Thermal cameras, for example, specifically target radiation of 10 microns: the part of the spectrum that most closely matches the heat released by living things. By measuring the stripes, Dr. Baker that they were also tuned to 10 microns — apparently based on life’s most common heat signature. “That was my Eureka moment,” he said.
He found the same distance in the equivalent hairs of a number of other species, including shrews, squirrels, rabbits and a small mouse-like marsupial called the agile antechinus. The antechinus hair, in particular, suggested “a really advanced optical filtering,” starting with a less sensitive absorber at the top of the hair and ending with patterns at the base that eliminated noise, he said.
Because these hairs are evenly distributed throughout the body, their potential infrared-sensing ability can help a mouse “spot” a cat or owl in any direction, said Dr. baker.
The suspicion of Dr. Baker that these hairs help small mammals spot predators is “plausible,” said Helmut Schmitz, a researcher at the University of Bonn in Germany who has studied infrared detection mechanisms in fire beetles. (These beetles use organs in their exoskeletons to sense the radiation, which leads them to the recently burned forests where they lay their eggs.)
But jumping directly from structural properties to a biological function is risky, he said. To show that the hairs serve this purpose, it is necessary to prove that the skin cells to which they are attached are able to recognize very small temperature differences – something that has not been observed, although these cells have been heavily studied, Dr. said Schmitz.
dr. Baker has continued to explore this issue by designing his own observational tests. (A recent effort includes filming how rats react to “Hot Eyes,” an infrared emitter he built that mimicss the eyes of a barn owl.) Because these experiments were not controlled, they were not included in the published article. But now that he’s lit this metaphorical torch, Dr. Baker to pass it on to others who can look deeper into these anatomical questions and design more rigorous experiments.
“Animals that operate at night have secrets,” he said. “There must be a huge amount that we don’t understand.”