“These guys are smarter than people say.” — manuel leal
Baboon bosses face high stress
By Bruce Bower
Baboon males fight ferociously
for power, only to have that
power bite back.
Top-ranking males generate
surprisingly high levels of stress
hormones, a sign that these primates pay a cost to be the boss,
evolutionary biologist Laurence
Gesquiere of Princeton University and her colleagues report in
the July 15 Science.
Stress-hormone levels in alpha males
are on par with those of low-ranking
males scuffling to survive, the study
shows. Baboon bosses are burdened
by having to fight off rivals and guard
fertile mates from others’ advances,
the scientists propose. At the opposite
end of the social spectrum, indignities
such as not getting enough to eat and
Two male baboons face off in a fight. male
group leaders display stress hormone levels about
as high as those of their lowest-ranking peers.
enduring harassment by higher-ranking
males stress out bottom dwellers.
“Alpha males have higher reproductive success than other male baboons,
but those benefits come at a significant
cost,” Gesquiere says.
The new findings indicate that “life is
considerably more stressful” for alpha
males than for baboons one rung lower
in status, writes Stanford University biol-
ogist Robert Sapolsky in a commentary
published in the same issue of Science.
learnin’ lizards
will flip for food
Clever reptiles still get snacks
when the rules are changed
FROM TOP: JEANNE ALTMANN; M. LEAL/DUKE UNIV.
By Susan milius
Lizards everywhere may be scampering
a little taller now that an Anolis species
from tropical tree canopies has passed
tests for behavioral flexibility.
“These guys are smarter than people
say,” says behavioral ecologist Manuel
Leal of Duke University. Cognitive scientists have studied birds’ and mammals’
powers to solve unexpected problems
and learn new rules, but research on
lizard cognition has been limited.
Yet several Anolis evermanni lizards
collected from Puerto Rico and brought
into the lab coped with devices not seen
in nature, Leal and Brian Powell, also
of Duke, report online July 13 in Biol-
ogy Letters. In a series of tests, four out
of six lizards figured out how to remove
plastic lids firmly stuck on a food box and
to ignore a differently colored lid intro-
duced as a possible distracter. Two lizards
eventually were able to undo their previ-
ous training and switch to an alternative
color after researchers reversed the rules.
In one test of mental ability, an anolis
lizard must select the lid of the correct
color and then move it to get a treat
of freshly killed fly larvae.
in England, who studies cognition in
New Caledonian crows, was not exactly
wowed by the Anolis lizards, though. The
ability to discriminate among options,
and reverse that learning, is also known
in fish, flies and bees, among other animals, he says. “It may well be that lizards do have the same flexibility shown
by other taxa,” Kacelnik says, “but the
results shown here are nowhere near
what we know in birds and mammals.”
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August 13, 2011 | SCIENCE NEWS | 11
