Nav: Home

Chimps caught crabbing

May 29, 2019

Kyoto, Japan -- Why do we fish?

At some point eons ago, our primarily fruit-eating ancestors put their hands in the water to catch and eat aquatic life, inadvertently supplementing their diet with nutrients that initiated a brain development process that eventually led to us. But how did this begin?

Now, according to a research team from Kyoto University, one potential clue may have surfaced thanks to observations of our closest genetic relatives: chimpanzees. The scientists report the first ever evidence of wild chimps habitually catching and consuming freshwater crabs.

Writing in the Journal of Human Evolution, the team describes year-round, fresh water crab-fishing behavior -- primarily among female and infant chimpanzees -- living in the rainforest of the Nimba Mountains in Guinea, West Africa.

"The aquatic fauna our ancestors consumed likely provided essential long-chain polyunsaturated fatty acids, required for optimal brain growth and function," explains first author Kathelijne Koops from the University of Zurich and Kyoto University's Leading Graduate Program in Primatology and Wildlife Science.

"Further, our findings suggest that aquatic fauna may have been a regular part of hominins' diets and not just a seasonal fallback food."

The study began in 2012 when the researchers first observed the chimpanzees fishing for crabs. For two years, they documented the demographics and behavior of these chimps, while also analyzing and comparing the nutritional value of the crabs to other foods in the chimpanzees' diet.

Crabbing, they learned, not only took place year-round -- without regard to season or fruit availability -- but intriguingly was negatively correlated with the chimps' consumption of ants, another diet staple. Mature males were the least likely to consume aquatic fauna.

"Energy and sodium levels in large crabs are comparative with ants," explains Koops, "leading us to hypothesize that crabs may be an important year-round source of protein and salts for females -- especially when pregnant or nursing -- and for growing juveniles."

The study further sheds light on our own evolution, by showing that fishing behaviors may not be restricted by habitat as initially assumed.

"This isn't the first case of non-human primates eating crabs," points out senior co-author Tetsuro Matsuzawa, "but it is the first evidence of apes other than humans doing so. Notably, previous observations were from monkey species in locations consistent with aquatic faunivory -- lakes, rivers, or coastlines -- and not in closed rainforest."

"It's exciting to see a behavior like this that allows us to improve our understanding of what drove our ancestors to diversify their diet."
-end-
The paper "Crab-fishing by chimpanzees in the Nimba Mountains, Guinea" appeared on 29 May 2019 in the Journal of Human Evolution, with doi: 10.1016/j.jhevol.2019.05.002

About Kyoto University

Kyoto University is one of Japan and Asia's premier research institutions, founded in 1897 and responsible for producing numerous Nobel laureates and winners of other prestigious international prizes. A broad curriculum across the arts and sciences at both undergraduate and graduate levels is complemented by numerous research centers, as well as facilities and offices around Japan and the world. For more information please see: http://www.kyoto-u.ac.jp/en

Kyoto University

Related Evolution Articles:

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.
Evolution of aesthetic dentistry
One of the main goals of dental treatment is to mimic teeth and design smiles in the most natural and aesthetic manner, based on the individual and specific needs of the patient.
An evolution in the understanding of evolution
In an open-source research paper, a UVA Engineering professor and her former Ph.D. student share a new, more accurate method for modeling evolutionary change.
Chemical evolution -- One-pot wonder
Before life, there was RNA: Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich show how the four different letters of this genetic alphabet could be created from simple precursor molecules on early Earth -- under the same environmental conditions.
Catching evolution in the act
Researchers have produced some of the first evidence that shows that artificial selection and natural selection act on the same genes, a hypothesis predicted by Charles Darwin in 1859.
Guppies teach us why evolution happens
New study on guppies shows that animals evolve in response the the environment they create in the absence of predators, rather than in response to the risk of being eaten.
Undercover evolution
Our individuality is encrypted in our DNA, but it is deeper than expected.
Evolution designed by parasites
In 'Invisible Designers: Brain Evolution Through the Lens of Parasite Manipulation,' published in the September 2019 issue of The Quarterly Review of Biology, Marco Del Giudice explores an overlooked aspect of the relationship between parasites and their hosts by systematically discussing the ways in which parasitic behavior manipulation may encourage the evolution of mechanisms in the host's nervous and endocrine systems.
Tracing the evolution of vision
The function of the visual photopigment rhodopsin and its action in the retina to facilitate vision is well understood.
Directed evolution comes to plants
Accelerating plant evolution with CRISPR paves the way for breeders to engineer new crop varieties.
More Evolution News and Evolution Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#540 Specialize? Or Generalize?
Ever been called a "jack of all trades, master of none"? The world loves to elevate specialists, people who drill deep into a single topic. Those people are great. But there's a place for generalists too, argues David Epstein. Jacks of all trades are often more successful than specialists. And he's got science to back it up. We talk with Epstein about his latest book, "Range: Why Generalists Triumph in a Specialized World".
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.