Drivers and sustainability of bird hunting in Madagascar

Bird conservation depends on robust data on the densities of and threats to each species, and an understanding of the choices and incentives of bird hunters. This first comprehensive study of bird hunting and its effects in Madagascar uses 8 years of data on 87 bird species to determine bird densities and hunting pressure, incentives, choices, methods, spatial variation, and sustainability on the Masoala Peninsula of Madagascar. We find that bird hunting is common, affecting human wellbeing and, for some species, long-term population viability. Hunters caught more abundant species of lower trophic levels and consumers preferred the flavor of abundant granivores and nectarivores, while they disliked carnivores, scavengers, and species with common cultural proscriptions. Wealth increased species selectivity among consumers, whereas food insecurity increased hunting pressure overall. Projected and documented declines in at least three species are concerning, qualifying at least two for increased IUCN threatened species categories. We provide novel, data-driven assessments of hunting's threat to Madagascar's birds, identify key species of concern, and suggest both species- and consumer-specific conservation actions

Data from: Deadwood structural properties may influence aye-aye (Daubentonia madagascariensis) extractive foraging behavior

The identification of critical, limited natural resources for different primate species is important for advancing our understanding of behavioral ecology and toward future conservation efforts. The aye-aye (Daubentonia madagascariensis) is an Endangered nocturnal lemur with adaptations for accessing structurally defended foods: continuously growing incisors; an elongated, flexible middle finger; and a specialized auditory system. In some seasons, ca. 90% of the aye-aye’s diet consists of two structurally defended resources: 1) the larvae of wood boring insects, extracted after the aye-aye gnaws through decomposing bark (deadwood), and 2) the seeds of Canarium trees. Aye-ayes have very large individual home ranges relative to most other lemurs, possibly owing to limited resource availability. Identification of limiting dietary factor(s) is critical for our understanding of aye-aye behavioral ecology and future conservation efforts. To investigate whether aye-ayes equally access all deadwood resources within their range, we surveyed two 100 × 100 m forest plots within the territories of two aye-ayes at Sangasanga, Kianjavato, Madagascar. Only 2 of 150 deadwood specimens within the plots (1.3%) appeared to have been accessed by the aye-ayes. To test whether any external or internal deadwood properties explain aye-aye foraging preferences we recorded species, height and diameter, and quantified the internal tree density using a 3D acoustic tomograph for each foraged and nonforaged deadwood resource within the plots, plus 13 specimens (5 foraged and 8 nonforaged) outside the plots. We did not detect any statistically significant preferences for species, diameter, or height. However, results from the acoustic analysis tentatively indicated that aye-ayes are more likely to forage in trees with greater internal (≥6 cm from the bark) densities. This interior region may function as a sounding board in the tap-foraging process to help aye-ayes accurately identify potential grub-containing cavities in the outer 1–4 cm of deadwood

Effects of agricultural transitions on the evolution of human sensory systems

The transition from hunting and gathering to agricultural food production, beginning around 10,000 years ago, represents a dramatic shift in how people acquire and process food. These shifts to agriculture resulted in major changes in human environments and biology. For example, previous studies have identified selective effects of agriculture in many genes, such as those involved in lactose and starch metabolism, as well as immune function. In other primates and non-primate mammals, sensory systems are often tightly linked to foraging strategy, such that dietary changes are associated with changes in the genes involved in taste, olfaction, and color vision. In this study, we investigated how the shift to agriculture, a major change in foraging strategy, influenced the evolution of human sensory genes. We used targeted capture methods to sequence 898 genes (encoding taste receptors, olfactory receptors, and cone photopigments) and 71 neutral intergenic regions in 165 individuals from two distinct geographic regions: Uganda and the Philippines. In each region, we sampled two hunter-gatherer populations and a neighboring agricultural population, thus allowing us to compare sensory genes between hunter-gatherer and paired agricultural populations across two independent transitions to agriculture. We employed allele frequency-based tests (FST, population branch statistics, and bayenv2) to identify candidate functional variants across sensory genes that may reflect subsistence strategy adaptations. Preliminary results suggest that subsistence strategy influenced subtle shifts of allele frequencies in functional variants in at least two bitter taste receptor genes and thirteen olfactory receptor genes in populations from both Uganda and the Philippines.First author draf

Thompson et al. deadwood foraging and structural property data

Thompson et al. deadwood foraging and structural property dat

Data from: Island-wide aridity did not trigger recent megafaunal extinctions in Madagascar

Researchers are divided about the relative importance of people versus climate in triggering the Late Holocene extinctions of the endemic large-bodied fauna on the island of Madagascar. Specifically, a dramatic and synchronous decline in arboreal pollen and increase in grass pollen ca. 1,000 years ago has been alternatively interpreted as evidence for aridification, increased human activity, or both. As aridification and anthropogenic deforestation can have similar effects on vegetation, resolving which of these factors (if either) led to the demise of the megafauna on Madagascar has remained a challenge. We use stable nitrogen isotope (δ15N) values from radiocarbon-dated subfossil vertebrates to disentangle the relative importance of natural and human-induced changes. If increasing aridity were responsible for megafaunal decline, then we would expect an island-wide increase in δ15N values culminating in the highest values at the time of proposed maximum drought at ca. 1,000 years ago. Alternatively, if climate were relatively stable and anthropogenic habitat alteration explains the palynological signal, then we would anticipate little or no change in habitat moisture, and no systematic, directional change in δ15N values over time. After accounting for the confounding influences of diet, geographic region, and coastal proximity, we find no change in δ15N values over the past 10,000 years, and no support for a period of marked, geographically widespread aridification culminating 900-950 years ago. Instead, increases in grasses at around that time may signal a transition in human land use to a more dedicated agro-pastoralist lifestyle, when megafaunal populations were already in decline. Land use changes ca. 1,000 years ago would have simply accelerated the inevitable loss of Madagascar's megafauna

Data for all individuals.

Isotope data, radiocarbon date, taxonomic, and locality information for all individuals included in our analyses