Beetles To The Rescue

New Zealand has decided that it has put up with “it” for too long. “It” is livestock dung. This month New Zealand has approved the importation of 11 species of dung beetle to address the growing problem with animal waste. Sheep and cows are foreign species (native to Asia) that were imported into New Zealand over a century ago. In their native range, sheep and cows are accompanied by dung beetles that process their dung. However, the native dung beetles of New Zealand are not adapted to sheep and cattle dung. Instead of dung piles disappearing in a couple of weeks due to the dung beetles, the cow patties can linger for months.

Dung beetles that feed on larger piles of manure, such as those produced by cows, will remove the manure from the site and bury it. Some dung beetles will form the manure into a ball and roll it to another site and bury it. The manure is food for the larvae of the dung beetles. (And you used to complain about what your parents fed you!). Burying the manure restricts access to only the larvae of the dung beetle.

Burying the dung is important for environmental reasons.  Burying keeps rain and running water from washing dung into nearby ponds and streams. Compared to the unprocessed cow pie, burying reduces water pollution.
Burying the dung aerates the soil so it is better at retaining urine and other animal byproducts.  Burying the dung allows soil microorganisms to process the greenhouse gasses emitted from the manure rather than emitting gasses to the atmosphere.
Livestock will not graze too close to cow pies. The dung beetles increase the effective pasture area.  Burying the dung reduces habitat for flies and reduces the pest fly population.  Parasites of livestock are eliminated as dung beetles ingest and kill them as they process the manure.

With all the positives, why did New Zealand wait until 2011 to import dung beetles? Australia, which has similar ecological problems with its livestock, successfully imported dung beetles decades ago. Basically, the fear that introducing new insect species into the environment might cause unknown ecological problems has been the stumbling block. Considering that intentionally imported species have wreaked havoc in numerous ecosystems, New Zealand is wise to be wary. However, sufficient time for study and experience with the beetles in Australia has convinced New Zealand that the benefits outweigh the risks.

After the importation this year, it may take up to a decade for populations to build to levels that will produce the desired impact on the manure problem. As the old saying goes, “A beetle’s work is always dung.”

Australian Dung Beetles Photo: Eliza Wood, ABC Rural