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Animal Homecoming

Dec 2018
Author : Green Power

Wildebeest, zebras, and antelopes perform annual mass migrations between Tanzania and Kenya. Salmon and green turtles return to their birthplace for breeding every year. Many animals have the habit of “homecoming”, even though this means they have to undertake long, hard journeys. Why is this?

Scientists have coined such behavior “philopatry” (combining the Greek root of “beloved” and Latin root of “homeland”); the tendency of repeatedly returning to a specific site (such as the birthplace) for foraging, breeding, overwintering or stopover, etc.

One factor in animal homecoming is that the specific site typically provides ideal conditions for their survival; for example, appropriate climate or abundant resources. It greatly reduces the trouble of looking for a new habitat. It brings extra benefits too if a large number of the same species come together through homing—they can find mating partners more easily, and reduce their risk of being preyed on when in a group. The annual massive migration on the African savannah has indeed formed a spectacular natural attraction.

Never lose way

Philopatric animals are all equipped with fine navigation systems—they make use of different senses to receive the environmental information and find their way. One very interesting example is the little dung beetles: they collect food (dung) at some distance from their home, then roll it into a ball to take it home. Before heading home, the beetles will perform a special “dance” on top of the dung ball. What they are really doing is taking a snapshot of the sun, the moon and the stars! They can then go straight back home by the shortest route. This kind of celestial navigation is matched by an internal circadian clock of the animals.

For many other animals, the earth's magnetic field is also utilised as an invisible map to direct their way. Homing pigeons, for example, use celestial navigation on sunny days and geomagnetic navigation on overcast days. Hong Kong Newts(Paramesotriton hongkongensis)return from the woodland to the streams for reproduction in autumn and winter every year. The most surprising thing is that they can return to the exact same pool to look for their mates. Research has shown that many frogs and salamanders can sense geomagnetic fields, in addition to having special sensory systems of sight and smell, so can easily find their way home.

By comparison, we humans are way behind in navigation skills!

Image
Dung beetle uses celestial navigation to find its way home.
Photo from Pixabay
Image
Homing pigeon uses both celestial and geomagnetic navigation systems.
Photo from Wikipedia:
Attribution: By Patrick Edwin Moran via Wikimedia Commons
https://en.wikipedia.org/wiki/Homing_pigeon
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The Hong Kong Newt(Paramesotriton hongkongensis)returns to the same pool every year to find its mating partner.

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