19 March 2022 | New Scientist | 45within 40 metres of an occupied warren
provide enough cover for rabbits to expand
their earthworks. In a two-year experiment,
more than 40 per cent of her brush piles ended
up with a warren underneath and more than
90 per cent showed signs of rabbit activity.
This simple, low-tech but effective intervention
could be used in any rabbit-dependent habitat,
she says. Rouco and Delibes-Mateos suggest
something similar could make previously
unsuccessful restocking efforts more effective.
Other interventions would be more general
habitat restoration, although there is little
money around for that, and to stop keeping
domestic rabbits in close proximity to wild
ones. Otherwise, however, it seems we have
little choice but to let evolution run its course
and hope the virus becomes less deadly.
Some point out that the current huge drops
in rabbit numbers are measured against
the 1950s, when populations were possibly
artificially inflated. Overall, it is clear rabbits
are in a hole, says Rouco – but then again,
they have bounced back before. “I’m 95 per
cent confident they won’t go extinct,”
he says. Here’s hopping. ❚JIMCLAR
K/ALA
MYGraham Lawton is a feature writer
for New Scientist. His latest book is
Mustn’t Grumblestruck in 2010 and caused further “massive
declines”, says Miguel Delibes-Mateos at
the Institute for Advanced Social Studies in
Córdoba, Spain. Between 2012 and 2014, the
rabbit population in the Doñana National Park
in Andalucía, Spain, once a rabbit stronghold,
fell by more than 80 per cent. Across Iberia,
declines of 60 to 70 per cent have been closely
mirrored by falls in lynx and eagles. The UK
Breeding Bird Survey, which also records
mammals, shows a 64 per cent decline in wild
rabbit populations between 1996 and 2018.
The origin of the RHDVs remains unknown,
says Kevin Dalton at the University of Oviedo,
Spain. Like myxomatosis, they might have
jumped species, or they could have arisen
from recombination events, where two
viruses mash up their genomes. But their
effects have been enough for the International
Union for Conservation of Nature to reclassify
the European rabbit from “vulnerable” to
“endangered” in Spain. As recently as 1996,
it was in the “least concern” category.
Conservation efforts so far have largely
failed, in part because many people still
consider rabbits a common pest and fair game.
“Why would a species that you kill 6 million of
a year by hunting need conservation?”, says
Carlos Rouco at the University of Córdoba.
Around 500,000 rabbits are released each
year in Spain and France in an attempt to halt
their decline, but more than 90 per cent die
from predation, disease and stress.
There are some glimmers of hope. In
some areas of Spain, 60 per cent of rabbits
now have antibodies to RHDV2. And not all of
Iberia’s rabbits are struggling. There are two
subspecies – Oryctolagus cuniculus cuniculus
and O. c. algirus, which diverged around
2 million years ago – that each occupy their
own halves of the Iberian peninsula, divided by
a diagonal line running north-west to south-
east. They coexist along the border, but don’t
interbreed; Delibes-Mateos has proposed that
they should be recognised as separate species.
The big declines are in the O. c. algirus zone to
the south, which is also where the lynx and
eagles live. To the north, O. c. cuniculus is stable
or even increasing. Exactly why isn’t known,
says Delibes-Mateos, but finding out could be
a route to stabilising populations in the south.
One way to help colonies seems to be to
increase their size, perhaps because rabbits
then have more exposure to the virus as kits
and develop immunity. In Breckland, Bell has
found that piles of brush placed strategically
Rabbit society is “really complex”, says
Diana Bell at the University of East
Anglia in the UK. They live in groups of
up to 20 individuals, which cooperate
to defend their territory, but fight like
rabbits in a sack for dominance over it.
The prize for being alpha female is
control of the group’s breeding rights;
for alpha males, it is access to females.
Once weaned, male offspring
leavethe warren to spread their
wild oats. Females stay put in the
territory, forming a matriarchal
society of mothers, daughters,
sisters, grandmothers and aunts
led by the dominant female. She
rules the warren with a rod of iron,
often killing her subordinates’ kits
by dragging them into the open to
be picked off by predators.
But the top job is often up for grabs:
while wild rabbits can live to nine,
average life expectancy is only about
four years. “In Spain, they have more
than 30 predators,” says Carlos
Rouco at the University of Córdoba.
Corre, conejo, corre!Rabbit rules
Rabbit grazing
maintains rich
“mosaic” habitats
such as in the
Breckland, UK