Conventional mouse cage
Fully enriched mouse cage
(One to fve)
9 FEBRUARY 2018 • VOL 359 ISSUE 6376 625
If they weren’t in the windowless base- ment of a cavernous biomedical re- search building, the “Aquatic Suites” might sound like a cushy vacation destination. But the zebrafish here at he University of Michigan (UM) still have it pretty good. In a large room full of aquaria, the striped, pinkie-size swimmers flit past fake green plants,
white plastic tunnels, and multicolored
marbles that may remind them of the bottoms of lakes and streams. These simple
accoutrements are a luxury for creatures
typically housed with little more than food
and the water they swim in. And the enrichments may make the animals better at
what they do: serving as important models
for human disease.
For decades, lab animals such as rodents
and fish have lived in barren enclosures: a
small plastic box, few—if any—companions,
and little else. The smaller the number of
variables, the thinking went, the greater
the accuracy of the experiment. But a growing number of studies suggests that this
approach may have backfired. Only one
in nine drugs that works in animals ever
succeeds in human clinical trials, and labs
often struggle to reproduce one another’s
results. Could the environment these creatures live in be part of the problem?
That’s what a new group of advocates
argues. “We’re trying to control these ani-
mals so much, they’re no longer useful,”
says Joseph Garner, a behavioral scientist
who runs a program to improve the value
and welfare of lab animals at Stanford Uni-
versity in Palo Alto, California. “If we want
animals to tell us about stuff that’s going
to happen in people, we need to treat them
more like people.”
Garner and others are pushing scientists
to enrich the lives of the creatures in their
care by giving them toys, companions, and
opportunities to exercise and explore—in
short, a life more like they would have in
the wild. These proponents are driven by
both a concern for the welfare of lab ani-
mals and a desire to make their contribu-
tions to research more meaningful. And
they’re beginning to conduct experiments
that show that such enrichments not only
benefit animals, but science as well.
However, other researchers fear that add-
ing extras to animal cages could muddy
experiments and exacerbate the reproduc-
ibility crisis. And given the tens of millions
of rodents and fish in U.S. labs alone, they
blanch at the cost. “There’s nothing natural
about what we’re doing, and adding a few
tubes to a cage is not going to change that,”
says Jonathan Godbout, a neuroscientist at
The Ohio State University (OSU) in Colum-
bus who studies aging and stress in mice.
“The more we spend on this stuff, the less
research we can do.”
LABORATORY ANIMALS didn’t always live
such a barren lifestyle. Researchers began
breeding rats for scientific experiments in
the mid-1800s, and early cages allowed the
rodents to burrow and run on wheels. But
by the 1960s, in an effort to standardize
care and limit variables, labs began to pri-oritize small, cheap, and sterile enclosures.
There was little regard for the animals’
natural habits, as long as they were free of
obvious pain and suffering. The goal, in essence, was to create furry test tubes.
Today, lab mice live in shoebox-size
cages hundreds of thousands of times
smaller than their natural ranges, and
rats can’t forage or even stand upright.
Both spend their days blasted by ventila-
tion and bright fluorescent lighting that
disrupts their day-night cycles. “We’re do-
ing the exact opposite of what we should
be doing to make these animals happy,”
Garner says. Lab animals tend to be obese,
have weak immune systems, and develop
cancer—all before scientists do any experi-
ments on them.
The first hints that enrichment could
help came in the 1940s. In 1947, psychologist Donald Hebb found that rats he raised
with his daughters and gave free rein in his
home were better learners than lab-raised
rodents. In the 1960s, researchers showed
that lab rats provided with wooden blocks
and a rotating assortment of mazes developed larger sensory regions of their brains.
Yet the only enclosures that changed
were those of nonhuman primates.
Amendments to the U.S. Animal Welfare
Act in 1985 required labs to promote the
psychological well-being of the monkeys
and chimpanzees in their care, giving them
more space, toys, and comrades. The U.S.
National Research Council’s 1996 Guide for
the Care and Use of Laboratory Animals
went further, prompting animal care staff
to add perches, blankets to make nests,
and even music and movies. But rodents
and fish were largely ignored.
Building a better
Mice and rats have traditionally been
housed in relatively barren cages,
with only food, water, and basic bedding
material. But advocates hope that
enriching their environment with
objects for play, exercise, and shelter will
give the animals a better life—and
make them better research models.
1 Running wheel
and rodents seem
to enjoy it.
A place to hide is
as mice may view
people as predators.
3 Tube maze
to boost rodent
4 Wood logs
mice of nature.
A mouse at the University of Michigan in
Ann Arbor is transferred from cage to cage
in a tube, rather than being hoisted by
its tail—a common, but stressful maneuver.