Cranes have a complex relationship with their environment, according to a study published in PNAS. An international team, including researchers from the Max Planck Institute of Animal Behavior In Germany, followed four different species of cranes worldwide and noticed how they match different environmental conditions to significant events in their lives. According to the authors, this knowledge is crucial to developing better policies to protect the environment.
The team used small solar-powered GPS trackers to follow the movements of more than 100 cranes in Frida, Asia, and Europe. The data revealed the massive migrations that cranes undertake during the year. Some routes are longer than 6,400 km and require birds to cross the Alps and Himalayan Mountain ranges, the desert of the Arabian Peninsula, and the Mediterranean Sea. In addition, the team calculated how the cranes’ movements are influenced by their environment, including crops or water bodies nearby, as well as the temperature and vegetation covering the land.
“Animals have to satisfy their own needs with what they can get from their environment, but both of these are changing constantly,” said Scott Yanco, first author of the study. “This creates an intriguing optimization problem that we wanted to know if cranes were solving through long-distance migration.”
It turned out that all four crane species experienced vastly different environmental conditions during the year, which was synchronized with significant events in their lives. This was especially relevant when comparing temperatures or food availability during the winter and mating season. For some animals, the migrations involved massive shifts in environmental conditions. For example, the demoiselle cranes migrate over the Tibetan plateau, where they endure massive fluctuations in temperature.
“We suspect this all has to do with different biological needs during these different times of the year,” added Yanco. Common cranes prefer agricultural areas during the late summer because this period coincides with raising their young and preparing for fall migration. “This is exactly when we would expect them to want easy access to food,” said the researcher.
For other species, access to food can be tricky. The black-necked cranes had to decide between a safe roosting habitat or abundant resources. “Amazingly, the balance between these competing needs changed over the year depending on what the birds were doing,” added Yanco. During migration, they preferred safe roosting conditions, while during the breeding season, they picked abundant food.
“This type of shifting emphasis depending on what cranes need at any given time is what we were expecting to see,” said Ivan Pokrovsky from the Max Planck Institute of Animal Behavior in Germany. “But we were blown away by how well the cranes used movement to resolve trade-offs among competing needs and to access certain environments during key periods of the year.”
The authors believe understanding how animals interact with their surroundings is crucial to developing policies to reduce climate change and biodiversity loss. This study provides a statistical tool to understand the complicated relationships between animals and their environments that can be applied to conservation and management projects.
“When we know how animals use certain environmental conditions, we can make better predictions about how species might respond to human-caused global change and develop more effective interventions that ensure we preserve the conditions species need to survive,” concluded Pokrovsky.
Yanco SW, Oliver RY, Iannarilli F, Carlson BS, Heine G, Mueller U, Richter N, Vorneweg B, Andryushchenko Y, Batbayar N, Dagys M, Desholm M, Galtbalt B, Gavrilov AE, Goroshko OA, Ilyashenko EI, Ilyashenko VY, Månsson J, Mudrik EA, Natsagdorj T, Nilsson L, Sherub S, Skov H, Sukhbaatar T, Zydelis R, Wikelski M, Jetz W, Pokrovsky I. Migratory birds modulate niche tradeoffs in rhythm with seasons and life history. Proc Natl Acad Sci U S A. 2024 Oct 8;121(41):e2316827121. doi: 10.1073/pnas.2316827121