The seed dispersal habits of small mammals have long been known to have a significant bearing on the health and growth of forests. A doctoral student at the University of Maine has found that the various personalities of these animals also determine whether seeds germinate and grow.
“People are generally willing to accept that dogs and cats have personalities because they can see behaviors that consistently differ among individuals of the same species. The same is true of mice,” said Allison Brehm, who conducted a study of how the personalities of small mammals affect forest structure. “Some are consistently more active or bolder than others, and we wanted to know whether small-mammal personality influences seed predation and seed dispersal.”
Brehm captured 648 mice, voles, and shrews and put them through a series of behavioral tests that determined their timidness, docility, and anxiety. Then she released them into forests undergoing three silviculture treatments, dispersed seeds of various sizes nearby, and watched what happened.
“We know small mammals have personalities. We know they play a role in seed dispersal, but the main question was whether all individuals contribute in the same way – or are some individuals playing an especially important role, and does personality predict their decisions in terms of seed dispersal?” Brehm said. “We wanted to see if personality influenced their selection of seed size, dispersal of seeds, the probability of them consuming the seeds, and if it influenced where they cached the seeds.”
And she found that, in almost every case, it did.
For instance, Brehm found that mice that were especially active were more likely to remove seeds from where they were found and consume the seeds rather than cache them. She also found that bold voles dispersed seeds farther than timid ones, perhaps because they were more willing to risk attack by predators while carrying seeds a greater distance. More docile voles, however, tended to store seeds in locations that were more optimal for germination, like close to fallen logs.
Brehm also discovered that the distribution of small-mammal personalities differed depending on habitat forest type. She captured few timid mice in even-aged forests, for example, but equal numbers of bold and timid mice in an unmanaged 100-year-old forest.
“It may be that the even-aged forest is a riskier environment to live in, so it pays to be a bolder individual, since there may be fewer resources available and bolder individuals are better competitors,” Brehm said.
The study suggests that it may be worthwhile to promote a diverse range of personalities within small- mammal populations as a way to help conserve ecosystems. How exactly to do that, though, is uncertain.
“Promoting behavioral diversity is probably best done by promoting diversity in the environment,” said Brehm. “Diverse environments will lead to a greater diversity of personality types that can survive there.”