[ad_1]
"The transferred animals were literally left out of a cattle trailer and started looking around their new environment," says Matthew Kauffman of the University of Wyoming. "And they have almost completely failed to migrate."
Kauffman knows this because the displaced sheep were often equipped with radio collars, which allowed him and his colleagues to compare their movements with those of the mouflons who had lived in the same place for centuries. Among these long-standing herds, between 65 and 100 percent of sheep have migrated. But in transferred herds, less than 9% migrated – only sheep that had been moved into established populations already familiar with the land.
The team also used satellite imagery to measure how closely sheep were following the waves of greenery. Then, they compared the performance of animals to two types of simulated – naive sheep that moved at random, and omniscient who knew the local plants very well. "Some of the recently transferred herds have followed the green wave, as have those who have wandered at random," says Brett Jesmer, who led the work. Older herds did a lot better – "not as good as the omniscient, but closer," he says.
"It changes the way we think about wildlife habitat," adds Kauffman. "Wildlife researchers have always focused on the physical landscape. How much grass is there? How many conifers? Then you may wonder if this habitat is good for a sage grouse or a grizzly bear. But our work suggests that the true measure of habitat quality for mobile animals is both the physical attributes of the landscape. and the knowledge that animals have of how to make a living there. Put the naïve animals in an impressive habitat and they can work very well, while the animals that know how to exploit the degraded landscapes can do very well.
Scientists have long wondered how migratory animals know where to go. In some cases, this knowledge is innate. Sea turtles read the Earth's magnetic field for specific directions, while hybrid songbirds will travel on roads halfway between those of their parents. In other cases, learning is important. White whooping cranes become more able to migrate with age, and groups with at least one elder are much more likely to stay on track.
Ecologists have long assumed that ungulates – haired animals such as deer, bison and sheep – are also learning to migrate, as many species seem to adopt the movement patterns of their mothers and peers. By studying the displaced bighorns, using the data collected in their snares, Kauffman's team finally confirmed this long-standing hypothesis.
To a certain extent, ungulates can find emerging greenness through local smells and sights. "But they also have excellent spatial memory," says Jesmer. "They can remember when a trail has cleared up and time their movements to go to this area next spring." Their mental maps are the foundations of migrations. They make the difference between an animal that comes just after the shoots nearby and an animal that travels long distances on the ground in anticipation of the greenery it knows to happen.
Source link
