Using animal tracking data to better predict animals' use of natural movement corridors through urban lansdcapes.
Many animals are adapting to human encroachment of their natural habitats. Carnivores, in particular, require large territories and so are often forced to move through developed areas to find good habitat. To date, scientists have used mathematical models to predict where exactly these important routes are, but fishers fitted with GPS sensors are now showing that their calculations may be missing the mark if they ignore animal behavior.
Animal movement corridors are thought to be vitally important for the survival of animals in fragmented landscapes. Humans use them too; how else would we get from the couch to the kitchen? Just like our hallways provide straight, efficient movement paths, animals in developed areas need travel paths to connect separate forest fragments. Maintaining these corridors in the face of continued development will help animals survive, but discovering where exactly these are has been a challenge.
In the past, map-based models were used to guess how an animal would get from one place to the other. New research, however, allows the animals to show us exactly which corridors they want to use, and finds these map-models to be surprisingly inaccurate. This new study, published this week by Dr. Roland Kays, director of the Biodiversity Lab at the North Carolina Museum of Natural Sciences and professor in the North Carolina State University College of Natural Resources, with colleagues from Max Planck Institute for Ornithology, used small GPS devices to track the weasel-like fisher through suburban Albany, NY.
"This is one of the first papers to show that individual animals actually to use movement corridors," says Kays, "and one of the first to actually test the predictions of mathematical models."
The models use information about the habitat preferences of the animals. Since fishers spend most of their time within forests and avoid open spaces, it was assumed that this rule would also apply to their corridors. “That assumption was not true, as the animals were much more flexible in their willingness to use corridors composed of a variety of habitat types, not just forests,” notes Scott LaPoint. To get from one place to another they would use lower quality areas, including over meadows, fields and even man-made landscapes such as golf courses and cemeteries.
How the fisher crossed the road was especially interesting, going under more often than over. "The tracking data showed us that an animal would return to the exact same place to cross a road," says Kays. "When we went to see what was so special about this spot we'd typically find a small drainage culvert with animal tracks in the mud or snow." Fishers are in the weasel family, and love crawling through small tubes. They have used this network of culverts to re-colonize suburbia, feeding on grey squirrels along the way.
Landscape planners and environmentalists are interested in wildlife corridors because they are considered worthy of special protection. Corridors facilitate a healthy spread of the animals, maintain gene flow between populations, and thereby reduce the risk of extinction. “They can also be very expensive,” explains LaPoint, “so it is important that our corridor model predictions are accurate and that we make sure that animals are indeed using them. To do so, we should ask the animals what they need, and by monitoring their movements, in effect we have actually created a way for the animals to communicate with us humans.”
This new work suggests scientists should just ask the animal, “What do you think? What do you want?” This could make landscape planning simpler and more transparent, and scientists could even learn something along the way.
- View the full paper  (PDF) published in the journal Landscape Ecology.
The New York Times' Scientist At Work: Tracking Urban Fishers Through Forest and Culvert  by Roland Kays