Figure 1.
(a) The experimental area beside a steep mesa, with sandstone (SS) and wood (W) anvils, and the Bigorna Nova (BN). (b) A sandstone anvil at the field laboratory in 2003, and (c) the same anvil in 2014, showing the erosive effect of capuchin pounding.
Table 1.
Age, sex and body mass of monkeys in the studied group, May 2011.
Figure 2.
Setting up the Bigorna Nova (BN).
(a) The original location and position of the stone SE of the field laboratory, with a 10 cm scale on the tilted face; (b) BN in position at the start of the experiment; the upper surface has chalked crosses every 5 cm to aid in determining strike positions.
Figure 3.
(a) Bigorna Nova (BN) experiment in progress, with RMC operating the video camera; (b) BN surface damage during the experiment, with tucum shells and quartzite hammer stone, scale is 10 cm; (c) BN at the end of the period of continuous monitoring, note the pitted surface and surrounding debris, scale is 10 cm; (d) BN 16 months after the experiment, surrounding stone and nut debris is extensive, scale is 5 cm.
Table 2.
Summary data for the BN experiment.
Figure 4.
BN pit measurements, with anvil survey data for comparison: (a) BN pit width and depth relative to length, and surveyed anvil pit widths relative to length; (b) ratios of pit length∶width and length∶depth formed on the BN surface during the experiment.
Figure 5.
Schematic BN cross-sections, 2011–2014: (a) South to North; and (b) West to East.
The uppermost level in each cross-section is the anvil shape at the start of the experiment (2011 start) and subsequent levels were taken at the end of the initial experimental period (2011 end), in September 2012, and in May 2014.
Figure 6.
Results of the stone-drop use-wear experiment: (a) pit width and depth relative to length (piaçava and tucum results combined); (b) ratio of pit length∶depth for three piaçava nuts, and one tucum nut (the tucum nut has sixty strikes, the others 100 strikes).