Monday, June 24, 2013

Jaguar (Panthera onca)

During the Pleistocene the Jaguar (Panthera onca) was abundant across the Northern Hemisphere and was much larger than it is today. Since the end-Pleistocene extinction event, however, it has become confined to the New World tropics and has shrunk in size. Despite being the third largest of the pantherine cats, Jaguars are exceptionally powerful predators whose strength easily matches that of their larger relatives.

The name Panthera may be derived from the Greek pan-, meaning “all”, and ther, meaning “prey”, translating literally as "predator of all animals”. The species name onca is derived from the Latin word lyncea, “lynx”. The word Jaguar comes from the Tupi (native Brazilian) word yaguara which means “beast”. Several  extinct subspecies from the Pleistocene have also been identified based on their geographic location; Eurasian specimens are referred to as P. o. gombaszoegensis while the South and North American specimens are attributed to and P. o. mesembrina and P. o. augusta respectively. This blog post will be focusing on the latter of the three while making comparisons to living representatives of the species.

Habitat & Distribution

Jaguars inhabit forest, woodland, savanna, scrubland, and wetland habitats preferring lowland areas with a permanent water source and vegetation cover. This species first appears in Eurasia about 2mya. When the Bering Land Bridge was formed during the early Pleistocene, Jaguars expanded their range to include virtually all of North and South America except for the extensive open grasslands, deserts, and mountainous areas. After the end-Pleistocene extinction event, Jaguars became extinct in the northern parts of their range until they were only left in the tropical forests of Central and South America. The northern limit for this species today are the states of Arizona and New Mexico.

Physical Attributes
Modern Jaguars display an interesting size variation through different parts of their range that appears to be tied to the abundance of large prey in their respective regions. Individuals from Central American rainforests are the smallest. The largest Jaguars are currently found in the Pantanal wetlands of South America where large prey over 100kg (220bs) is abundant and are more readily encountered than it is elsewhere in the species' range. Mature males from this region reach shoulder heights of 70cm (2ft 4in) and body weights of 158kg (350lbs), the weight of a small female Lion or Tiger. During the Pleistocene, however, Jaguars could attain shoulder heights of 90cm (3ft) and body weights of up to 210kg (465lbs), nearly the weight of a male African Lion! 
A size chart to illustrate the size difference between the Pleistocene (left) 
and the average modern Jaguar (right).
Pound-for-pound the Jaguar is the most powerful of any living cat and is comparable to saber-toothed cats of the genera Smilodon, Dinofelis, and Xenosmilus in the relative robustness of its bones. It is nearly twice the weight of a Lion, Tiger, or Leopard of the same head-and-body length. The forelimbs are particularly robust with thick bones and the body is compact and well-muscled. The hindlimbs are somewhat more lightly-built relative to the forelimbs and are adapted for acceleration and agility. Jaguars also have the shortest tail of any pantherine cat both proportionally and absolutely. As a result, Jaguars must catch their prey by leaping on it from cover rather than by chasing it. An exceptionally massive skull and jaw muscles endow this animal with the strongest relative bite force of any living cat. The canines are thick and adapted for piercing the skulls of its prey.

A melanistic Jaguar. Note that the rosette markings are
still faintly visible. 
Jaguars are often confused with the Leopard, which has a similar coat pattern. However, the former is noticeably stockier with a larger head, shorter legs and tail. The base coat color is tawny yellow with white underparts. The head, lower legs, and tail are marked with basic spots. On the neck, body, and upper legs these spots are arranged into rosettes with a light brown center, and often with one to four smaller spots within. On some individuals, the spots on the underside of the body become elongated into stripes, sometimes forming a "necklace" marking on the neck area. Many individuals born in densely forested environments are melanistic; having excess pigment producing a pure black color. However, although the the rosetted/spotted pattern may be visible when light is shined on them.

Ecology & Behavior
Jaguars are solitary ambush predators that specialize in hunting relatively large prey, generally preferring animals weighing 50 to 500kg (110 to 1,102lbs). Its strength is incredible; not only can it pull down and kill prey 4 times its size, but it can then drag such a kill a considerable distance to a secluded location to feed in peace. Although it will opportunistically take more nimble animals like deer when it can get them, Jaguars are better suited for tackling the slower-moving or more heavily-built herbivores of its environment such as tapirs, capybaras, and peccaries. During the Pleistocene, the Jaguar prey menu is likely to have included some of the smaller ground sloths, as well as juvenile glyptodonts and pampatheres. Capybaras (Hydochoerus hydrochaeris) are a favorite prey of Jaguars where they live near open marshlands. These large rodents were formerly abundant throughout North America during the Pleistocene. Another tempting prey item for Pleistocene Jaguars were giant beavers (Castoroides). Peccaries are the most common type of animal preyed upon by modern Jaguars. In addition to modern species like the Collared (Pecari tajacu) and White-lipped Peccaries (Tayassu pecari), there is evidence that Pleistocene Jaguars also hunted larger extinct species like the Long-nosed Peccary (Mylohyus nasutus) and Flat-headed Peccary (Platygonus compressus). When larger prey is unavailable Jaguars will opportunistically kill smaller animals less than 50kg, including reptiles, monkeys, armadillos, and fish.

Jaguars tend to be crepuscular or nocturnal, but they will hunt during the day when given the opportunity. It actively tracks down its prey by moving silently along game trails. Once its prey is detected it stalks it carefully, easily getting to within 2 or 3 meters from an intended target. It then launches itself from cover in its prey's blind spot, landing on its back in one or two leaps. Its short and powerful arms enable it to cling on and grapple with large, struggling animals and position it for the killing bite. It will employ any of three killing techniques depending on the type of prey, though its preferred method is to bite through the temporal bones of its prey's skull and pierce the brain. For this reason, it has developed the strongest jaws and teeth of any living cat. It also employs the throat and nape bites used by other cats. Larger kills may be fed upon for days. 

A female Jaguar preparing to move her cub.
Although adult Jaguars spend most of their time alone, they seem to be surprisingly tolerant of each other to the point that they allow other adults to feed from their kills. Noticeable feeding hierarchies exist with males feeding from large carcasses first and females moving in after he leaves. Even adult males (as long as a receptive female is not in the vicinity) will tolerate each other's presence as long as one shows submission. Breeding can take place at any time of the year with females remaining in estrus for 6 to 17 days within a 37-day cycle. Females give birth to up to 4 cubs after a gestation of 90 to 105 days. Cubs remain in their mothers company for 1 or 2 years with males usually departing earlier.

References & Further Reading
Nye, April Season, "Pleistocene peccaries from Guy Wilson Cave, Sullivan County, Tennessee." (2007). Electronic Theses and Dissertations. Paper 2115. <Full text>

Lange. Ian M. “Ice Age Mammals of North America: A Guide to the Big, the Hairy, and the Bizarre”. Mountain Press Publishing Company 2002. Missoula, Montana <Book>

Cuvier M, Johnson WE, Pecon-Slattery J, O’Brien SJ (2000). “Genomic Ancestry of the American Puma”. Journal of Heredity 91(3): 186-97. doi: 10.1093/jhered/91.3.186. PMID 10833043 <Full article>

Nuanez R, Miller B, Lindzey F (2000). “Food habits of Jaguars and pumas in Jalisco, Mexico”. Journal of Zoology 252 (3): 373 <Full article>

Turner A (1997). The Big Cats and their Fossil Relatives. New York: Columbia University Press. ISBN 0-231-10229-1 <Book>

Macdonald, David W. The Princeton Encyclopedia of Mammals. Princeton, New Jersey: Princeton University Press, 2009. 750-751 <Book>

Kurten B & Anderson E. “Pleistocene Mammals of North America”. Ann Arbor, Michigan: University of Michigan Press, 1980. 192 <Book>

Agustin IJ, Franklin WL, Warren JE, Kent RH (1990). “Biogeographic variation of food habits and body size of the South American puma”. Oecologia 85(2): 185. doi: 10.1007/BF00319400 <Full article>

Schultz CB, Martin LD, Schultz MR (1985). “A Pleistocene Jaguar from North-Central Nebraska”. Transactions of the Nebraska Academy of Sciences and Affiliated Societies. Paper 228 <Full Article>

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