Even Howler Monkeys Think Veganism Is Whack (Sorry PETA)

Alright fine. Maybe these black and gold howler monkeys are not Whitney Houston and they don't think veganism is whack but new observation had shown that these howler monkeys actually raid chicken coop (or bird nests) for eggs. Yes, for food not to paint Easter eggs.

Male (left) and female (right) black and gold howler monkey . Flickr photo from lemai13

Thought to be exclusively folivores, the black and gold howler monkeys (Alouatta caraya) feed mainly on leaves, fruits and other parts of the plants such as flowers and bark. However, the population of black and gold howler monkeys in the forest of Rio Grande do Sul, Brazil had been observed eating eggs. "Alouatta is the most studied New World primate genus in the wild and there is not a single observation of intentional ingestion of animal matter in the literature", said primatologist Dr. Julio Bicca-Marques.

In 2005 Ms Helissandra Prates, a student of Dr Bicca-Marques, observed two juvenile black and gold howler monkeys (Alouatta caraya) licking the interior of a dove's nest at Estancia Casa Branca, a 2 ha orchard forest in Alegrete. The nest contained a broken egg shell. She later found evidence of egg remains in howler monkey dung collected from the orchard floor.

Then in 2007, Ms Muhle, another of Dr Bicca-Marques's students, witnessed howler monkeys eating birds' eggs at a separate woodland site at Beco Xavier. Over an eight month period, she recorded 19 separate instances of egg predation by a group of five individuals. All these later cases involved chicken eggs, which the monkeys stole from a chicken coop. While all five monkeys were seen to enter and investigate the coop, most of the eggs were actually eaten by a single subadult male.

-  Walker M. 2009. Monkeys 'reject vegetarianism'. BBC.

The evolution of egg-eating is localized in this population, leading researchers to think that it is a response to environmental conditions. There is a high density of howler monkeys living in a habitat with low food sources. Bicca-Marques et al. think that eggs act as a surrogate supplementary source of protein because of the low food diversity. The shift from folivory to omnivory reflects the flexibility of the black and gold howler monkey's diet. Watch the video of a black and gold howler monkey raiding a chicken coop.

Dr Julio Bicca-Marques and her colleagues from the Primatology Research Group published their findings in the International Journal of Primatology. The paper, "Habitat Impoverishment and Egg Predation by Alouatta caraya" is available in .pdf form through SpringerLink for free.

A quick Google search reveals that local zoos feed their black and gold howler monkeys meat and eggs such as Connecticut's Beardsley Zoo. Interesting. Coincidence?

This finding reminds me of the dietary shift and exploitation of new food sources in chimpanzees. We know that Gombe chimpanzees (Pan troglodytes schweinfurthii) prey on red colobus monkeys (Colobus badius tephrosceles) (Stanford et al., 2005) while savanna chimpanzees (Pan troglodytes verus) from Fongoli hunt lesser bushbabies (Galago senegalensis) using spear-like tool (Pruetz and Bertolani, 2007). Will we see more published paper about dietary shift and exploitation of new food sources? I guess it would have to be a trend as these primates lose more and more of their food sources and habitat. Perhaps those with a flexible diet will better adapt to their changing environment and ecology.

Sorry PETA. It seems that omnivory is in and veganism is out.

References:

Bicca-Marques JC. Muhle CB. Prates HM. De Oliveira SG. Calegaro-Marques C. 2009.
Habitat Impoverishment and Egg Predation by Alouatta caraya. International Journal of Primatology 30 (5):743-748. [doi:10.1007/s10764-009-9373-y]

Pruetz JD. Bertolani P. 2007.Savanna Chimpanzees, Pan troglodytes verus, Hunt with Tool. Current Biology 17(5): 412-417. [doi:10.1016/j.cub.2006.12.042]

Stanford CB. Wallis J. Matama H. Goodall J. 2005. Patterns of predation by chimpanzees on red colobus monkeys in gombe national park, 1982-1991. American Journal of Physical Anthropology 94 (2): 213-228. [doi:10.1002/ajpa.1330940206]

Walker M. 2009. Monkeys 'reject vegetarianism'. BBC. Retrieved September 30, 2009, from http://news.bbc.co.uk/earth/hi/earth_news/newsid_8270000/8270801.stm

Hobbits Might Not Be A Homo After All

The controversies over the hobbits or Homo floresiensis just refuse to end. It seems that the hobbits might not be a Homo after all. I guess they found the index and ring fingers of the hobbits (Sorry, inside joke. Read this post if you want).

 Homo floresiensis (LB1) skull. Photo from Science Museum.

Homo floresiensis, LB1, skull (left) and human skull (right). Photo from BBC.

Anyway, Peter Brown from the University of New England who first described Homo floresiensis said that he is considering of stripping the hobbits from the genus Homo. Brown and his colleague, Tomoko Maeda, said that the Homo floresiensis lineage possibly left Africa before the evolution of the genus Homo. Their paper had been accepted and will be published in an upcoming special Homo floresiensis edition of the Journal of Human Evolution.

I can't wait for the paper to come out. In the meantime, you can read this article from The Australian.

So Adowable

A baby white-handed gibbon was born at Vienna's Schoenbrunn Zoo to father Robert (aged 11) and mother Sipura (aged 21) on Sept 23rd. The baby was dubbed "ET" by the Vienna media after the famous Hollywood blockbuster alien although the zoo does not have an official name for the baby yet. Isn't he adorable? I can't stop saying "awwwwww".

 "ET" snuggling with his mother. Photo from Austrian Times.

White-handed gibbons or Lar gibbons (Hylobates lar), are listed as near threatened in the International Union for Conservation of Nature (IUCN) Red List. The Philadelphia Zoo has white-handed gibbons in their PECO Primate Reserve. Awwwwww ........

Two Rare Primates From China and Vietnam Given a Second Chance

Two new protected areas were designated in China and Vietnam recently to protect two of the world's most endangered primates by Fauna and Flora International (FFI). The Tonkin snub nosed monkey (Rhinopithecus avunculus), found only in Vietnam, numbers about only 200 individuals in the wild while the eastern black crested gibbon or cao vit gibbon (Nomascus nasutus), second most endangered primate in the world, numbers only just 110 individuals. Both species are listed as "critically endangered" in the International Union for Conservation of Nature (IUCN) Red List. The Tonkin snub nosed monkeys were thought to be extinct until a small population was rediscovered in the early 1980s.

Read more about the Tonkin snub nosed monkeys, cao vit gibbons and the new nature reserves from Wildlife Extra.

Male (left) and female (right) cao vit gibbons. Photo from Fauna and Flora International.

The Tonkin snub nosed monkey. Photo from Fauna and Flora International.

Can I See Your Fingers Please?

That is what University of Liverpool's Emma Nelson probably would have said if she were to meet our hominan ancestors in person. Known to hold true in anthropoids (humans, apes and monkeys), the index (second digit) to ring (fourth digit) fingers ratio or 2D:4D is an indication of how much an individual were exposed to androgen (such as testosterone) in the womb. The more androgen you are exposed to, the longer the ring fingers are (and the shorter the index fingers are compared to the index fingers).

Photo of a human's left hand. From left to right: thumb, index, middle, ring and little finger. Photo modified from Wikipedia.

Nelson et al. believe that a high ratio (longer index finger, shorter ring finger) suggests monogamy (or pair-bonded) while a low ratio (shorter index finger, longer ring finger) suggests polygamy (or non pair-bonded). Simply put, individuals with high androgen level is likely to be non pair-bonded and the telltale sign is in the index and ring fingers. Also, some controversial studies had suggested that both men and women who receive high levels of androgen in the womb are more likely to be stronger, faster, and more sexually competitive.

Nelson and her researchers recently looked at the fossils of two Neandertals and one Australopithecus afarensis with complete index and ring fingers to determine their 2D:4D. They found that Neandertals had long ring fingers, suggesting that they were polygamous just like modern day primates that live in groups. A. afarensis on the other hand, had long index fingers. Nelson is puzzled by this discovery. "These were small creatures that probably lived in groups and were being eaten by predators. How do you keep from mating with different members of the group?", she said.

Indeed it does not make sense for A. afarensis to be monogamous if they live in groups. Notice that Nelson et al. only used one A. afarensis fossil to get the 2D:4D. Perhaps it is not their fault that only one A. afarensis specimen had complete index and ring fingers but such are the dilemma of using fossil specimens to generalize a whole species.The result might just be a statistical outlier. However, I can't speculate the result or the implications but anyone that are familiar with statistical data knows that a small sample size leads to a higher sampling error. Also what would a 2D:4D = 1 (same index and ring finger length) be?

Interesting enough, John Hawks at John Hawk's Weblog mentioned the correlation of 2D:4D with male homosexuality (Robinson and Manning, 2000). I would know about this. In fact, my 2D:4D is indeed low.  Robinson and Manning predicted right! Maybe ...

I do find both Nelson et al. and Robinson and Manning (2000) research interesting but I would like to stress that the results are mere predictors and correlations. Take it with a grain of salt. Don't go measuring 2D:4D of your future spouse, boyfriend or girlfriend and accuse them of not being monogamous or a homosexual.

Emma Nelson and her team presented their research at this year's Society for Vertebrate Paleontology meeting held in Bristol, United Kingdom. Read more about Emma Nelson's research.

References:

Reilly M. 2009. Human Ancestors Conflicted on Monogamy. Discovery News. Retrieved September 25, 2009, from http://dsc.discovery.com/news/2009/09/24/human-monogamy.html

Robinson SJ. Manning JT. 2000. The ratio of 2nd to 4th digit length and male homosexuality. Evolution and Human Behavior 21(5): 333-345. [doi:10.1016/S1090-5138(00)00052-0]