An Indomitable Beast by Alan Rabinowitz

Author:Alan Rabinowitz
Language: eng
Format: epub
Publisher: Island Press
Published: 2014-03-14T04:00:00+00:00

As a graduate student memorizing the taxonomic nomenclature of mammal families, genera, and species, I was told by my instructors not to worry about subspecies classifications because they were not definitive. But I was intrigued by the number of subspecies names that scientists assigned to every large carnivore species when they all looked essentially the same to me. While some subspecies divisions were based on clear anatomical differences between populations that had been separated for long periods of time, others used less substantive criteria such as size, weight, and coloration. Among the cats alone there were supposedly 6 subspecies of tigers, 7 subspecies of lions, 8 subspecies of jaguars, 11 subspecies of leopards, and potentially as many as 32 subspecies of puma. Then there were 39 subspecies of wolves, 19 subspecies of coyote, 45 subspecies of red fox, and 16 subspecies of the American black bear. The take-away message for me as a graduate student was that the proliferation of subspecies was the norm for large, wide-ranging carnivores. Paradoxically, it also implied geographic separation of populations and limited genetic exchange—a possible fast track to extinction.

The first comprehensive summary of jaguar taxonomy, published in 1933 by biologists Edward Nelson and Edward Goldman, listed 16 subspecies of jaguars (5 in North America and 11 in South America) based on measurements of 92 jaguar skulls. Acknowledging small sample sizes and “imperfect” classifications, the authors described two subspecies of jaguars in the northern extremity of the species’ range alone: the larger Arizona jaguar and the slightly smaller Northeastern jaguar, differentiated only by a single skin and a few skull measurements. This taxonomic classification was revised in 1939 by British zoologist Reginald Pocock using characteristics from 59 jaguar skulls but more accurately considering the range of individual variation that could occur in skull measurements. Pocock divided jaguars into eight subspecies, as follows:

• Panthera onca onca (topotype—lower Amazon basin)

• P. o. peruviana (coastal Peru)

• P. o. centralis (El Salvador, Nicaragua, Honduras, Costa Rica, Panama, Colombia)

• P. o. hernandesii (Mexico west of Central Plateau)

• P. o. arizonensis (Arizona, Sonora, and New Mexico)

• P. o. veraecrucis (eastern and southeastern Mexico to Texas)

• P. o. goldmani (Yucatán Peninsula, Mexico, to Belize)

• P. o. paraguensis (Mato Grosso, Brazil, to northern Argentina and Paraguay)

Pocock’s classification of jaguars held for nearly six decades. In 1997, a paper published by Shawn Larson in a journal little read outside the zoo world, Zoo Biology, examined data from 170 jaguar skulls. Using sophisticated statistical analysis of 11 morphometric variables that are definitive for skull formation, Larson found some variation between extreme northern and southern jaguar populations but no significant taxonomic differences between jaguars throughout their range. She went so far as to recommend that jaguar populations should be managed as a single taxon (one species with no subspecies). Despite these findings, which I read shortly after the paper was published, I and other jaguar biologists continued to assume that the relatively diminutive 45-kilogram (100-pound) jaguars of Mexico had to be a different subspecies from the 115-kilogram (254-pound) jaguars of southern Brazil.

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