---
title: "What the sources say about the Gelada | AnimalTracks.wiki"
description: "46 claims from the Gelada profile, each beside the words of the source that backs it."
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canonical: "https://animaltracks.wiki/animals/gelada/sources/"
---

# What the sources say about the Gelada (*Theropithecus gelada*)

> 46 claims from the Gelada profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Gelada](https://animaltracks.wiki/animals/gelada/)

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

https://animaldiversity.org/accounts/Theropithecus_gelada/

| The page says | The source says |
| :--- | :--- |
| A 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 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) |
| if an outside male tries to take over by force, they can chase off whichever male they don't want, whoever wins the fight | If 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. |
| When 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 | When 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) |
| It grows a ring of red beads | When a gelada female comes into estrus a ring of red beading develops in the naked patch on her chest (note: faq 4 opening answer) |

## Gelada. San Diego Zoo Wildlife Alliance.

https://animals.sandiegozoo.org/animals/gelada

| The page says | The source says |
| :--- | :--- |
| Geladas (*Theropithecus gelada*) stand 20 to 30 inches (51 to 76 cm) tall | Height: 20 to 30 inches (note: height is species-wide in SDZ's size box; 20-30 in = 51-76 cm) |
| Males weigh about 40 pounds (18 kg) | Weight: 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) |
| females about 24 to 28 pounds | with females weighing about 28 pounds and males about 40 pounds (note: SDZ gives 28 lb in its body text and 24 lb in its facts box, so the page gives the range) |
| 24 to 28 pounds (11 to 13 kg) | Weight: Females, about 24 pounds (note: the 24 lb end of the range, from SDZ's facts box; 24-28 lb = 11-13 kg) |
| Wild geladas live about 14 years, and captive ones up to 30 | 14 years in the wild; up to 30 in captivity |
| Grass makes up more than 90 percent of a gelada's diet | Geladas are genuine grazers, with over 90% of their diet being grass blades. |
| Reinforced patches of skin on its rear end, called ischial callosities, come in handy for sitting while it grazes | They also have reinforced buttocks called ischial callosities, which come in handy when sitting on the ground foraging on grass. |
| when grass runs short it switches to flowers, rhizomes, and roots instead | They can handily shift to flowers, digging up rhizomes and roots, and foraging for herbs when the availability of grasses decreases. |
| Geladas 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 | Geladas 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) |
| Dogs, jackals, servals, foxes, hyenas, and leopards threaten geladas, though with people close to many of their habitats, predator pressure is fairly low | Dogs, 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. |
| At night, large bands sleep close together on cliffs and ledges for warmth and safety, then climb up to the plateaus to graze | The 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 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 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. |
| It's why geladas are nicknamed bleeding-heart baboons | Geladas are also called bleeding-heart baboons, due to the unusual reddish skin on their chest. |
| One breeding male and three to five females share a reproductive unit called a one-male unit, or OMU, along with their offspring | Geladas 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.') |
| OMUs join together into foraging bands of 30 to 350 animals | family units join to form large foraging bands of 30 to 350 animals |
| Although 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 | Though 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). |
| Geladas also have more than 30 distinct calls, which they combine into sequences for contact, reassurance, appeasement, and aggression or defense | Geladas 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. |
| Montane grasslands, high plateau meadows, and precipitous cliffs of the Ethiopian Highlands (about 1,500–4,500m) | Geladas 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 sites (note: stats.habitat; 5,000 ft = 1,500 m, 14,700 ft = 4,480 m, rounded with 'about') |
| Over 90% grass blades, plus flowers, rhizomes, roots, and herbs when grass runs short | Geladas 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) |
| a monkey with more than 30 different vocalizations that it combines into sequences | Geladas have a diverse repertoire of over 30 different vocalizations—typical of highly social animals. Vocalizations can be combined into sequences |

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

https://doi.org/10.2305/iucn.uk.2025-1.rlts.t21744a274974485.en

| The page says | The source says |
| :--- | :--- |
| Least Concern | IUCN 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) |

## 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.

https://doi.org/10.1002/ajpa.22559

| The page says | The source says |
| :--- | :--- |
| geladas are the only primates alive today that live mainly on grass, a diet scientists call graminivorous | As the only living primate graminivores, gelada monkeys (Theropithecus gelada) can yield insights into the dietary strategies pursued by extinct grass- and sedge-eating primates. |
| A 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 | Geladas 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 items (note: 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) |
| Over those seven years the Guassa geladas also ate at least 20 kinds of invertebrates, one reptile species, and the eggs of one bird species | Geladas 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 Only Living Primate Grazer | As 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) |

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

https://doi.org/10.1186/s40168-020-00977-9

| The page says | The source says |
| :--- | :--- |
| That diet even reshapes gelada gut bacteria by season | Microbial changes were driven by differences in the main components of the diet across seasons |
| In one study in Ethiopia's Simien Mountains | We collected fecal samples from a wild population of geladas living in the Simien Mountains National Park (note: scopes the gut result to the one study population) |
| bacteria that digest grass dominated the gut in rainier periods, while bacteria that break down starches in underground plant parts took over in dry ones | in 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 |

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

https://doi.org/10.1007/s10764-012-9618-z

| The page says | The source says |
| :--- | :--- |
| Primatologists call this layered arrangement a multilevel society, a structure also found in hamadryas baboons and humans | The 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) |

## 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.

https://doi.org/10.1002/ajpa.24031

| The page says | The source says |
| :--- | :--- |
| The 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 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') |
| It 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 | We 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 approach (note: 'looks fierce': sdz-gelada itself describes the lip flip as threatening ('threatening lip rolls ... in a threatening manner'); the study's own finding follows) |
| No other primate can do this. | The 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 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 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) |
| Opposable-finger precision grazing, a lip-flip no other primate can perform, and cliff-ledge sleeping refuges | The 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) |
| A Bleeding Heart and a Grimace No Other Primate Can Copy | The 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) |

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

https://doi.org/10.1002/ajp.23098

| The page says | The source says |
| :--- | :--- |
| In 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 | geladas 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) |
| They did not mob it | Geladas 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) |

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

https://doi.org/10.1126/science.1213600

| The page says | The source says |
| :--- | :--- |
| Usually, 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. | Here, 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 researchers' data suggest that ending the pregnancy benefits females whose babies would otherwise be at risk of being killed, known as infanticide | data on interbirth intervals suggest that pregnancy termination offers fitness benefits for females whose offspring would otherwise be susceptible to infanticide |

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

https://doi.org/10.1073/pnas.0910891106

| The page says | The source says |
| :--- | :--- |
| the more two individuals groomed each other, the more contagious their yawns were | the contagiousness of yawning correlated with the level of grooming contact between individuals |
| One study found that a yawn can pass from gelada to gelada, especially between friends | in 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 individuals (note: 'friends' = 'socially close' for young readers) |
| The researchers suggest this could be a building block for full-blown empathy, which has been proposed to lie behind contagious yawning in humans | Yawn 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. |