The research team, led by investigators working across the conservation area’s full elevational range of 3,505 to 4,284 meters above sea level, spent months tracking two focal gelada groups whose combined home ranges spanned the region’s primary ecological gradients — from extensive Festuca grasslands to mixed communities dominated by the endemic Giant Lobelia (Lobelia rhynchopetalum). Using instantaneous scan sampling across both the dry season (February to April 2021) and the wet season (June to August 2021), the observers generated 960 scan samples and 761 discrete feeding records encompassing 25 distinct food items. The dataset represents the first comprehensive assessment of Southern Gelada feeding ecology in this purely Afro-alpine setting, which lacks the sub-Afro-alpine buffer zones found at other Ethiopian study sites and therefore amplifies every seasonal fluctuation to its biological limit.

The headline result is a diet dominated not by grasses, as might be expected for the world’s most graminivorous primate, but by forbs — herbaceous plants whose roots, leaves, flowers, stems, and young shoots constituted 55.7 percent of all feeding records. Grasses accounted for 42.7 percent, while insects contributed a marginal 1.6 percent. This proportion deviates notably from gelada populations at Borena Sayint National Park, where grasses make up nearly 80 percent of the diet, and the discrepancy likely reflects the steep slopes, heavy livestock grazing pressure, and reduced grass palatability characteristic of Abune Yosef’s high-altitude terrain. Among individual species, Festuca simensis emerged as the clear staple, representing 24.05 percent of total diet utilization — a role consistent with its abundance and relatively high digestibility across gelada habitats throughout Ethiopia.

Seasonal comparisons revealed a highly significant association between season and plant-part consumption (chi-square = 65.29, p < 0.001), with standardized residuals pinpointing the exact nature of the shift. Grass-blade consumption rose significantly in the wet season, while root consumption rose significantly in the dry season. Underground roots and rhizomes — energetically expensive fallback foods requiring substantial excavation effort — comprised 65.93 percent of dry-season feeding records but only 22.09 percent in the wet season. This pattern aligns precisely with the Fallback Food Hypothesis, which predicts that primates broaden their diet during periods of scarcity by incorporating less preferred but accessible resources. As above-ground biomass desiccates and loses nutritional quality in the dry months, geladas switch to digging up roots and rhizomes that provide essential water and carbohydrates when other options vanish.

Dietary niche breadth, quantified using the Shannon Diversity Index, expanded dramatically in the dry season (H’ = 2.31) and contracted in the wet season (H’ = 1.92). Monthly analysis using the Friedman test confirmed that feeding diversity declined progressively from February (H’ = 2.38) to August (H’ = 1.82), with Dunn’s post-hoc contrasts showing significantly higher diversity in the early dry months than in the later wet months. This trajectory confirms that geladas progressively narrowed their dietary niche as the wet season advanced and high-quality grasses became abundant — exactly the selective foraging predicted by Optimal Foraging Theory when preferred resources are plentiful. Levin’s niche breadth index, which measures the variety of broad food categories utilized, similarly indicated a wider dietary niche in the dry season, reinforcing the picture of a species that broadens its ecological footprint under stress and specializes when conditions improve.

Perhaps the most striking finding concerns dietary selectivity. Using three complementary indices — the Forage Ratio, the Electivity Index, and Jacobs’ index — the researchers demonstrated that geladas do not feed randomly or in proportion to availability but exercise strong, context-dependent selection that shifts almost completely between seasons. Overall, Haplocarpha schimperi (Forage Ratio = 5.87, Electivity = 0.71) and Lobelia rhynchopetalum (Forage Ratio = 5.26, Electivity = 0.68) were the most preferred species, consumed disproportionately to their abundance. Yet in the dry season, both of these highly preferred species were actively avoided, while Rumex nepalensis and Festuca richardii became the primary targets. When the wet season arrived, Delosperma abyssinicum, Festuca richardii, and Thymus schimperi rose to prominence as the main selection targets, and avoidance of Haplocarpha and Lobelia intensified further. The weak Spearman correlation between seasonal preference rankings (rs = 0.36) confirms that foraging strategies are anything but static.

This dynamic reorganization of selectivity suggests that plant choice is closely tied to shifting phenological states — flowering, new leaf growth, desiccation — rather than to any intrinsic, year-round nutritional superiority of particular species. Lobelia rhynchopetalum, for instance, is known to have high water content, which could be crucial for hydration in the arid Afro-alpine environment, while the preference for Haplocarpha schimperi might reflect nutrient density or low concentrations of secondary compounds such as tannins. Conversely, the active avoidance of Festuca abyssinica and Bidens macroptera, despite their presence in the environment, points to possible physical or chemical defenses — Bidens species often bear hooked bristles that might cause irritation, and F. abyssinica might be tougher or chemically protected. The researchers caution that without direct phytochemical analyses, the underlying drivers of these preferences remain speculative, though the strong correlation between availability and consumption (rs > 0.8) indicates that selectivity operates within the boundaries of what the environment actually offers.

The temporal dimension of gelada foraging adds another layer of sophistication. Kernel density estimation of feeding activity across 960 scans revealed a consistent bimodal pattern in both seasons, with distinct peaks in the early morning (07:30–09:00) and late afternoon (15:00–16:30), and a pronounced midday decline between 12:00 and 14:00. This schedule likely represents a thermoregulatory adaptation, synchronizing the most energetically demanding activities with cooler ambient temperatures to reduce the risk of hyperthermia under intense high-altitude solar radiation. Intriguingly, the composition of the diet also shifted across the day: morning feeding was predominantly grass-based in both seasons (72 percent in the dry season, 65 percent in the wet season), while afternoon feeding incorporated a higher proportion of forbs and insects. The researchers suggest this diurnal shift might reflect a strategy for managing digestive constraints — consuming grasses earlier in the day to maximize fiber digestion through longer gut retention times, then balancing nutrient intake with forbs and insects later on.

The narrow dietary richness recorded at Abune Yosef — just 22 plant species, compared with 56 at Guassa Community Conservation Area, 74 at Borena Sayint National Park, 61 at Arsi, and 41 at Abo Gedam — most likely reflects the extreme altitudinal constraints of a purely Afro-alpine ecosystem rather than behavioral rigidity. Between 3,505 and 4,284 meters, the landscape inherently supports lower floristic diversity than the sub-Afro-alpine or transitional ecosystems at those other sites. The physical limitation of available forage species, rather than any inability of the geladas to diversify, therefore explains the narrower dietary breadth observed here. This distinction matters for conservation: the Southern Gelada’s remarkable plasticity is being expressed at the very edge of what the habitat permits, and any further reduction in floristic heterogeneity — whether from climate change, overgrazing, or habitat conversion — could push the population beyond its adaptive limits.

The study opens several critical avenues for future research. Combining phytochemical and proximate analyses of key forage species and seasonal roots would determine whether preference shifts are driven by fluctuating protein content, specific mineral requirements, or changes in plant secondary metabolites. Targeted investigation of the persistent midday feeding decline — pairing fine-scale microclimatic data with physiological measures such as body temperature and respiration rate — would test whether this rhythm is strictly thermoregulatory or governed by other ecological constraints. And comparing multiple social units across varying degrees of human disturbance will be essential to quantify the true behavioral limits of the Southern Gelada’s ecological plasticity. For now, the geladas of Abune Yosef stand as a vivid reminder that even in the harshest corners of the biosphere, evolution has equipped some primates with a foraging flexibility so complete that the line between specialist and generalist dissolves with the seasons.

Subject of Research: Behavioral Ecology

Article Title: Seasonal niche shifts and foraging plasticity of the Southern Gelada ( Theropithecus gelada obscurus Heuglin, 1863) ( Cercopithecidae , Papionini ) within the extreme Afro-alpine ecosystem of the Abune Yosef Zigit Community Conservation Area, Ethiopia

Article References: Seasonal niche shifts and foraging plasticity of the Southern Gelada ( Theropithecus gelada obscurus Heuglin, 1863) ( Cercopithecidae , Papionini ) within the extreme Afro-alpine ecosystem of the Abune Yosef Zigit Community Conservation Area, Ethiopia. (n.d.). https://doi.org/10.3897/biorisk.24.206086

Image Credits: AI Generated

DOI: 10.3897/biorisk.24.206086

Keywords: geladas, Ethiopia, Afro-alpine, foraging behavior, primates, fallback foods, optimal foraging, behavioral plasticity, Abune Yosef, seasonal diet, Seasonal, niche

Archaeologists have long treated small prey, including mollusks, as a signature of something big. In foraging theory, prey body size acts as a proxy for rank, and when large, high-value game grows scarce, smaller and slower resources enter the diet in response to declining foraging efficiency. This logic underpins the Broad Spectrum Revolution, the Late Pleistocene and Early Holocene diversification of diets that some researchers link to the eventual emergence of food production. Yet small animals, from birds and beavers to tortoises and snails, appear in human contexts far earlier than that transition, sometimes as early as the Plio-Pleistocene deposits of Olduvai Gorge. The earliest solid evidence for cooking land snails comes from Border Cave in South Africa, roughly 170,000 years ago, and systematic gastropod consumption shows up in Mediterranean sites from the Upper Paleolithic onward, including the famous Capsian escargotieres of North Africa. The question is what these assemblages mean: a fundamental reshaping of subsistence, or a routine seasonal response that leaves subtler traces?

Distinguishing human snail consumption from natural accumulations is the central technical challenge. Land snails can pile up in caves and open sites on their own, attracted to organic debris, burrowing into soil during aestivation, or simply dying where they live. Researchers have therefore developed a suite of markers for anthropogenic assemblages: monospecific composition, tight spatial association with artifacts and hearths, evidence of burning on shells or chemical alteration of shell minerals, homogeneity in shell size, and a high proportion of complete shells relative to fragments, since nonhuman predators tend to crush shells during digestion. The problem, Lupo and Edwards argue, is that most of these criteria rest on limited experimental and ethnographic grounding. Their fieldwork in the Central African Republic offered a chance to build that missing foundation, because the snails in question were demonstrably collected by people whose camps and discard patterns could be examined directly.

The giant West African snail turns out to be a remarkable resource. Its meat is extraordinarily protein rich, comprising 37 to 51 percent of dry weight and comparing favorably with fish, chicken and beef, and it delivers all nine essential amino acids along with substantial amounts of iron, zinc, magnesium, phosphorus and iodine. Most strikingly, the meat is a potent natural source of calcium, with recorded values as high as 421 to 472 milligrams per 100 grams, far exceeding cow’s milk at roughly 120 to 130 milligrams per 100 milliliters. In forest diets where calcium sources are scarce, snails fill a genuinely critical nutritional niche. Stable isotope work on regional foods further shows that the nitrogen signature of snail meat resembles that of small forest mammals. There are risks: land snails can carry bacterial pathogens such as E. coli, Salmonella and Listeria, though studies suggest pathogen loads track environmental contamination and are far lower in rural forest settings than in urban ones.

The ecology of the snails shapes how people harvest them. During the hot, dry season, A. marginata aestivates, sealing its shell opening with a mucus epiphragm and burrowing into the top 10 to 15 centimeters of soil. When the rains arrive, the snails become active again, climbing onto tree trunks and vegetation. They are not spread evenly across the landscape but cluster in patches where microhabitats favor shell growth, often near certain trees, and they avoid agriculturally disturbed soils. Foragers exploit this predictability. Lupo and Edwards accompanied 18 collecting expeditions and found that parties of two to four women with children walking along village roads encountered roughly one snail every eight minutes, but once they moved onto forest paths toward known patches, the encounter rate rose to one snail every 2.6 minutes. Most snails clung to tree trunks and leaves, hidden in leaf litter on the ground, so foragers knocked them down with makeshift poles or, occasionally, sent children up the trunks to retrieve them.

The timing of snail collecting is what gives the practice its archaeological significance. Prey availability barely changes seasonally in this forest, but hunting technology does. During the dry season, cooperative net hunts involving men, women and children bring in large quantities of blue duikers, and meat acquisition rates in the study villages were 16 to 96 percent higher than in the wet season, when rain damaged and weighed down the fiber nets. Wet season hunters fell back on snares, spears and hand capture. Meanwhile, agricultural labor demands on forager women also peaked in the dry season, when they were hired by farming households. The wet season thus opened a window in which women and children, freed from both cooperative hunting and fieldwork, could pursue other forest resources, and snail collecting became a dedicated activity embedded within broader foraging trips that also targeted Irvingia gabonensis nuts, Treculia africana seeds and wild greens.

Quantitatively, snails are a low return but low risk resource. The average post-encounter return rate for collecting and processing, excluding cooking, was 194 kilocalories per hour, comparable to the 106 to 215 kilocalories per hour yielded by net hunted duikers but lower than any other wet season prey type. Yet collecting always succeeded, with an average live weight yield of about 750 grams per trip, whereas many hunts routinely failed. Snails were processed in several ways, some of them ethnically distinctive. Foragers typically crushed live shells by hand or with a knife handle or wooden baton, picked out the larger fragments, rinsed the meat and cooked it skewered over fire, in stews or in shallow pans. Farmers more often levered the meat from unbroken shells or skewered whole live snails through the foot once the animals raised their breathing pores above water and roasted them. Shells and fragments were discarded differently depending on technique: complete unburned shells went into leaf packets or trash middens, while crushed fragments were swept into hearths. Nothing was preserved or commercially traded; snails were consumed the same day or exchanged alive with local farmers.

The real analytical payoff came from Sungu, a wet season camp of roughly 120 people occupied for about three and a half months in 2000 and recorded four months after abandonment. The site covered some 3,375 square meters with around thirty domestic structures, unprepared interior and exterior fires, roasting pits for rats, pangolins and caterpillars, and five ash and charcoal dumps. Surface collection and test excavation of eleven combustion features recovered a faunal assemblage dominated by pangolins, giant pouched rats and giant snails. Because snail shells are friable and shatter easily, the researchers counted both fragments and whole specimens, comparing completeness, burning and spatial distribution against the rest of the small fauna. About 37 percent of snail specimens were complete shells, almost all clustered behind domiciles inside dried leaf packets, a pattern reflecting the levering technique and on-site consumption. A statistical comparison showed no significant difference in completeness between snails and other small prey. Burning appeared on 31 percent of snail fragments but never on complete shells, and a chi-square test found the incidence of burning statistically indistinguishable from that of other small game. Spatially, shell fragments clustered near hearths much as other faunal remains did, suggesting site clean-up or casual tossing into fires rather than cooking itself, since fire was not needed to extract the meat.

The broader implication is a caution and an invitation. The Sungu data validate several criteria archaeologists already use, including completeness, burning and association with combustion features, while showing that these traits can also encode preparation technique, and perhaps even ethnic identity and disposal habits, rather than diet alone. More provocatively, the study demonstrates that a nutritionally valuable, low ranked resource can enter the diet as a purely seasonal strategy, pursued when protein is temporarily depressed and when available labor is not otherwise engaged, without any large scale shift in foraging efficiency. Seasonal responses, the authors warn, can mimic the broad spectrum signatures of genuine dietary transition, so archaeologists should weigh taxonomic richness, seasonal indicators and processing traces together before declaring a revolution. Given that land snails require no special technology, pack critical calcium and protein, and may have been exploited for millennia, the humble escargot may have far deeper and more nuanced roots in the human story than the shell piles alone have ever suggested.

Subject of Research: Seasonal exploitation of terrestrial gastropods by Central African forest foragers

Article Title: Eating escargot: seasonal terrestrial gastropod exploitation by forest foragers in the ethnoarchaeological record of Central Africa

Article References: Lupo, K. D., & Edwards, N. M. (2026). Eating escargot: seasonal terrestrial gastropod exploitation by forest foragers in the ethnoarchaeological record of Central Africa. Archaeological and Anthropological Sciences, 18(10), Article 197. https://doi.org/10.1007/s12520-026-02560-z

Image Credits: AI Generated

DOI: 10.1007/s12520-026-02560-z

Keywords: ethnoarchaeology, land snails, Central Africa, forest foragers, Archachatina marginata, zooarchaeology, dietary diversification, Broad Spectrum Revolution, seasonal foraging, gastropod taphonomy, optimal foraging, Sungu camp