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Exploring One of the Last Untouched Tropical Grasslands Left on Earth: Madidi´s Pampas de Heath


By Rob Wallace

[Note: this is the sixth in a series of reports from WCS (Wildlife Conservation Society) on the Identidad Madidi expedition currently taking place in Bolivia’s Madidi National Park]

The first leg of the Identidad Madidi expedition in 2017 was to one of the most remote sites of those contemplated in this three-year research and outreach effort for Bolivia´s Madidi National Park: the Amazonian grasslands of the Pampas de Heath and surrounding tropical forests on the Heath River.

In late June, the team flew north from La Paz to the city of Cobija in the northernmost Pando Department. Once we crossed the Andes, the scenery below was covered by an overcast sky until suddenly a break in the clouds revealed the Heath River below. Excitedly, the team got a bird’s eye view of the very location of our intended research, where the natural grasslands are closest to the river and allow access to both the savannas and the rainforest.

The trip was planned for the dry season so as to ensure we recorded as many fish species as possible. At the same time, we also wanted to maximize the chances of registering migratory bird species, especially in the relatively poorly studied natural grasslands. Rain a few days previous to our arrival meant that water levels were not too low, but progress up the Heath was slow because of the sheer size of our flotilla.

Indeed, as thirteen boats and 58 people left Chive on the Madre de Dios river, I did think about the probability of a motor breakdown – and at least one motor was struggling throughout the first two days, with the final boat carrying the most proficient local mechanic attending the stricken engines almost the entire time.

Low water levels meant that we were not using normal outboard motors. Rather our fleet was equipped with long tail, or mud, motors (affectionately known as the peque peque in most of the Amazon). Inelegant, clumsy, relatively slow, and just plain loud, these motors have changed little since they were first introduced to the Amazon almost a century ago.

As a British biologist who has lived and worked in Bolivia for the last 25 years, I find it hard not to be reminded of the travels of Colonel Percy Harrison Fawcett, who in 1910 defined the border between Bolivia and Peru. As labored as our progress may have been, it was nothing as compared to Fawcett and his team, who paddled canoes further up the Heath almost to its source.

Our objective was access to the hypnotic Pampas de Heath, a swathe of Amazonian savanna with a quality that is at once very special and unfortunately almost unique: it is completely devoid of cattle and thus one of the last natural, tropical grasslands left on Earth. My first afternoon off the boats was spent forging a pica (or minimalist trail) east from the Heath River, through Amazonian rainforest and seasonally flooded forest, and out on to the grasslands just in time for sunset.

If sunset was something to behold, the dawn was equally magnificent. On several occasions as we sought a glimpses of the magnificent marsh deer (Blastocerus dichotomus) or the wonderfully weird maned wolf (Chrysocyon brachyurus) – both of which are adapted to these often seasonally flooded grasslands – we experienced some of the most sublime sunrises I have had the privilege to enjoy.

The Heath proved as rich as we had hoped, with our efforts revealing thirteen new mammal records for the park, including the seven-banded armadillo (Dasypus septemcinctus), the yellow armadillo (Euphractus sexcinctus), the Brazilian guinea pig (Cavia aperea), several mice and small marsupials from the grasslands, the Brazilian porcupine (Coendou prehensilis), gray four-eyed opossum (Philander opossum), and only the second Bolivian record for the Amazon dwarf squirrel (Microsciurus flaviventer), as well as four bats – including a first record for Bolivia for the yellowish Myotis (Myotis levis).

The Madidi bird list also increased to 1,011 confirmed species with the addition of six new records in the forests and grasslands of the Heath. None of these new records were migrants. Rather, we encountered a grassland specialist in the white woodpecker (Melanerpes candidus); a rarity in the least bittern (Ixobrychus exilis); and four primarily Amazonian rainforest species that included the rufous-fronted antthrush (Formicarius rufifrons), the Peruvian recurvebill (Syndactyla ucayalae), the brown-rumped foliage-gleaner (Automolus melanopezus), and the blue-backed manakin (Chiroxiphia pareola).

In total, the team registered 620 vertebrate species, 65 of which were new records for the park. As expected, fish provided the bulk of those new records, largely because we were sampling for the first time in the Madre de Dios watershed, but also because of some particularly rich and unique aquatic habitats. For example, the acidic (pH 3.2 grassland source, pH 7 mouth on Heath River) clear waters of the Moa River born in the natural grasslands of the Pampas de Heath result in a distinct suite of fish species, including new records for the dwarf wood catfish (Helogenes marmoratus) and the three-striped pencilfish (Nannostomus cf. trilineatus).

A couple of these fish may end up being species new to science, increasing to an astounding 22 the number of new vertebrate species candidates registered by Identidad Madidi. With more than 60 new plant species candidates to add to this, Madidi is proving more amazing than any of the team ever imagined. You can follow our progress in more detail on our webpage or on Facebook, where updates are most frequent.

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Dr. Rob Wallace is a Bolivia-based senior conservation scientist in the Latin America and Caribbean Program at WCS (Wildlife Conservation Society).