Zebras appear to be guided by memory in their annual migrations, research suggests.
Memory based on past average conditions provided a clear signal that best directed zebras to their destination, scientists have concluded.
In contrast, current vegetation conditions along the way were less important for the direction of the migration, according to a computer simulation conducted by researchers from the Senckenberg Research Institute and Natural History Museum in Germany.
The findings of the study, published this week in the journal Proceedings of the Royal Society B, highlights that migration routes of large land mammals such as zebras could be more inflexible than previously thought.
Each year, thousands of African animals, including zebras, wildebeests and gazelles, migrate in turn with the seasons between foraging grounds.
The animals walk long distances in their search for forage.
While science has explained certain aspects of this migration, it is not fully understood how the animals know where to go.
Chloe Bracis, a researcher at the German Senckenberg Biodiversity and Climate Research Centre and the Goethe University Frankfurt, has found that memory is the key to zebra migrations.
“Zebras appear to migrate to the location where foraging conditions were best in the past,” she said.
“They seem to navigate to their destination based on memory, and importantly, forecast conditions several months after arrival.”
As part of the study, Bracis and her colleague Thomas Mueller modelled migration routes of zebras using computer simulations.
Zebras migrated about 250km from the Okavango Delta in Botswana to the Makgadikgadi grasslands in November.
“We tested two mechanisms which can influence the direction,” explains Mueller.
“Simulated zebras could use perception, and sense, for example, the vegetation greening up in their current surroundings.
“Alternatively, zebras could use memory – that is, information from previous migrations, to forecast where to go.”
The researchers compared the simulated tracks with real-life tracks from GPS-tagged zebras which were collected by other researchers.
Memory using past average conditions was able to predict the migration destination of the modelled zebras up to four times closer than those modelled using perception to find their way.
However, perception was still important, they said. Other studies have shown the importance of perception of current local conditions on the timing and speed of the zebra migration, but these may be less important for zebras in terms of direction.
Migration routes of zebras are threatened by climate change and land use change in southern Africa.
The zebra migration examined in this study, for instance, was blocked by a fence from the late 60s until 2004.
The researchers therefore see the study as contributing to the conservation of large migratory terrestrial mammals such as zebras.
Mueller said migration routes could be efficiently protected only if mankind knew how the animals migrated.
If memory of past conditions helped migrating animals decide their route, it suggested migration routes could be relatively inflexible, concludes Mueller.