Some Lizards Smell Tougher Than Others

Sean Markey
for National Geographic News

February 21, 2007

Some people may be able to smell a good fight. But some male lizards can smell a bad one too, giving the animals clues as to whether to stand their ground or turn tail, a new study suggests.

Male Iberian rock lizards secrete a cholesterol-laden scent from glands in their thighs that signals their fighting ability and social status, according to scientists reporting in the online edition of the journal Biology Letters last month.

The bigger, more dominant the lizard is, the more cholesterol he secretes.

(Related: "Moles, Shrews Can Smell Prey While Underwater, Study Suggests" [December 20, 2006].)

Boxing Matches

After staging a series of lizard "boxing matches," researchers discovered that males sniff these "scent badges" to size up their potential opponents.

The bouts paired males of equal size but not equal scent—the scientists rubbed extra cholesterol on one contender in each match-up. His opponent often fled after the first whiff or two.

The scent cues serve the same role as visual displays used by other animals—such as the large racks of antlers on male deer or moose or the colorful breast feathers on some birds—the scientists say.

Love Hurts

Not surprisingly, perhaps, the reptile fisticuffs are motivated by romance—or at least its reptilian equivalent.

In hopes of wooing a mate, male Iberian rock lizards duke it out with other males to establish their dominance.

But as the saying goes, love hurts.

At a minimum, fighting costs males time and energy. Brawling can also cause serious injury or worse, notes study co-author Jose Martin, a biologist at the National Museum of Natural Sciences in Madrid.

By communicating the likely outcome of a brawl ahead of time, lizards big and small save themselves the trouble of an actual bout. As for evenly matched lizards, well, bring it on.

Studies have shown that scent mediates brawls in some fashion in other animals, including cockroaches, lobsters, crayfish, salamanders, mice, and rabbits.

But such behavior tends to be the exception, rather than the rule, Martin contend. Scientists often study visual displays and overlook the significant role played by chemical cues, he adds.

"Humans seem not quite aware of the importance of scent even for their own social relationships," Martin said via email.

"I think that the new findings in this 'sensory channel' could give us a more rich and diverse understanding of how social signals and social behavior evolve."

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