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(02-17-2020, 03:01 AM)Pckts Wrote: Competition in the pantanal is 2nd to none, but for the most part I agree with you.
But when you see Jaguars, you realize how similar their body is to a giant river Otter.
Obviously they're still very different but, they still share similarities that no other big cat shares.
This has got to do with the fact that they're hunting animals that are more adept in the water than land.
I'm not saying that they'll stop running on land, I'm just comparing their features to that of a specialized aquatic predator.
In regards to large mammals, they dont occur nearly as often in north, whether due to human hunting or Jaguar densisty is up for debate but regardless, they just dont exist like that in the North. The main animals you see there are capybara and Caiman.
They're both very adept swimmers and never stray far from the waters edge. They also usually sit with one another so they probably require the same tactics.
Tapir are no slouch, they can be double the size of a male jaguar.
But they are predated on more often in the areas they are more abdundent.
Put it this way, if you go on safari in the northern pantanal, the odds of you seeing a tapir are 1/100.
Well competition in the Pantanal is high (not sure if I'd say second to none though) with pumas, caimans, and anacondas. I was mostly speaking of terrestrial predators, though.
But yeah I definitely see their similarities with river otters. I think these characteristics are derived from different naturally selective pressures, though; the jaguar's long, flexible spine, for instance, is an adaptation for a different behavior than is the similarly long and flexible spine of the otter. The former is for great agility & athleticism for predation, while the latter is for swimming.
I totally agree that jaguars are the most aquatic of the big cats, mostly due to the fact which I stated on them taking advantage of a diverse prey base that largely includes semi-aquatic animals. But jaguars are generalists, and I doubt they'd specialize in this aquatic prey when they also take other animals, like giant anteaters.
Yeah tapirs aren't slouches, though they should be well within the capabilities of a jaguar sized felid. It's also worth noting that they're also rather aquati, and they're largely nocturnal. They also live at low densities being large solitary animals with rather slow maturation and gestation periods. But nevertheless mammalian megafauna don't make up a significant portion of the jaguars diet in way it usually does for the other extant big cats.
In regards to competition, I'm speaking on intraspecific ones. In that regards, I'd say the jaguar has the highest densisty of cats in a localized area.
And I'm not talking about females and cubs, I'm talking about adult specimens and mostly males.
In the meeting of the 3 rivers *tourism zone of the northern pantanal* there were 65 identified adult individuals last season. Cubs there are rarely seen and usually are pushed out to never be seen again.
Tapir are rarely seen in the north, in the south they are seen much more often.
My theory is the reason tapir and green anaconda are rarely seen in the north is because of the densisty of Jaguars. Both are slowing moving animals that may prefer a more vast space with a lower density of Jaguars.
It's kind if a perfect storm in the north, caiman were hunted and killed by the millions, decreasing jaguar numbers and increasing piranha numbers, when protection was finally offered to Caiman, they rebounded fast due to the increase in piranha after missing their main predator.
Now Caiman are everywhere, same with Capybara and both are mostly aquatic animals.
Cattle is a large ungulate and obviously easily killed by Jaguar. Tapir are going to be a tough animal to kill for any cat, especially one that they are double the size of.
Boar that are equal size as cats can be extremely tough prey, when they're double the size of a cat they are going to be very dangerous prey.
Lastly, in regards to their spine, it definitely contributes to Jaguars agility in the water.
They are so comfortable in the water and make kills in the water as well then they need to swim animals from the water up a steep, slippery slope and through dense floating grass.
It's a perfect combination of flexibility and strength, but with the ever changing habitat and aquatic prey preference, it should only benefit the Jaguar to continue its aquatic evolution imo.
Ah okay haha. I was speaking of interspecific competition, which is a very different naturally selective pressure from the intraspecific competition that you spoke of, as the former drives speciation.
When interspecific competition is high, niche partioning occurs, i.e. specialization. When it is low, animals can take advantage of all available resources, and be generalistic. So my point was that since jaguars' competition isn't unusually high, there isn't any competitive drive for them to specialize.
I think we can both easily observe that jaguars are the most generalistic of the big cats in terms of diet. Mammalian megafauna, ungulata particularly, make up a very small part of the jaguar's diet compared to all other big cats. This is because there is less abundance of large mammals in the rainforest which the jaguar inhabits, especially ungulata. Tapir are very strong and robust animals as you said, although I would say that if jaguars preferred them they could indeed hunt them more often than they do, as evidenced by tigers/lions taking on prey at least similarly large in relation to their mass. So the jaguar could not specialize in this prey, and instead had to generalize his diet with other species, including capybara, giant anteater, and a number of reptiles (i.e. caimans).
There isn't a specific pressure that would cause jaguars to specialize, because specialization does have cost, while it will make a predator more adept at hunting specific prey, it narrows the prey base and disallows the predator to take advantage of other prey.
So, there isn't any reason in my opinion to suggest that jaguars might begin to specialize in hunting semi-aquatic or aquatic species. Yes, in the Pantanal they hunt capybara and caiman very prevalently, i.e. the most abundant species; this is a product of their generalist, highly adaptable diet, and not evidence of specialization. They are well adapted to hunt semi-aquatic animals (moreso than other big cats), but they are also well-adapted to hunting terrestrial species.
As far as the morphology/spine is concerned: I agree that the jaguar's defining characteristics -- short but powerful limbs, long flexible spine, and large paws -- make him a good swimmer, I also will state that swimming is a secondary use for these characteristics and isn't the behavior from which they are derived. For one, all cats share these traits, albeit jaguars seem to be most extreme in at least the former (short limbs). The long, flexible spine in particular is an adaptation for rapid maneuverability and agility for the 'explosive power' felids specialize in for predation. Secondly, there doesn't seem to be any difference in morphology between jaguar subspecies that would suggest wetland jaguars were very specialized, something you would expect given how long they've inhabited the area.
Comparing big cats - differences/changes with time
