Tag Archives: smithsonian

Now posting on PLoS blogs!

Good news everyone! I’ve been invited by Jean Flanagan and PLoS blogs to join their Sci-Ed team: a blog that focuses on science education. My contribution will be on science education in museums, zoos and aquaria. My first post is up:

It was my third time meandering the halls of the Natural History museum – and first as a volunteer interpreter – when I glimpsed a bird without arms: no wings, no arm bones, no hands, no wrists, and no fingers. Nothing. That skeleton I was seeing had once been a statuesque, NBA player-tall bird. Its neck accounted for nearly half its height; its slender legs, almost the rest, with a globular region in between. That was my first sighting of a moa.

Moa (Smithsonian Natural History Museum). Photo by the author.

The moa is a gigantic extinct flightless bird from New Zealand. Imagine an ostrich, but delete the wings and give it some serious growth hormones. This 12 ft tall, 500 lbs bird was driven to extinction in the early 13th century, when humans hunted and ate them all.

Continue reading after the jump…

For the bio- and anthropologically-curious, I’ll post more info on the moa next week!

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Animal Kingdom’s Halloween – part II

Wolf Crystal cautiously examines her Halloween treat. Photo credit: Smithsonian’s National Zoo.

Recently I’ve started volunteering at the Smithsonian’s National Zoo. The new American Trail exhibit opened last Summer, and expecting a flurry of visitors, the Zoo asked for extra help. The goal of American Trail, as one might expect, is to portray animals native to the US,  like beavers, ravens, sea lions, river otters, a bald eagle, and (my favorite) grey wolves.

Last week, American Trail  celebrated its first Halloween. Meanwhile, I was part of  the Boo at the Zoo event, but this time from a different point of view – zoo staff, instead of a visitor. I chose to talk about the bald eagle to a score of power rangers, princesses, iron men, and Marios – who also lined up for my newly-invented “are you a seal or a sea lion?” game.

From my booth in the Zoo’s main path, I could hear the sea lions barking. Where they responding to the children’s philosophical conundrum of “trick or treat”?

Sea lion Sophie has a treat and a toy at the same time. Photo credit: Smithsonian’s National Zoo.

Instead, they were busy investigating their own Halloween treats. A collection of photos of the animals and their pumpkins has been posted to the zoo’s Facebook page. Besides being cute and hilarious, the Halloween treats serve the important purpose of enrichment. I’ve talked about this strategy on the blog before, which is an attempt to encourage natural behaviors in captive animals (and some might say, to avoid boredom). Animals will fall back to behaviors they display in the wild, like hunting or scavenging. They exercise their curiosity by investigating the treat (some, like Sophie above and raven Iris, event get a lot of play out of it). Mental abilities are tested as the animals figure out how to open the pumpkin to retrieve the goodies inside.

Selkie feasts on squid she found inside her pumpkin. Photo credit: Smithsonian’s National Zoo.

Grey wolves Crystal and Coby got their share of treats. They were able to scavenge for meat hidden inside their pumpkins. It is only after Hurricane Sandy left that I can reflect on those events – specially considering DC and the National Zoo came out of it mostly unscathed. But in pre-hurricane times, people’s minds were filled with Halloween. And, with the risk of anthropomorphizing, I believe both animals and infant humans had a great time.

Animal Kingdom’s Halloween – part I

Vampire bat. Photo credit: Barry Mansell/naturepl.com via NewScientist

Last week I wrote a short piece about bats, which was published on my employer’s website. I was inspired by Halloween, but mainly I wished to talk about something dear to my heart: anticoagulants.

Most of my master’s dissertation revolved around mosquito molecules and the design of anti-clotting drugs. Mosquitos and bats do have a lot in common. You get a Halloween treat if you guessed its because both have a blood-based diet. Below is an excerpt (property of Owen Software) of the post I wrote for work:

The bad reputation of bats stems from their blood-filled diet, even though the vast majority of bat species eat insects or fruit. Out of more than a thousand species, only one drinks blood from other mammals: the aptly named “common vampire bat” (Desmodus rotundus), which preys on cows, pigs, or horses. But did you know these blood-sucking creatures can help scientists design new drugs?
Medical conditions like heart disease and stroke are caused when blood flow is interrupted, in many cases because of a blood clot lodged in an artery. Blood coagulation (or clotting) is a natural process in which blood clots plug wounds and help us recover from injuries and even prevent us from bleeding to death. One way to slow down the clotting process in stroke patients is to dose them with a class of molecules called anticoagulants. Besides halting coagulation, these molecules also dissolve the clot and boost blood flow.
Given the vampire bat’s need for blood, it might seem counterintuitive that those animals can be a source of drugs for heart disease and stroke. Through the course of evolution, vampire bats have developed their own natural anticoagulants. Their saliva is full of anticoagulant molecules that prevent their host’s blood from clotting and allow the bat to drink it. This ingenious feeding solution is not a novelty: in the animal kingdom, many other parasitic species have developed similar mechanisms (e.g, mosquitos, leeches, and ticks). Molecules from the bat’s saliva are the inspiration for new anti-stroke drugs. (…) Fittingly, scientists have paid homage to Halloween when choosing a name for a bat anticoagulant: they called it draculin.
I hope you enjoyed that cross-over of work post into my hobby blog.
Now that hurricane Sandy is gone, a mostly-unaffected Washington DC starts to celebrate Halloween. And that includes the National Zoo and its animals. On Part II of Animal Halloween I will talk about pumpkins treats as enrichments and of my participation on Boo at the Zoo.

Zebra piñatas and shrimp popsicles: keeping animals busy at the Zoo

Lioness attacks a zebra piñata. Photo credit.

It was graduation day at the Seattle Aquarium when I first heard of animal enrichment. I had been training for about two months before starting weekly shifts as an interpreter at the invertebrate tanks. My class was composed of about 60 other biologists, naturalists, teachers, and divers. As a treat – both for us and for the animals – after completing our training, we were taken to the sea otter tank. We watched from behind the glass as one of the Aquarium workers brought up a tall ladder – the same ladder which would later become my best friend in Aquarium activities. The Aquarium keeper also brought it a big iced bucket. Holding on to it, bucket and ladder, the she climbed up to a point where she was above the tank, dangling over the water. The three sea otters reconvened at the sight, and starting rolling around in the water as they waited for their precious bucket. This was an enrichment session.

Sea otter and his shrimpsicle. Photo: Seattle Aquarium.

“Enrichment” is a way a Zoo can save their animals from cabin fever. It is the equivalent of Internet or Facebook for a freelancer stuck in his studio apartment during a snow storm. It is distraction, curiosity, and novelty. It offers animals a chance to explore and behave like they would in the wild: forage for food, or hunt for prey (more on this later).

The sea otters got a bucket containing a plastic toy, which had been filled with water and frozen. Toy popsicle, or toysicle (they also get fishsicles and shrimpsicles). The entire frozen contraption is then tossed to the animals so they can play and exercise their mental abilities – or simply to find out what is inside. It reminded me of those dog toys with a treat inside – the dog has to chew, tinker, roll, and play with it, until the treat is released. Torture? We torture ourselves working through puzzles or, you know, curing cancer.

Preparing toysicles. Photo credit: Seattle Aquarium.

Turns out the “frozen bucket of something” is a common practice in Zoos and Aquariums. This “popsicle” can be made of frozen fruits for monkeys or pandas, or seafood for otters. For feline carnivores like lions, Sarah Putnan of the Smithosnina Zoo has designed the quail-pop or quailsicle: a quail is placed inside a bucket with its legs sticking out, filled with water, and frozen.

Jaguar unlocks the secrets to the meat hidden inside the blue container. Photo credit: Houston Zoo.

But frozen buckets are not the only enrichment option. The giant octopus I used to feed (atop the giant ladder mentioned above) at the Seattle Aquarium enjoyed playing with an empty peanut butter jar (Youtube is full of examples). Unscrewing the lid is sudoku for molluscs. At the National Zoo, apes play with towels, pandas interact with burlap sacks, lions shred cardboard boxes (really) and chew on horsetails (the National Zoo has a facebook photo set with some animals and their popsicles and towels). Animals can also “attack” too: small felines will hunt for small goldfish the keepers place in their ponds . Sounds like a busy life.

African wild dogs also enjoy zebra pinatas. Where can I order one? Photo credit: Houston Zoo.

But what my colleagues and I got that day at the aquarium was also “human”enrichment – the chance to meet the animals and get to learn about their personalities. Back then they were just “the otters”. Only later I would start distinguishing them – one male and two females – and calling each one by their names (the Alaskan Aadas, Lootas, and Aniak, which was recently joined by pup Sekiu). Even river and sea otters looked alike before I started interpreting. Now I don’t understand how I could have been so blind: they are worlds apart, like a human and a chimp.

Dire Wolves on Ice

Ghost – a Game of Thrones dire wolf (HBO).

Game of Thrones fans, rejoice: the dire wolf is real. Here’s the bad news: the dire wolf went extinct 10.000 years ago. The enormous beasts who roamed the ice wasteland beyond The Wall are based on a real North American animal, who in turn left behind thousands of fossils. I have to admit that the dire wolf Ghost and his pack are the main reason why I continue to watch that show.

Ford in a snow quasi-wasteland.

The dire wolf is a close relative of the grey wolf and also (drum roll) of the dog. Meet my toned-down version of the dire wolf: Ford. Like Ghost, my dog also loves snowy wastelands. Ford is the only canine in a small pack of three (the two other members are human beings), where I am pack leader (or at least I like to think I am). That means Ford will obey me when I tell him not to chase that delicious squirrel or pounce on that fatty pigeon.

Ford.

Ford weighs around 60 lbs, which is about half the size of a large dire wolf. Large wolves could reach 175 lbs, and the ones featured on Game of Thrones were as big as a horse (fictional wolves don’t count: they had magical powers; the evidence of magical powers has not been found in fossils yet). If Ford was a dire wolf 10.000 years ago, he would have probably hunted on a pack with 30 other buddies, and something tells me this group would not be after squirrels or pigeons. Instead, dire wolves hunted for mammoths. 

A fantastic wall of thousands of dire wolf skulls. Photo by the Page Museum.

A wall of skulls

The Rancho de La Brea, in Los Angeles, is fossil site where thousands of prehistoric ice age animals were entrapped, their bones perfectly preserved in tar. In this tar pit, fossil bones of 3600 dire wolves were found. This is the largest amount of a predator specimens ever found in one site, and it way outnumbers all other mammals found in the same site. Saber-toothed cats are next on the list, but not nearly as numerous (“only” about 2000 are found on the tar pits). Much fewer prey animals were found, about 200 horses and 300 bison, which means there’s a ratio of ten predators to each prey.

What happened here? It seems one unlucky prey animal – say, a bison – would fall in the pit and become trapped. Right after, packs of dire wolves and saber-toothed cats would believe it an easy meal and jump in. Result: prey and predator – specifically one prey and dozens of predators – die together.

Today, the Page Museum displays finds from the tar pits (including an impressive wall of dire wolf skulls). Fossils are so numerous that the Page Museum recruits and trains volunteers to help with the ongoing excavations (volunteer finds are posted on the museum’s blog).

Dire wolf artistic depiction by Mauricio Anton.

Lions, tigers, and bears, oh my! (Or: the hunting habits of carnivore predators)

Before they went extinct, the dire wolf and the saber-toothed cat were as dominant predators as the lion and hyena are today in Africa. The high number of skeletons found on the tar pits suggested they (both dire wolves and saber-tooth) hunted in large packs and were able to tackle enormous prey – bison and camels, but also mammoths, mastodons, ground sloths, and Irish elk. Carnivores weighing more than 46lbs need to eat prey that is as large or larger than themselves. Those predators cannot survive only on small prey, because they would spend a disproportionally higher amount of energy hunting the prey than they would get by eating it. So, the efficient way to eat is to hunt for large prey. The devised strategy adopted by many carnivores is to form a pack. Grey wolves exhaust the prey, but lions or dire wolves, who are larger and more stockish, pounce and grab them.

From left to right: dire wolf, saber-toothed cat, short-faced bear, cheetah-like cat (Miracinonyx sp.), American lion. (Modified from Turner, A., and Anton, M., The Big Cats and Their Fossil Relatives. Columbia University Press: New York, 1997)

Extinction

The dire wolf’s cousin, the grey wolf, is now considered a top North American predator. But the grey only reached this post after many large carnivores went extinct. Both the grey wolf and the dire wolf co-existed with 10 other species of large carnivore: the puma, jaguar, two species of short-faced bear, florida-spectackled bear, black bear, scimitar-toothed cat, saber-toothed cat, grizzly bear, and the American lion. All 12 carnivores competed for similar prey. Most of those predators became extinct 10.000 years ago (ever wondered why there are no lions, tigers, or elephants in the US? Because they died off after climate change or food depletion). Now only the puma, black bear, and grizzly bear remain.

Compared to the grey wolf, dire wolves had shorter stouter legs and smaller brain cases. They also had stronger teeth, comparable to a hyena’s in its bone-crunching abilities (which probably means food was scarce and every bit of bone marrow was precious). Dire wolf teeth is more adapted for “carnivority”, which means they are not as versatile in eating alternatives (other carnivores, like bears, will eat even bugs and honey). All of that contributed to their demise.

Ford looks at his extinct canid relatives.

Survival of the coldest

But here’s a fact Game of Thrones did not tell us: dire wolves were creatures of warm weather! They preferred tropical or subtropical regions. One of the reasons the grey wolves survived and dire wolves didn’t is because the grey wolf’s hunting range extended to the cold arctic. During the Ice Age, the dire wolf was left behind, to die and disappear.

But I guess the appeal of a beast of the tropics does not suit Game of Thrones. Ford, for once, prefers snow and cold, and becomes very depressed on the summer. Instead of the dire wolf, Ford would have fit in perfectly in Winterfell.

Got lactase?

(Ms Felicia Gomez and Dr. Jibril Hirbo give a talk at the Smithsonian's Human Origins Topic. Photo by the author.)

The human is the only mammal who continues to drink milk throughout adulthood. Most mammals completely loose the ability to digest milk after weaned, a gradual process that starts as early as 16 weeks. Humans can normally digest milk for the first 5-7 years of life, but after that, lactose digestion is slowly lost, and most people become what we know as lactose intolerant. In fact, the majority of the world is lactose intolerant, to various degrees; not surprisingly, considering this is the norm in most mammals. Then why are some humans able to consume milk and drool over ice creams, butter and cheeses?

Lactose intolerance has someone else to blame: lactase!

Lactose is the main sugar present in milk. As a rule of thumb, sugars are carbohydrates whose names end in “ose” (think  glucose, fructose, galactose, lactose). The enzyme lactase  – where “ase” endings indicate an enzyme name – works as a little molecular engine, breaking down lactose into smaller pieces: glucose and galactose. Lactase is abundant in infant mammals, but much less present in adults. The deficiency of this breaking down enzyme results in lactose malabsorption and is the cause of lactose intolerance.

However, in many population groups where milk is a key dietary source, humans adapted and continue to digest lactose after adulthood. This trait is named “lactase persistence”, and I guess you could say it is the opposite of lactose intolerance.

(Pockets of lactase persistence shown in pie charts. Ingram et al, Hum Genet 124:579–591, 2009)

Lactase persistence is well know in Europeans

Lactase persistence has evolved independently in several population groups around the world. It is assumed the environmental pressures drove adaptation in pastoral communities who rely heavily on milk products for nutrition and even for a water source. In other words, if a population is required to consume milk derivatives, given time its DNA could adapt to process it. And have done so, a few times and in different places of the world.

(Two groups that have independly adapted to lactose digestion: the swiss and the masai. Photo credit: the evolution group at Berkley)

I first got interested in this topic after I participated on the “Human Origins Topic” at the Smithsonian, where Dr. Jibril Hirbo and Felicia Gomez, from the Sarah Tishkoff group, talked about their work (see top photo). They collect DNA samples from many african populations and track down differences in DNA sequences of specific genes. A single DNA nucleotide base change is named SNP, for Single-nucleotide polymorphism (pronounced as “snip”), and Tishkoff’s group has been cataloging SNPs for lactase persistence in african populations.

Lactase persistence in europeans is well known and documented, and is caused by the SNP C/T-13910 (the numbers represent the position in the gene where the DNA change occurs). 90% of northern europe (specially in Sweden and Denmark) is lactase persistence, and ~50% of southern europe (Spain, French).

The cause for lactase persistence in african populations was still unknown, and was studied by Tishkoff, whose findings were published in the  “Convergent adaptation of human lactase persistence in Africa and Europe“.

(photo from the evolution group at Berkley)

Capturing SNPs in remote african locations

In order to detect SNPs associated with lactase persistence, Tishkoff’s group collected and sequenced DNA from 470 individuals from 43 african ethnic groups (Tanzanias, Kenyans and Sudanese). A majority of this collection work was done by Dr. Jibril Hirbo, who explained his approach:

“The biggest challenge was to get to communities we intended to sample because of poor infrastructure. Once we got to our destination we usually approached the community leaders and talk to them about our research, then the leaders organize something like a ‘townhall” meeting where we explain our research to the villagers  and make sure they understand what we were doing. It was easy talking to the people because I spoke the local language and know the cultures…so I just broke it down to them in the way they could understand.”

The test – named LTT for lactose tolerance test – is very straightforward, as Dr. Hirbo points out:

“The sampling was in two part – initial blood/saliva collections for the study of genetic variation of human population and second lactose tolerance test that involved drinking the orange solution that contain lactose sugar that is found in glass of milk followed by monitoring blood glucose level in blood drops from finger prick over one hour period.”

The DNA collected from the saliva is brought to lab, and sequenced, to identify SNPs correlated to the lactase persistent populations. The correlation between SNP and phenotype (the presence of lactase persistence) can be obtained by matching the DNA with the results from the LTT.

They found that each population group has a different mutation that resulted in lactase persistence. None have the european SNP (C/T-13910), and instead, each of the tested african groups displayed unique SNPs (G/C-14010, T/G-13915 and C/G-13907).

This is a clear case of convergent evolution: where 4 distinct variants correlated with lactase persistence independently arose in the world. These genetic variation was associated with pastoral groups and its migrations. Tishkoff’s group even goes further to say that the pattern of genetic distribution might match the cultural and linguistic distribution in Africa.

(Scheinfeldta et al, PNAS vol. 107 no. Supplement 2 8931-8938, 2010)

Can we safely conclude that the genetic spread accompanies culture? Pastoral, ethnic, and lactase persistent groups appear to indicate that.

Forensic Friday

Forensic Fridays, phot by the author

I stopped by the Smithsonian National Museum of Natural History for Forensic Friday, where I talked to paleobiologist David Bohaska. He showed me 6 million year old fossilized vertebra from whales and dolphins. Last Friday’s theme was “Marine debris & ocean life”, and the scientists brought in a few marine mammals (whale, dolphin and manatee) bones, used to speculate the animal’s cause of death. I photographed the bones and injury sites, but I’m not sure yet if I  am allowed to publish the images. The fossils are part of off-the-shelf collections, not available to the general public, so I will need to clear it with the Smithsonian first. Regardless of publishing the photos, I can’t wait to share the stories I heard about those animals lives…