We have done it. After navigating 1760 km of winding rainforest rivers, living out of a boat for over 90 days, slogging along 80 km of river edge, and wading up 36 km of jungle streams we have information on over 150 clay licks, most of which have never been visited by scientists. It was one of the most intense research experiences I have ever experienced. We had all manner of problems insects, caimans, illness, motor failure, and inexplicably long and complex bureaucratic delays nearly thwarted our efforts. But we succeeded.

Team leader Gabriela Vigo, with the support of myself and Dr. Armando Valdes-Velasquez, took her team of 2 – 3 assistants up five remote rainforest rivers in the Department of Madre de Dios, Peru. Her goal was to find, describe, and measure as many clay licks as possible. The problem is that nobody had ever tried to search for clay licks over such a large area. So we had to make it up as we went along. She used a wide variety of tactics in the hopes of finding as many clay licks in as little time as possible. She asked local people about the clay licks they knew of in the area and how they used them. She talked to ecotourism companies and visited the clay licks they used. We also developed systematic census techniques for clay licks. We tried walking forest transects. . . lines 1 – 2 km long straight through the forest, but that didn’t produce any results. So we settled on walking the edges of rivers and forest streams checking each exposed soil area for animal bite marks. For each site with bite marks we measured the area used, and identified the tracks, feathers, feces, and even the types of the bite marks to figure out which species were using each clay lick. In this way, Gaby’s team described over 150 different areas where animals eat soil in southeastern Peru.

We found all sorts of different types of clay licks. We found the typical large river bank clay licks used by parrots and macaws like the ones visited by thousands of tourists each year. We also found shallow, wide, muddy pits used by hundreds of peccaries (relatives of the wild pigs). But we also found lots of other types too: tiny little spots were a few pacas (20 lb rainforest rodents) regularly chew on exposed patches of clay, small patches of high river banks visited by monkeys and squirrels, and deep holes along streams where tapirs (South America’s largest mammal) chew out clay rich soils. In total we found licks used by 14 types of mammals and 25 types of birds (including 19 species of parrots). Nearly all of the licks (95%) were used by at least one mammal, while about 51% were used by birds.

We found that the different species used different types of clay licks: parrots and macaws used large open clay licks, tapirs used low licks with little vegetative cover, peccaries used wide low licks with lots of vegetative cover, and pacas used tiny little licks with lots of cover. The mammals apparently like to stay in their preferred habitats, even when visiting clay licks, as species which prefer the forest interior avoided river edge licks and vice versa.

Much to our surprise, we found that different rivers had significantly different numbers of clay licks along them. The rivers in the northern side of the study area (Piedras and Amigos) had more clay licks than the rivers on the southern side of the study area (Tambopata and Colorado). We are not certain why this is and what repercussions this will have on the wildlife that lives in these areas but our analyses continue and it is clear that these questions will need more research. It seems that some of the largest and most diverse clay licks are those in areas where there are few. As a result, we suspect that these big clay licks may be the most important for conservation.

As part of this work we also quantified how humans use clay licks. Specifically we looked at hunting and tourism. We had heard reports of market hunters shooting large numbers of mammals (peccaries, tapirs, deer, etc) at clay licks and selling them. We also know that some parrot and macaw licks are also used by hunters who kill the birds for soup and sell their feathers. We were worried we would find many licks full of shotgun shells and hunting platforms. Fortunately we found no hunting platforms and shotgun shells at only one lick. Our discussions with local people show that at least 7% of the licks are visited by hunters, but the intense sit and wait market hunting is very rare.

We found that only 10% of all clay licks in our study are visited by tourists. The large parrot and macaw clay licks are the most popular with tourism but even for these, only about 40% are visited by tourists. This means that over half of these licks, many of which are visited by hundreds of parrots daily, remain unused by the tourism industry.

Our study was the first of its kind and it was definitely a learning experience for us all. But now that we have the largest data set on tropical clay licks ever assembled, we are ready to move forward. The data show that clay licks are much more common than I would have imagined. They also show interesting patterns of use by different animal species. We found that humans are using clay licks much less than expected. This line of research will help us better understand why animals use clay licks, what impact these licks have on animals, and how to best preserve the animals that rely on these sites. The most encouraging finding of this first round of study is that there is still time to protect these important resources through a mixture of good science, protected areas, tourism management, and community based management of hunting.