From April, 2014 to August 2014, the Biokryptos team undertook the first camera trap transect survey of Auyan Tepui. The intent of this survey was obtain a baseline biological diversity measurement of the southern talus slope on the way to the summit, as the talus area of Auyan is notoriously under-surveyed. We followed the trails laid out by the Pemon for tourists traveling to the summit of Auyan, setting up camera traps at two camp areas, Guayaraca and Penon. As we learned during the 2012 camera trap pilot studies, the talus slopes are transition zones, subject to a complex interplay of ecosystems and floral assemblages. As the earth enters a period of extreme warming due to human activity (Anthropogenic Climate Change), monitoring the biodiversity of the talus slopes is more important than ever. With an anticipated upward climate envelope shift of 500 to 700 meters by 2100 (or sooner, depending on the climate model), dramatic changes and high extinction rates in the summit ecosystem are anticipated as plants and animals move toward higher altitudes. Changes in floral and faunal assemblages in the talus transition zones need to be monitored to track the rate and extent of climate driven vertical migration.
The survey area are the two major campsites on the talus slopes of Auyan Tepui; Guayaraca and Penon. Guayaraca (1100 meters in altitude) is a heavily forested area, with vegetation similar in structure and composition to the surrounding lowland forests. There are numerous small streams and creeks in and around Guayaraca and the ecosystem is complex and rich. Penon, (1500 meters altitude) is a steep and rocky area, with mixed vegetation typical of a mountain talus forest. Forest canopy height is highly variable, with large trees and dense forests around steep scarps and waterfalls where sufficient substrate has developed. Where the substrate has eroded away, exposed rocks and shrubs dominate large areas bordering these forests. Both Guayaraca and Penon have been surveyed from the initial explorations of the Phelps expedition (1937-38), and are host to a comparatively high volume of tourists (approx. 500 people per anum) attempting to make the summit camp of Libertador. Despite the tourist presence, the surrounding area outside of the camps remain little explored, and Biokryptos is again the first organization to place camera traps in these two locations.
|Southern Auyan Tepui talus structure, with trail from Uruyen and camp locations included.|
Survey Results and analysis
1) Guayaraca. Out of 40 photos, the traps at Guayaraca had 40 positive captures from 3/27/2014- to 5/1/14. Four cameras were operational at Guayaraca, Biokpt 1 through Biokpt 4. The results were images of a large predatory bird, numerous deer, and a paca. While the 2012 camera trapping pilot study obtained photographs of the crab eating fox Cerdocyon thous thous at Guayaraca this animal was not photographed during the current survey period. The cameras were set up within 100 meters of the camp location, near a stream which provides the primary water source for the camp site.
2)Penon. Out of 523 photos, the camera traps at Penon had 245 positive captures from 5/4/14 to 7/30/2014. At Penon, the camera traps obtained images of a tayra (Eira barbara), and a southern naked tailed armadillo (Cabasous uncinctus), as well as a variety of squirrels, rodents and mouse possums (species pending identification), as well as birds. At Penon, these animals were recorded in forested areas which border high altitude scrub within 100 meters of the campsite. The vegetation can be described as a mixture of mountain forests and low canopy talus slope vegetation.
As this is the first camera trap survey of Auyan Tepui, I am comparing our results to the 1937-38 Phelps expedition to Auyan Tepuy to obtain a baseline of faunal presence and distribution. This gives us the earliest historical survey with which to cross reference current Biokryptos efforts on Auyan.
There are three species of Cervidae in the Guiana Shield: Mazama americana (red brocket deer), Mazama gouazoubira (Gray brocket deer) and Odecoileus cariacou (white tailed deer). Biokryptos camera traps recorded numerous deer at Guayaraca, with image captures spread out over several weeks. Tate mentions two specific instances of sightings of deer at Auyan Tepui:
“1)Cervidae- “I (Tate) saw but failed to secure a fully antlered buck at Mt. Auyan Tepui, 3000 feet” and
2) Mazama nemorivaga (Amazonian Brown Brocket, now M. gouazoubira)“Material Thirteen specimens from British Guiana; Mt Auyan tepui (1) (small teeth), Mt Duida (3); the type of Murelia from Caqueta."”
Tate does not mention the collection altitude for M. nemorivaga (M. gouazoubira), though he does mention a smaller tooth size in the animals he recorded. The size of individual members of Cervidae is variable both with individuals and in accordance with Bergmanns rule, therefore Tate's observation may be irrelevant- tooth size is variable within a species. With regard to his "fully antlered buck", the antlers of M. gouazaoubira are less impressive than those of O. cariacou, so I would tentatively assume that Tates unspecified Cervid was in fact a the white tailed deer O. cariacou. The location of the sighting, (3000 feet) roughly corresponds with the altitude of Guayarca; therefore I conclude that Tate may have seen this species at this location. After consulting with Bioryptos lead investigator Arturo Berti, it seems that deer are well known to range up into Guayaraca, and the Pemon are aware of their presence on the talus slopes. As they are not considered unusual at this altitude and location, verification of Tates sighting is not surprising, and represents a continuum of deer activity at 1000 meters from the 1930s to the present date.
Paca (Cuniculus paca)
The Paca (formerly Agouti Paca, now Cuniculus Paca) is a widely distributed rodent in the Guiana Highlands, and is IUCN Redlisted as Least Concern (LC). We recorded three captures of a paca at Guayaraca during the camera trapping period. Pacas were sighted by Tate on the talus of Auyan, at 1000 meters. The presence of pacas at Guayaraca is not unusual, though it is the first evidence of these animals at this location on the talus. Pacas are highly frugivorous, and are known seed dispersers. Although it remains to be seen if Cuniculus paca are in fact present on the summit of Auyan, if they are summit invasive pacas would provide a potential food source for any bush dogs that would invade the summit of Auyan. They are a primary food source of the bush dog Speothos venaticus, which has an implication for an animal sighting made by Alexander Laime in the 1970s on the summit of Auyan. Laime reported what he described as a "small bear, like a North American Grizzly bear", on the summit of Auyan near one of his camps south of the second wall. Superficially, bush dogs have a striking physical similarity to ursids, although they are completely unrelated. During the 2014 expedition, our team also found footprints on the summit of Auyan which strongly resemble the prints of Pacas.
The traps at Penon captured images of animals which were more unexpected in their distribution than those at Guayaraca. Whereas the faunal composition at Guayaraca was expected to contain a variety of large bodied lowland mammals, Penon is a different story. The camp is located in an altitudinal zone in which tepui like floral assemblages are more prevalent, gallery forests are less prevalent and give rise to more scrub and herbaceous assemblages. This is a mid-mountain environment, complex, diverse, and highly fragmented with a significant altitudinal gradient.
1) Tarya (Eira barbara), Venezuelan subspecies E. b. poliocephala.
There are two subspecies of Tayra in Venezuela, E. b. poliocephala east of the Ornioco and present into Guyana and North East Brazil, and E. b. sinuesis to the west and into Colombia. Tayras are IUCN Red listed as being Least Concern (LC), although their population trend is decreasing as a result of human activity. The subspecies photographed was E. b. poliocephala, based on pelage colour and markings. Although rare at elevations above 1,200 meters, Taryras can be found up to 2,400 meters. Tayras are opportunistic highly omnivorous mesopredators; they will feed on small vertebrates, carrion, and fruit, and will actively pursue prey, however they have not been observed stalking or ambushing prey species. They are heavily diurnal, though also active nocturnally when crossing grasslands between forests. They favour an arboreal lifestyle, and inhabit most forest ecosystems in Central and South America, ranging from scrub forests to alpine forests and jungle. Tayras maintain large, overlapping home ranges, traveling between 24 to 16 square kilometres during the course of a year, and are unidirectional in their foraging movements.
It was considered unusual by the expedition members to see this animal at Penon, and Tayras were not mentioned by Tate as being present at Auyan. While this may be the first recorded sighting to a Tayra on a tepui talus slope, the presence of this animal at 1500 meters is consistent with its known altitudinal range, and fits within the modalities of the Tayras ecological preferences. The location of this sighting, in the highlands of Venezuela at Auyan, is in the extreme west of this subspecies known range.
2) Guiana squirrel (Sciurus aestuans)
Sciurus aestuans is IUCN redlisted Least Concern (LC) through out its range, although it is understudied in Venezuela an its population dynamics outside of Brazil are unknown. It inhabits forest canopy, and seems to be ubiquitous in Penon. A frugivore, and seed predator, this squirrel was photographed 8 times at Penon, and is well known to the local people. Its presence in the forested talus slopes of Auyan was expected. S. aestuans is strongly diurnal, and highly active in its range. Their population density in the talus slope is unknown, as are its seed dispersal capabilities and feeding preferences. During the 2014 expedition, expedition member Paul Stanley saw a squirrel with extremely red pelage at Campo Dragon, on the summit of Auyan. We have identified this as the squirrel species Sciurus flammifer. Photographic evidence will be necessary to confirm the presence of this rodent on Auyan, as S. flammifer is considered to be restricted to the lowlands.
3) Southern naked tailed Armadillo (Cabassous uncinctus)
With an IUCN status of Least Concern (LC), C. uncinctus is a fairly common armadillo in South America, and is present in lowland and sub-mountain forests. This is the first time it has been successfully recorded on a tepui talus slope, and its presence there surprised the expedition members. Tate observed evidence of an armadillo on the talus of Auyan, though he never identified the species. He states: "At Mt Auyan -Tepui many small holes, probably the work of this armadillo, were observed in open, sandy places. Neither we, nor the Indians who were offered a substantial bonus for specimens, ever managed to secure one.".
Our efforts represent a solution to Tate’s problem, solved some 77 years later. Correspondence with Venezuelan scientists confirmed the unusual nature of this encounter- C. uncinctus is usually considered absent from the highlands of the Guiana Shield, it is listed as being primarily an inhabitant of the lowland Venezuelan savanna in Canaima National Park. The animals are fossorial and insectivorous, eating termites and ants. They are considered solitary and nocturnal, with a population density that varies from approx. 1 animal per square kilometer in the mountainous regions of eastern Venezuela to 0.25 individuals per square kilometer in the Brazilian Cerrado. The population density of Cabassous unicinctus at Penon (ie 1500 meters on a tepui talus slope) is completely unknown, as is the trophic strategy of the animal in this location. Finding this animal at this location, and at this altitude, was very fortunate, and unusual.
|Southern naked tail armadillo, Penon|
4) Small bodied mammals: rodents and marsupial mice.
Our cameras recorded numerous captures of rodents and marsupial mice: approximately 80 in total, with about 9 blurry photo with some anatomical features (feet or tails) visible. The diversity and complexity of marsupial mice and rodents in the Guiana Highlands is beyond the current scale of this update. A future blog post detailing the phylogeny, distribution, and ecological dynamics of this diverse group of marsupials and rodents will follow at a later time, when more camera trap data is analyzed in detail so that the myriad of small animals photographed by Biokryptos camera traps can be identified. There are ten species of marsupial mice (family Didelphidae), 33 species of new world rats and mice (family Muridae), and eleven species of spiny rats (family Echimyidae) in Venezuela, and they deserve a more detailed blog post in the future.
This is the first camera trap reconnaissance of a tepui talus slope to date. As such, we are not yet in the position to to make any detailed conclusions regarding the faunal composition of the talus ecosystems. While the flora of Auyan has been studied in depth, the distribution and population densities of the talus and summit vertebrate fauna remains understudied. Topographically complex and with a single known trail leading to the summit, Auyan has some 200 square kilometers of discontinuous talus slope area- little of which has been surveyed, and the bulk of which remains almost entirely inaccessible. The entire north and eastern talus of Auyan is dominated by enormous forests, with canopy height far outstripping the scrub forests in the west. Classifying the talus slope by region beyond lowland/sub mountain/mountain is difficult. Future surveys will be necessary to map and classify ecosystems of the talus, which vary according to substrate, topography, micro climate, and hydrology. However, at this time we can make some broad statements about the current conditions on the slopes, at least on the southern prow of Auyan.
1)Lowland fauna extends up to 1000 meters
Up to 1,000 meters, lowland fauna can be expected to be present, including large canines and herbivores. Lowland fauna can and does range into this elevation, and given the topography of Auyan the 1000 meter contour offers a fairly large area in which lowland animals may exist. The phenomena was observed by Phelps as well, so it seems safe to assume that this is a historical distribution, and not one effected by recent climate change.
2) Faunal composition beyond 1000 meters is more diverse than anticipated
On the talus slopes, lowland fauna may be present given lowland analogous ecosystems and sufficient food sources. The fauna in the midlands and mountain region of the slopes includes Tayras and Armadillos. The positive identification of an armadillo at 1500 meters confirms Tates observations after more than 70 years, indicating another historical continuity in fauna distribution. The presence of Tayras at this location was a surprise to the Pemon experts, who normally do not observe this animal at this altitude. The faunal composition of the talus may represent a unique mixture of lowland and summit organisms, or it may be continuous from the lowlands up the physical barriers such as steep escarpments 200 meters below the summit.
3) Barriers to lowland faual summit invasion exist, but may not be uniform
There is a barrier to distribution of lowland animals, evident in high levels of tepui summit herpetofaunal endemicity. However, determining how permeable this barrier is, and what specific species it effects, is important. The barrier for highly vagile non-volate mammals may be much less than what it is for reptiles. Where the camera trapping efforts took place, the geomorphology of the tepuis is gradual sloping talus cutting off at around 1700 meters, followed by steep escarpments, upwards of 200 meters, followed by flat summit topography. In the north of Auyan, the talus is steep but escarpments are less common, although known trails from the lowlands to the summit are mostly absent. Phelps noted that fire seemed to have reached up to 1500 meters and possibly beyond during the 1937-38 expedition, which may have affected the current vegetation in the south of Auyan. The north talus slopes are different in composition than the south, and support a high canopy gallery forest from 1000 meters up to the summit.
4) The barriers may be climate envelopes
Barriers to species distribution may be based more on climate and ecology rather than physical separation. The summit vs. lowland and talus climates differs in terms of temperature and precipitation. At 0-500 meters the mean annual temperature is above 24 degrees, falling to 24-18 degrees at 500-1000 meters, 12-18 degrees at 1500 meters and above, and around 10 degrees and below at 2300 plus meters. Precipitation at the highest altitude is very high (2000-3000 mm per year), due to dense clouds and high moisture. While soils and substrate on the summit are different than those of the lowlands and talus, corridors of lowland friendly substrate may exists on the talus. If this is the case, then climate change over the next 100 years may allow for upward lowland vegetation migration through the talus, allowing for the accompanying migration of lowland species upward.
If the IPCC projections for climate change are come to pass, and the kind of vertical migration described by Rull and his colleagues is accurate, then this talus slope has been, and continues to be, a transition zone between the summit and lowland biota. In an era of intense climate change, with some 500 to 700 meters of vertical ecosystem displacement anticipated by 2100 A.D., intensive surveys of the talus slope environments, as well as long term monitoring, is absolutely critical from a conservation standpoint. By observing the spatial location of fauna currently, it may be possible to predict their distribution as long term climate change alters the tepui ecosystems. This is a daunting undertaking, and will require a combination of high resolution satellite reconnaissance and in depth filed work placing camera traps across the uncharted and unknown talus slope environment.