Evolution of Rivers

Bull Creek- click to enlarge

I hadn't given much thought to how our rivers were formed until I came across an article in Livescience.com.  It turns out that a major factor in their shape and size over millions of years was the evolution of plants. 

Rivers were pretty lackluster affairs 500 million years ago in the Cambrian period, straight, wide and extremely shallow, leaving no discernible banks in the geological record.  How wide were they?  Some estimates are that they were 1000 times as wide as they were deep.  There was no mud yet to support banks.

The first primitive plants developed around 470 million years ago around the time of the development of mud which is more cohesive than sand and gravel.  This wasn't a coincidence as plants are instrumental in the formation of mud.  Acids they produce break down rock and later the development of roots causes physical cracks.  Plant death added to the mud, producing soil.

Soil not only binds the particles together to create firmer banks, but it facilitates the growth of plant roots which holds acts as reinforcement.  When this evolved, we see evidence of meandering streams appeared around 416 million years ago, providing habitat for evolving fish and insects.

By planting trees along streams we enhance the riparian corridor, just our humble way of restoring what nature accomplished millions of years ago before the attack of our plows.

Birds Identify Trees

Bluebird- Mike Onyon redorbit.com

It appears that birds can select their trees to feast on just like we pick a nice restaurant.  According to an article at sciencedaily.com, birds are able to pick the right tree species to increase their chance of finding a great meal.  The study reported in the American Naturalist showed that chickadees and other birds select the type of trees that they dine in as well as their targeted caterpillar variety.

Many caterpillar species have a limited number of tree species to choose from as their obligate food source.  In addition, their mother's choice of the tree where she lays the egg affects their success.  The healthiest tree would feed the greatest number of juicy caterpillars.  Apparently birds figure this out and select their tree species, so the individual caterpillar's survival odds on a great dinner tree are much smaller.

That being said, there are two competing strategies.  Eating on a less desirable tree may produce smaller and less healthy caterpillars with a lesser chance of successful survival.  Dining on the healthy tree may increase the gastronomic odds but at the risk of increased predation.  Caterpillars living on an nice juicy black cherry had a 90% chance of being eaten by a bird.

Although the nutritious cherry tree leaves produce "fat cats" (think 5 star Michelin guide) we don't know which strategy produces the most adults in the long run.  But at least they don't have to go far for a good meal.  As the saying goes, "Fat cats don't hunt."
redorbit.com

Ticks in February

Adult Deer Tick- Wikimedia

An article at livescience.com discusses the downside of the balmy days we are having this winter.  Barb and I have found at least three reasons to look forward to a good hard freeze, and all of them had 8 legs.  Along Bull Creek, one Lonestar tick and two deer ticks have crawled on us this week, and those are just the ones we saw!

We are not alone in this warm spell.  The Northeastern United States is having its fifth warmest December on record.  Minneapolis temperatures first reached zero on January 19th, only seen once before in over 140 years.

What effects can we expect from this?

• Mosquitoes, ticks and fleas may be out earlier (amen!) and even be more fruitful in multiplying.
• Plant pests may be out earlier and have a greater impact this year.
• Plants may come out of their winter protection and bud earlier.  This always raises the concern about a late freeze killing off the buds and their fruits.  The same applies to frogs and salamanders which might end hibernation and then face a killing frost.

As Patrick Byers, horticultural specialist for the University of Missouri Extension points out in the latest edition of Greene Magazine, a late freeze may well kill off many of the emerging pests and their eggs and larvae which are freshly hatched.

Meanwhile you had better get out now and enjoy the warmth while you can.  But remember, that faint crawling sensation might just be Rip Van Tickle waking up from his winter nap.

Rat Zombies?

Research described in Sciencedaily.com suggests that a parasite named Toxoplasma gondi which lives in a rat's brain alters the behavior of infected rats, making them lose their fear of cats and possibly even seek them out.

Cats are the main host for Toxoplasma which can only reproduce in a feline's body.  To spread its species in absence of legs or wings, Toxoplasma requires a way of getting more cats to ingest its offspring.  That is where the rat comes in.  Toxoplasma spreads by infecting hosts which  are eaten by cats.

The Toxoplasma organism lives benignly in the brain of rats and other animals, using its host for just enough energy to survive, generally without harming the host.  It is in its best interest for an infected rat to remain healthy, that is until it encounters a cat.  Then it ends its friendly relationship, encouraging the rat host to get eaten.  This is where the zombie comes in.

The new study by Patrick House of Stanford University suggests that the Toxoplasma infected brain causes the rat to lose some of its fear of a cat while maintaining its normal anxiety and fear brain responses to other predators.  The male rats brain also shows stimulation response to rat urine odor in an area usually activated when a female rat approaches.  The result is similar to the fate of a turkey gobbler responding to a hunter's call.

Patrick House summarizes his study in this Stanford interview.  A detailed description of the Toxoplasma life cycle, which includes frequent human hosts is at  stanford.edu/.

If you found this interesting or are a naturalist who likes Stephen King stories I have just the book for you.  Parasite Rex by Carl Zimmer has been reprinted in paperback and covers the lives of various parasites with clarity and an occasional dose of humor.  He summarizes this type of parasite behavior as follows:

"Simply living within another organism - locating it, traveling through it, finding food and a mate inside, altering the cells that surround it, outwitting its defenses - is a tremendous evolutionary accomplishment.  But parasites such as Sacculina do more: they control their hosts, becoming in effect their new brain and turning them into new creatures.  It is as if the host itself is a simply puppet, and the parasite is the hand inside."

You will be startled by the number of parasites that are around and even in us, and their influence on behavior.  Then try to get a good night's sleep.

More on Toxoplasmosis and suicide at Scientific American.

Mosquitoes Keep Their Cool

New research on how mosquitoes keep their cool is reported in sciencecodex.com. 

Mosquito- Wikimedia

If you have ever swatted a tiny mosquito and seen the blood left on your skin, you can imagine how much blood they can stuff in their body.  However, your warm blood creates a risk of overheating in this coldblooded insect.  You probably aren't feeling any sympathy yet for this poetic justice.

The study which was reported in Cell Press helps explain how the mosquito handles this heat stress.  A mosquito doesn't sweat like we do or pant like a dog.  Insects generally control their temperature by extruding fluid such as nectar or sap.  The mosquito puts itself at great risk of a crushing blow when it is sucking the blood it needs to reproduce. 

To cool itself, it apparently has to ooze out a little of that blood.  Using a heat sensing camera, researchers determined that the mosquito's head was the temperature of blood while the body remained cool.  The cooling was due to the loss of liquids out their backsides. Learning how this is controlled could be of practical value if a method of blocking or delaying the excretion of fluid could be developed.


The microbes on your skin determine how attractive you are to mosquitoes, which may have important implications for malaria transmission and prevention, according to a study published Dec. 28 in the online journal PLoS ONE.  Human sweat is odorless to our nose, so the mixture of microbes on your skin help determine your special body odor.

Eurekalert.org reports that researchers, from Wageningen University in the Netherlandsstudied the Anopheles gambiae sensu stricto mosquito, which plays an important role in malaria transmission.

"They found that individuals with a higher abundance but lower diversity of bacteria on their skin were more attractive to this particular mosquito. They speculate individuals with more diverse skin microbiota may host a selective group of bacteria that emits compounds to interfere with the normal attraction of mosquitoes to their human hosts, making these individuals less attractive, and therefore lower risk to contracting malaria.  This finding may lead to the development of personalized methods for malaria prevention."

The next time someone tells you that they always attract more mosquitoes than anyone around them, you might suggest that they try changing skin bacteria.  On the other hand, you might not.

Where Did I Put That Nut?

Squirrel Proof Bird Feeder

When a squirrel buries acorns and then forgets them, it is also planting little oaks.  Good for trees, bad for squirrels.  They accommodate for this loss just like Walmart, by volume.  So can a squirrel remember where it hid a nut?

The first answers on the internet are mixed.  Many web sites say "No," they locate the nuts by smell.  It turns out that this is only partially right.  A 1991 study published in PDF found evidence that they could locate the nuts they buried.

"Captive squirrels were released alone into an outdoor arena, where they cached l0 hazelnuts each.  After a delay of 2, 4, or l2 days, each squirrel was returned to the arena and tested for its ability to retrieve nuts from its own cache sites and from l0 cache sites used by other squirrels. Although each squirrel's own caches were close to the caches of other squirrels, the squirrels retrieved significantly more nuts from their own sites than from sites used by other squirrels after all delays  The retrieval accuracy of the squirrels under these conditions indicates that while grey squirrels can locate buried nuts by their odor, they can also remember the individual locations of nuts they have buried."

Squirrels use a system of triangulation to remember where they have hidden their food. A study at the University of California Berkeley show that they triangulate the location of hiding places using what we would call "landmarks." While the human brain might be able to remember 4 or 5 triangulations to locate something, the tiny squirrel brain can remember 300 to 400 triangulations to locate the food they have hidden.

Even more amazing is these backyard bandits ability to get to illicit food sources such as bird feeders and vending machines.  This 2007 British video is well worth a watch.

More on squirrels but storing strategies is a this link.  They handle selected acorns differently, discussed here..

The Temperatures, they are a Changing

When we talked to people about our new southern Missouri home almost forty years ago we would brag that there was an occasional day in January when you could play tennis outdoors in fifty degree weather.  It seems this year we have a lot of them, and some days you would play in shorts!  A possible reflection of this trend can be seen in the new USDA Plant Hardiness Map.

The map is used by gardeners to select plants that are best suited to the local climate, as described by temperature range.  This is the first revision since 1990.  Although it is not a guide to climate change as such it does show some area of significant changes over the last 20 years.

As described in USA Today, the changes are not dramatic with none over a half a zone.  Most of the changes show a warming to the north.  In the words of gardening consultant Charlie Nardozzi:

"If you want to look at what might be the most politically correct thing, you can say something's happening.  But the climate is changing. Spring is coming sooner and lasting longer. Fall lasts longer, and overall the weather is so much more erratic now."

While these designations are accurate generalizations, local landscape can make a difference which the map cannot describe.  Our Bull Creek valley runs north-south with fairly steep sides.  The sun hits it late and goes down early behind the hills.  The evening temperatures are between 5-10 degrees cooler than the surrounding uplands.

Meanwhile, Matt Ridley has an interesting take in his Wall Street Journal article,
Are We Holding a New Ice Age at Bay?  He points out that even considering the Little Ice Age (1550-1850) our 10,000 years of developing civilization has occurred in an unusually warm spell.  Temperatures like ours have occurred in less than 10% of the time over the last one million years.  Indeed, one theory is that the unusual warmth allowed our predecessors to develop agriculture, the first step in civilization.

He discusses some of the hot and cold history of our planet and the theory of some that the current warming may be postponing the next ice age.  Before you run out and buy a heavier coat, note that experts are talking about the next 1500 years.  As with all climate theory, it is interesting but nothing to hang that heavy coat on.