From a very early age, we are taught to place disparate aspects of nature in discrete conceptual boxes. Children’s field guides and Facts on File-type cards tell us that particular animals live in specific places, eat particular foods, and otherwise give simple, easy-to-remember summations of the essence of nature. But the natural world – past and present – is not so easily simplified. Herbivores, such as hippos, sometimes scavenge meat, and many dinosaurs – traditionally characterized as being “good reptiles” – were marked by a slew of characteristics that we once thought were unique to birds. Among extant organisms, however, there is scarcely a better test of our preconceptions about animals than their constant cycles of travel over the planet, and National Geographic now celebrates these phenomena with their new miniseries Great Migrations.
The show’s section of the migration of the great white shark is a good example of how species don’t always do what we think they should. These massive predatory fish are well-known denizens of North America’s Pacific coast (among other places), but they do not spend the whole of their lives haunting the shorelines. As a globally distributed species, different populations have different migration routes, but the vignette presented by Great Migrations is of sharks which hunt elephant seals off Mexico’s island of Guadalupe but often travel over 3,000 miles to Hawaii (a trip which takes about seven months to complete). Just why the sharks undertake this long journey is unclear, but the fact that they do forces us to reconsider what we thought we knew about their natural history.
Numerous other examples of nature’s complexity could be picked from the ranks of migrating animals featured in the show. The red crabs of Christmas Island, the wildebeest of eastern Africa, North America’s monarch butterflies, and the little red flying foxes of Australia are among the many familiar creatures which are tracked as they move from place to place. Among the most impressive of the show’s examples, however, is contained entirely within Jellyfish Lake. This marine lagoon, located on Palau’s Eil Malk Island, is home to scores upon scores of golden jellyfish – a subspecies of the more common spotted jellyfish which has evolved in isolation within the lagoon’s confines. Inside them live tiny zooxanthellae which internally nourish the jellyfish, but to keep their symbionts healthy the jellyfish must track the movement of the sun at the surface of the lagoon. This would seem like a pretty safe lifestyle, cycling according to the movements of the sun each day, but it is not so simple as that. As they float along some jellyfish end up getting caught by white sea anemones – another tentacled cnidarian anchored onto a surface rather than floating free – and meet their demise.
Narrated by Alec Baldwin and organized into four main parts – “Born to Move”, “Need to Breed”, “Feast or Famine”, “Race to Survive” (along with supplemental, behind-the-scenes features), the programs feature a variety of migratory events of differing scales. Given that this is a prime-time, cable flagship event, the show is more about narrative than hard science – viewers wanting to know the details of how birds navigate and what creates the “super generation” of monarch butterflies which fly almost the length of North America will be slightly disappointed – but the show is to be praised for collecting a wide array of transitory tales spanning army ants to elephants. Each program provides an extraordinary look into the lives of various creatures, from the familiar feast of the Nile crocodiles during the annual wildebeest migration to the search of Botswana’s zebras to find salt in the baking Kalahari desert.
If I have one criticism of the show, however, it is that I was hoping for the influence of humans on these migrations to be made more starkly apparent. Nature documentaries are often filmed in such a way that humanity does not enter the shot, as if there are still places of pristine wilderness not bordered by cities, cattle ranches, or shipping lanes. David Wilcove highlighted how our species is altering the migration patterns of other species in his excellent book No Way Home, and while the show often mentions human influence it is only rarely that the effects our activities are having on migrations is truly made tangible. Nevertheless, the episode “Race to Survive” contains several stories which meet my expectations, including an excellent look at the plight of American’s pronghorn. The last remnants of a once more prolific group of artiodactyls, these migratory mammals are being squeezed by human development along their migration routes, having to duck through backyards and dodge eighteen wheelers as they hoof it across Wyoming. I would have liked to see the migrations of other animals in the show documented in a similar way, but during a time when conservation messages can be a tough sell for documentary producers I think National Geographic should be applauded for taking such steps to put animal migrations in the context of the world we are quickly altering.
There is still much we do not know about animal migrations. We can track organisms and document where they go, but the reasons why and how they do it are still incompletely understood. And, with every passing day, we are creating barriers to these migrations, forcing animals to find new paths or risk crossing paths with our species at their peril. Great Migrations documents some of the most wonderful events in the natural world, but how much longer these ancient migration patterns are followed is something that our species will increasingly influence as our relationship with global ecology continues to change.