PostHeaderIcon Animal Astronomy

by Guest Writer Sophie Arlow

Many people assume that astronomy is solely a human endeavor. After all, we have named constellations, created telescopes, and even landed on the Moon. However, humans are not the only species to use astronomy – from the Moon and stars to magnetic fields, animals also use information from the earth and skies.

The Mystery of Magnetite

What do salmon, dolphins, sea turtles, and whales have in common? These animals share much more than an underwater habitat – all are believed to use a mineral called magnetite to assist in navigation and migration. Magnetite is a special type of iron oxide which, as you might have guessed, is magnetic! Early humans used naturally-occurring deposits of magnetite, called lodestones, as primitive compasses.

Some specialized types of aquatic bacteria contain magnetite, which scientists hypothesize allows them to tell up from down. When exposed to a strong magnetic field, these bacteria all align perfectly, like miniature compass needles. On a larger scale, whales, dolphins, and salmon use magnetite to navigate deep below the water’s surface, where landmarks and visual cues like the sun and stars are not visible.

Expert Nautical Navigators

A serious contender for the title of most skilled animal navigator is the loggerhead sea turtle. Loggerhead hatchlings, only two inches long, emerge from their eggs, dig themselves out of the ground, and, with no help from their parents or other turtles, enter the ocean to begin their spectacular journey. Over a period of several years, loggerhead turtles travel more than 9,000 miles, spanning entire oceans before returning home to coastal regions in North America.

Loggerhead turtles travel over 9,000 miles in the Atlantic Ocean, guided by the Earth’s magnetic field.

Loggerhead turtles travel over 9,000 miles in the Atlantic Ocean, guided by the Earth’s magnetic field. Credit: UNC Biology

How do hatchlings, never having seen the ocean before, maintain their headings across a vast expanse of often-featureless ocean? As hatchlings reach the water, they begin swimming directly into ocean waves until they are several miles from shore. At this point, hatchlings must use a new navigation method: orienting themselves using the Earth’s magnetic field. It also seems that they have a built-in magnetic map that guides them throughout their migration and allows them to return to the exact location where they hatched to lay their eggs.

How is this amazing feat possible? Scientists aren’t entirely sure. However, they do know that sea turtles’ brains contain tiny crystals of magnetite, which may allow them to sense the direction of the Earth’s magnetic field. This could enable them to find their way across thousands of miles of ocean and return to their birthplace decades later.

Moon Phases Trigger Coral Blooms

The Moon also influences various animals – including those in the sea! Coral reefs (made of huge colonies of coral – a tiny invertebrate animal closely related to a sea anemone) usually spawn once a year. For such a rare event, the coral polyps need to synchronize exactly when they release their gametes.

One trigger that helps them stay in synch is the phase of the Moon. One coral reef in the Caribbean spawns every year on the eighth day after the full Moon in August. That’s pretty specific. Other coral reefs are triggered by different Moon phases, but water temperature, currents, and tides also influence exactly when the coral bloom happens.


Magnetic Bacteria
The Innovations Report

Sea Turtle Navigation
University of North Carolina Sea Turtle Research
National Geographic Today – Animal Migration

Coral Blooms

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