04 October 2013

Beetle News

Welcome back. Fifty years ago, when I was writing verse about insects for a creative writing course (see: Praying Mantis Photo Addendum), I discovered the dung beetle. It offered so many avenues for metaphor or parable--Egyptian scarabs, the Greek Sisyphus, life as an overwhelmed engineering college student.

Although the acquaintance and appreciation was renewed last January by the report of the beetle’s astronomical GPS, I was blogging about other bugs. Then new research surfaced. Unlike the January finding, which simply advanced understanding, this dung beetle deed potentially affects humanity.

Dung Beetles

Found on every continent but Antarctica, in farmland, forest, grassland and desert, there are thousands of dung beetle species in two insect families Scarabaeidae and Geotrupidae. They grow to about 0.5 to 2.5 inches, depending on species, and generally live no longer than 3 years. 
Dung beetles in action in Namibia, Africa. (photo from
commons.wikimedia.org/wiki/File:Namibia-dung-beetle-feast.jpg)
There’s no getting around it, dung beetles feed on dung, animal manure. They also do more with their food, which is why they’re classed as rollers, tunnelers and dwellers.

Roller Beetle Navigation Research

I’ll skip over the romance in roller dung beetles’ lives--the chance meeting, small talk, going off to mate--and note only that rollers take a piece of dung, form it into a ball, roll it away quickly to evade other dung beetles, then bury it. The ball is used as food or as a brooding ball for the female’s eggs.

Roller dung beetles. (multiple websites)
Earlier research found that rollers use the sun and moon to ensure they’re steering the ball straightaway from the dung deposit and other beetles. Unknown was how they navigated on moonless nights.


Investigators from Sweden’s Lund University and South Africa’s Witwatersrand and Pretoria universities monitored nocturnal rollers under moonlit, moonless and cloudy conditions. They used a 10 foot diameter sand-filled arena, first in a South African game reserve, then in a planetarium. Get this: To block the bugs’ view of the sky, they fitted the beetles with cardboard caps, designing transparent caps for controls.
Milky Way seen from Australia (photo
 from One-Minute Astronomer, 17 Jan 2011
 www.oneminuteastronomer.com)
The study demonstrated for the first time that dung beetles also use stars to navigate--not individual stars, but the glow of the Milky Way galaxy.

Dung Beetle Greenhouse Gas Research

Knowing their primary food source, you won’t be surprised to learn that dung beetles deserve awards for cleaning up pastures. In parts of Texas, for example, the little recyclers reportedly remove 80 percent of the cow manure. Now there’s more.

A study from Finland’s University of Helsinki, with contributions from the UK’s Oxford University, found that, while the Northern European dung beetles are dwelling and tunneling and chomping away, they’re also modifying the profile of greenhouse gas emissions from the cow manure.

Employing a closed chamber system, the researchers measured fluxes of carbon dioxide, methane and nitrous oxide from cow manure on a grassy surface, with and without dung beetles present.

With the bugs in action, total emissions of methane were significantly lower (good), but because of an unexplained short-term spike, total emissions of nitrous oxide were higher (bad).
U.S. Greenhouse Gas Emissions in 2011
(www.epa.gov/climatechange/ghgemissions/gases.html)
Although those emissions were small compared to carbon dioxide, the pound for pound impacts of methane and nitrous oxide on climate change are thought to be 20 and 300 times greater, respectively, than that of carbon dioxide.

Wrap Up

So, here I am, dying to step carefully into a cow pasture to observe any of Wisconsin’s estimated 60 dung beetle species. Cow pasture? Seven months on a farm in the dairy capital of the US, and I’ve yet to see a single cow. I think I remember seeing a horse down the road. Thanks for stopping by

P.S.

-Dung beetle navigation paper in Current Biology and example articles:
www.cell.com/current-biology/retrieve/pii/S0960982212015072
cosmiclog.nbcnews.com/_news/2013/01/23/16668013-dung-beetles-guided-by-milky-way
news.sciencemag.org/2013/01/dung-beetles-navigate-milky-way
-Dung beetle greenhouse gas paper in PloS One and ScienceDaily article:
www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0071454
www.sciencedaily.com/releases/2013/08/130822105031.htm
-Background on dung beetle and greenhouse gases:
en.wikipedia.org/wiki/Dung_beetle
www.ces.ncsu.edu/depts/ent/notes/forage/guidetoncdungbeetles.pdf
hayandforage.com/grazing/better-manure-breakdown-with-beetles-0501
www.epa.gov/climatechange/ghgemissions/gases.html

1 comment:

Bill Teng said...

Sounds like they are "essential" employees.