Howler monkeys’ eyes, new research


This video is called Howler Monkeys | National Geographic.

From Science News:

Howler monkeys may owe their color vision to leaf hue

Distinguishing red from green makes healthier leaves stand out

By Laurel Hamers

5:59pm, February 21, 2017

BOSTON — A taste for reddish young leaves might have pushed howler monkeys toward full-spectrum color vision. The ability to tell red from green could have helped howlers pick out the more nutritious, younger leaves, researchers reported February 19 at the annual meeting of the American Association for the Advancement of Science. That’s a skill their insect-eating close relatives probably didn’t need.

Primates show substantial variation in their color vision capabilities, both between and within species, said Amanda Melin, a biological anthropologist at the University of Calgary in Canada. Trichromatic vision (how most humans see) requires three light-sensitive proteins in the eye that can detect different wavelengths of light. Within most monkey species in Central and South America, only some individuals have trichromatic vision. Males have dichromatic vision — they’re red-green colorblind — and only some females can see the whole rainbow. Howlers are an exception — thanks to a duplicated gene on their X chromosomes, trichromatic vision is the norm for both males and females.

Howlers graze on leaves from Ficus trees and other plants when fruit can’t be found. In field observations of mantled howlers (Alouatta palliata) in Costa Rica, the monkeys preferentially munched on the younger, more nutritious leaves, Melin’s team found. The reddish hue of new leaves makes them pop more when seen with trichromatic vision than dichromatic vision, the researchers reported in a paper accepted for publication in Ecology and Evolution. Because young leaves are a fleeting treat and not a constant resource, monkeys able to spot them more quickly could have had a selective advantage.

Similar selection pressures might also help explain why Old World monkeys from Asia and Africa also have consistent trichromatic vision, Melin said. “What we might be seeing is a convergent evolution for animals who fall back on leaves when fruit isn’t around.”

On the other hand, other Central and South American monkeys usually go for insects, instead of leaves, when there’s no fruit. Dichromatic vision might be a better fit for their lifestyle, Melin said. “Color can impede ability to see patterns, borders and textures. Insects hide and camouflage.”

I was privileged to hear and see howler monkeys in Suriname and Costa Rica.

Baboons in Kenya, video


This video from Kenya says about itself:

10 October 2016

The Tyack family are back on safari on Ol Pejeta Conservancy and have an interesting encounter with a troop of baboons.

Dogs against monkeys at Japanese farms


This video says about itself:

Dog Vs Monkey In Japan – Wild Japan – BBC

11 July 2016

Japanese farmers have been using the internet’s favourite dog to protect their crops from thieving monkeys.

Baboons save impala, other animal lives saved, video


This video says about itself:

20 April 2016

AMAZING: Baboons Save Deer [rather: impala antelope] From LeopardHyena Helps Deer [rather: antelope], Bear Saves Crow

New monkey species discovery in Peru


Urubamba brown titi

From New Scientist:

7 August 2015

New species of titi monkey discovered in remote Peruvian forest

A new species of monkey has been discovered on an expedition to the remote Urubamba river in Amazonian Peru. It has been named the Urubamba brown titi, Callicebus urubambensis.

Titis are the largest group of South American monkeys, and the discovery pushes the number of known species to 34, though the exact number is still a matter of some debate. Most are the size of a domestic cat, live in small family groups and defend their territories with howl-like roars.

“Its appearance is very distinct from other titis, the entire body and tail are much darker, and the face is all black,” says co-discoverer Jan Vermeer, coordinator of the Peru-based primate research programme, Proyecto Mono Tocón.

Each titi species has a specific colour pattern, and these patterns seem to be evolutionarily important.

Surprisingly, the new monkey seems to be common along a swathe of forest some 350 kilometres long.

“So often when a new monkey is discovered it is already threatened with extinction” says Vermeer. “This is a remote area with very little hunting, so for once this is not the case.”

The region in which the research was conducted, the Madre do Dios section of the Peruvian Amazon, is an area of extraordinary biological richness, with many species restricted to the forests between two large rivers. The width of the rivers – and the voracious piranhas that live in them – provide natural barriers to dispersion.

The expedition also allowed scientists to study another titi monkey species for the first time since it was described 100 years ago, the Toppin’s titi monkey (Callicebus toppini).

Vermeer and colleagues hope the discoveries will shed light on titi monkey evolution and dispersal, as well as help raise awareness of this remote and little-studied region.

Titi monkeys are small and discreet. We are only just beginning to understand the factors driving their diversity,” says Stephen Ferrari of the Sergipe Federal University in Brazil. “A few decades ago, only five titi species were known. I think many more will be discovered as we explore southern Amazonia’s biologically uncharted forests.”

Journal reference: Primate Conservation

See also here. And here.