Gelada feeding ecology in an intact ecosystem at Guassa, Ethiopia: Variability over time and implications for theropith and hominin dietary evolution

Abstract

Recent evidence suggests that several extinct primates, including contemporaneous Paranthropus boisei and Theropithecus oswaldi in East Africa, fed largely on grasses and sedges (i.e., graminoids). 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. Past studies of gelada diet were of short duration and occurred in heavily disturbed ecosystems. We conducted a long-term study of gelada feeding ecology in an intact Afroalpine ecosystem at Guassa, Ethiopia. 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, although geladas exhibited wide variability in diet across months at Guassa. Edible forbs were relatively scarce at Guassa but were strongly selected for by geladas. Tall graminoid leaf and tall graminoid seed head consumption correlated positively, and underground food item consumption correlated negatively, with rainfall over time. Geladas at Guassa consumed a species-rich diet dominated by graminoids, but unlike geladas in more disturbed habitats also ate a diversity of forbs and invertebrates along with occasional vertebrate prey. Although graminoids are staple foods for geladas, underground food items are important "fallback foods." We discuss the implications of our study, the first intensive study of the feeding ecology of the only extant primate graminivore, for understanding the dietary evolution of the theropith and hominin putative graminivores, Theropithecus oswaldi and Paranthropus boisei.

Bryobia abyssiniae(Prostigmata: Tetranychidae), a new species from the highlands of Ethiopia

“…Specimens were collected at Guassa, a 111 km 2 Afroalpine grassland in the Menz Highlands, North Shoa, Ethiopia (campsite GPS: N10 20.010, E39 48.636, elevation 3438 m; see Discussion section "Collection Area" and Fashing et al (2014) for more details concerning the study site). The presence of mites on giant lobelias was first noted in December 2005 when Peter J. Fashing and Nga Nguyen began a study of gelada monkeys (Theropithecus gelada (Rüppell, 1835)) at Guassa.…”

“…The presence of mites on giant lobelias was first noted in December 2005 when Peter J. Fashing and Nga Nguyen began a study of gelada monkeys (Theropithecus gelada (Rüppell, 1835)) at Guassa. On numerous occasions, geladas were observed searching through the leaves of giant lobelias for animal prey, including caterpillars which sometimes shared the surface of the leaves with the mites (Fashing et al 2014). Specimens of the mites were collected by Peter J. Fashing, Nga Nguyen, and their research assistants several times between 2007 and 2015.…”

“…It is bordered by the Great Rift Valley to the east and by farmland to the west, north, and south. Guassa is characterized by Afroalpine vegetation consisting mostly of tall graminoids, forbs, and shrubs (Ashenafi et al 2012;Fashing et al 2014). The climate at Guassa is typical for Afroalpine ecosystems in that it is much rainier and colder than for lower-elevation African grassland ecosystems such as Amboseli (Kenya) or Serengeti (Tanzania) (Altmann et al 2002;Ritchie 2006).…”

“…The climate at Guassa is typical for Afroalpine ecosystems in that it is much rainier and colder than for lower-elevation African grassland ecosystems such as Amboseli (Kenya) or Serengeti (Tanzania) (Altmann et al 2002;Ritchie 2006). Rainfall is bimodal, averaging 1650 ± 243 mm annually with the driest months occurring from October to March and just 2 months, July and August, accounting for two-thirds of the annual rainfall (n = 6 years; Fashing et al 2014). Temperature variation in alpine regions of Africa is less seasonal than rainfall and has been described as "summer every day, winter every night" (Hedberg 1964).…”

Sichuan Snub-Nosed Monkeys (Rhinopithecus roxellana) Consume Cicadas in the Qinling Mountains, China

“…For example, adult geladas (Theropithecus gelada) , which weigh between 11 and 18 kg, consume more than 20 species of invertebrates, including snails, ants, caterpillars and leafhoppers [Fashing et al, 2014]. Similarly, lowland gorillas (Gorilla gorilla) and chimpanzees (Pan troglodytes) , which are among the largest living primates, consume social insects, such as bees, termites and ants [Deblauwe and Janssens, 2008;Raubenheimer and Rothman, 2013].…”