What does it take to navigate? Think of the requirements. You have to have a map of some sort, a compass, and robust locomotion anatomy. You have to know where you want to go, and possess the sensory equipment and the stamina to get there. Illustra Media spotlighted some spectacular examples of navigation in the animal world in the Design of Life series. To show those cases are far from unique, consider these recently-reported findings, some of which are quite astonishing.
In Science Magazine, Elizabeth Pennisi relates that, “Like birds, insects may travel in sync with the seasons.” Here’s a wonder hidden to the naked eye. Consider these “stunning” stats that made one evolutionary ecologist exclaim, “Wow”:
Birds and human vacationers aren’t the only creatures that take to the skies each year to migrate north or south. An analysis of a decade’s worth of data from radars specifically designed to track airborne insects has revealed unseen hordes crossing parts of the southern United Kingdom–2 trillion to 5 trillion insects each year, amounting to several thousand tons of biomass, that may travel up to hundreds of kilometers a day. [Emphasis added.]
Pennisi refers to a study reported in the same issue of Science about a “mass movement of invisibles.” The University of Haifa calls says, “This movement constitutes the largest migration found in today’s world, creating a mass that is almost eight times that of birds that migrate from Britain to Africa.” Put another way, that’s the equivalent of 20,000 flying reindeer, Phys.org quips. Seriously, when you consider that 30,000 songbirds take off for Africa each year, but the mass of migrating insects is seven times that, you’re talking oodles of bugs going the distance. The migrators include flies, butterflies, hoverflies, ladybirds, and other beetles, aphids, and moths. This has been going on overhead for eons, but has only been reported now? The reason is that we never had the equipment or inclination to look.
The study did not examine the starting points and destinations of each insect population, but the researchers believe that this migration takes place over distances of at least several hundred kilometers, and possibly much more. “Since there is evidence that this migration also takes place over sea, and since Great Britain is an island, these insects must have come to Britain in the spring, and at least some of them must reach continental Europe in the fall,” Dr. Sapir explains.
The researchers do not elaborate on the equipment necessary for insects to navigate over the open ocean, other than to note, “The ubiquity of tailwind selectivity in such a diverse group indicates that compass mechanisms must be universal in larger insect migrants.” Wow, indeed.
Let’s not overlook ground transportation. The BBC News reports that ants use the sun and memories to navigate. “Ants stand out in the insect world because of their navigational ability,” Helen Briggs writes. Ants are also remarkably ambidextrous with their six legs, able to maintain their orientation when moving forward or backward, such as when hauling food to the nest. What tools are required to do this?
Scientists say that despite its small size, the brain of ants is remarkably sophisticated.
“They construct a more sophisticated representation of direction than we envisaged and they can incorporate or integrate information from different modalities into that representation,” Dr [Antoine] Wystrach added.
The details are reported in Current Biology. The open-access paper states, “This reveals substantial flexibility and communication between different types of navigational information: from terrestrial to celestial cues and from egocentric to holonomic directional memories.”
Navigating underwater presents a different set of challenges. You can’t see the stars, vision underwater is impaired, and the sea is full of predators. We learned how salmon, whales, and sea turtles meet these challenges in Living Waters, but here we encounter additional talented animal migrators — both large and small.
What could be smaller than the larva of a coral reef fish? Current Biology says that packed into that tiny organism a magnetic compass lurks. The abstract relates another “wow” story:
Many coral reef fish larvae spend days to months in the open ocean before settlement on coral reefs. Early in development, larvae have limited swimming capabilities and will therefore be greatly affected by currents. This can potentially result in dispersal distances of tens of kilometers. Nevertheless, up to 60% of surviving larvae have been shown to return to their natal reefs. To home, the larvae must develop strong swimming capabilities and appropriate orientation mechanisms. Most late-stage larval reef fish can, after being passively drifted for days to weeks, swim strongly, and Ostorhinchus doederleini larvae have been shown to use chemotaxis to identify their natal reef once in its vicinity and a sun compass for longer distance orientation during the day. But how do they orient at night? Here, we show that newly settled fish caught at One Tree Island (OTI) at the Capricorn Bunker Reef Group (Great Barrier Reef) can use geomagnetic compass information to keep a south-east heading. This behavior might help them return to their natal reef in the absence of any celestial cues at night.
Moving to large fish, Fox News Science reports that a male mako shark migrated 13,000 miles in less than two years. That’s equivalent to swimming over halfway around the globe — a new record for a fish. “He was like the Energizer bunny — he kept going and going and going,” one marine biologist remarked. The team used an electronic tag to monitor his movements by satellite. For fun, you can track him and other fish on the Nova Southeastern University website.
In the middleweight category, shannies, like sea turtles, find their way back to their favorite nesting sites. “This behaviour is reminiscent of migratory birds such as white storks or swallows,” New Scientist reports. “But unlike them, the fish does not migrate over long distances. Instead, it disappears for months on end from its rocky shore breeding sites along the western coasts of Europe and North Africa, travelling offshore to feed.” The scientists don’t yet know how they do find their way back home, but they understand the requirements:
Returning to breeding sites, much like sea turtles do, requires homing abilities, including well-developed navigation skills and an aptitude for keeping track of your position….
“Many species of intertidal rock-pool fish have excellent homing capabilities backed up by fantastic spatial learning,” says Culum Brown at Macquarie University in Sydney, Australia.
One way to appreciate bird migration is to fly with them. A “human swan” flew in a powered paraglider, Live Science reports, to trail endangered swans on their epic 4,500 mile migration. Sacha Dench was glad that the swans accepted her presence and essentially ignored her. This allowed her to document the entire migration path across 10 countries, aided by a ground team that monitored five tagged birds. It took three months to fly the “absolutely stunning” route. See photos here.
Phys.org reports that migrating birds tend to fly when resources are at their peak. How they determine these peaks is not known, but three species monitored by ornithologists at the University of Copenhagen — shrikes, nightingales and cuckoos — revealed that “all three birds cross continents to match highest levels of resource supply” thanks to “innate programmes” of some sort.
Many kinds of mammals migrate, particularly herbivores like wildebeest, elephants, and bats, but we’ll save their stories for another time. Suffice it to say that a multitude of diverse species carry sophisticated navigational equipment in their bodies. Are we to believe that this equipment evolved by trial and error over millions of years? Timothy Standish pointed out in Living Waters that it all has to be present at the same time to succeed. He also pointed out that finding this ability in such different animals as fish, sea turtles, and birds — members of entirely different orders of vertebrates — to say nothing of different phyla like insects (arthropods) and even bacteria, is entirely expected by design but presents a serious challenge to natural selection, despite the oft-cited but vacuous appeal to “convergent evolution.” We hope these latest findings about animal navigation will serve to amplify your appreciation of intelligent design in the living world.
Source: These Animals Really Get Around