Posts Tagged ‘Grand Canyon’

The Contents of Pleistocene Condor Nests

October 19, 2012

The fossil remains of California condors (Gymnogyps californianus) have been found in at least 13 caves located in Arizona, New Mexico, and Texas.  The bones range in age from ~11,000-~25,000 calender years BP.  Apparently, packrats carried the condor bones, along with leftover bones from the bird’s meals, back to their nests where combined with sticks, they became an actual part of the nest itself.  I discussed how packrat urine acts as a preservative in the blog entry I wrote previous to this one.

California condor nest.  Although they often nest in rocky crevices, they also nest in hollow trees, explaining how they lived in the forested areas of eastern North America during the Pleistocene.  Condors can live to be 60 years old but reproduce slowly.

Most of the condor bones belonged to nestlings or individuals that died just prior to the time they would learn to fly and leave the nest.  Sandblast Cave in Arizona contained 64 specimens from 5 individuals as well as egg shells and feathers.  Stanton Cave, also within the Grand Canyon, produced even more–70 bones from 5 individual California condors, plus 1 bone from a teratorn, an extinct condor with a 12 foot wingspan.

The California condors living in the southwest during the Pleistocene scavenged dead mammoth, bison, horse, camel, and an extinct species of mountain goat (Oreomnos harringtoni).  The bones of all 5 species were associated in the packrat middens with the condor bones.  All 5 species are (or were) grass-eaters.  Some mammoth dung found in Bechan Cave (Bechan is an Indian word that literally means bullshit) was 85% dropseed grass by weight.  The environment in the Grand Canyon during the Ice Age must have consisted largely of grassland.

Skull of Harrington’s mountain goat.  It probably looked similar to a modern day mountain goat.  Condors scavenged goats.

Unlike mastodons which primarily ate twigs, aquatic plants, and fruit; mammoths mainly ate grass.  A dead mammoth or mastodon provided tons of meat for scavengers.

During the Pleistocene the California condor ranged all across North America where its fossils have been unearthed in Florida, New York, and even Cuba.  It’s larger extinct cousin, the teratorn, also lived as far east as Florida.  The extinction of the megafauna led to the extinction of the teratorn, and the extirpation of the California condor everywhere except the Pacific coast.  The population of condors living there survived by learning to scavenge dead whales that washed up on the beach.  The author of the below referenced study mentions that it is an ecological mystery why they didn’t survive on the Atlantic coast by scavenging whale carcasses there.  He also wonders why they didn’t persist on the Great Plains where they could have scavenged from the massive bison herds. I’ll offer my conjecture.

Eastern condors may simply never have learned to scavenge primarily on marine mammals.  Although an occasional individual may have fed upon a dead whale on an Atlantic beach, perchance not enough acquired the habit of cruising the beaches for dead marine mammals. Eastern condors may have even been a separate subspecies.  They were heavier and had wider bills.  I suspect they failed to adapt in the east due to sheer random chance.  The explanation for the condor’s extirpation from the prairie region is more complex.  Perhaps, bison populations became scattered and rare following the extinction of the rest of the megafauna.  Forest may have covered much of the prairie region early during the Holocene.  Indian-set fires probably created much of the prairie land, and bison herds later expanded as a result but not til after the condors were gone.  Still, it’s an enigma why they never recolonized the southwest, though a few were sighted there in the 19th century after European livestock were introduced, augmenting the potential food supply.  Man has re-introduced condors to the Grand Canyon, and a few live there today.


Emslie, Steven

“Age and Diet of Fossil California Condors in Grand Canyon, Arizona”

Science, New Series 237 (4816) 1987

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