[Aztlan] Jaguars in Formative Valley of Mexico

[Bruce Rogers]

Listeros,

Travis Doering asked if the jaguar (Pantera onca,  Linnaeus, 1785) 
was indigenous to the Valley of Mexico during Formative time and if 
so, what were the ecological constraints on its range.

 From my limited knowledge and reference searching (remember: I'm a 
geologist, not a mammologist...),  it appears that historically the 
jaguar was present in the Valley of Mexico during Formative times. 
Although the jaguar prefers a fairly dense rain forest and adjacent 
open water such as rivers and such, it was/is known from semi-arid 
scrub forest.  It prefers lower elevations below about 1000 m, but 
current sightings have been recorded up to 3,800 m.

The paleontological record has shown that jaguars evolved from 
leopards, a genus that itself apparently evolved in India some 5 
million years ago, or at least that's what the current fossil record 
tells us.  Panthera gombaszoegensis evolved in Eurasia shortly there 
after.  Panthera agusta was the first "grandaddy" jaguar to migrate 
to the New World from Siberia somewhere between 3 and 1.5 million 
years ago; the fossil record is spotty and open to debate at this 
point.  Evolving during the latest Pliocene and following Pleistocene 
Epochs, fossil remains of jaguars as a distinct species have been 
found that are as old as 40,000 years ago in the latest Pleistocene 
Epoch.  The Missouri fossil "population" was much heavier and more 
robust than present species and dated to between less than 40,000 and 
10,500 years old.  Another 14 inch-long skull and long bones of a 
jaguar (exact species unidentified-it's still under study) was found 
in 1995 at Oregon Cave National Monument in southwestern Oregon near 
the California border.  This is the northernmost occurrence of fossil 
jaguars known in the New World and dates to about the latest 
Pleistocene Epoch, some 38,000 years ago.

New World fossil jaguars, in general, evolved in North America during 
the latest Pliocene Epoch, then spread south, crossing North America 
towards South America about 2 million years ago after the Isthmus of 
Panama finally connected the two continents some 3.1 million years 
ago (a milestone in New World tectonics).  The oldest fossil big cats 
in South America found so far date to the end of the Pleistocene 
Epoch, just under 2 million years old.

It appears that availability of prey, dense vegetative cover, and 
availability of water (a habitat preferred much like its solitary 
cousin the tiger, P. tigris) are key elements in its ecological niche.

With the tremendous changes in the Valley of Mexico (clearing of 
vegetation, draining of Lake Texcoco, and intense urbanization) this 
part of the big cat's range has become untenable.  Indeed, current 
range maps indicate the species has been largely extirpated in the 
northern part of Mexico and adjacent southwestern USA (although 
reliable observations exist for solitary animals from as recent as 
2004) and its longitudinal range now limited to the Sierra Madre 
Occidental and areas to the west.

In particular, Lake Texcoco (site of the modern Mexico City) has 
existed for about 100,000 years, was possibly fairly deep with 
extensive surrounding marshland fed by bordering springs emanating 
from the porous volcanic rock and alluvial soils.  By about 10,000 
years ago, the lake fauna was replaced by shallow water, marshy 
fauna, most probably caused as the lake started shrinking due to the 
end of the Pleistocene Ice Ages.  The marshy lake margins supporting 
dense vegetation would have been prime habitat for the jaguars over 
the last several hundred millennia.

What a loss . . . .

Cheers,
  Bruce Rogers, earth scientist (& part time naturalist) on a good day