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Tuesday, March 22, 2011

For Sea Turtles, Feeling Excluded is a Good Thing!

Life as a sea turtle can be rough.  Not only do you sometimes have to migrate hundreds to thousands of miles to reproduce, sometimes you get caught in commercial fishing nets and drown. Ungh.

Hopefully your good friend TED will help you out with that.  Not Ted Nugent.  While I am sure sea turtles like "Cat Scratch Fever" as much as the next species, when they find themselves swept up in a fishing net, they can escape through a Turtle Excluder Device. Oh, that TED!

As Lekelia Jenkins writes in today's New York Times Scientist at Work blog, a Turtle Excluder solves what would seem like an insurmountable problem: creating a hole in the net big enough for a huge turtle to pass through but that prevents the escape of smaller critters like shrimp.  The solution is actually quite simple: cover the hole with a trapdoor flap of netting that can only be opened by something heavy (like a sea turtle) but not something small (like fish or shrimp).  Check it out:

Happy World Water Day!

In other news, Knut, arguably the world's most famous polar bear, died today at the age of four.  He became famous as a cub because his mother rejected him and he was successfully hand-reared by a human.  Among his accomplishments: sharing the cover of Vanity Fair with Leo DiCaprio.  RIP Cute Knut.

Saturday, March 19, 2011

Female Promiscuity: Darwin's Benefit of the Doubt

If you have been following this blog, female philandering in various animal species should come as no surprise to you.  (If you have not been reading along but are interested, check this out. Or this.) 

However, a new book by scientist and author Tim Birkhead illustrates how the greatest naturalist of all time got it wrong.  And how generations of scientists also got it wrong as a result.

In his book, The Wisdom of Birds: An Illustrated History of Ornithology, Dr. Birkhead discusses one of the biggest misconceptions in the study of animal behavior: that female songbirds are sexually monogamous.  Most songbird species are socially monogamous, forming pair bonds in which one male and one female cooperate to raise offspring.  But it wasn't until the last decade or so that we could determine with DNA fingerprinting that the male in the pair is not always (quite often not!) the genetic father of the chicks in the nest. 

Mommy's babies are daddy's maybes.

So perhaps Charles Darwin can be forgiven for assuming that social monogamy is the same thing as sexual monogamy among songbirds when he wrote The Descent of Man, and Selection in Relation to Sex.  After all, Mr. Darwin knew nothing of DNA or genes.  Despite being a contemporary of Gregor Mendel, he missed the boat on the principles of inheritance we take for granted today.

Dr. Birkhead argues that Mr. Darwin should have known better.  After all, he observed it himself!  Darwin, like many gentlemen of his day, was a breeder of doves and therefore surely observed the occasional dalliance by pair-bonded females.  He knew about female promiscuity among thief pigeons - in which females were known to abandon a mate in favor of setting up shop with a sexier male. 

Dr. Birkhead discusses additional examples of female promiscuity described by Mr. Darwin and then addresses the question: Why, in the face of evidence to the contrary, did Darwin conclude that only males were evolving promiscuity under sexual selection?

Interestingly, it may have been due to his Victorian sensibilities: it was simply impolite to discuss such a scandalous notion as female philandering.  To compound matters, his daughter was his editorial assistant and he may have been uncomfortable sharing such conclusions with her.

Whatever Darwin's reasons, Dr. Birkhead argues that generations of scientists - including such ornithological  heavyweights as David Lack - went on to largely dismiss female promiscuity in birds because Mr. Darwin said it was unimportant!

I teach a course on Evolutionary Biology every academic year.  One of the first lessons in the class is that uncritical acceptance of any theory or idea is bad practice for a scientist.  That even though I consider Mr. Darwin's theories about natural and sexual selection to be powerful and well-tested ideas, as a scientist I must be among the most skeptical of them.

Dr. Birkhead's book is an excellent splash of cold water in the faces of uncritical scientists.  I believe it will make an excellent addition to my course reading list.

Thursday, March 17, 2011

What is the most common predator in North America? Thufferin' Thuccotash!

If I was a contestant on Jeopardy, I probably would have guessed "What is Homo sapiens?" 

But as Laura Tangley reports in her blog, The Wildlife Society announced on Tuesday that the domestic cat, Felis catus, is the most bloodthirsty of killers these days.  It seems there as many as 157 million cats running loose in the United States.

Wait. Read that again: 157 million cats running loose!

Maybe it is because they do not compete with us for the kind of prey found at Dunkin' Donuts that most of us have failed to notice the body count these legions of carnivores have racked up.  According to The Wildlife Society, they are racking one up to the tune of one million birds per day and up to a billion birds per year.

Assuming there are four and twenty blackbirds baked in a pie that adds up to about 41,666,666.66 sixpence per year.  Quite the butcher's bill. 

Folks, one-third of the birds in North America are threatened or endangered.  Keep kitty inside.

Friday, March 11, 2011

Why do they eat poop? The answer might save your life!

Anyone who has ever kept a pet rabbit has seen Mister Hoppypants gobble up feces like it was Cocoa Puffs.  Bunnies like poop!  So do hamsters, guinea pigs, and koalas.  Gorillas, elephants, hippopotamus.  Puppies.  Terrestrial isopods.  Chimpanzees.  The list goes on and on.  Animals have a culinary craving for kaka!

Assuming that you do not occasionally sample your own stool, news of this phenomenon may be somewhat hard to swallow. (ba-dum-bump)  There are, however, a number of good reasons why it makes biological sense.

For herbivores that (lacking the enzyme to break down plant cell walls) are unable to completely digest food the first time around, re-eating food as feces gives the digestive system more time to break it down.  It may also help the animal reclaim limiting vitamins and nutrients.  It might remove cues that a predator could use to find the pooper.

Or, as Nicola Jones writes for Nature.com, eating fecal material might prevent pathogens from killing you.

According to a study presented by Brett Finlay (University of British Columbia) at the International Human Microbiome Conference, mice that ingested particular kinds of poo were far more likely to survive exposure to gut pathogenic bacteria.  The experimental design was straightforward: one strain of mice was resistant and a second strain susceptible to Citrobacter rodentium (the pathogenic bacterium).  Dr. Finlay killed all the bacteria in the susceptible mice with antibiotics and then fed them feces from resistant mice.  The resistance was thereby transferred and most of the recipients survived.  The key appears to be that other bacteria living in the guts of resistant mice prevent the pathogen from doing damage.

While this approach is new, it nonetheless may not come as much surprise to the medical community. After all, they have been performing fecal transfusions for years.

What?  You've never had a fecal transfusion?

For some forms of colitis, medical practitioners will administer enemas of gut bacteria from the feces of close relatives to the patient.  A 2003 study published in the journal Clinical Infectious Diseases by Johannes Aas and colleagues found that most patients treated with donor stool survived diarrhea and colitis associated with the bacterium Clostridium difficile.  They further reported that "no adverse effects associated with stool treatment were observed."

That's good, because just reading about how the enemas were prepared using household blenders and coffee filters had an adverse effect on me.

And I think I will skip that bowl of Cocoa Puffs this morning.

To read more, visit Nature.com:


Wednesday, March 9, 2011

Why don't humans have spines on their penises? Ask a chimpanzee!

Yes, you read the title correctly. Other primates have spiny penises, including our closest cousins. The question is: why don't we?

Several theories have been proposed to account for penis spines in those species that have them. It is possible (as with the earwigs I wrote about recently) that penis spines serve to remove sperm left by other suitors that previously copulated with a female. Another theory is that the spines injure the female during copulation, ensuring that she will not be in the mood for sex again for a while - long enough, at least, that competitor sperm arrives too late.

Whatever the reason spines grow from the penises of other species, they decidedly do not grow there in humans. No doubt this comes as quite a relief to many of my female readers.

We may not know exactly why our species dropped this peculiar prickly penile adaptation, but thanks to the work of McLean and colleagues at Stanford University (published today in Nature) we know how we dropped it.  We lost some of our DNA.

McLean and colleagues (including Gill Bejerano and David Kingsley) used a novel - and very clever - method of analyzing the DNA of chimpanzees and humans. Rather than looking for similarities (as many studies do), McLean et al. looked at the differences. They found more than 500 regions present in the chimpanzee genome that is missing in humans.

One of the sequences missing in humans is located near the Androgen Receptor gene in chimpanzees.  When the sequence was inserted into mice, embryos developed penis spines.  They also developed sensory whiskers - another trait that our ancestors dropped sometime after we shared a common ancestor with chimpanzees.

The missing sequence in humans appears to be a developmental switch: something that turns on genes for particular traits (such as spines or whiskers). Lose the switch, lose the trait.

The correlation between these two traits is interesting: Perhaps we lost our whiskers because of selection against penis spines? Or did we lose our penis spines because of selection against whiskers?  Some have argued that loss of penis spines accompanied our foray into monogamy. I have always been suspicious of this theory, though, because human cultures are not all socially monogamous and there is plenty of philandering in those that are.

As much as we men like to think everything revolves around our genitals, perhaps it revolves more around our whiskers! (or lack thereof)

Tuesday, March 8, 2011

60 year old albatross hatches chick. Talk about stamina!

Photo Credit: John Klavitter, U.S. Fish & Wildlife Service

Her name is Wisdom and she certainly knows something about life.  Not only is Wisdom the oldest wild bird in North America, she's also perhaps the oldest mother.  At sixty years of age, Wisdom successfully hatched a chick, according to the US Fish and Wildlife Service.

And this is hardly an anomaly.  She is known to have successfully reproduced for at least the last several years and has more than 30 chicks under her belt total.

To put this in perspective, elephants can live up to 70 years (the oldest I am aware of died at age 82) and giant tortoises around 100 (although some have been reported to break 175).  Other Methuselah species include sturgeon (100+ years) and crocodiles (70+ years).

But for a bird, Wisdom is off the charts.  In 1986, according to Dr. M. Kathleen Klimkiewicz of the Bird Banding Laboratory (USFWS), the longest lived bird was another albatross that clocked in at 37 years and 5 months.  And even THAT was an old-timer for a bird.  Most avian species live between 3 to 20 years.

Because most of us are far more familiar with dogs than albatrosses, I will leave you with one final frame of reference.  The American Kennel Club will not register pups from females breeding past the age of 12 years.  Wisdom has our dogs beat almost six times over!

Monday, March 7, 2011

The Sperm Queen passes away: RIP JoGayle Howard

Photo Credit: Smithsonian National Zoological Park

Dr. JoGayle Howard, well-known for her ability to help even the most not-in-the-mood endangered species breed in captivity, passed away Saturday at the age of 59.  She is perhaps best known for  her role in the birth of giant panda cub Tai Shan at the National Zoo in 2005.  She also played a critical role in captive breeding of the highly endangered clouded leopard and black-footed ferret.

As a theriogenologist (drop that one in conversation to impress your friends), Dr. Howard pioneered techniques in sperm cryopreservation, sperm processing and laparoscopic artificial insemination.

From Smithsonian.com:

"Howard, the subject of the upcoming Smithsonian Channel program Nature’s Matchmaker, pioneered new techniques in animal reproduction. She achieved “countless breakthroughs, trained hundreds of students and foreign colleagues and played an instrumental role in saving species,” reports the National Zoo, where Howard worked for three decades. Howard’s reputation as an animal matchmaker and reproductive sleuth, solving the difficult issues of breeding endangered species, garnered her the sobriquet, “Sperm Queen,” a nickname she relished."

Sperm Queen?  Perhaps she will become the patron saint of The Birds and the Bees.

I can think of nobody more fitting.