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El infierno verde, the green hell, as the chaco is known, straddles Paraguay and Bolivia. It is one of the most inhospitable places on the planet: hot, dry and dusty and the dense thorny forest is all but impenetrable save for the handful of dirt tracks that have been bulldozed through. It is also home to some interesting mammals, best of which is the fabulous Chacoan Peccary, the largest of the three peccaries and unknown to science until 1975 when the first live animals were found (remains had been found in the 1930s and thought to be from an extinct pig).
Ever since hearing about Fauna Paraguay’s mammal tour of the Chaco, and reading Sjef Ollers' excellent trip report, I was keen to visit. In August 2010 I got there.
I arranged the trip through Fauna Paraguay. I was the first customer for their mammal tour, which involves looking for the larger animals but also trapping for small mammals and mist netting for bats. Fauna Paraguay’s website is already a fabulous resource for the country’s wildlife and Paul Smith, one of the partners, is in the process of writing a complete guide to all of Paraguay’s mammals (with the PDFs available on the site). I only had a week so decided to spend my time just in the Chaco. I was originally tempted to try to spend a few days in the Atlantic Forest too but it wasn’t possible in the time I had available.
August is the depths of the Paraguayan winter. The temperatures can vary considerably. The week before I arrived it had got down to below freezing one night and several thousand cattle had dropped dead, apparently from hypothermia. It warmed up a bit by the time I arrived but got steadily colder and we had frost on the last night. We had a couple of warm days in the mid-30s, but it was often a bit too cold at night for many bats to be flying and perhaps the weather also explained the disappointing lack of Armadillos other than Three-banded.
The tour was organised by Hugo Del Castillo Cordero, another of the FP partners and though primarily a birder he knew a lot about the mammals and where to see them. He also drove, cooked and arranged as much beer as I could drink. We were accompanied by Robert Owen, a US mammalogist who has settled in Paraguay. Robert was in charge of all the trapping and netting and (thankfully) identifying the things we caught.
Robert and Hugo met me at Asuncion airport on Saturday morning, with a loaded ute. We crossed the Rio Paraguay and started the long drive north through the Chaco.
Very few people live in the Chaco. There are a growing number of cattle stations, and a few small Indian communities, but much of the area is wilderness. A patchwork of “self protected” national parks are scattered across the forest (self protected means no resources are spent on them, but as the forest is so difficult to enter there are few problems with people other than hunting along the roads that border the park). Mammal watching revolved mainly around driving the same roads and hoping that an animal would cross the road in front of us.
We spent the first night in the little Mennonite community of Loma Plata, 450km north of Asuncion. It’s a prosperous town that could have been Australian at first glance (other than the posters in Spanish and German).
As soon as we had checked in to the hotel, Hugo offered to take me for an evening/night drive to a patch of protected bushland managed from the Tunokojai Indian reservation. A Yellow-toothed Cavy shot across the road just after dark and we later we saw 3 separate Three-banded Armadillos, the first of which Hugo caught. They are brilliant little critters, running on their tip toes like obese ballerinas.
Defensores del Chaco National Park
The next morning we left for the 6 hour drive north to Defensores del Chaco National Park, where we would spend the next three nights. Its dirt road all the way, but the road was in surprisingly good condition so we drove the 240km in 5 hours, not the 8 that Hugo had expected. The only mammal was a very large brick coloured Tapir near a farm dam. It was a surprise for me to see these animals living in such dry habitat, but they are quite common in the Chaco. Hugo has often see Chacoan Peccaries along the road but it sees a lot more traffic than it used to, and the wildlife sightings have probably deteriorated as a result.
We stayed at Madrejon in the south-east corner of the park at what might best be described as a ranger station (though in fact the people working there are not really rangers… the park is ‘self protected’). And we spent our time setting traps and nets and looking for wildlife along the road.
It is a gloriously remote area, very reminiscent of outback Australia.
Black-tailed Marmoset: the closest site that Hugo knows for these is Agua Dulce (about 80km or 2 bumpy hours) north of Madrejon. We arrived at dawn on a cold morning but didn’t spot any primates until about 9am, and got good views of just a single Marmoset. This is the same species found in the Pantanal though and is again perhaps a candidate for a split.
Crab-eating Fox: one seen crossing the road after dark near Madrejon.
Gray Brocket: one or two seen every day.
Azara’s Agouti : we probably heard one early in the morning near Agua Dulce.
Mist betting for bats at Madrejon was disappointing, with numbers of captures inversely correlated with the numbers of nets (though I suspect more related to the declining temperatures each night). On the first night Robert quickly caught 4 little Dwarf Dog-faced Bats (Molossops temminckii) in one net. The second night, with three nets open, brought one more Molossops temminckii and a couple of Argentine Brown Bats (Eptesicus furinalis). Despite having all 5 nets open on the last night we caught nothing.
Small mammal trapping was patchy as you might expect in such dry habitat. We set 100 sherman traps at Madrejon for 2 nights and then in the rockier habitat, and around the dam, at Cerro Leon for a night. At Madrejon we caught two groovy Agile Mouse Opposums (Gracilinanus agilis), one Small and one Large Vesper Mouse (Callomys laucha and Callomys callosus) and several of the quite chunky Chaco Leaf-eared Mice (Graomys chacoensis). I would have wasted hours and hours trying to identify these so it was great to have Robert around to quickly id each animal. At Cerro Leon we caught nothing in the rocky forest, but the swampy grassland around the dam was fully of Callomys callosus (with one in nearly every trap through the swamp).
Enciso National Park
This national park is about 220 kms west of Defensores, but the drive there is more like 300 kms because there is no direct road. The accommodation is similar to Defensores, though there is also permanent electricity here. The forest is a little more open in places and the soil sandier so there were some different mammals including Plains Viscacha. We spent 3 nights here, again trapping and mist netting each night, and looking for stuff during the day and night.
Our only (surprisingly) Pampas Fox was around the accommodation 2 nights running.
Tapirs are common throughout the Chaco but I was not looking for them. Rob saw one very close to the accommodation at Enciso, but their tracks and scats were everywhere.
Hugo also spotted a Yellow-toothed Cavy which gave fleeting glimpses as it dashed from one clump of vegetation to another.
The mist netting and small mammal trapping here was disappointing, though the low temperatures could not have helped. We caught only two bats: one Eumops species that I am happy to put down as the rather unusual Dwarf Bonneted Bat (Eumops bonariensis) given it had all the characteristics, though if we had wanted to be completely sure it would have been better to have taken the skull, and one robust Broad-eared Bat (Nyctinomops laticaudatus). Hugo saw a bat fall out of the air in front of the truck while we were spotlighting. It was still alive and I have no idea why it had crashed but it was another Dwarf Dog-faced Bat (Molossops temminckii). Within a couple of hours of setting the Sherman traps we caught a great little Small Fat-tailed Opposum (Thylamys pusillus). But after that the traps caught only a few more Chaco Leaf-eared Mice (Graomys chacoensis).
We saw a few Grey Brocket Deer along the road, and had a distant and very brief look at a dark cat that jumped off the road. I wouldn’t be surprised if it had been a Jaguarundi but we will not know for sure. We had good views of a white cat along the road both at dawn and after dark 12 hours later. It was more than 5km from the nearest cattle station and I would love to turn it into a white morph Geoffroy’s Cat, but I guess it was just a Feral Cat.
One day we took the very sandy road up to Medanos del Chaco national park. The Chaco gets progressively sandier as you head north and there were heaps of Tuco Tuco diggings along the road. We stopped at the Pykasu community to ask whether anyone could catch us a Tuco Tuco. After the Guarani Indians had stopped laughing – why would anyone be interested in Tuco tucos – they advised that they weren’t simple to catch. A few Guanacos live in Medanos NP but they are very hard to see. Hugo has also heard rumours that second, larger species of Agouti (alongside the normal Azara’s Agouti) lives in the park. Possibly Dasyprocta punctata. But we didn’t see one and the Indians didn’t have any skulls or skins to show us.
The Lower Chaco
We stopped for a night at the insalubrious Buffalo Bill hotel. It was certainly a cowboy operation. Hugo had to let them use our camping stove to cook us dinner because they had run out of gas... something they didn't mention until 9pm when we arrived to eat. But the surroundings were nice and there was evidence of Tapir, Crab-eating Raccoon and lots of Armadillos (including perhaps 6 Banded). But it was a very cold night (there was frost in the morning) and we caught no bats. The small mammal trapping was more successful and we caught more animals than we had on any other night - both of the two Callomys species (callosus and laucha) and the only Chacoan Pygmy Rice Rat (Oligoryzomys chacoensis) of the trip which unfortunately had frozen to death in the trap.
We stopped briefly at Los Pioneros nearby to visit their unpleasant zoo. It was interesting to see all three Peccary species side by side. The Chacoan flavour really are very different.
About half way between the airport and Loma Plata (maybe 20 minutes south of the Buffalo Bill) we stopped at a bat roost under a bridge. A few Lesser Fishing Bats were tucked away among hundreds of Myotis, probably Black Myotis (Myotis nigricans).
Stuff I missed
We weren’t particularly lucky with cats either. I had hoped too that we might have seen Geoffroy’s Cat and/or a Jaguarundi but that was not to be either (though it may well have seen a Jaguarundi on the road at Enciso). With a few more days I guess we would have bumped into both species. I didn’t spend time looking for Jaguars but they are quite common around Defensores in particular and we saw several sets of fresh tracks. I think you’d have a very good chance of seeing them if you set out to look for them.
Interestingly, Romain Bocquier (whose 2012 report is here) told meI "In the Chaco, we tried to meet wildlife during the early morning, late evening and night. But during 5 days nothing !! ( only mara and foxes ). Finally a hunter ( of peccaries ) said that he saw, almost every day, pumas or other cats when he walked in the middle of the day during winter. The last day we walked the road from cerro leon to madreiron in the middle of the day and we saw -in four/five hours - the jaguarundis and the Geoffroy's cat. " I wish I had known!
Other nice species occasionally seen in the Chaco include Lesser Grisons, and Tuco Tucos which occasionally come above ground.
So fun week, with 24 species and 15 of them lifers. It was the first full-on trapping field trip I had taken since I left Australia and I had forgotten how much I enjoy trying to catch the smaller things as well as see the larger stuff. Its a great county and Hugo and Rob are the people to see it with - excellent at their jobs and great companions. My feeling is that it might be better to go when it is a little warmer though the summer must be almost unbearable in the day time. Hopefully I can get back and try and see some bloody hairy armadillos one day. There is a lot of space for them to hide....
plus a possible Jaguarundi, the sound of an Azara's Agouti, the remains of a Lesser Hairy Armdaiilo and a dead Chacoan Pygmy Rice Rat.
Other People's trip reports
Paraguay 2009: Sjef Ollers, 3 weeks & 24 live species plus a few dead ones. Excellent report including Jaguar, Puma, Geoffroy's Cat and Chacoan Peccary.
FAUNA Paraguay - "Dedicated to the study of the Paraguayan fauna, this site counts on a huge image gallery of photos and videos, as well as supporting local conservation projects. Expert-led eco-tours to the Chaco (a paradise for mammals) and Atlantic forest also on offer." They now offer a special mammal trip, which includes bat and small mammal trapping (see my report above) www.faunaparaguay.com/mammtours.html