New coati video and implications

A dead coati presents us with a big mystery

As part of our ongoing Tepui Watch project, Biokryptos lead investigator Arturo Berti performs field expeditions to the summit of Auyan Tepui for reconnaissance and data collection from our many camera traps. As a seasoned field guide and leader, Arturo's observations and opinions are vital to the success of the Tepui Watch project and Biokryptos operations on Auyan.

During our last expedition to Auyan, Arturo  found something unusual: a dead coati along the entrance trail to the summit of Auyan, known as La Ventana. The location of this dead coati is technically the talus at 1800 meters. Arturo is of the opinion that this animal died after falling from the summit onto the trail.

Now, as coatis are good climbers and unlikely to fall off cliffs, and no necropsy was conducted, the cause of death remains unknown. Thus, we have a mystery; how did this animal die? What is the distribution of coatis on Auyan? Is there migration and gene flow between the summit and lowland coati populations? What is the rate of lowland invasion onto the summit, and is there continuous gene flow between lowland and summit populations? What are the implications of this phenomena for endemic fauna?

Talus slope questions, and fauna distribution

The real question regarding this coati is the ability of lowland animals to establish populations on tepui summits. The consensus is that tepui summit fauna is depauperate, as tepui talus slopes and disjunctive topography are barriers to lowland faunal migration. Examples of this include highly endemic herpetofauna and endemic  tepui specific floral assemblages. The inference from the high percentage of endemic organisms is that isolation is a historical phenomena, and that the tepui summits contain something akin to a highly adapted paleofloral and paleofaunal assemblages, due to the isolation of summit species. This view has been challenged by recent molecular research, and the entire model of long term endemism is in need of more research and review. Our project Tepui Watch is biased toward capturing images of mammal as opposed to reptile (though we are working to change that bias), so we cannot contribute directly to the debate regarding the origin and natural history of tepui summit endemic herpetofauna. However, we have captured enough data from the talus to the summit to begin to model mammalian distribution; and the evidence does not fit a model of isolation. As we collect larger volumes of data, Biokryptos will utilize software programs to begin to model mammal populations on Auyan by statistical analysis and spatial analysis of species records.

Area of surveillance: bottom to top

One objective of Tepui Watch is to understand how the biogeography of the tepuis functions. As such, a simple spatial distribution of a few summit species is not sufficient to understand tepui ecological dynamics. We need to examine the distribution and population dynamics of faunal assemblages from the lowlands to the highlands, from bottom to top. We surveyed two locations in the talus, Campo Guayaraca at 1100 meters and Campo Penon at 1500 meters. In these two locations, we recorded a variety of animals: deer, foxes, and pacas at Guyaraca, and armadillos, tayras, squirrels and anteaters at Penon. Strangely, we did not record any coatis at Guyaraca and Penon, although Arturo and the other field investigators have seen them in these locations. On the summit, we have recorded data from Campo Naranja to the Lagoon and river systems near Angel Falls. In the summit locations, we have recorded tamanduas, coatis, tayras, weasels, a good deal of opossums, two species of squirrels, and observed evidence of big cats.

The primary difference between the animals recorded on the talus vs summits seems to be the niche of the animal, and to a degree body size. At 1100 meters, we have deer, which are larger bodied animals than anything we have recorded at the summit to date. Equally, the dietary requirements of the summit animals are more omnivorous to carnivorous, where as lower elevation talus species were herbivorous, frugivorous, or omnivorous.

Barriers and gene flow

When we look for commonalities and differences between the populations of animals at each elevation, we are also looking at habitat differences in each location, topography, and vascular plant assemblages.
For the most part, the tepui summit forests have monoriche gallery forests as opposed to the lowland forests which have a greater diversity of vascular plant species. Tepuis also have spatially limited gallery forests, and the rest of the tepui is composed of shrub lands, bogs, and swamps. Furthermore, we have differences between tepui summits and lowlands in terms of soil composition, limiting lowland vascular plant colonization from the lowlands to the highlands. There is also the issue of temperature gradients and precipitation, which act as barriers between the lowlands and highlands.

As anthropgenic climate change continues to alter the climate on a global scale, we should expect to see fragmentation of tepui summit biota, and colonization by upward migration of lowland flora into the tepuis. As this current climate change is unprecedented in Earth's history in terms of the speed of temperature increase, the predicted altered ecosystems will have a composition which is currently unknown. At this time, and going forward, it may become advantageous for larger bodied lowland herbivores to enter the tepui ecosystems to forage as the structure of lowland and highland ecosystems change. Again, soil composition and precipitation will effect future distributions, and while the end result is unknown, extinction in summit flora (particularly endemic flora) is expected to occur, and may be occurring concurrently with the writing of this blog.

So, while vegetation is a barrier, we should be able to monitor the rate of change and the effects of this change based on faunal distribution, as well as more direct methods. However, vegetation and substrate is not the only barrier. There is a very obvious topographic difference between the tepuis and the surrounding lowlands. This difference is what engendered the literary and scientific "Lost World" scenario hypothesis to begin with. Equally, within the tepui itself there are areas which are topographically disjunctive and complex. An area on the north of the tepui known as the Valle de los Mil Columnas comes to mind, with a series of spires isolated from the plateau and each other. Certainly, this fragmentation is a barrier to colonization, from reasons ranging to surface area to substrate retention on bare rock surfaces. In this tortured landscape, we see evolution in action via punctuated equilibrium, and valleys and labyrinths create the conditions for speciation. And yet, these conditions only effect organisms of certain body size and ecological requirements: frog populations may become new species in isolation, while widespread coatis forage for food in areas which to humans find practically inaccessible.

To summarize, we have two types of factors limiting the colonization of the summits by contemporary lowland organisms: biotic and abiotic. The biotic factors are plant assemblages, competition with adapted summit species, and the metabolic pathways for the available nutrients on the summit. The abiotic factors include topography, elevation, climate and temperature, spatial availability, and substrate. Now that humans have permanently altered one of these abiotic factors, climate, we have a resultant change in biotic factors. The change will cascade across the entire tepui summit ecosystem, altering substrate. The stable abiotic factors which are physical/spatial will remain unchanged by human alterations, assuming the conservation regime which protects the tepuis remains in place.

What can we do to now?

As Biokryptos project Tepui Watch continues despite current political disruptions and a rise in irrational skepticism regarding climate change, we continue to collect greater amounts of data. This data is observational (from field work), surveillance (from aerial surveys and camera traps) and genetic (from future eDNA studies) and physical (from geology and cartography). The challenge going forward is to process and analyze this data so that we can not only fulfill  our goal of cataloging 100% of Auyan tepuis biodiversity, but also to make predictions based on what we know of the tepuis themselves. This process will require a tremendous amount of data interpretation, and will benefit from the advent of new technologies in remote sensing and image processing. We will need a detailed map of the vegetation of Auyan Tepui, with the entire plateau being imaged and salient feature geotagged. The Google Earth engine would be useful for such an endeavor, and if combined with 360 degree camera images and video could produce highly valuable virtual models of Auyans forests and marshes. We will then need to combine this data with projected climate change models, taking into account both biotic and abiotic variables as we model the projected shrinking of tepui summit ecosystems as they are replaced with new hybrids which incorporate lowland vascular plants and animals.

In effect, we need to know both the biodiversity and functional diversity of the tepuis, as we move from simply inventorying the tepuis toward the greater task of preserving their biodiversity in the coming mass extinction.