After three days, a number of animals were spotted feeding on the seeds, including mice, chipmunks, squirrels, birds and rabbits. But two animals in particular differed between quiet and noisy sites mice, which preferred noisy sites, and western scrub jays, which avoided them altogether.
Pion pine seeds that are eaten by mice don't survive the passage through the animal's gut, Francis explained, so the boost in mouse populations near noisy sites could be bad news for pine seedlings in those areas.
In contrast, a single western scrub jay may take hundreds to thousands of seeds, only to hide them in the soil to eat later in the year. The seeds they fail to relocate will eventually germinate, so the preference of western scrub jays for quiet areas means that pion pines in those areas are likely to benefit.
In keeping with their seed results, the researchers counted the number of pion pine seedlings and found that they were four times as abundant in quiet sites compared with noisy ones.
It may take decades for a pion pine to grow from a seedling into a full-grown tree, Francis said. This means the consequences of noise may last longer than we thought. "Fewer seedlings in noisy areas might eventually mean fewer mature trees, but because pion pines are so slow-growing the shift could have gone undetected for years, he explained.
"Fewer pion pine trees would mean less critical habitat for the hundreds of species that depend on them for survival," he added.
|Contact: Robin Ann Smith|
National Evolutionary Synthesis Center (NESCent)