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GeladaTheropithecus gelada

Every figure, record and mechanism on the Gelada profile was written from a source, and this is the working table behind it: 46 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

Animal Diversity Web, University of Michigan

Theropithecus gelada (gelada baboon). Animal Diversity Web, University of Michigan.

The page saysA gelada's index finger and thumb have the highest opposability of any catarrhine primate, the group of Old World monkeys and apes, letting it pluck individual grass blades and, in the dry season, sort the good from the bad
The source saysThe opposability of their first two digits is the highest of all the catarrhine primates and allows them to pick grass blades individually so that they can sort good grass from bad grass during the dry season.Note: 'first two digits' = thumb and index finger; catarrhine glossed for readers
The page saysif an outside male tries to take over by force, they can chase off whichever male they don't want, whoever wins the fight
The source saysIf an outside male attempts to take over the group by supplanting the male using physical force, the females may choose to support or oppose either male. Regardless of who wins the fight between the two males, the females can chase the unwanted male from the group with their own show of physical force.
The page saysWhen a female comes into estrus, the phase when she is ready to mate, red beading develops in the bare patch on her chest, and the skin around her rear end visibly swells
The source saysWhen a gelada female comes into estrus a ring of red beading develops in the naked patch on her chest and her ano-genital region swells visibly.Note: 'ready to mate' glosses estrus
The page saysIt grows a ring of red beads
The source saysWhen a gelada female comes into estrus a ring of red beading develops in the naked patch on her chestNote: faq 4 opening answer

Source
02

San Diego Zoo Wildlife Alliance

Gelada. San Diego Zoo Wildlife Alliance.

The page saysGeladas (*Theropithecus gelada*) stand 20 to 30 inches (51 to 76 cm) tall
The source saysHeight: 20 to 30 inchesNote: height is species-wide in SDZ's size box; 20-30 in = 51-76 cm
The page saysMales weigh about 40 pounds (18 kg)
The source saysWeight: Females, about 24 pounds; males, about 40 pounds.Note: 40 lb = 18 kg. ADW (2000) gives a male mean of 20.25 kg; the current institution page wins
The page saysfemales about 24 to 28 pounds
The source sayswith females weighing about 28 pounds and males about 40 poundsNote: SDZ gives 28 lb in its body text and 24 lb in its facts box, so the page gives the range
The page says24 to 28 pounds (11 to 13 kg)
The source saysWeight: Females, about 24 poundsNote: the 24 lb end of the range, from SDZ's facts box; 24-28 lb = 11-13 kg
The page saysWild geladas live about 14 years, and captive ones up to 30
The source says14 years in the wild; up to 30 in captivity
The page saysGrass makes up more than 90 percent of a gelada's diet
The source saysGeladas are genuine grazers, with over 90% of their diet being grass blades.
The page saysReinforced patches of skin on its rear end, called ischial callosities, come in handy for sitting while it grazes
The source saysThey also have reinforced buttocks called ischial callosities, which come in handy when sitting on the ground foraging on grass.
The page sayswhen grass runs short it switches to flowers, rhizomes, and roots instead
The source saysThey can handily shift to flowers, digging up rhizomes and roots, and foraging for herbs when the availability of grasses decreases.
The page saysGeladas live on the open high plateaus of the Ethiopian Highlands, from about 5,000 feet (1,500 meters) up to over 14,700 feet (4,480 meters), with large populations in the Simien Mountains
The source saysGeladas are found in the Ethiopian Highlands in open, high plateaus along the gorges and escarpments that transect them, from about 5,000 feet in elevation up to over 14,700 feet. ... There are large populations of gelada in the Semien Mountains.Note: 5,000 ft = 1,500 m; 14,700 ft = 4,480 m; Simien is the park's official spelling of SDZ's Semien
The page saysDogs, jackals, servals, foxes, hyenas, and leopards threaten geladas, though with people close to many of their habitats, predator pressure is fairly low
The source saysDogs, jackals, leopards, servals, foxes, and hyenas threaten geladas. ... Due to the proximity of humans to many habitats, predator pressure is fairly low for the gelada.
The page saysAt night, large bands sleep close together on cliffs and ledges for warmth and safety, then climb up to the plateaus to graze
The source saysThe monkeys stick close to cliffs to use them as sleeping sites and climb up to the plateaus for their daily grazing and social activities. ... The monkeys form large bands at night, sleeping close together on rocky cliffs and ledges for warmth and safety.
The page saysThe gelada's signature feature is a bare, hourglass-shaped patch of pink or red skin on its chest, ringed in females by small, pearl-like bumps of skin
The source saysThe gelada's most striking feature is the hairless, hourglass-shaped pink or red area of skin located on the chest. In females, pearl-like knobs of skin surround this skin patch.
The page saysIt's why geladas are nicknamed bleeding-heart baboons
The source saysGeladas are also called bleeding-heart baboons, due to the unusual reddish skin on their chest.
The page saysOne breeding male and three to five females share a reproductive unit called a one-male unit, or OMU, along with their offspring
The source saysGeladas live in one-male reproductive units that contain one breeding male and 3 to 5 females and their offspring.Note: 'one-male unit, or OMU' naming from adw-gelada: 'These groups are called one male units, or OMUs.'
The page saysOMUs join together into foraging bands of 30 to 350 animals
The source saysfamily units join to form large foraging bands of 30 to 350 animals
The page saysAlthough females are about a third smaller than males, they run the unit: they decide when an aging male should be replaced by a younger rival
The source saysThough females are about one-third smaller than the males, they run the show and decide when an aging male should be replaced by a younger rival (though he will fight to defend his status).
The page saysGeladas also have more than 30 distinct calls, which they combine into sequences for contact, reassurance, appeasement, and aggression or defense
The source saysGeladas have a diverse repertoire of over 30 different vocalizations—typical of highly social animals. Vocalizations can be combined into sequences to address necessary contact, reassurance, appeasement, solicitation, ambivalence, and aggressive-defensive communications.
The page saysMontane grasslands, high plateau meadows, and precipitous cliffs of the Ethiopian Highlands (about 1,500–4,500m)
The source saysGeladas are found in the Ethiopian Highlands in open, high plateaus along the gorges and escarpments that transect them, from about 5,000 feet in elevation up to over 14,700 feet. The monkeys stick close to cliffs to use them as sleeping sitesNote: stats.habitat; 5,000 ft = 1,500 m, 14,700 ft = 4,480 m, rounded with 'about'
The page saysOver 90% grass blades, plus flowers, rhizomes, roots, and herbs when grass runs short
The source saysGeladas are genuine grazers, with over 90% of their diet being grass blades. ... They can handily shift to flowers, digging up rhizomes and roots, and foraging for herbs when the availability of grasses decreases.Note: stats.diet
The page saysa monkey with more than 30 different vocalizations that it combines into sequences
The source saysGeladas have a diverse repertoire of over 30 different vocalizations—typical of highly social animals. Vocalizations can be combined into sequences

Source
03

Gippoliti et al. 2025

Gippoliti et al. (2025). Theropithecus gelada. The IUCN Red List of Threatened Species 2025: e.T21744A274974485.

The page saysLeast Concern
The source saysIUCN Red List category: Least Concern (LC). Theropithecus gelada (Rüppell, 1835), IUCN taxon 21744.Note: stats.conservationStatus; read through GBIF's copy of the Red List, checked against taxon id 21744 inside the assessment DOI, per docs/fact-check.md

Source
04

Fashing et al. 2014

Fashing et al. (2014). Gelada feeding ecology in an intact ecosystem at Guassa, Ethiopia: Variability over time and implications for theropith and hominin dietary evolution. American Journal of Physical Anthropology.

The page saysgeladas are the only primates alive today that live mainly on grass, a diet scientists call graminivorous
The source saysAs the only living primate graminivores, gelada monkeys (Theropithecus gelada) can yield insights into the dietary strategies pursued by extinct grass- and sedge-eating primates.
The page saysA seven-year study of geladas at Guassa, Ethiopia found their yearly diet there was 56.8 percent grasses and sedges (grouped together as graminoids) and 37.8 percent broad-leaved plants called forbs, with invertebrates and other food making up the rest
The source saysGeladas at Guassa consumed ≥56 plant species, ≥20 invertebrate species, one reptile species, and the eggs of one bird species over a 7-year period. The annual diet consisted of 56.8% graminoid parts, 37.8% forb parts, 2.8% invertebrates, and 2.6% other itemsNote: Guassa result, scoped as that site's; the abstract defines graminoids as grasses and sedges; SDZ's species-wide >90% grass blades stays in the body
The page saysOver those seven years the Guassa geladas also ate at least 20 kinds of invertebrates, one reptile species, and the eggs of one bird species
The source saysGeladas at Guassa consumed ≥56 plant species, ≥20 invertebrate species, one reptile species, and the eggs of one bird species over a 7-year period.
The page saysThe Only Living Primate Grazer
The source saysAs the only living primate graminivores, gelada monkeys (Theropithecus gelada) can yield insights into the dietary strategies pursued by extinct grass- and sedge-eating primates.Note: heading; 'grazer' = graminivore, scoped to living primates as the source is

Source
05

Baniel et al. 2021

Baniel et al. (2021). Seasonal shifts in the gut microbiome indicate plastic responses to diet in wild geladas.

The page saysThat diet even reshapes gelada gut bacteria by season
The source saysMicrobial changes were driven by differences in the main components of the diet across seasons
The page saysIn one study in Ethiopia's Simien Mountains
The source saysWe collected fecal samples from a wild population of geladas living in the Simien Mountains National ParkNote: scopes the gut result to the one study population
The page saysbacteria that digest grass dominated the gut in rainier periods, while bacteria that break down starches in underground plant parts took over in dry ones
The source saysin rainier periods, the gut was dominated by cellulolytic/fermentative bacteria that specialized in digesting grass, while during dry periods the gut was dominated by bacteria that break down starches found in underground plant parts

Source
06

Grueter, Chapais & Zinner 2012

Grueter, Chapais & Zinner (2012). Evolution of Multilevel Social Systems in Nonhuman Primates and Humans. International Journal of Primatology.

The page saysPrimatologists call this layered arrangement a multilevel society, a structure also found in hamadryas baboons and humans
The source saysThe primate species whose social systems have been described as multilevel include several colobine, most notably snub-nosed monkeys ( Rhinopithecus spp.), proboscis monkeys ( Nasalis larvatus ), and the papionin species hamadryas baboons ( Papio hamadryas ) and geladas ( Theropithecus gelada ) as well as humans.Note: 'also' because the source names colobines too; the 'closely related' gloss was cut

Source
07

Lazow & Bergman 2020

Lazow & Bergman (2020). The structural and motivational role of the unique lip-flip movement in the gelada (Theropithecus gelada) facial display repertoire. American Journal of Physical Anthropology.

The page saysThe gelada is the only one that can roll its lip back to bare its gums and teeth, a movement scientists call a lip-flip eversion
The source saysThe gelada (Theropithecus gelada) is the only primate that can produce a lip-flip eversion.Note: 'roll its lip back to bare its gums and teeth' from sdz-gelada: 'lip rolls (also called "lip flip") to expose gums and teeth'
The page saysIt looks fierce, but in one study of filmed gelada interactions, the lip-flip went most often with nonaggressive, submissive behavior, and it followed an approach more often than a plain bared-teeth display did, especially in males. The researchers suggest it may signal good intent after an approach
The source saysWe reviewed videos of gelada social interactions. ... Both the bared-teeth display with and without a lip-flip occurred most frequently with nonaggressive, submissive behaviors. The lip-flip was more frequently preceded by approach than the bared-teeth display, especially in males. ... The lip-flip may potentially function as an indicator of benign intent after an approachNote: 'looks fierce': sdz-gelada itself describes the lip flip as threatening ('threatening lip rolls ... in a threatening manner'); the study's own finding follows
The page saysNo other primate can do this.
The source saysThe gelada (Theropithecus gelada) is the only primate that can produce a lip-flip eversion.Note: covers both the blockquote's bold lead-in and its restatement in the body; the flip itself is the next sentence's claim
The page saysThe Ethiopian highland monkey that grazes mainly on grass, flashes a bleeding-heart chest patch, and rolls its lip back to bare its gums in a facial display no other primate can make.
The source saysThe gelada (Theropithecus gelada) is the only primate that can produce a lip-flip eversion.Note: tagline; the grass-diet and chest-patch clauses are separately backed by the sdz-gelada/gelada-2014 diet claims and the sdz-gelada chest-patch claim above
The page saysOpposable-finger precision grazing, a lip-flip no other primate can perform, and cliff-ledge sleeping refuges
The source saysThe gelada (Theropithecus gelada) is the only primate that can produce a lip-flip eversion.Note: stats.superpower; the finger-dexterity clause is backed by the adw-gelada claim above and the cliff-refuge clause by the sdz-gelada/leopard-2020 claims above
The page saysA Bleeding Heart and a Grimace No Other Primate Can Copy
The source saysThe gelada (Theropithecus gelada) is the only primate that can produce a lip-flip eversion.Note: heading; the 'grimace' is the lip-flip, the bleeding heart is the sdz-gelada chest-patch claim

Source
08

Lin et al. 2020

Lin et al. (2020). Leopard predation on gelada monkeys at Guassa, Ethiopia. American Journal of Primatology.

The page saysIn one study at Guassa, Ethiopia, geladas facing a leopard typically gave alarm calls, bunched closer together, and fled to or stayed at their sleeping cliffs
The source saysgeladas typically gave alarm calls (n = 7 of 7 encounters), reduced interindividual distances (n = 5), and collectively fled towards or remained at their sleeping cliffs (n = 7)Note: 'bunched closer together' paraphrases 'reduced interindividual distances'; scoped to Guassa
The page saysThey did not mob it
The source saysGeladas did not engage in mobbing behavior towards leopards.Note: Guassa result; SDZ reports males elsewhere mobbing a leopard, so this stays in the past tense of the one study

Source
09

Roberts et al. 2012

Roberts et al. (2012). A Bruce Effect in Wild Geladas. Science.

The page saysUsually, she ends it. One study of wild geladas found that females terminated 80 percent of pregnancies in the weeks after a dominant male was replaced.
The source saysHere, we report a strong Bruce effect in a wild primate, the gelada (Theropithecus gelada). Female geladas terminate 80% of pregnancies in the weeks after a dominant male is replaced.
The page saysThe researchers' data suggest that ending the pregnancy benefits females whose babies would otherwise be at risk of being killed, known as infanticide
The source saysdata on interbirth intervals suggest that pregnancy termination offers fitness benefits for females whose offspring would otherwise be susceptible to infanticide

Source
10

Palagi et al. 2009

Palagi et al. (2009). Contagious yawning in gelada baboons as a possible expression of empathy. Proceedings of the National Academy of Sciences.

The page saysthe more two individuals groomed each other, the more contagious their yawns were
The source saysthe contagiousness of yawning correlated with the level of grooming contact between individuals
The page saysOne study found that a yawn can pass from gelada to gelada, especially between friends
The source saysin gelada baboons (Theropithecus gelada) yawning is contagious between individuals, especially those that are socially close, i.e., the contagiousness of yawning correlated with the level of grooming contact between individualsNote: 'friends' = 'socially close' for young readers
The page saysThe researchers suggest this could be a building block for full-blown empathy, which has been proposed to lie behind contagious yawning in humans
The source saysYawn contagion in humans has been proposed to be related to our capacity for empathy. ... This phenomenon, here demonstrated in monkeys, could be a building block for full-blown empathy.

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.