Friday, November 29, 2013

Kusad's forest floor

Our time at Kusad was short—we had only six full days to document as many species as we could.  The pressure was on for the Ant Team—Leeanne Alonso, Samson and me.  We were the first people to collect ants in the area.  In all likelihood, we might also be the last.

There are probably at least around 200 species living on and around Kusad, many of which are undescribed.  Of course we wouldn’t find them all.  In fact, we’d probably find less than half.  But the more species we documented, the more information we could provide to conservation planners and to science in general.  The other teams—plants, fish, mammals, etc.—faced similar challenges.

The Rupununi is a patchwork of different habitats and each one would yield different species.  Likewise, by sampling at night we could get nocturnal species.  We would also use different trapping methods; each one is more likely to get some species than others.  Most importantly, to capture as many species as we could we would have to maximize our time in the field—searching, waiting and observing.  Of course, we also helped each other out.  Other teams brought us ants they found, and we brought back plants and frogs and reported our mammal sightings.

Perhaps the best way to find many ant species in a short period is by litter sampling.  The most diverse part of many forests is the leaf litter—the decaying leaves, wood, fruits and seeds on the forest floor.  An entire community of animals, fungi and microbes lives here, fueled by the rain of nutrients from above and living in the crevices provided by the soil, roots and litter.  Searching through leaf litter by hand is iffy at best—many species are tiny, blend in with the litter, and flee or curl up and play dead when disturbed.  Finding a tiny brown motionless ant in a pile of soil is nearly hopeless.  So we trap them.

An ingenious device called a Winkler trap uses gravity to separate ants from leaf litter.  The first step is to collect litter, scooping up all the leaves and twigs.  We put this raw litter into a sifter—a sack with a layer of metal mesh—and distill it by shaking.  Tiny bits of broken down leaves and small animals fall through the mesh, leaving all the big stuff on top to be put back where we found it.  We take this distilled litter—the siftate—back to the lab tent and load it into the Winkler traps.

Leeanne and Samson and I collected and sifted leaf litter in different forests throughout the trip (photo by Leeanne Alonso)

Each trap is a hanging bag that narrows to a small opening at the bottom, where we attach a container of alcohol.  We pour the siftate, crawling with ants, into mesh sacks and hang them in the traps.  As the ants move around they occasionally fall through the mesh, through the bottom of the trap, and into the waiting alcohol below.  After two days you have a concentrated assortment of dozens of ant species, ready to take back to the lab to identify.

Winkler traps use gravity to sort mobile ants from immobile leaf litter, allowing us to sample the diversity of the forest floor (photo by Leeanne Alonso)

Kusad was a difficult place to sample litter.  The ancient eroded slopes are rocky and covered in boulders, with little flat ground and a thin soil layer.  The forest itself produced little litter, especially now during the transition from wet to dry season.  It hadn’t rained in a while and the forest floor was dusty, with few moist rotten logs and fungi.  We collected litter every ten meters through 200 meters of forest, and the pickings were slim the entire way.

The dry forest on Kusad’s rocky slopes was a difficult place to collect litter

Rocks, a thin soil layer and dry conditions limited litter concentrations

We worried how many ants the litter would produce.  But after the traps had run their course we had plenty.  Now to just sort through them back in Oklahoma…

Monday, November 25, 2013

To Kusad

Kusad rises from the plains, a green monument amid the surrounding grasslands.  The largest of many forested outcrops in the Southern Rupununi, these mountains were our first destination.  Traveling individually on motorcycles, the local Wapichan people can get from Lethem to Kusad in a couple hours.  For a large party, however, things are more difficult.

In Lethem we were already well over 20 people—scientists, students from the University of Guyana, local experts, organizers, drivers and a few others.  Some folks rode in two pickup trucks.  The rest of us climbed into the back of an open Bedford truck.

Getting from Lethem (red dot) to Kusad (circle) involved several hours of dirt roads and river crossings

The back of the Bedford promised a rough, dusty ride from Lethem to Kusad

We bounced over dirt roads through grasslands and over creeks.  Unlike our remnant grasslands in the US, the southern Rupununi is almost entirely unfenced, allowing natural processes to continue unhindered.  The drive through vast unfragmented grassland was thus a rare and welcome experience.  As we put Lethem behind us the road narrowed and roughened.  In wooded areas sandpaper trees (Curatella americana) closed in around us and the truck brushed against them, tossing snapped branches and leaves into the back.  About an hour short of our camp with Kusad looming in the distance the truck lurched to a stop, sunk up to its axles in mud.

Just north of Kusad our truck got stuck in a dried sedge marsh

Hot sun aside, the mud provided a respite from the bouncy ride and gave us a chance to enjoy the open grassland

Though we did get unstuck eventually, we took the opportunity to enjoy the landscape.  We were in a drying sedge marsh.  Sprinkled among the sedges were low carnivorous sundews (Drosera sp.) the size of a quarter.  Small brown Leptodactylus frogs sat in mud pockets.  And the savanna was all around, broken by distant mountains—the Kanukus in the north, Kusad and Saddle Mountains to the south, and the Shiriri Mountains to the east.

From where we were stuck the Rupununi stretched away in all directions, broken only by occasional mountains

We arrived at Kusad to meet the rest of our expedition, comprised of members of the Wapichan community.  Here I met Samson, the local assigned to the ant team.  The two of us would become close as the trip wore on.

We camped alongside a creek that had dried into a series of pools—the Mokoro Wa’o.  Three anacondas were found in these pools while setting up camp, one of which was reportedly 15 feet long.  Despite the anacondas, one of the rock pools quickly became the favored bathing spot.

 We camped in dry forest along the Mokoro Wa'o at the foot of Kusad

While most hung hammocks in the communal sleeping tent, I cleared a spot in the forest for my tent

In places the Makoro Wa’o flows over bedrock, forming a chain of rock pools inhabited by anacondas and catfish

By the time we settled in and everyone introduced themselves it was nearing sundown.  But there was still time to acquaint ourselves with some of our neighbors in the dry forest around us.  After a dinner of rice, beef, spam, shredded beets, and macaroni with corn and vegetables, several of us went on a night hike in the forest along the creek.

In addition to the anacondas, the banks of the Mokoro Wa’o were lined with fishing spiders and frogs, and small catfish swam in its pools.  Cactus and agave grew in thin soil on the rocky banks.  A horsehair worm (Nematomorpha) swam in a rock pool, large enough for Andrew Snyder to catch with snake tongs.  The forest was filled with wolf spiders and dotted with tarantula burrows.  Scorpions crawled on the ground and I collected one next to my tent.  Back in camp we caught insects at a light—mantisflies, owlflies, mantids and mole crickets.

Fishing spiders (Dolomedes sp.) hunt on boulders along the banks of the Mokoro Wa'o

Tarantula burrows were a common sight on the forest floor, but this was the only one I managed to see aboveground

I wasted no time getting attacked by ants and was promptly stung by a trap jaw ant (Odontomachus sp.).  A large carpenter ant (Camponotus sp.) major bit me deeply enough to draw blood.  It was the first time an ant made me bleed.  A smelly aggressive ant—Dolichoderus bispinosus—pestered us by climbing on and attacking our tents, hammocks and clotheslines.

The dry forest at Kusad was filled with life, promising much discovery in the days ahead.

I went to bed exhausted, inspired by the life around us and anticipating the next day’s collecting.

Wednesday, November 20, 2013

Rupununi arrival

Welcome back to M2M and thanks for your patience while I was away.  I’ve just returned from a successful expedition to Guyana, where I joined a Biodiversity Assessment Team organized by WWF Guianas and Global Wildlife Conservation.  Our mission was to explore the southern part of the Rupununi Savannah on the Brazilian border.  Two other expedition members are also blogging about the trip: entomologist Andrew Short blogs for National Geographic and herpetologist/photographer Andrew Snyder for Amphibian Survival Alliance.  I encourage you to check out their sites for different stories, perspectives and photographs.  M2M, as always, will record my personal experience of the landscape.

Guyana is in northern South America on the Guiana Shield—the largest remaining patch of rainforest on Earth.  Many of my posts are about biodiversity hotspots—places that have already lost at least 70% of their natural land cover and have high extinction risks.  As one of the world’s last great wilderness areas, the Guiana Shield is a fundamentally different experience.  My accounts of hotspots (e.g. New Zealand, Indonesia, Madagascar, and eastern Australia) are of landscapes covered in farmland or pastures, with long journeys to isolated patches of remaining vegetation.  Guyana, in contrast, is almost all natural vegetation with nearly 90% forest cover, as is evident by even the most casual glance at a satellite image.

Unlike most places on Earth, Guyana still retains most of its natural land cover.  With the exception of coastal farms (light green patches), most of Guyana is covered in forests and grasslands.

The forests of the Guiana Shield merge with the Amazon to form the massive rainforest collectively referred to as Amazonia.  In the northwest, where Venezuela, Brazil and Guyana meet, this forest surrounds a large isolated savanna (the brown patch on the map).  The portion in Guyana is called the Rupununi—the name of the major river drainage.  The lower and more remote of the two triangular patches is the southern Rupununi, where we focused our efforts.

Like savannas in the US and elsewhere, the Rupununi is a patchwork of grassland and forest maintained by fires that sweep through in the dry season and floods that turn much of the area into marsh in the wet.  Depending on soil moisture, the grasslands range from sedge marshes to two meter tall grasslands to gravelly short bunch grasses.  Isolated hills and mountains protected from fire or high enough to receive more rainfall are covered in tropical dry forest.  Gallery forest snakes along wet riverbanks.  Wetter low-lying parts of the grassland—marshes, ditches and shallow creeks—are lined by moriche palm savannas called morichal.  To top it all off, the Rupununi peters out into tropical rainforest at its southern edge.  The result is a heterogeneous landscape in which one can visit rainforest, dry forest, marshes, grasslands or palm savannas in the same day.  Our goal was to explore these varied habitats and document the region’s biodiversity with the hope of informing future conservation and management efforts.

The southern Rupununi is at once both vast and heterogeneous, a mosaic of different habitats maintained by fire and flood

Windblown fires sweep across the landscape leaving tongue-shaped burnt patches, soon to be filled in with new green growth

Smoke rises from several grassland fires, which generally spare the forest lined wet riverbanks

Moriche palms (Mauritia flexuosa) dot low-lying wet areas

Our first leg was a flight from Georgetown on the north coast to Lethem at the edge of the southern Rupununi.  Lethem is a tiny frontier town, but still the largest in the region.  To give some idea of how rural the southern Rupununi is, the administrative district to which it belongs, Region 9, is about the same area as West Virginia… but West Virginia has 95 times as many people.  Thus the population density of the Rupununi is only 1% that of West Virginia, a state many people in the eastern US consider rural.  As another measure, during the 1800s the US government considered a frontier “closed”—meaning it was sufficiently populated to lose frontier status—if it had over 6 people per square mile.  Region 9 has a population density of only 0.87 people per square mile.  Just getting to Lethem involved flying over 150 miles of continuous tropical rainforest, broken only by the occasional gold mine and the nation’s only road south.

Guyana is characterized by large expanses of intact rainforest, as seen during our flight from Georgetown to Lethem

Lethem was our last stop before entering the field and the last “city” we would see for some time.  It’s located in the Amazon basin on the Takutu River which forms the border with Brazil.  Due to the influx of Brazilians across the bridge, local stores and restaurants cater to Brazilians and many locals speak Portuguese.  Stores invite Brazilians to shop with the words “Bem vindo” in their windows, and road signs remind them to drive on the left side of the road in Guyana, not the right.

We stayed the night in Lethem, stocking up on supplies and enjoying our beds, cold drinks and air conditioning.  The next day we headed south into the savanna, not to return for two weeks.