Guatemala: Requiem for a Grebe

In southern Guatemala there is a large lake of volcanic origin. Though it’s surrounded on all sides by massive cylinder shaped mountains that look as if they could be engulfed in smoke and flame at any moment, the water fills the ancient caldera of an even more massive volcano that erupted and collapsed in on itself about 84,000 years ago. As a result, this lake is deep.  So deep even, that the bottom hasn’t been completed mapped and it’s estimated that in some places it could reach up to 600 meters into the earth, an appropriate counterpoint to those 3,000 meter volcanoes that surround it. This is a lake that has held an important place in the culture of those who have lived on its shores for as long as people have lived in Guatemala, from the Mayan civilizations of the pre-Columbian era to the Spanish invaders to the descendants of both, the modern Guatemalans who grow coffee and corn and call the lake Atitlán.

More than that, though, the lake itself has been the site of some remarkable natural selective pressures. Not only is it smack in the middle of a region of high endemism, a process that reaches its bizarre peak with the fantastic and bizarre Horned Guan, but the lake itself hosted its very own endemic species, a sort of bulked up Pied-billed Grebe the natives called Poc, but has alternately been known as Giant Grebe, Giant Pied-billed Grebe, and the preferred name that best illustrates how important this lake was to the bird, Atitlán Grebe (Podilymbus gigas).

Painting by Peter Schouten from his book, A Gap in Nature

The story of the rise and fall of the Atitlán Grebe is as fascinating as the species itself, not only because it was witnessed in real time by those who studied it, but because even though it took place on the huge continental land-mass it most closely mirrors the issues facing island species more than any continental extinction. This is because the Atitlán Grebe was reportedly flightless, though that seems to be unclear and they may have been able to fly short distances.  Not that they needed to, however, as the lake supported substantial populations of crabs and small fish enough to feed many pairs of the grebes.  What is certain is that they were certainly unable to disperse far beyond Lake Atitlán, essentially stranding them in a way no different from an island species surrounded by miles of ocean. The lake’s fate was there’s too.

As seems to be inevitable with beautiful places, folks with dollar sign eyes looked to make a buck off of Lake Atitlán. This time it was Pan-American Airways encouraging the Guatemalan government to stock the lake with gamefish, specifically North American species like Large and Smallmouth Bass, in the hopes that sportsmen and their money would be drawn to the lake. But bass, as anyone with experience fishing for them knows, are voracious predators, and in short order they’d stripped the lake, vacuuming up its native crabs, two-thirds of its native fish and the occasional grebe chick. When the bass were introduced to Atitlán in 1960 the population of Atitlán Grebes sat at 200. Five years later there were only 80.

Struck by the situation of the endemic Grebe, American scientist Anne LaBastille got to work, raising enough awareness and money to found a refuge for the birds on the shore of their lake, protected by the generous addition of a fish toxicant to the surrounding water to prevent encroachment of the predatory game fish. It appeared to work. By 1973, the grebes had rebounded, reaching their numbers prior to the introduction of the bass. But when things seemed to finally be progressing in a positive direction for once, disaster struck again.

Occasionally, the same processes that set a species down its evolutionary path can be the impetus for its extinction, and in an ironic bookend to the volcanic eruption that created the lake that selected for a bizarre mostly flightless grebe, an earthquake, a 7.5 richter monster, stuck Guatemala in 1976. The quake was so substantial that it fractured the bed of Lake Atitlán such that water from the lake drained into the earth, dropping the water’s surface two whole meters in one month. That may not sound like a lot, but it left LaBastille’s refuge, along with the Grebe’s primary foraging areas and the reedy banks where they made their nests, high and dry. They never really recovered. By 1983 there were only 32 individuals, and most of them hybrids of the extremely similar, but flighted and flexible, Pied-billed Grebe.  Their co-gener had not only swamped their habitat, but apparently their gene pool as well. The last two unequivocal Atitlán Grebes were seen in 1989 and none since.

The prevailing wisdom now states that the Grebes were never a full species, but merely a subspecies of the wide-ranging Pied-billed Grebe. Does that make their loss any easier for us to take? Does Lake Atitlán suffer their extinction any less when conventional Pied-billed Grebes nest in the reeds on the banks instead of their larger sibling?

Regardless of their genetic pedigree, the Atitlán Grebe was a distinct form, well suited to its lake island in the mountains of southern Guatemala. Its loss is obvious from the perspective of those who wish to preserve biodiversity in all its forms, but less obvious is the attraction to potential bird tourists of an avian attraction in a country that has no other national endemics. Whatever the case, it’s hard to be at Lake Atitlán without at least considering the Grebe’s story.

Because even if it passes into the mists of history, the lake still remembers.