Open space, not traffic, may be why small animals hesitate to cross roads    2007-11-21 05:30:02    

London, Nov 21 : Ever wondered why small mammals have a habit of avoiding paved roads and being hesitant to cross them? Well, a new study has hinted that it's the open space, rather than the noise or pollution of traffic, that puts them off.
Ever wondered why small mammals have a habit of avoiding paved roads and being hesitant to cross them? Well, a new study has hinted that it's the open space, rather than the noise or pollution of traffic, that puts them off.

In order to make roads, forests are carved up, which isolate animal populations. Carving up the forest is major concern for fragmented populations of endangered small mammals, such as Vancouver marmot, Preble's meadow jumping mouse and Nelson's antelope squirrel, which to breed widely to maintain genetic diversity in their dwindling numbers.

For encouraging migration of animals, conservationists have various options such as shutting down roads, control traffic or build corridors underneath the highways. However, to make the best decision they need to know why roads are problematic for them in the first place.

For the study, a team of biologists at Carleton University in Ottawa captured Eastern chipmunks (Tamias striatus) and white-footed mice (Peromyscus leucopus) and tagged their ears so that their movements could be tracked.

They relocated 159 chipmunks and 244 mice with varying numbers of roads standing between them and their homes. The team then looked to see whether the number of roads, or the frequency of traffic on those roads, was linked to how many animals made it home. Some roads were practically deserted; others carried more than 15,000 vehicles a day.

The team of biologists reported that 51 percent of the mammals that were relocated across one road returned home, compared with 77 percent of those moved a similar distance but with no roads to cross. In relocations in which multiple roads needed to be crossed, the probability of returning was reduced by about 50 percent for each additional road. Perhaps surprisingly, traffic levels made no difference to these numbers.

Also, the team observed that areas adjacent to roads were just as populated with small mammals, as were sites farther away from roads. This also suggested that noise and traffic aren't a major issue for these animals.

"They are avoiding paved roads, but don't seem to mind being near them," Nature quoted Lenore Fahrig, an author on the study, as saying.

Fahrig said that previous research with amphibians and reptiles have shown worryingly high death rates owing to traffic. However, the situation with small mammals is clearly different - they seem to be able to dodge the cars better. That's good news for the mammals, but it complicates the problem of how to protect all wildlife.

"This is a strong signal that aside from ripping out roads completely, we do not yet have a single solution that is going to work for all species," says Fahrig.

Likewise, large animals seem to react differently to roads. Extensive work has shown that traffic volume does put off elk, deer and moose, for example.

"Many assume that patterns demonstrated by animal 'A' will apply to animal 'B', yet this rigorous study shows that isn't true," ecologist Joel Berger at the Wildlife Conservation Society in New York, said.

However, as far as chipmunks are concerned, the study has hinted that animal-friendly tunnels might be a good solution.

The findings have been reported in The Journal of Applied Ecology. (ANI)
© 2007 ANI

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