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BackgroundComponents of diet known as fallback foods are argued to be critical in shaping primate dental anatomy. Such foods of low(er) nutritional quality are often non-preferred, mechanically challenging resources that species resort to during ecological crunch periods. An oft-cited example of the importance of dietary fallbacks in shaping primate anatomy is the grey-cheeked mangabeyLophocebus albigena. This species relies upon hard seeds only when softer, preferred resources are not available, a fact which has been linked to its thick dental enamel. Another mangabey species with thick enamel, the sooty mangabeyCercocebus atys, processes a mechanically challenging food year-round. That the two mangabey species are both thickly-enameled suggests that both fallback and routine consumption of hard foods are associated with the same anatomical feature, complicating interpretations of thick enamel in the fossil record. We anticipated that aspects of enamel other than its thickness might differ betweenCercocebus atysandLophocebus albigena.We hypothesized that to function adequately under a dietary regime of routine hard-object feeding, the molars ofCercocebus atyswould be more fracture and wear resistant than those ofLophocebus albigena. MethodsHere we investigated critical fracture loads, nanomechanical properties of enamel, and enamel decussation inCercocebus atysandLophocebus albigena.Molars ofCercopithecus, a genus not associated with hard-object feeding, were included for comparison. Critical loads were estimated using measurements from 2D µCT slices of upper and lower molars. Nanomechanical properties (by nanoindentation) and decussation of enamel prisms (by SEM-imaging) in trigon basins of one upper second molar per taxon were compared. ResultsProtocone and protoconid critical fracture loads were significantly greater inCercocebus atysthanLophocebus albigenaand greater in both than inCercopithecus. Elastic modulus, hardness, and elasticity index in most regions of the crown were greater inCercocebus atysthan in the other two taxa, with the greatest difference in the outer enamel. All taxa had decussated enamel, but that ofCercocebus atysuniquely exhibited a bundle of transversely oriented prisms cervical to the radial enamel. Quantitative comparison of in-plane and out-of-plane prism angles suggests that decussation in trigon basin enamel is more complex inCercocebus atysthan it is in eitherLophocebus albigenaorCercopithecus cephus. These findings suggest thatCercocebus atysmolars are more fracture and wear resistant than those ofLophocebus albigenaandCercopithecus. Recognition of these differences betweenCercocebus atysandLophocebus albigenamolars sharpens our understanding of associations between hard-object feeding and dental anatomy under conditions of routine vs. fallback hard-object feeding and provides a basis for dietary inference in fossil primates, including hominins. 

Abstract Conservation funding is currently limited; cost‐effective conservation solutions are essential. We suggest that the thousands of field stations worldwide can play key roles at the frontline of biodiversity conservation and have high intrinsic value. We assessed field stations’ conservation return on investment and explored the impact of COVID‐19. We surveyed leaders of field stations across tropical regions that host primate research; 157 field stations in 56 countries responded. Respondents reported improved habitat quality and reduced hunting rates at over 80% of field stations and lower operational costs per km²than protected areas, yet half of those surveyed have less funding now than in 2019. Spatial analyses support field station presence as reducing deforestation. These “earth observatories” provide a high return on investment; we advocate for increased support of field station programs and for governments to support their vital conservation efforts by investing accordingly.