The bunny that
Fossil rabbit was six times
the size of modern relatives
By Susan Milius
It may not be Harvey (it’s visible),
but paleontologists have found fossils of a giant rabbit — the largest ever
described — on the Mediterranean island
Three to 5 million years ago, a rabbit
species there grew about half a meter
high with an estimated weight of 12 kilo-
grams (about 26 pounds), researchers
report in the March Journal of Verte-
brate Paleontology. Six times the size of
today’s wild European rabbit, the hefty
extinct species outweighed not
only all known rabbits, but all
species in the broader group of
rabbits, hares and pikas, say paleontolo-
gist Josep Quintana Cardona of Minorca
and his colleagues.
Fossils discovered on the island of
Minorca reveal the largest rabbit spe-
cies ever described (right, compared
with a modern European rabbit at left).
related groups like rodents, comments
paleontologist Łucja Fostowicz-Frelik
of the American Museum of Natural
History in New York City.
So far no plausible rabbit-eaters have
turned up among fossils from the same
time period on Minorca, so the big bun-nies could have evolved larger and larger
body size without pressure to maintain
speed and agility to escape predators.
The relatively short, stiff spine of the
fossils suggests that Nuralagus didn’t
hop much, if at all.
Data may point to monarch decline
Butterflies overwintering in Mexico appear to be on the wane
By Susan Milius
North America’s beloved monarch butterfly may be sliding into long-term decline.
While monarch numbers have fluttered
up and down over recent decades, one
research group now says that there’s
enough data to spot a downward trend.
Over the last 17 years, the area of
Mexican forest patches covered by
overwintering butterflies has been shrinking
overall, says conservation
biologist Ernest Williams
of Hamilton College in
Clinton, N.Y. He and his
colleagues use the area
occupied, which has averaged 7. 24 hectares since
the end of 1994, as a rough
index of winter monarch
“We have enough data
now to say that we are see-
ing a long-term decline,” Williams says.
Seven of the 10 below-average years
in the study followed one another in a
worrisome streak through the winter of
2010–2011, Williams and his colleagues
report online March 21 in Insect Conservation and Diversity.
That trend in winter populations does
pass a simple statistical test, says monarch researcher Karen Oberhauser of the
University of Minnesota
in St. Paul. She and other
researchers are now working on a broader analysis
of monarchs and the challenges the insects face
throughout the year to get
a better handle on whether
the population is declining
Monarch butterflies winter-
ing in Mexico can cluster
so densely that they hide
the bark of a tree trunk.
and, if so, why. “I am not arguing that mon-
arch populations are not facing threats,
nor am I saying I’m not concerned,” she
says. “I don’t think the [wintering] trend
data clarify the situation.”
Orange-and-black monarchs dart and
waver over North American summer
landscapes coast to coast and as far north
as Canada, seeking milkweed plants as
sites for laying eggs. The species’ annual
migration is perhaps its most dramatic
feat, though. Butterflies that hatch dur-
ing summer and fall — never having been
to Mexico — find their way to the same
patches of forest as earlier generations.
Winter monarch retreats are officially
protected, but illegal logging chews away
at Mexico’s forests. Plus, looming climate changes may bring more episodes
of severe weather, which can hammer
the butterflies. Monarchs across North
America are finding less breeding habitat than they used to as open land for
milkweeds is falling to development.
And researchers warn that a boom in
genetically engineered crops is changing herbicide-use patterns and thinning
the ranks of milkweeds.
FROM TOP: ARTWORK B Y MEIKE KÖHLER; E. WILLIAMS