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

[Pckts]

(05-20-2021, 11:28 PM)Balam Wrote:

(05-20-2021, 11:05 PM)Pckts Wrote:

(05-20-2021, 12:33 AM)Balam Wrote:

(05-19-2021, 10:48 PM)Pckts Wrote:

(05-19-2021, 07:27 PM)Balam Wrote:

(05-19-2021, 06:59 PM)Pckts Wrote:

(05-19-2021, 06:03 PM)Balam Wrote: From my subreddit r/jaguarland, a really nice poster gave more background on the past distribution of jaguars in Argentina during the Holocene, going as far as places in the high Andes such as Nahuel Huapi. 

u/DeskCareless


It is known that the jaguar inhabited the pampas and even the Patagonian steppe canyons, there are also mentions in the Limay river in the Nahuel Huapi National Park, in fact the name Nahuel Huapi translates as Isla Jaguar, the sightings of jaguars in Patagonia by part del European settlers reach the Magellan Channel, unfortunately there are not so many records pertaining to the campaigns of Argentina and Chile further south of the Chubut River. According to descriptions, the jaguars in this region were quite large and the fossil record supports this idea It is estimated that the Patagonian Jaguars were larger than those of the Pantanal . The prey that the Jaguar could find in Patagonia are Rheas, Guanacos, Andean Deer, also the Deer of the Pampas that came to inhabit the north of Santa Cruz in the past and the Patagonian Mara that although it is smaller and faster than the Capybara It is still a good appetizer. Otters, Armadillos, Penguins, Land Turtles, Sea Lions and Seals could also be a good prey and it is known that collared peccaries inhabited northern Patagonia. Of course, you should share these prey with the Puma and the Culpeo Fox, although with the Puma they are generally nice and the Culpeo is not a direct competitor.

https://www.laizquierdadiario.com/IMG/jp...12_-27.jpg

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map of its possible distribution taking into account the Patagonian records.

This Text, which is in Spanish, talks about the subject and corresponds in fact to the time of the campaigns carried out by Argentina and Chile.

http://naturalis.fcnym.unlp.edu.ar/repos...003221.pdf

I have a hard time believing that prey base could produce larger Jags than the wetlands.

I'm not sure if they meant fossil records pertaining to Holocene jaguars or Pleistocene ones, we know the Pleistocene Patagonian forms were much larger than extant jaguars. Before the European settlements in Argentina and Chile there were millions of guanacos prowling the steppes of the Patagonia, I think prey like that is large enough to sustain really big cats. Guanacos extended all the way through the dry Chaco but most of the Chacoan guanacos have gone extinct, this is also another one of the reasons why Chacoan jaguars grew so big, we know they average around 95 kg today but I think they were even larger a few centuries ago

My doubt comes from the hunting styles. I think the marshland style of hunting is going to give Jaguars their best specimens. They don’t seem to produce as impressive sizes when elevated terrains come into play. Their morphology isn’t as suited for the rocky terrain in comparison to explosive bursts of power from the waters edge.

At elevated terrains jaguars definitely appear just as stocky, in this case, the Yungas is the only eco-region left where jaguars inhabit high altitudes albeit still lower than the Andes, both jaguars and cougars from this area appear particularly stocky to me:

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This trend seems to be consistent among felids in general, Barbary lions were thought to have been lower at the shoulder and more robust than their Sub-Sharan savanna counterparts, northern Indian and Nepalese tigers are probably the most robust tiger eco-types, and Persian leopards appear more stocky than their savanna counterparts as well. Usually, big cats become less robust in the environments where they live a more cursorial lifestyle, IMO in this case Llanos jaguars appear to show a lighter build but with a larger body frame, akin to a lion:

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It's all speculative but they do give me that impression. In regards to the morphology of the now-extinct Patagonian jaguars, my guess is that they would've been very stocky like the Yungas specimens but greater in size. It's such a shame we've almost lost all information concerning these jaguars as they were hunted very rapidly during the initial European settlements, it would've been super interesting to see what that jaguar eco-type would've looked like, but I don't doubt it was big.

Camera trap photo's are difficult to determine but we know that these Jaguars shown aren't in the Pantanal/Llanos weight class. 
Cougars are a different case, they should thrive in elevated terrain since their morphology contributes to a better suited cat for that habitat. Long legs with a lighter frame allows them to chase prey in deep snow or uneven ground while a Jaguar being very stocky with short limbs and a long body doesn't seem as suited for that. Not to mention the hunting style of land mammals vs semi aquatic animals. I think the marshland is just the perfect habitat for Jaguars and it shows in their size, they've always been quoted as being the largest in these areas no matter how far back we go when eye witness accounts are involved. 

In regards to other felines, as of now Barbary Lions have shown no difference in morphology, at least off the minimum data we have and N. Indian Tigers may or may not be larger than their C. or S. Indian counter parts but the weights and measurements we have now all overlap considerably. In fact, possibly the largest Lions and Tigers alive today  come from wet habitats. (Delta and Kaziranga) with notable mentions from the Crater and Terai Arc.

Like you said, it's all speculative and Bergmans law contributes to larger cats but it's not the only landscape that does.

That's not my point, jaguars from the Yungas are likely smaller than Pantanal/Llanos ones, I was referring to what their morphology entails in terms of robusticity, they're just as robust IMO. Jaguar weights we know are completely dependant on the prey biomass of the biomes they live in which is why they grow so big in the flooded savannas, but in certain higher terrain areas where they used to inhabit and had access to very large and plentiful ungulate prey like Patagonia and the certain parts of the US (post-Pleistocene), jaguars could've grown very large as well, as detailed by writings from centuries ago. My comparison with other species is also related to this area of stockiness, I actually don't subscribe to Bergmann's rule because it is not consistent throughout, to me it's clear that genetic diversity and proper nutrition during developmental years are the key factors in the overall body mass of different felid populations.

For example, jaguar from northern Mexico and southern Arizona are among the smallest as their main prey are coatis and collared peccaries, the moment these jaguars get reintroduced in areas of central or northern Arizona where elk are found, they will progressively increase in size with each generation and become more robust as well.

I'm no disagreeing that given the addition of a proper prey base in elevated terrain that these Jaguars wouldn't grow large. But all things being equal, both would have an abundance of prey but my opinion is that the marshland habitat is going to contribute to the largest Jaguars. Their bodies are built to succeed there where as they don't seem as suited for chasing mammals through mountainous terrain. Reply