Thursday, January 18, 2018

The Nosara Dry Forest

Hi Everyone,

While staying in Nosara near the Pacific Ocean, we made a tour of a dry forest.  On previous trips, we stayed at field stations in the dry forest for several days, but on this trip we just got a taste of this different ecosystem.

Like all days, this one started with....

Breakfast.  Here, Tim enjoys his morning cuppa while he writes in his journal and waits for vittles to be served.

There are a lot of beautiful flowers, but I didn't spot any orchids.

The group went to a beach on the bay.

It was beautiful, and not very crowded.

That's the Pacific Surf crashing on the other side of the bay.  There were a lot of surfers in town.

We spent a while identifying shore birds and learning a little about their life history.

This was one of the more peculiar.  This is a frigate bird, which has evolved with very long thin wings (like a glider) and a very very low weight to wing area ratio.  So, these birds can fly effortlessly for a very long time.  They fly up to 25,000 feet high.  However, this wide wingspan makes it such that the birds can't land in the water - seemingly a giant shortcoming for a bird that is an ocean bird.  Instead, the birds are opportunists.  They either catch fish when fish are jumping from the water in a frenzy, or they are "vomitavores."  You've likely heard of carnivores, herbivores, and omnivores, but a vomitavore is a rare thing.  Here's how it works.  The frigate bird will fly down, catch another bird in its mouth, and shake the other bird until it vomits up its food.  Then the frigate bird will drop the bird, swoop down, catch the vomit, and eat it.  Truth.  It's stranger than fiction.

Mark, thumbing through one of the many guidebooks he always carries along.  It's wicked hot, and since we're within 10 degrees of the equator, the sun is very intense.  Students mostly kept their shirts on, wore hats, and put on loads of sunblock.  Here, Mark is wearing one of those hats with the cloth neck shade.  I don't think I remember him wearing a hat anywhere else on the trip.

Here, Sam takes notes.

Kate and Tim check out a bird.

Bridget takes notes and uses her phone to take photographs (as did most students).

The group went on down the beach.

Mark caught a butterfly and Heather and Chloe identify it.

An osprey flies over.

We went into the Nosara Biological Reserve, a dry forest.

Finally, we get out of the sun and into the cooler shade of the dry forest.  Here, Mark is explaining some of  the dynamics of the dry forest.  This area doesn't have a warm season and a cold season, like in New England (and most of North America).  Instead, it has a wet season and a dry season.  The dry season is so dry, that trees would lose all their water through evaporation and transpiration.  So, many trees evolved to be deciduous and lose their leaves during the dry season.  Then, at the onset of the wet season, the trees grow leaves again.  

Many trees in the dry forest evolved with thorns.  Some long and thin like needles, some short and stout like rose thorns on steroids.  Mark showed us some hollow thorns where ants had a mutualistic relationship with the tree.  The ants live in the hollow thorns and get sustenance from the sugary tree sap, while the trees get protection from herbivory.  Any time an herbivore tries to eat the tree, the ants swarm out of their thorn homes and sting the herbivore.  There are a lot of weird relationships like that in the forest. 

This tree is a balsa tree relative.  It has lost its leaves, but has a little bit of chlorophyll in its bark which allows it to still photosynthesize a little bit during the dry season.

This is a limb from the tree.   You can see how the chlorophyll makes the bark green.

This butterfly evolved so that it's back end (to the right of the picture) looks like a head.  The patterns on the wings and the shape of the wings and its thorax all contribute to this ruse.  The object is that predatory birds, which tend to go for the heads of butterflies, will be fooled.  All a bird would catch is a bit of wing, leaving the butterfly alive and free to fly away.

Here, you can clearly see the crown of a dry forest deciduous tree with its leaves off, cause we're in the dry season.  Summer is when most rains come.  There might be a howler monkey in there too.

Here's Tim with a butterfly, which I think was called a Sap Butterly.  These butterflies are poisonous.  They get this poison by their caterpillars consuming certain plants.  They have distinctive wings patterns and colors, so when a predator catches one, tastes it, and finds it unpalatable, the predator learns the pattern and color and leave the other butterflies of the species alone in the future.  Numerous other species have evolved to have similar wing and color patterns and mimic the poisonous butterflies, also gaining protection from predation.

Now, in these pictures, the world looks calm and wonderful.  In reality, the storm I told you about in the last post was blasting this whole forest with an incredible windstorm, to the point that we could hear trees cracking and falling over.  Eventually, Tim and I decided it wasn't safe enough, and we "hastened" the group along to the mangrove forest, where the trees were smaller and the branches were not so high or heavy.  On the plus side, the strong "breeze" kept us cool on a very hot day.

The mangrove roots are NUTS.  The tree puts out this broad base of roots to give it stability on the unstable ground.  Normally, these trees would either be in brackish water most of the time, or at least be flooded by brackish / salt water twice a day during tide changes.  Here, though, something wildly different happened.

A few years ago (I think 2012), there was a very violent, long earthquake.  The result of that is that the area of land where these mangrove trees sits raised up approximately 2 meters.

So, where there should be mangroves in water, now there's mangroves on dry land that might be occasionally flooded during storms, but mostly is relatively dry.

In addition to the cool root system, the mangroves have thick leathery leaves, which have evolved to help retain water.  The trees can also pump salt out, an evolutionary trait that allows them to live in what would have been a very saline environment.

It's crazy to think that the plate tectonics that we think of as slowly moving the continents around over eons of time is a critical (and current) factor in determining the makeup of this ecosystem.  Nobody knows if these mangroves will be able to survive in their new environment.

Here, Chloe checks out a spider.

Bridget is worried that her mum will find out that the shirt she borrowed got permanent ink marks on it.

On my camera, when there's something that I want to remember in a photograph, after I take it I take a second picture of my hand.  So, I've got a lot of pictures of my hand.  I took one after this picture.  I THINK I'm supposed to remember that the black blob in this picture is a Howler monkey.  Or not.  

Hope you enjoyed this short tour of a dry forest and this unusual tour of a dry mangrove swamp!

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