DESPITE their cold-blooded demeanour, lizards can form personal relationships
with people. A team of scientists has shown that iguanas recognise their human
handlers and greet them differently, compared with strangers.
Scott McRobert and his colleagues at Saint Joseph鈥檚 University in
Philadelphia had often joked that their lab鈥檚 pet iguana 鈥淔ido鈥� would bob his
head when McRobert approached but ignore everyone else. They decided to design
an experiment to find out if Fido really did know his handler. They also wanted
to see if the twelve-year-old lizard remembered a lab student who had cared for
him four years earlier.
McRobert, the student and around forty strangers took turns reading the Dr
Seuss children鈥檚 book Oh, the Places You鈥檒l Go! to Fido. They read it
aloud or silently, in front of Fido鈥檚 cage or behind a screen, while another
researcher counted the iguana鈥檚 head bobs.
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When Fido could see the readers but not hear them, he bobbed his head roughly
equally to both the student and McRobert, but almost totally ignored the
strangers. When they read aloud, however, Fido bobbed his head around three
times as often to McRobert than to the student. 鈥淰isual cues alone are enough
for him to recognise individuals,鈥� says McRobert, but he suspects that Fido
鈥渇ine-tunes鈥� his response with audio cues.
鈥淚鈥檓 pretty sure that this is the first time human recognition by a lizard
has been demonstrated in a scientific way,鈥� says McRobert, who described the
study this week at a meeting of the Animal Behavior Society in Lewisburg,
Pennsylvania. He suspects Fido singles him out because iguanas are not normally
handled and see handlers as a threat: 鈥淚t鈥檚 not that he loves me,鈥� McRobert
says.
He plans to use recorded voices to see what Fido will do when visual and
audio cues don鈥檛 match up. 鈥淲e may actually learn something about how these
animals recognise individuals.鈥�