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Migratory birds and mammals that consume a lot of energy by traveling long distances to chase food or find a prime nesting spot tend to live fast and die young, scientists reported Tuesday.
In a study published in Nature Communications, researchers found that migratory animals have a shorter lifespan than their domesticated counterparts.
But they make up for it by having more offspring in less time.
Analyzing over 700 birds and 540 mammal species, the study determined that from an evolutionary point of view neither strategy is “better” than the other.
“These are just two different ways to solve life’s problems,” said UK Exeter University professor Stuart Bearhop, an author of the study.
“One way is to live fast and die young, the other is to live slowly” and produce offspring for a longer life.
It balances, otherwise one group – migratory or non-migratory species – would dominate the other.
“An animal that has a shorter lifespan but produces more offspring eventually leaves as many copies of itself to reproduce as an animal that has a slower life and produces fewer offspring,” Bearhop told the phone.
Some species can swing in both directions.
Blackcap – olive gray warblers with distinctive black or brown spots on the head – can be resident or migratory.
– Climate change –
Those that roam the lands typically live shorter lives, reach maturity at a young age, and produce more chicks.
Migration can take place in the skies, underwater or across different landscapes.
Climate change could skew the evolutionary tables against migratory species, which have to “cope with changes in multiple places, instead of just one for residents,” said Bearhop, who teaches Animal Ecology.
They travel between their breeding and non-breeding sites based on the seasons and depend on predictable weather patterns such as winds and ocean currents.
But global warming is disrupting these patterns, through rising temperatures, modified rainfall and changes in vegetation.
The blue whale travels between tropical calving areas in winter and high-latitude feeding areas in summer.
As sea temperatures rise, the abundance and distribution of their food – plankton, fish and squid – changes, weakening females and increasing the intervals between births, previous research has shown.
– Size matters –
“Climate change is not happening uniformly and its effects are already proving much worse at higher latitudes,” Bearhop said.
The Arctic, favored by migratory birds, is one such area.
Scientists expect to see differences in reproduction and survival rates due to climate change.
The study also found that size matters.
“Migrant flyers like birds and bats tend to be smaller in body size than residents, while migrant walkers and swimmers – all mammals except bats – tend to be larger,” the authors said.
Only older walkers and swimmers can store enough energy to complete long-distance migrations.
Larger birds face energy problems when forced to use fluttering flight, the authors added.
“That’s why there are no migratory mice, for example,” Bearhop said. “They just can’t cover the ground efficiently.”
by Eléonore HUGHES
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