Dung beetle wooed by science for pasture cleanup
Practical farmers have long recognized the value of cow dung as
a fertilizer, but they likely have also observed some of its drawbacks. If not
well mixed with the soil, cattle droppings linger on the surface, smothering
forage growth and offering an ideal breeding ground to flies and intestinal
worms that can exact a heavy toll on domestic livestock, wildlife, and humans.
Some US studies have indicated that cattle will not graze close to droppings if
they can avoid it. Australian research has shown that 80 per cent of the
nitrogen in cattle manure escapes into the air when droppings are left on the
surface until dry. Someone else, presumably a mathematician, has calculated that
the annual droppings from 25 cattle would cover a full hectare.
With about 25 million head of cattle, mostly on the range,
Australian farmers obviously have some interest in dung management and they are
now getting help from Australian scientists in this respect. The Australian
solution has been to turn to dung" eating beetles - the scarabs once so revered
in ancient Egypt - which they began to import from Africa in the late 1960s.
The value of the dung beetle, of which more than 4 500 species
have been identified worldwide, lies in its habit of aggressively searching for
fresh manure. They will fly several miles to find it and once it is located they
fight fiercely among themselves for the most succulent morsels.
After feeding on the fluids, they break off small balls of dung
and push them down tiny tunnels they dig in the soil beneath the droppings.
Female beetles then lay an egg in each dung ball. Not only does this activity
help to remove the offending dung heap, providing perhaps as much as five per
cent more pasture, but it also disrupts the reproductive cycles of internal
cattle parasites who also lay their eggs in dung - but require an above-ground
environment for their survival.
The first batches of African beetles were set loose in
Australia's Northern Territory and in Western Australia in 1967. Finding few
natural enemies they established themselves quickly and went to work. Since then
some 20 species have been introduced and many are becoming acclimatized. Today,
tens of millions of African beetles are busily burying Australian cow manure.
In the United States, Department of Agriculture entomologists
have also been working with dung beetles for the past 15 years and have been
introducing new species from Africa, Pakistan, and Argentina. One entomologist
worked out detailed economic benefits that would accrue to cattle producers if
dung beetles could promptly bury all the cattle droppings on US grazing lands;
he reached the figure of $2 billion annually
Although the establishment of new colonies of dung beetles takes
time, scientists appear optimistic about their potential. The fact is that
cattle are alien species on many of the world's grazing lands and their
droppings are only slowly destroyed by native organisms. Australia's native dung
beetles, for instance, successfully remove kangaroo and koala dung in the
woodlands, but rarely venture out on the range to attack cattle droppings.
Most scientists agree that the dung beetles are unlikely to
become pests. Adults have no jaws and feed only on the fluids of the dung. They
live three quarters of their lives in the dark, under dung, or underground. The
larvae cannot survive outside the dung