis from cat fecal matter, also plague the animals.

Because of their threatened status, all sea otter necropsies (animal autopsies) are performed by the California Department of Fish and Wildlife. However, many of the specimens end up here, in the Academy’s collections. The result is that we have the largest collection of southern sea otter specimens in the world. The number was up to 1,300 specimens last year, but several hundred have yet to be cataloged and processed, according to Flannery.

Researchers come from all over the world to study the specimens—last year scientists from UC Davis came to study dental pathologies in 1200 sea otter skulls!  They found that 93% of our southern sea otter specimens had problems with their teeth.

Luckily, most of us don’t have to study 1200 sea otter skulls to learn more about these engaging animals. For events around Sea Otter Awareness Week, including this week’s Nightlife at the Academy, click here. Celebrate!

Image: Mike Baird/Wikipedia

Earlier this year, scientists announced the mother of all placental mammals. Their discovery wasn’t due to an unburied fossil, but rather a database called MorphoBank.

The researchers used both genetic and physical traits of known animals (living and extinct) to reconstruct this common ancestor that likely diversified after the extinction of dinosaurs 65 million years ago.

The scientists recorded observational traits for 86 placental mammal species, including 40 fossil species. The resulting database contains more than 12,000 images that correspond to more than 4,500 traits detailing characteristics like the presence or absence of wings, teeth and certain bones, type of hair cover and brain structures. The dataset is about 10 times larger than information used in previous studies of mammal relationships. On MorphoBank, this study is known as Project 773. And it’s just one of nearly a thousand such projects…

MorphoBank began over ten years ago as a partnership between several institutions to create a “web application providing an online database and workspace for evolutionary research, specifically systematics (the science of determining the evolutionary relationships among species),” according to its website.  The information is open to everyone and the framework provides access to computing power that scientists might not otherwise have.

Cassie Graff, the Early Childhood Program Lead here at the Academy, was an undergraduate at UC San Diego in 2009, when the San Diego Supercomputing Center (SDSC) was looking to beta test MorphoBank. The SDSC wanted to determine how actual researchers would use the application and reached out to their local colleagues.

Annalisa Berta, an evolutionary biologist at San Diego State University, was working on a long-term project to create a morphology matrix of whales at the time, and it seemed a perfect fit for MorphoBank. Berta and her team, which included Graff, entered several morphological characteristics of extinct and extant (living) whales into the database. Graff entered color patterns like streaks and saddles and flipper coloration as codes into the matrix. This work eventually became Project 182 on MorphoBank.

“The database includes not only morphological traits, but also can provide genetic data and images to create taxonomic trees,” Graff explains. “It can hold all of your research and later everyone can access it, anyone can download matrices.”

For a more recent project, MorphoBank approached Academy and UC Davis postdoc Hannah Wood. They asked about her recent publication on pelican spiders and wanted to make the morphological datasets within that article available. Generally these datasets appear as an appendix to a publication. “MorphoBank makes it much easier for other scientists to access the data,” says Wood. And it’s important that scientists have that access, she explains. Her co-author, the Academy’s Charles Griswold, agrees. “One could look at other, existing spiders to see similarities and identify a new find.” Their pelican spiders are Project 847 on MorphoBank.

As researchers work to revise and grow the tree of life, they need to build upon the work of scientists that came before—and leverage the work of their modern day colleagues. MorphoBank, along with similar applications, promises 21st-century solutions to studies that began centuries ago.

With the rate our world is changing and warming, there’s an urgency to cataloging and monitoring Earth’s diversity. Traditional efforts are often expensive and require many scientist- (and citizen scientist-) hours visiting remote lands that are often inaccessible.

But researchers are discovering other ways to monitor regional biodiversity and animal populations. Last year, Danish scientists found they could extract mammal DNA from leeches’ last blood meals. Now, German researchers are grabbing mammal DNA from widespread carrion flies.

Carrion flies (Calliphoridae and Sarcophagidae) feed on animal corpses, open wounds, and feces. While disgusting, the flies are widely distributed, found in diverse habitats and, perhaps most importantly, easy to catch. And since they don’t have acids in their guts like we do, scientists are able to retrieve viable DNA fragments from their stomachs.

For a recent study, published in the February 2013 issue of Molecular Ecology, the German scientists looked at carrion fly guts from two different forests—Taï National Park in Côte d’Ivoire, a rainforest, and the Kirindy Forest in Madagascar, a dry, deciduous forest. Among the mammals identified from the DNA fragments in the carrion flies were monkeys, lemurs, rodents, shrews, antelope, bats and even a hippopotamus. The DNA also revealed two bird species and one amphibian species.

Using deep sequencing technology, researchers are able to identify exact species, and hopefully at some point, they can glean information about population sizes and the spread of diseases.

The authors of the recent paper argue that with carrion flies and leeches performing their normal, albeit gross duties, perhaps scientists and conservationists can have entire armies of biodiversity monitors in the field.

Calliphora vomitoria image: JJ Harrison/Wikipedia

The findings may help explain why mammals evolved such large and complex brains, which in some cases ballooned 10 times larger than relative body size. The authors reconstructed fossils of two Early Jurassic Period small shrew-like pre-mammals – Morganuocodon and Hadrocodium—using a medical imaging technique called X-ray computed tomography or CT.

The 3D images gave the researchers a magnified, inside view of the brain and nasal cavities of the fossils. The team observed that the nasal cavity and related smell regions were enlarged in the pre-mammal fossils, along with areas of the brain that process olfactory information. Both characteristics indicate an improved sense of smell in pre-mammals.

“Now we have a much better idea of the historical sequence of events and of the relative importance of the different sensory systems in the early evolution of mammals. It paints a much more vivid picture of what the ancestral mammal was like and how it behaved, and of our own ancestry,” says lead author Tim Rowe, of the University of Texas.

In fact, comparing the mammal brain endocasts with fossils of other groups, like those of primitive reptiles called cynodonts, revealed that the brains of the Morganuocodon and the Hadrocodium were almost 50 percent larger than the brains of mammal precursors.

Nature News reports that

With this foundation in place, later mammals could have siphoned off some of those resources for colour vision, echolocation and even, in the case of the platypus, the ability to sense electric currents.

Rowe says this is just step one. “Now that we have a general picture of the brain in mammals ancestrally, we plan to explore the subsequent diversification of the brain and sensory systems as mammals evolved and diversified. This will unlock new secrets about how huge brains and extreme sensory adaptations evolved in mammals… It is all very exciting!”

Image: Matt Colbert, Univ. of Texas at Austin

Her latest study is three years in the making and a collaboration with a team of pale­on­tol­o­gists, evo­lu­tion­ary biol­o­gists and macro­e­col­o­gists from uni­ver­si­ties around the world.  The team studied the growth of mammal size after the dinosaurs went extinct around 65 million years ago and published their results last week in the journal Science.

Smith and her colleagues found that mam­mals grew from a max­i­mum of about 10 kilo­grams (22 pounds) when they shared the Earth with dinosaurs to a max­i­mum of 17 tons after­wards. They found that this pat­tern was sur­pris­ingly con­sis­tent glob­ally and across time and trophic groups and lin­eages—that is, ani­mals with dif­fer­ing diets and/or descended from dif­fer­ent ances­tors.

From the Observations blog in Scientific American:

But across all of the major continents, during the first 25 million years after the dinosaurs were wiped out, mammals underwent an explosive growth spurt. By 42 million years ago, however, the researchers found, the intense growth had leveled off.

What was the peak of land mammal growth? Indri­cotherium tran­souralicum was the largest mam­mal that ever walked the Earth. It was a horn­less rhinoceros-like her­bi­vore that weighed approx­i­mately 17 tons, stood about 18 feet high at the shoul­der and lived almost 34 mil­lion years ago.

The overall results give clues as to what sets the lim­its on max­i­mum body size on land — the amount of space avail­able to each ani­mal and the cli­mate they live in. The colder the cli­mate, the big­ger the mam­mals seem to get, as big­ger ani­mals con­serve heat bet­ter.  The results also show that no one group of mam­mals dom­i­nates the largest size class.

Size does matter, says Smith, “Under­stand­ing the con­straints oper­at­ing on size is cru­cial to under­stand­ing how ecosys­tems work.”

Image: Alison Boyer/Yale University

Often we try and gather clues from extinction events to get hints about our future, but perhaps we’ve been missing the forest for the trees. Now, a team of researchers from Stanford and UC Berkeley are looking at past biodiversity loss for clues.

“If we only focus on extinction, we are not getting the whole story,” said Jessica Blois, PhD, lead author of a study published online in Nature yesterday.

Focusing on the last major warming event about 12,000 years ago, Blois and her Stanford colleague Elizabeth Hadly searched the Samwell Cave near Mt. Shasta for small mammal fossils. They also sampled the modern small mammal community by doing some live trapping in the area of the cave. (Jenny McGuire, a graduate student at the UC Berkeley, did the radiocarbon dating of the samples.)

They found big changes in the small mammal population. “In the Pleistocene, there were about as many gophers as there were voles as there were deer mice,” Hadly said. “But as you move into the warming event, there is a really rapid reduction in how evenly these animals are distributed.” As some species such as deer mice flourished, many other species declined.

Deer mice are considered a “weedy” species and, like the plants, don’t have a strong habitat preference—they are generalists that will move in wherever there is an opening. When they replace other small-mammal species, the effects ripple through the ecosystem.

“Small mammals are so common, we often take them for granted,” Blois said. “But they play important roles within ecosystems, in soil aeration and seed dispersal, for example, and as prey for larger animals.” And different small mammals play those roles differently. What’s more, “Even though all of the species survived, small mammal communities as a whole lost a substantial amount of diversity, which may make them less resilient to future change,” Blois said.

And according to Hadly, an extraordinarily rapid change is looming.

“The temperature change over the next hundred years is expected to be greater than the temperature that most of the mammals that are on the landscape have yet witnessed as a species,” she said.

Creative Commons image by r.i.c.h.