{"id":2519,"date":"2023-10-02T14:30:29","date_gmt":"2023-10-02T14:30:29","guid":{"rendered":"https:\/\/horizon.peachpuff-wolverine-566518.hostingersite.com\/?p=2519"},"modified":"2023-10-02T14:30:29","modified_gmt":"2023-10-02T14:30:29","slug":"stars-and-inner-compass-guide-moths-and-birds-say-researchers","status":"publish","type":"post","link":"https:\/\/scienceblog.com\/horizon\/2519\/stars-and-inner-compass-guide-moths-and-birds-say-researchers\/","title":{"rendered":"Stars and inner compass guide moths and birds, say researchers"},"content":{"rendered":"

Longstanding questions about how migratory animals navigate are being answered through the study of eye molecules and the quantum realm.<\/p>\n

By<\/em><\/strong> \u00a0Gareth Willmer<\/p>\n

Grey-brown bogong moths may not be much to look at, but every year they perform a nocturnal journey worthy of attention. Billions of them fly as many as 1 000 kilometres from plains in eastern Australia to mountain caves to escape the summer heat.<\/p>\n

Arriving in late September from their breeding grounds, up to 17 000 moths pack each square metre of cave wall and lie in a dormant state in a southeast mountain range known as the Australian Alps.<\/p>\n

Extra sense<\/strong><\/p>\n

\u2018It usually looks like the scales of a fish if you go into these caves during the summer,\u2019 said Professor Eric Warrant, a biologist at Lund University in Sweden. \u2018It\u2019s absolutely amazing.\u2019<\/p>\n

In autumn, the moths fly back to mate, lay eggs and die. Their progeny repeat the voyage without any experience of it \u2013 a feat that has long puzzled researchers.<\/p>\n

While it has been known that insects, birds, turtles and fish can navigate using the Earth\u2019s magnetic field, the specific mechanisms employed to activate this \u201csixth sense\u201d have remained mysterious. So too has the connection with other potential sensory cues.<\/p>\n

Greater knowledge in this area could bolster conservations efforts and help stem widespread losses in biodiversity amid warnings from scientists that the world is facing a sixth mass extinction.<\/p>\n

In 2019, the bogong-moth population suffered a 99.5% collapse<\/a> as a result of drought. Although the numbers have risen since, they\u2019re still well down compared with before.<\/p>\n

Crucial species<\/strong><\/p>\n

The moths are crucial for plant life that they pollinate and for wildlife that depends on them for food. One such animal is the critically endangered mountain pygmy possum.<\/p>\n

\u2018The bogong month is a keystone species in the alpine ecosystem, so their survival is critical,\u2019 said Warrant.<\/p>\n

He led a project that received EU funding to uncover some of the secrets of the bogong moths\u2019 navigating abilities. Called MagneticMoth<\/a>, the project ended in August 2023 after six years.<\/p>\n

Warrant\u2019s team tethered migrating bogong moths in an outdoor flight simulator. In doing so, the researchers confirmed that the moths did indeed use the Earth\u2019s magnetic field to navigate.<\/p>\n

The next task was to find out how the moths do this and where the mechanisms responsible are located.<\/p>\n

The team investigated molecules called cryptochromes. In birds, evidence suggests that cryptochrome in the eyes may enable them to \u201csee\u201d magnetic fields.<\/p>\n

While the project\u2019s genetic analysis has yet to yield final results, Warrant believes they will prove that cryptochromes are responsible for magnetic sensing in bogong moths.<\/p>\n

Starry surprise<\/strong><\/p>\n

The team also made discoveries that took matters in new directions.<\/p>\n

\u2018We found out a few other things that I think are actually even more exciting than this sensing,\u2019 said Warrant.<\/p>\n

One is that bogong moths use the stars \u2013 in addition to the Earth\u2019s magnetic field \u2013 to navigate. In the laboratory, their brain cells responded to the rotation of a projected night sky.<\/p>\n

Warrant said the ability to use night-sky cues to navigate in a specific compass direction was previously known only in humans and in some species of nocturnally migrating birds. The moths possess it while having a much smaller head.<\/p>\n

\u2018The moths seem able to travel in their inherited migratory direction under a starry night sky even if we remove Earth\u2019s magnetic field,\u2019 Warrant said. \u2018If you have this tiny insect with a brain a tenth the volume of a grain of rice and eyes smaller than a pinhead, that they can do this is surprising.\u2019<\/p>\n

The finding suggests bogong moths may also be using a \u201chierarchy\u201d of cues to navigate, with the ability to rely on different ones when others aren\u2019t available. Pending further research, Warrant suspects the stars may even be the dominant cue.<\/p>\n

Quantum ideas<\/strong><\/p>\n

Understanding how migratory birds use Earth\u2019s magnetic field has also been a challenge with implication for conservation efforts.<\/p>\n

That\u2019s partly because the magnetic interactions at play have seemed too weak to trigger the required chemical reactions.<\/p>\n

But attention is now turning to one possible explanation: atomic and subatomic \u201cquantum\u201d scales, at which behaviour of matter doesn\u2019t follow typical rules.<\/p>\n

\u2018There\u2019s a quantum-mechanical mechanism by which such weak magnetic interactions can affect chemistry,\u2019 said Professor Peter Hore, a chemist at the University of Oxford in the UK.<\/p>\n

He\u2019s pursuing this avenue as co-coordinator of an EU-funded project called QuantumBirds<\/a>. It runs for six years until the end of March 2025.<\/p>\n

Blue light<\/strong><\/p>\n

As with bogong moths, the focus is on cryptochromes serving as a compass for birds to navigate during migration.<\/p>\n

Derived from the Greek for \u201chidden colour\u201d, cryptochromes are molecules sensitive to blue light in certain animals and thought to be involved in magnetic-field sensing in a number of species.<\/p>\n

\u2018Migratory birds have at least six different cryptochromes in their eyes,\u2019 said Hore. \u2018We needed to work out which was most likely to have a magnetic-sensing function.\u2019<\/p>\n

The team settled on a candidate called cryptochrome 4a \u2013 Cry4a \u2013 for several reasons including changing levels of the protein in night-migratory European robins.<\/p>\n

\u2018Cryptochrome 4a shows a seasonal variation, with higher levels in the spring and autumn,\u2019 said Hore. \u2018That would be consistent with migration.\u2019<\/p>\n

With Cry4a in lab cultures, the QuantumBirds team found evidence that the molecule was indeed magnetically sensitive \u2013 and more so than the same proteins in non-migratory pigeons and chickens.<\/p>\n

While testing Cry4a in live robins would be needed to confirm this as the mechanism, the results are promising, according to Hore.<\/p>\n

\u2018This cryptochrome seems to have the right properties to be the basis of the birds\u2019 magnetic compass,\u2019 he said.<\/p>\n

Homing instinct<\/strong><\/p>\n

Understanding how migratory birds navigate could be key to future conservation, particularly given that it is difficult to relocate them because of an instinct they have to fly back to their habitat, according to Hore.<\/p>\n

\u2018If we could understand the mechanisms they use to navigate, maybe we could fool them into thinking they want to stay where we\u2019ve put them,\u2019 he said.<\/p>\n

For his part, Warrant at Lund University said greater knowledge about how creatures including bogong moths navigate could lead to the development of alternative navigation systems to GPS for people to use.<\/p>\n

Understanding the homing instincts of moths \u2013 coupled with the pivotal role that they play in the ecosystem \u2013 is yet another reason to ensure their protection.<\/p>\n

\u2018Raising awareness that even a humble insect is worth saving is an important step in the right direction,\u2019 Warrant said.<\/p>\n

Research in this article was funded by the EU.<\/em><\/p>\n

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