麻豆传媒

Species: Pterodroma baraui

Habitat: Reunion Island in the western Indian Ocean, mating 鈥榥eath the pale moonlight

Name an animal that is most active during the full moon, and even those of us untouched by the charms of the Twilight movies might think werewolf.

Our subject today is no mythical beast, however. The Barau鈥檚 petrel is one of a handful of tropical birds that uses the moon as a kind of alarm clock. During breeding season, the bird travels to mating sites on the aptly named Reunion Island off the shore of Madagascar to meet its mate.

The monogamous birds synchronise their journeys using the full moon as a kind of Bat-Signal to indicate that it鈥檚 time to mate. 鈥淔irst arrival at the colony is crucial in the mating system of colonial animals like seabirds,鈥� writes of the University of R茅union, France.

Daily rhythms

滨迟鈥檚 not uncommon for birds to take cues from the intensity of sunlight or the length of the day to determine the seasons for migration and mating. Circadian clocks are influenced by melatonin secretions, which reflect the amount and intensity of daylight.

But the Barau鈥檚 petrel migrates longitudinally 鈥� that is, parallel to the equator 鈥� so there isn鈥檛 much difference between the hours of sunrise and sunset in winter and summer.

Still, the slight changes in daylight do affect the petrels. Daily and seasonal changes in melatonin secretion indicate time of day and the time of the year for these birds. But to migrate at the right time to ensure they meet their partners, they need something that varies more reliably.

Pinet and colleagues studied Barau鈥檚 petrels over two years to see if the animals adjusted their behaviour according to moonlight levels.

Full-moon party

During nights with a full moon the birds were significantly more active, spending 80 per cent of their time in flight, instead of resting on the water. Pinet鈥檚 team also found that arrival dates to the colonies during mating season coincided with the full moon.

Pinet鈥檚 team was the first to use 鈥渂io-loggers鈥� to track the influence of light levels on the behaviour of free-flying birds. These small, lightweight devices were tied to the birds鈥� feet, where they did not interfere with flight. Sensors recorded the amount of time submerged in water and the amount of light taken in, which gave the team a good estimate for the birds鈥� location and activity.

The team speculate that the increase in activity could mean the petrels are foraging for prey that is easier to see and more active itself in the moonlight.

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0027663

Read previous Zoologger columns: Cannibal shrimp shows its romantic side, The only cross-dressing bird of prey, The biggest spider web in the world, Slime killer hagfish feasts in rotten flesh, Female monkeys indulge in synchronised sex, The toad that鈥檚 part clone, part love child, The first reptile with a true placenta, The fearsome jaws of a mini movie monster, Stealth millipede wears living camouflage, Dozy hamsters reverse the ageing process, World鈥檚 nicest bird murders chicks, Architect mouse builds a food mansion, The amphibious fish that mates with itself.