MOSCOW, 28 Mar - RIA Novosti. Galapagos gulls prefer the darkest nights of the new moon for hunting, as plankton rises closest to the surface of the water during this time, according to a study published in the journal PLoS One.
Zooplankton, small fish and squid go to the depths during the full moon, so as not to become easy prey for their natural enemies - including seagulls. In the new moon, plankton, on the other hand, stays close to the surface of the water, scientists write. Galapagos gulls cannot dive deeper than a meter. At the same time, in the process of evolution, they have developed adaptations that help to successfully hunt in almost complete darkness: the features of their vision allow them to see prey in the water column even in the light of the stars, and melatonin (a hormone that regulates falling asleep) is produced in a "free" rhythm, thus , these birds have virtually no "biological clock".
Bird watchers at the Max Planck Institute in Radolfzel, Germany, led by Martin Wikelski, have shown that Galapagos gulls "plan" their hunt based on the phases of the moon. Scientists supplied 37 birds with satellite transmitters and tracked their movements for 120 days. Ornithologists distinguished "hunting" flights from ordinary ones with the help of additional sensors that gave a signal upon contact with water. After analyzing the data obtained, the researchers came to the conclusion that birds hunt almost twice as actively on the new moon.
Galapagos gulls (Creagrus furcatus) live only on the Galapagos Islands, the total population is up to 30 thousand individuals. These gulls have a unique "daily routine" for these birds: they hunt at night in the open sea, and spend the day in the nest on the shore, while all other species of gulls, lacking such adaptations, hunt in the daytime.