How many ants are there alive on the planet? (Jane, Montana, USA)


Hi,

I'm developing some educational materials on ecology for high school students in western Montana. As a small part of the project, I'd like to help the students to expand their idea of "population" to organisms other than human. So I am including information on the number of people (~91000), cattle (~13200), trees (~1.2 billion), bears (still waiting on that number), and would love to include an estimate of the number of ants! This is an area in northern Montana (Flathead County), mostly forested, some urban, and some agricultural... also some sagebrush steppe. Can you suggest a way for me to estimate the ant population within a couple of orders of magnitude? More than a trillion, perhaps? Any guidance would be welcome. Thank you!

Jane

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Dear Jane,

Thank you for contacting AntBlog. We are glad to hear you are including ants in your ecology high school materials. Your question is related to a question we addressed regarding biomass:

http://www.antweb.org/antblog/2010/10/do-ants-really-have-the-largest-biomass-of-all-species-on-earth-laurie-usa.html

In summary, estimating the number of ants alive right now in Flathead County, Montana is likely impossible. But, you if you assume that all the ants alive today in Flathead County weigh as much (and likely more since Montana has a low population density) than all the humans in Flathead County, Montana. So if you calculated the average weight of a human and multiplied it by the number of humans and then took that number and divided it by the average weight of an ant, this would give you an estimate for the number of ants alive today. Here is my back the envelope calculations of this formula using average adult weight (which is likely a bit to high for the average of all humans if you include non-adults) and an "average" weight for an ant (which varies immensely between ant species - think of calculating an average weight of mammals from species as small as mice to as large as elephants - that is the equivalent in the size ranges of ants):

Number of ants in Flathead County, Montana:
91000 humans x 150 lbs. average weight of a human = 13,650,000 lbs. of humans in Flathead County, Montana

1.5 mg (= 0.0000033069 lbs.) average weight of an ant

13,650,000 all human weight / 0.0000033069 single ant weight =

4,127,732,922,072 ants alive in Flathead County, Montana today


Number of ants on Earth:
If we do the same exercise for all the ants alive on the planet, here is what you get:
7,077,551,385 human on the planet x 150 lbs. average weight of a human = 1061632707750 lbs of humans on Earth

1.5 mg (= 0.0000033069 lbs.) average weight of an ant

1061632707750 all human weight / 0.0000033069 single ant weight =

321,035,624,829,901,000 ants alive on the planet today


That is a lot of ants!


On a related note, you might be interested in this blog post (and many others - feel free to read through them) on why ants are important in the environment for your ecology materials:

http://www.antweb.org/antblog/2012/08/what-good-are-ants-david-panama-city-florida-usa.html


Best regards,
Corrie Moreau & the AntAsk Team

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