Wednesday, September 30, 2009

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.


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

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