Landscape setting of gigantic snakes The prominent placement of monumental panels indicates that they were intended to be seen from some distance (Figures 5 & 6); up close (<1m), the engravings are faint due to the shallow depth of the abrasions. The hills bearing monumental rock art are also visible from much further away than the rock art itself, and likely acted as reference points in the landscape. Our analysis focuses on this quality, aiming to 1) identify locations in the landscape from which these sites could be seen individually, 2) detect commonalities between panels bearing gigantic snakes and 3) map the positioning of snake motifs in relation to one another and the wider landscape. Affordance viewsheds for the rock art sites bearing gigantic snakes were developed in the open-source geographic information system QGIS (v. 3.26). The precise locations of the Pirari-ame and Grulla snakes are awaiting confirmation; as such, we do not include them. Viewshed analysis is a geospatial method for modelling what can be seen from a given observer point, based on the input of an elevation model (Gillings Reference Gillings2015). Affordance viewsheds ask the opposite: from what proportion of the environment is a given point observable (Čučković Reference Čučković2016)? To answer this we use individual elevation model cells as potential observer points and project lines of sight through each neighbouring cell until blocked by a higher elevation cell. Here, we employ NASA shuttle radar topography mission 1-arc second data to generate observer points, offset by 1.7m to represent average observer height. The resulting viewsheds are summed and expressed as a proportion, where a cell value of 1 indicates a target is fully visible from all cells in a neighbourhood and a value of 0 represents no visibility. Following Gillings (Reference Gillings2015), we limit our analysis to viewpoints within 6880m of the gigantic snakes and correct for the Earth's curvature. We assume that dominant vegetation patterns—open savannas with riverine gallery forests—have remained stable over the last two millennia, the period in which most archaeological dates from the Middle Orinoco fall (Lozada Mendieta et al. Reference Lozada Mendieta2022). As noted, gigantic snake engravings are located high above the savanna and gallery forest on prominent inselbergs and will always have had commanding views regardless of the nature of vegetation cover at lower elevations. Inselbergs themselves do not have dense forest cover. Regional environmental reconstructions indicate an increase in fire activity despite a wetter climate over the last 3000 years, which would have suppressed forest expansion, except in the case of moriche palm stands in low-lying, wet terrain (Behling & Hooghiemstra Reference Behling and Hooghiemstra1998). If potential vegetation shifts towards forest have affected the reciprocal visibility of gigantic snakes in relation to their environment, these differences are likely to be minor. To investigate the visual reciprocity of the panels and the landscape, we intersect the affordance viewsheds with visibility maps generated from the snakes. Using the intersection as a mask, we extract the facing (expressed as an azimuth) of the original elevation map used to create the affordance viewsheds. We exclude flat areas with no facing, such as open water. In effect, our combined approach summarises: 1) the overall visibility of gigantic snake panels in their landscape setting (Figure 7); 2) the direction that observers face when viewing the snakes; and 3) the facings of the snakes towards the river (Figure 8). Our results show that, due to their elevation above the relatively modest relief of the riparian savannah in the study area, it is other prominent hills that provide the best viewing points for monumental engravings. Savannahs tend to have the overall lowest proportion of visibility, although sections of river provide views of snakes that are comparable to hills. Riverine areas of high visual affordance fall within and downstream of the Atures Rapids. The stretch of river adjacent to Dagua and Casuarito provides open views of these hills, while the southernmost snake in our sample (Cerro Maipures) has the most restricted visual catchment. Casuarito is notable for being mainly visible from the river. The Palomazón and Pintado panels appear to fall between these ranges, but still above the surrounding savannah values. In addition to prominent topographical features and the Orinoco River, other notable areas of high visual affordance include riverbanks. Major archaeological sites do not appear to coincide directly with areas of visual affordance but are more commonly located on the outskirts (Figure 7). In summary, the cultural significance and function of the rock art is likely connected to how these panels were experienced. Against this backdrop, the consistent visual association of gigantic snakes with the river, rapids and riverbanks is particularly noteworthy considering the aquatic and voyaging associations of large snakes in Indigenous myth.
Conclusion We anticipate that future surveys will continue to encounter monumental rock art sites along the Orinoco River and its tributaries. The precise chronology of these sites remains unresolved, despite apparent artistic parallels in late pre-Columbian material culture. The representation of similar but smaller motifs in other rock art loci (Figure 4) likewise needs to be explored in relation to the monumental panels. Further characterisation of the range of variation within monumental sites will help to clarify how they were used and perceived, including in sites located further away from the Orinoco River that lack snakes, such as Cerro Humeante. Additional exploratory fieldwork is needed to determine their full geographical distribution, particularly in the Upper Orinoco, the Casiquiare and towards the Guiana Shield. We hypothesise an absence of monumental rock art in regions that are historically less characterised by ethnic pluralism, for example in Piaroa-dominated highlands immediately to the east of our study area. This would serve to affirm their role as markers of group identity along contested and variously negotiated stretches of the Orinoco River. The potential occurrence of gigantic snakes upstream of the Guaviare and Atabapo confluence with the Orinoco awaits confirmation. Future work must equally focus on engaging Indigenous groups to deepen our knowledge of their perspectives and understandings about the roles, significance and meanings of the images displayed in rock art sites. Concordantly, it is vital that monumental rock art sites are afforded protection under national and international legislative frameworks to ensure their preservation and continued study. The Indigenous peoples of the Orinoco region must be central to this process.