Moths Navigating by the Stars?

Actually, the whole subject of animal navigation is fascinating evidence that it is not only human beings who are ‘fearfully and wonderfully made’.

Many creatures perform annual return migrations involving many thousands of kilometres—organisms as different as the green sea turtle, the salmon, and the garden warbler bird.

Many of these feats of navigation are truly amazing, and appear to involve inbuilt, genetically programmed skills. What do these creatures use to orientate themselves, and how do they know when to go? There are still many unsolved mysteries about the mechanisms involved, but research shows that in varying degrees and differing combinations among different species, the following are various factors which may be involved.

Timing migration

• An internal calendar which helps the particular creature to ‘know’ when the time is approaching and helps it to deposit fat as a store of fuel for the journey, for instance. This calendar can be fine-tuned by …
• A sensitivity to changes in the number of hours of daylight, especially among birds, and also …
• Certain whale migrations appear to be triggered by a seasonal drop in water temperature.

Clues to drection

• Sensing the position of the earth’s magnetic field. Some species not only use this as a simple compass, but can detect local variations in the earth’s magnetic field (of less than 0.2%!) and use them as familiar landmarks.
• The direction of air and water currents can be used as points of orientation.

Visual landmarks.

• Odours (minute particles) in the air.
• The position of the sun in the sky. Because the sun moves through the day, as seen from earth, this works only if the creature ‘knows’ what time of day it is. This is done with another internal clock.
• The pattern of polarized light. The proportion of light which is scattered (and thus partially polarized, as compared to direct unpolarized sunlight) varies with the position of the sun. This may be particularly important when the sun is hidden by cloud.
• Star patterns in the night sky. Some young birds, for instance, are capable of ‘learning’ the pattern of rotation of constellations of stars and using it to tell which way is north. (It is not being suggested that they logically deduce this, but many innate migratory instincts appear to be genetically programmed to flexibly respond to learned cues.) The discovery that not only birds, but even insects (some moth species) are capable of such stellar navigation is astonishing.

Evolving migration?

The genetic program can vary within a species. Blackcap birds, for instance, migrate in several different directions. If you cross two of these which migrate in separate directions, the hybrid offspring migrate in a separate direction again from either parent. In each instance, they are able to cope by being able to develop a ‘map sense’ using certain landmarks, learning staging areas along the way, and so on.

Of course, where there is variation within genetic information, both breeding and natural selection can act on a population. Research has shown that some blackcaps have undergone a change in their migration patterns in only 30 years.² This built-in ability for a population to respond and adapt to changing circumstances involves utilizing the built-in programmed information already present in its kind, not ‘evolving’ any extra information. It is crucial in conserving populations of wild animals.

In the case of migration patterns, such flexibility makes great sense. In a devastated, post-Flood world, climate and vegetation patterns would have been changing rapidly for centuries, making it necessary for migratory habits to change. If these populations had been created only with an inflexible ‘map’ and a rigid migration program, with no genetic variation and no built-in potential for ‘learning’, they would have rapidly become extinct. In any case, such a created ‘map’ would have been superseded after the Flood had changed the face of the earth.

References

1. New Scientist, ‘Inside Science’ supplement #56, September 12, 1992.
2. Nature, vol. 360, December 17, 1992, pp. 625–626, 668–670.

(Further reading: Animal Migration, Scientific American Books Inc., 1989.)