Musings on Nature

Ants and Agriculture

People like to find things that make us unique among animals.  Anthropologists seem to have settled on three main features that distinguish us from the rest of the animals: we use tools, we think and speak symbolically, and we have developed agriculture.  However, in the 1960s, Jane Goodall observed chimpanzees using sticks as tools to fish termites out of their nests.  So now we have to say that we are unique because we make and use the best tools.  As for symbolic thinking and language, there is evidence that apes are also capable, and we are left saying that we are still the best at it.

What is left, thus far unchallenged by the apes, is agriculture.  To select, tend, and maintain crops or livestock requires a fair amount of sophistication.  Agriculture was the basis for civilization; it allowed people to build cities.  It shapes the evolution of domesticated species.  Surely no other animal can do those things.

As far as we know, humans are the only species of mammal to have developed agriculture, but this behavior is not unique in the wider animal kingdom.  There are actually hundreds of species of fungus-growing ants—ants—that grow and tend to their own food source in what can only be rightfully recognized as farming.  These species include the leafcutter ants, which collect leaves and other plant material to bring back into their nests.  They cut the plants into tiny pieces, adding saliva and feces, and they use the resulting mixture as food for the fungus they grow and eat.  The ants prune the fungus as it grows, and they even remove pathogens from them.  The fungi are so dependent on their farmers for care that the fungal species have not been found outside of these leafcutter gardens.  Surely, this is agriculture.  I guess you could argue that we have “better” agriculture than ants, but isn’t it amazing that ants have agriculture?

If it is important to you to be able to list qualities that make people different than other animals, carry on.  But know that they might be steadily debunked by the behavior or apes or ants. Don’t be disappointed; stop for a moment and revel in the fact that we are not alone.

Interesting links:

A BBC article about slave-making ants: http://news.bbc.co.uk/earth/hi/earth_news/newsid_9160000/9160744.stm

Are humans unique? http://www.psychologytoday.com/blog/minds-animals/200907/are-humans-unique

Do animals think? http://www.cerebromente.org.br/n17/opinion/animal-think.htm

References

Bass, M. & Cherrett, J.M. 1996. Leaf-cutting ants (Formicidae, Anttini) prune their fungus to increase and direct its productivity. Functional Ecology 10:1, 55-61.

Currie, C.R., & Stuart, A.E. 2001.  Weeding and grooming of pathogens in agriculture by ants. The Royal Society 268, 1033-1039.

Shipman, P. 2010. The animal connection and human evolution. Current Anthropology 51:4, p1-19. http://pennstate.academia.edu/PatShipman/Papers/320573/The_Animal_Connection_and_Human_Evolution

Sabbatini, R.M.E. 2003. Do animals think? http://www.cerebromente.org.br/n17/opinion/animal-think.htm, accessed 3/2012

Social Lessons from Vampire Bats

Vampire bats are accurately named, as they come out at night and drink the blood of sleeping animals.  Nevertheless, they are somewhat charming, once you get to know them.  In fact, the common vampire bat is one of the few animals known to share food; the others include wild dogs, hyenas, and chimpanzees.

Food sharing is a rare behavior because it would, in most cases, decrease an animal’s evolutionary fitness.  Fitness describes an individual’s genetic contribution to future generations, and so it is entirely dependent on an organism’s ability to survive and reproduce.  Taking care of offspring increases the parents’ fitness, but sharing food with neighbors would be more likely to reduce it.  Such detrimental behavior simply would not be preserved through natural selection.  But as with most things in nature, there are exceptions to the rule.

Vampire bats are one exception; sharing meals directly supports their survival and fitness. On any given night, when vampire bats go out to feed, 7-30% of them don’t manage to eat.  If a bat fails to feed for two nights in a row, it will die.  If a bat misses a second meal, however, a neighboring bat will regurgitate its own meal for it, keeping the hungry bat alive.  The sharing bat is more vulnerable to hunger now, but it is less vulnerable than the receiving bat.  And, should the first bat miss a second meal, it can expect help from another bat.

Whether or not food sharing in vampire bats is “pure altruism,” i.e., a completely selfless act, is debatable, since everybody benefits.  But who cares if it is completely selfless?  What could be better than a situation in which everybody benefits?  This brings us to our first social lesson from vampire bats: being kind pays off.  George Washington Carver put it well: “How far you go in life depends on your being tender with the young, compassionate with the aged, sympathetic with the striving and tolerant of the weak and strong. Because someday in your life you will have been all of these.”

The second lesson we can take away from the bat’s behavior is that the relative magnitude of a generous act works favorably for both parties.  In the case of a starving bat, the giver helps out at some cost to itself, but the meal means life or death to the second bat. Thus, it is beneficial for members of society to share, especially when you can expect to be repaid at a later date, and especially since your help costs you so little.  We make choices about how we treat each other every day.  When it costs you little, but would mean the world to someone else, you have found an opportunity to be generous like a vampire bat. Take it.

For a detailed description of the vampire bat food-sharing  behavior, see Wilkinson’s article at: http://facstaff.unca.edu/cnicolay/BIO379/wilkinson-foodsharing.pdf

To learn more about vampire bat feeding behavior and to read about the possible medical uses of vampire bat saliva, check out this blog post:  http://thegnawblog.com/incredible-facts-about-vampire-bats/

For more information about bats and their conservation, visit Bat Conservation International’s website at: http://www.batcon.org/

References 

Wilkinson, Gerald S. 1990. Food Sharing in Vampire Bats.  Scientific American 262:2, p. 64-70.

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