Posts Tagged ‘La Brea tar pits’

Pleistocene Turkeys (Meleagris sp.)

November 16, 2012

Early European colonists reported seeing flocks of wild turkeys numbering in the hundreds.  Turkeys flock together in the fall when they concentrate in areas abundant with such favored foods as acorns and grapes.  The hens and their young stay in separate flocks from the adult toms because the latter will peck the juvenile toms to death on sight.  In late winter and early spring the adult toms battle each other for the right to mate with the hens, and these battles also can sometimes cause fatalities.  The champion turkeys get to mate with several hens.  By mid-spring the hens leave the toms and lay as many as 20 eggs in cleverly concealed spots that they cover with leaves.  J.J. Audubon wrote the hens “…separate themselves, in order to save the eggs from the male, who would break them all, for the purpose of protacting his sexual enjoyments.”  The hatchlings follow the mother around and grow quickly on a diet of insects, arthropods, small vertebrates, grass, and fruit; so that by mid-summer they’re capable of escaping predators more often than not.

Two tom turkeys (Meleagris gallopavo).  Turkeys were common across most of North America during the Pleistocene.  There also were two now extinct species of turkey restricted to the southwest and California.

The oscellated turkey (Meleagris gallopavo), the only other extant species of turkey besides the eastern turkeys pictured above.  It resembles a peacock.  Turkeys evolved from an ancient species of peacock that crossed the Bering landbridge 30 million years ago.

Today, there are only 2 species of turkeys–the eastern turkey (Meleagris gallopavo) which lives over a wide swath of varied habitats in North America, and the oscellated turkey (Meleagris oscellata) which is restricted to the Yucatan penninsula in Mexico.  During the Pleistocene there were 2 additional species of turkeys though they were much more localized in distribution than the eastern turkey.  The southwestern turkey (Meleagris crassipes) lived in Arizona and New Mexico.  The California turkey (Meleagris californicus) lived in southern California.  The California turkey left more fossils at the La Brea tar pits than any other species of bird other than the golden eagle.  Scientists believe the turkeys scratched the surface away from the top of tar seeps, and the weight of the birds caused them to become mired in the tar.  Turkeys can weigh up to 50 pounds.   As of 2006, 11,116 specimens from at least 791 individual turkeys had been found in the tar pits.  Golden eagles attacking prey stuck in the tar pits became entrapped in turn, explaining the abundance of golden eagle specimens here.  Turkeys were probably a common item in the diet of the eagles. 

Range map of the eastern turkey colored purple.  The yellow is the estimated range of the Pleistocene California turkey.  Eastern turkeys have been introduced to California and other areas of the arid west where in some areas they depend upon manmade water sources for survival.

Anatomical evidence suggests California turkeys evolved from eastern turkeys, probably after the 2 ancestral populations became geographically separated when the territory between them became desert.  Turkeys require trees for roosting and a daily water supply, so desert habitats are unsuitable for them.

The extinction of the California turkey and the southwestern turkey can be blamed on a combination of environmental and anthropogenic factors.  The extinctions coincide with a dry phase of climate that lasted for hundreds of years and began about 11,500 BP.  However, scientists noted the 2 species survived an even drier period that occurred ~38,000 BP.  The scientists authoring the below referenced study suggest California turkeys flocked around shrinking sources of water where they were completely rubbed out by paleoindians.  If not for man, these 2 extinct species of turkeys would likely still be extant.  Trees and bodies of water have always been abundant in eastern North America, explaining why eastern turkeys survived man’s onslaught, until Europeans raped the environment and almost drove them into extinction too before modern conservation practices saved them.

David Steadman, one of the world’s foremost experts on Cenozoic bird evolution, thinks turkeys share a common ancestry with the peacock based on anatomical similarities.  He believes a peacock-like fowl crossed the Bering landbridge ~30 million years ago, and all subsequent turkey species were descendent from this species.  A fossil species, Rhegimornis calbates, dating to the early Miocene, had anatomical characteristics intermediate between the turkey and the peacock.  Remains of Rhegimornis were found in Florida.  The modern turkey probably evolved by late in the Pliocene–~2.5 million years BP.   Fossils of Pleistocene-aged turkeys have been found in Georgia from Ladds and Kingston Saltpeter Cave.

Turkeys evolved from a peacock-like ancestor that crossed the Bering landbridge ~30 million years ago.


Bochenski, Zbigniew; and Ken Campbell

“The extinct California turkey, Meleagris californicus, from Rancho La Brea: Comparative Osteology and Systematics”

Natural History Museum of California Publications 2006