ON THE EDGE OF EXTINCTION - C - THE JAGUAR (Panthera onca)

[Balam]

Information pertaining to the jaguar in Uruguay, where it has been locally extinct since the beginning of the 20th century, and speculation of jaguar mass across overlooked areas of South America:

The book El Jaguar en el Siglo XXI. La Perspectiva Continental contains some very detailed information about jaguars from historical narratives and data across their historic Holocene range. Jaguars used to be very plentiful in Uruguay, where most of the land consists of grasslands that belong to the Pampa biome. The historic fauna from this area was very similar to what is seen in most floodplains from southern South America (i.e. the Pantanal, Chaco, Ibera, etc.), with very large populations of capybara, peccary, deers, and rheas; as a result, the jaguars that inhabited this area were described as very large and strong. Sadly, not many records exist of jaguar skulls, prints, or gathered weights and measurements from Uruguay, as the jaguar was thought extinct by 1901; however, we do have one record of one specimen whose weight and measurements were provided, and descriptions from people visiting Uruguay at the time:

*This image is copyright of its original author

"In 1715, William Toller reported the presence of the species in several areas of its territory. This author alludes to the tigers on the east coast of the Plata river, likewise mentions sightings in Santa Lucia (east of the department of Montevideo), and the capture of a jaguar that measured 1.4 meters from head and body, 0,6 meter in tail length and 95 kilograms in weight (Toller, 1715)"

*This image is copyright of its original author

"... mentiones tigers that were common to see at the shores without showing fear for the presence of humans (Buschiazzo, 1941). Describes the species and is amazed by its size for being much greater than the African leopard, highlighting that when trying to measure one skin, it was taller than his body with his arm extended. Mentions as well the indigenous habit of sleeping outdoors surrounding a fire to avoid being attacked by the jaguars. Likewise, when being close to the vicinities of Salto Grande, he stated that an "invasion of tigers that came to visit us, attracted by the smell of meat" of cattle they had in the "camp", as well as several encounters and hunting of jaguars in the area, even of cubs they drowned in the river for fear that "their relatives would come to visit us".

All this suggests that the jaguar was an abundant species, that had an extensive distribution in the country, that they were of large size and didn't see humans as a threat."

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It's important to highlight that the sex of the specimen spoken about in question was not given, but nonetheless, the habitat in which these jaguars existed had all the essential elements required to sustain larger specimens, as reaffirmed by their descriptions from people who had seen other felid species around the world at the time. 

As the size of jaguars is a direct reflection of the environment and biomass they live in, we can infer that extinct Holocene populations in the Pampas, and places from central and southern Argentina, like the Ibera wetlands, held jaguars that likely were similar in size to those from the Pantanal and the Llanos: the prey items they consumed were similar and at times the same (i.e. capybara, caiman, mid-sized and large-sized cervid, peccaries, etc.), and used to be found in large congregations as well. We will never know the exact extent of their sizes since the information on it was lost with their extinction, but it's very clear that jaguars were capable of attaining a large mass of over 100 kg in several places of South America outside of the two well-known floodplain populations that have been recently popularized as being the only areas that support big jaguars (the Orinoco Llanos and the Pantanal).

Another area that has all the right conditions to sustain jaguars large in mass is the Bolivian Beni savanna, also known as Llanos de Moxos. This area is very sparsely populated, but it is the third-largest floodplain ecosystem in South America after the Orinoco Llanos and the Pantanal and contains a mixture of species from the Pantanal and the Amazon rainforest, where taxa like Melanosuchus meets with Blastocerus. This area is so remote and unstudied that there are no records of photographs or video footage of jaguars, but thankfully they have not gone extinct there yet. In-depth studies about the ecology and morphology of these jaguars, as well as the health of populations inhabiting the biome, are long overdue and I'm hopeful we will get them eventually within the next decade. 

To summarize, large jaguars are not a rare phenomenon that occurs exclusively in the two aforementioned floodplain areas, as it's wildly believed online. Instead, there are historical areas and present biomes where jaguars became extinct on, or are understudied, where their size potential is similar to the Pantanal or the Orinoco Llanos: Pampas (extinct), Ibera wetland and surrounding area (extinct, being reintroduced), the Cerrado, the Llanos the Moxos, and the Great Chaco.

Historically the Atlantic forest and the forested areas of the valleys and basins of northern South America such as the Magdalena Medio and the Maracaibo lake, too display cases of jaguar reaching or slightly surpassing the 100 kg mark, but the health of these ecosystems have been greatly compromised and it's likely that their size potential has been diminished by the reduction in the abundance of prey, and the depletion of their DNA thanks to the lack of proper corridors that connects these populations and being overhunted. Reply