Fast living means shorter lives for migrating species

Researchers have long thought that migrating species pay a cost for the energy they spend making long journeys. But what exactly is the tradeoff for these journeys? And what role could climate change play as it alters the world these animals are migrating through?

“When you migrate, you can’t invest time and energy into doing something else,” said Andrea Soriano-Redondo, who studied this tradeoff as a postdoctoral researcher at the University of Exeter. “It has a strong influence on the rest of your cycle.”

In a study published in Nature Communications, Soriano-Redondo and her colleagues looked at a number of characteristics — including longevity, sexual maturity, reproductive strategy, body mass and more — in about 1,300 mammal and bird species, some that migrate and some that don’t. At one end of the spectrum were species with high longevity, delayed sexual maturity and small annual reproduction outcomes. At the other extreme were animals that reproduce more often, have a higher number of offspring per year and die sooner.

To collect the data, Soriano-Redondo and her colleagues tapped into a massive dataset for birds that included these characteristics as well as another dataset that included migratory strategies. But gathering the data proved a bit more difficult when it came to mammals. “I had to go through the literature, including a new handbook of mammals of the world,” she said. “I skimmed through it for key information. It took months.”

The team found that after correcting for size of species, migratory animals — whether American robins (Turdus migratorius) or saiga antelope (Saiga tatarica) — generally developed faster, produced offspring earlier and died younger than their non-migratory counterparts. Those with a slower pace tended to be residents. That could have important implications in times of climate change, she said. Species that have a fast pace of life have less flexibility to skip reproductive events, but if migratory species arrive at their breeding area early or late, when conditions aren’t optimal, they could lose their chance to reproduce.

“If they fail to breed one year, they’re much more affected than species that have a large lifespan and more opportunities,” she said.