Migrating animals at greater risk from changes in the climate

‘Live fast and die young’: Migratory animals are in decline because their fast-paced lifestyles mean they are less able to adapt to changing climates and habits, study claims

  • Experts from the University of Exeter studied the ‘pace of life’ of 1,296 species
  • They looked at metrics including longevity and the frequency of breeding
  • The team found that migrants often grow faster, breed earlier and die younger
  • Flying migrants are typically smaller than their static-living counterparts
  • However, those migrating animals that swim or walk are often larger instead 

Changing climates and habits pose a greater risk to migrating animals — especially those that fly — because they ‘live fast, die young’ and are thus less able to adapt.

Experts from Exeter studied nearly 1,300 mammal and bird species — finding that those who migrate typically grow faster, have offspring earlier and die younger.

The findings could help to explain why many migrant species appear to be declining, as they are less able to, for example, delay breeding conditions are poor.

They could also help to predict how migrating species may respond to environmental shifts in the future. 

The team also noted that migrating animals that swim or walk are typically larger than their non-migrating equivalents, while flying migrants are usually smaller

Changing climates and habits pose a greater risk to migrating animals — especially those that fly — because they ‘live fast, die young’ and are thus less able to adapt. Pictured, a flock of fruit bats migrates across the sky as the sun begins to set

‘Many species migrate over long distances and this requires substantial amounts of energy,’ said paper author and conservation biologist Andrea Soriano-Redondo of the University of Exeter.

‘This energy cannot be used for other purposes such as self-maintenance or reproduction, so we would expect animals to adjust the amount of energy they use for these things,’ she added.

‘By prioritising reproduction over survival, “fast-living” species have the potential to increase numbers more rapidly — which may balance the long-term energy costs and short-term risks of migrating.’

In their study, Dr Soriano-Redondo and colleagues examined the so-called ‘pace of life’ of 1,296 species — looking at such metrics as longevity, the ages at which the female individuals reach sexual maturity and breeding frequencies.

‘We have long thought that migration is a risky behaviour,’ said paper author and animal ecologist Stuart Bearhop, also of the University of Exeter.

‘Animals often take a chance when they migrate, hoping to find the right conditions in their destination,’ he added.

‘In the case of birds that migrate to the High Arctic, they arrive in spring and have a short window in which to breed.’

‘Some will only attempt this if conditions are right — and if climate change degrades habitats, these “fast-living” species might miss their chance entirely.’

 ‘We have long thought that migration is a risky behaviour,’ said animal ecologist Stuart Bearhop of the University of Exeter. ‘Animals often take a chance when they migrate, hoping to find the right conditions in their destination,’ he added. Pictured, migrating geese

‘We think that walking and swimming migrants are generally larger because only large animals can store enough energy, and use it efficiently enough, to make long-distance land or sea migrations,’ added paper author and ecologist Dave Hodgson.

‘Among flying species, the opposite is true, as a large body mass makes flying more costly in terms of energy,’ he explained.

The full findings of the study were published in the journal Nature Communications.

WHY DO MIGRATING BIRDS FLY IN A V-FORMATION?

Birds fly in a v-formation to help them fly more efficiently, staying aloft while expending as little energy as possible.

Scientists learned the aviation secrets of migrating birds after attaching tiny logging devices to a flock of 14 northern bald ibises that not only tracked their position and speed by satellite but measured every flap of their wings.

The 14 birds used in the study were hand-reared at Vienna Zoo in Austria by the Waldrappteam, an Austrian conservation group that is re-introducing northern bald ibeses to Europe. 

Birds fly in a v-formation to help them fly more efficiently, staying aloft while expending as little energy as possible (stock image)

The birds were studied as they flew alongside a microlight on their migration route from Austria to their winter home in Tuscany, Italy.

Lead researcher Dr Steve Portugal, from the Royal Veterinary College, University of London, said: ‘The distinctive V-formation of bird flocks has long intrigued researchers and continues to attract both scientific and popular attention, however a definitive account of the aerodynamic implications of these formations has remained elusive until now.

‘The intricate mechanisms involved in V-formation flight indicate remarkable awareness and ability of birds to respond to the wingpath of nearby flock-mates. Birds in V-formation seem to have developed complex phasing strategies to cope with the dynamic wakes produced by flapping wings.’

When flying in a V formation, the birds’ wing flaps were approximately ‘in-phase’, meaning all the wing tips followed roughly the same path, the scientists found. 

This helped each bird capture extra lift from the upwash of its neighbour in front.

Occasional shifts of position within the formation meant that at times birds flew directly one behind the other. 

When this happened, the birds altered their wing beats to an out-of-phase pattern to avoid being caught by downwash.

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