Humpback whales' songs at subarctic feeding areas are complex, progressive

January 23, 2019, Public Library of Science

Humpback whales overwintering in feeding areas may sing complex, progressive songs which closely resemble those associated with breeding grounds, according to a study published January 23, 2019 in the open-access journal PLOS ONE by Edda E. Magnúsdóttir and Rangyn Lim from the University of Iceland.

Humpback whales (Megaptera noveangliae) migrate annually between summer subarctic feeding areas to winter tropical breeding grounds, where males are known to sing characteristic songs which are linked to mating. However, recent studies indicate some humpback pods may overwinter in their feeding grounds rather than migrating, raising the question of whether and how males sing in these circumstances. The authors of the present study used acoustic recorders in the feeding grounds of Skjálfandi Bay in northeast Iceland between January and March of 2011, recording the songs of male humpback whales which were overwintering here. Whale songs were recorded on 42 of the 46 recording days, producing a total of 70 ten-minute song files used for analysis.

The authors identified 15 distinct phrases and themes within the whale songs. They noted that the songs they recorded may represent a characteristic song type with a sophisticated structure and order of themes—and closely resemble the songs associated with breeding grounds. Song themes also appeared to evolve gradually over the recording period, possibly indicating the existence of song exchange and cultural transmission in these feeding grounds.

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Fewer monarch butterflies are reaching their overwintering destination

January 2, 2019, De Gruyter

Arguably, one of the world's most famous insects, the monarch butterfly, is currently experiencing dire problems with its migration in eastern North America. Fewer and fewer monarchs are successfully reaching their overwintering destinations, and scientists aren't sure why. Because of this, the need for research on the migration has never been more urgent. New research published in De Gruyter's Open Access journal Animal Migration, aims to help with this effort.

The dwindling numbers of overwintering monarchs in the mountains of central Mexico have been the subject of debate among researchers, with some arguing it reflects a large-scale drop in numbers of breeding adults, while others point to increasingly perilous migration as the cause. Now, a new research study "Alternate migration strategies of eastern monarch butterflies revealed by stable isotopes" led by Dr. Hannah Vander Zanden, from the University of Florida, throws another potential explanation into the mix—maybe the monarchs are simply travelling elsewhere to overwinter, like to the balmy coast of southern Florida.

Dr. Vander Zanden and her team captured and examined monarchs that wintered in South Florida, using a special analytical technique that can pinpoint where the monarchs came from based on a sample of their wing or body tissue. Amazingly, they discovered that half of the monarchs sampled appeared to originate from the American Midwest, which is typically thought to represent the core breeding range of the eastern population. For years, researchers assumed that monarchs from this region only travel to the mountainous region of Mexico each fall. But, this new discovery means that at least some of the Midwestern monarchs are choosing not to fly to Mexico after all, and instead they appear to fly in nearly the opposite direction until they reach southern Florida.

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