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High fidelity

5 September 1998

A MALE sleepy lizard’s devotion to its female partner is puzzling
biologists.

Michael Bull of Flinders University near Adelaide tracked sleepy lizards
(Tiliqua rugosa) in South Australia. The lizards formed pairs in early
spring, and remained together until they mated in November. Some pairs stayed
together for five years. “That long-term monogamy has never been reported in any
other reptile in the world,” says Bull.

The researchers also carried out “divorce experiments”, in which males and
females were swapped around. Male sleepy lizards showed no interest in the
female divorcees, the team will say in Behavioral Ecology and
Sociobiology.

Why the lizards are monogamous is unclear, as neither males nor females care
for the young. Bull suspects that staying in pairs helps protect them from
predators and disease.