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Comparing big cats - differences/changes with time
Comparing big cats - differences/changes with time
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Comparing big cats - differences/changes with time
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 (02-17-2020, 08:07 PM)Pckts Wrote:(02-17-2020, 07:26 PM)BlakeW39 Wrote: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.(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. 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. All said though, a very interesting conversation! 
It's not that Jaguars dont prefer Tapir it's that they dont have a chance to hunt them in the north, caiman and capybara are everywhere, they are by far the most hunted prey a long with cattle during the wet season.
Tapir, anteaters, green anaconda, etc. Have higher numbers in the south, amazon and cerrado, in those areas you see more predation on said animals, except green anaconda which are much harder to see and less abundant in Jaguar land. In north you will almost never see any of those animals I just named so documented hunts on them will be even less likely. But obviously they've learned to prefer capybara and Caiman since they're everywhere so it will only behoove the Jaguars to continue their aquatic transition. Now in regards to morphological differences, we really cannot make that claim since to my knowledge there has been no study for it and the data is limited. What we can say is that in the Pantanal the Jaguars are longer, heavier and have much larger skulls while the shoulder height doesn't really change. The only two places this occurs are where there are an abundance of Caiman. The spines of Jaguars are very different from all other cats, they are more curved and arch almost towards the middle which is a similar trait to an Otter. When a cat grows a longer spine with a large curve without increasing shoulder height, that isn't a benefit for land but more so for the aquatic lifestyle. Like Otters who share the same traits, it helps them maneuver their bodies in water.
@BlakeW39, everything you mentioned about jaguars from adapting to surroundings, developing a wide range of diet, to becoming more aquatic are all applicable to tigers of marshy ecosystems (unfortunately only Sunderbans is a marshy ecosystem home to tigers at present times but this was not the case only 150 years ago as Mangrove and marshy ecosystems all across SouthEast Asia had tiger presence covering over 150,000 sq.km)
So, when you say “I think jaguars evolved to have the most generalized diet of big cats. This is because the tropical rainforest they've adapted for uniquely biodiverse but yet lacks the large herbivores found elsewhere” That is exactly the case for Sunderban tiger. A tiger in Sunderbans can eat anything from a boar to a monitor lizard. They even eat bee larvae! alongside snakes like cobras and even rarely king cobras. 20% of their diet is made up of turtles, crab and fish. What a lot of people don’t know is till a 100 years ago, their biggest prey was the Javan Rhino. Their varied diet and lack of big game has pushed their average weight down (opposite of jaguars). The tigers in Sunderbans were radio collared and it was found out that they swam 29 kilometres in a day shuttling from island to island. So, the claim of jaguars being most aquatic is also debatable one. Let us not forget tigers have evolved webbed toes like ducks to displace a large amount of water when swimming using their enormous paws. What I am trying to say is big cats are an evolutionary success story and their adaptability is absolutely fascinating but not any one species is that different from another in evolving to their surroundings. The one thing I am miffed about is how humans and their activities robbed us of so many more potential opportunities to study this whole extraordinary family. (02-18-2020, 10:38 PM)Ashutosh Wrote: @BlakeW39, everything you mentioned about jaguars from adapting to surroundings, developing a wide range of diet, to becoming more aquatic are all applicable to tigers of marshy ecosystems (unfortunately only Sunderbans is a marshy ecosystem home to tigers at present times but this was not the case only 150 years ago as Mangrove and marshy ecosystems all across SouthEast Asia had tiger presence covering over 150,000 sq.km) I've never been to the Sunderbans so I cannot say which is more aquatic, Sunderban Tigers certainly live in an aquatic dominate landscape but the prey they hunt doesn't seem to be as comfortable in the water as Jaguars which IMO tends to make Jaguars even more accustomed to the water, but that is a theory based off of my personal observations. But both have developed traits to benefit their aquatic lifestyle and given enough time they should continue their evolutionary journey to becoming more water dominate creatures.
True, @Pckts. But, Jaguars are the absolute apex predator in their landscape. On the other hand, tigers in Sunderbans have to deal with saltwater crocodiles and highly venomous sea snakes and both of those are better in water than the tiger, and no other animal is worrying the jaguar on such levels. Patrolling a territory is so much harder with such dangers lurking around. So, should the criteria for a more aquatic cat be based only on the prey? Personally, I think the fishing cat is the most aquatic cat around, but there is so little known about them.
(02-18-2020, 10:59 PM)Ashutosh Wrote: True, @Pckts. But, Jaguars are the absolute apex predator in their landscape. On the other hand, tigers in Sunderbans have to deal with saltwater crocodiles and highly venomous sea snakes and both of those are better in water than the tiger, and no other animal is worrying the jaguar on such levels. Patrolling a territory is so much harder with such dangers lurking around. So, should the criteria for a more aquatic cat be based only on the prey? Personally, I think the fishing cat is the most aquatic cat around, but there is so little known about them. Valid point, I'm sure a Jaguar would be much less at home in the waters of the Pantanal if 15' Crocs were lurking. But in terms of any other cat being more or less aquatic, I'm not sure since I haven't seen them. But in the Northern Pantanal there is hardly any dry land and the sand bars will come and go with the seasons. In fact when you see tall grass in which you think has dry land beneath it, there really is just water and that tall grass will rock with the wakes that the boat creates as you drive past. It's truly amazing how much water actually dominates the Pantanal, it's unlike any place I've seen personally.
@Ashutosh first of all, thanks for showing me that there's a much more efficient way of replying to someone haha.
That's definitely a very interesting point. Big cats are indeed an evolutionary success story, seeing as hoe they outcompeted most other carnivores as apex predator, likely pushing many taxa to extinction. Sundarban tigers are, likewise, a good example of big cats' adaptability. But, nevertheless, I'm not so sure Sundarban tigers and jaguars are a great comparison. This is because Sundarban tigers, while insularly isolated, are only a subpopulation of tiger, and thus aren't derived enough to have developed the morphological divergence that jaguars have. Tigers, though adaptable (as are all large predators), specialize in hunting terrestrial megafauna which is something you can see in their diet across their range. Sundarban tigers are still tigers and are adapted to this purpose, but very recently have been deprived of large prey, and so had to adapt to other prey. You've already seen them converge in with jaguars by becoming smaller and feeding often on aquatic and semi-aquatic species, as well as reptiles. But they haven't the time to change their physiology significantly. So in my opinion my theory on how jaguars became the most generalistic big cat still stands. Of course that's what's great about the conversation, we can't know for sure and we all have our separate ideas :) but jaguars show very definitively divergent morphology. They have a disproportionately large head, massive jaws, and short limbs. I see the reason for this being a need to generalize their predation based on a lack of large prey and need to prey on smaller but often very compact creatures, and often on armored reptiles, by ambushing them in dense habitat and kill them efficiently. Because cats are adaptable but they are also quite diverse and I see clear differences between jaguars and tigers. As for who is more aquatic, that's debatable but I'd say jaguars are at least more well adapted for aquaric life and more frequently rely on these habitats. But it's totally up for debate, both cats do well in wetland. @Pckts well, the studies I have reviewed all seem to indicate that where jaguars overlap with tapirs, that tapirs aren't preferred prey. Similarly, jaguars do indeed overlap with ungulata but where they do, these prey are also not preferred. Likewise, I've also seen it put that jaguars prey preference seems to have the least consideration for the morphology of prey, and take the smallest prey relative to thwir body mass of large felids. Jaguars, then, can be inferred to be the most generalist big cats. We are in agreement that jaguars are well adapted for water. Moreso than the other large felids. Pantanal jaguars do seem to be the most aquatic of jaguars. But these differences are slight variations of characteristics they already have, and while it is possible they continue to grow more aquatic, I personally think it's implausible. Jaguars' adaptability is much of their success and their adaptation to the Pantanal is a product of this great adaptability and generalized diet. I don't see them becoming any more water-adapted but that's not something that's predictable, so I guess we will see in 100 years haha. As for their skull, spine, stocky build; I don't see the former or the latter as adaptation for swimming in any matter, but a flexible spine is helpful for this purpose I agree. However I find it unlikely this was the sole reason for their curved spine as it can be justified for other reasons, even as a product of their stocky build and short limbs.
@BlakeW39
There's an older study on Jaguars prey preference from the Southern Pantanal. In this study its shown that Jaguars 1st preferred prey was cattle, then caiman and peccary. This was dependent on the time of year and individual cat as certain individuals preferred cattle over another. Cattle between calf and adult were both taken, showing that Jaguars take animals larger than Tapir often. It's also shown that while both Collared and White lipped peccary were present, Jaguars preferred the white lip peccary which is a larger species. Tapir were also taken but only by male Jaguars. But there are a few factors that differentiate the South from the North. In the South, floods are worse and cattle are preyed upon more often. The Tourism there is also more rugged and the lands more molested. Farmers will bait their properties with cattle to attract Jaguars and the tourists dollars that follow them. Caiman is also less dense there, capybara as well. But in that study they found that when the water dispersed and the Caiman spread out across the landscape, Jaguars preferred Caiman to Cattle. But in the North, Cattle isn't a preferred prey due to the abundance of Caiman and Capybara. Now who's to say that Tapir wouldn't be preyed upon more often if Cattle weren't so available. Cattle directly compete with Tapir for habitat and essentially replace that prey item for Jaguar with even less natural caution towards Jaguars. If Tapir existed in the numbers that animals like Caiman, Capybara and Peccary do then I'm sure they would be as common a prey item as all the rest. Here is a beautiful display of how profecient they are while hunting in the water. For me, this is a good example of where a Jaguars evolution may be heading. They'll still need limbs to drag prey to shore when available but they need to be maneuverable in water to capture prey. It seems to be equally as important to sneak up from behind the waters edge as it does to sneak in to shore from the water itself.
I put this thread here for discussions, which are concerning differences and similarities between species and as in one recent discussion, between certain populations of two different species.
This thread is meant therefore for such discussions which involve observations in possible evolutionary changes, behavior changes etc. Mainly in it, that how do these animals hunt, behave and are there maybe some physical changes happened in time, which other big cat´s or populations/subspecies don´t have. I´ll move one recent discussion here, because it was moved by accident to wrong place blocking some participant(s) to write there.
Now everyone involved that earlier discussion should be able to participate.
 (02-18-2020, 05:50 PM)Pckts Wrote: It's not that Jaguars dont prefer Tapir it's that they dont have a chance to hunt them in the north, caiman and capybara are everywhere, they are by far the most hunted prey a long with cattle during the wet season. I think that comparison between pantanal jags and otters is quite interesting and the morphological adaptations to aquatic life for them would make for a good thread. Would be interesting comparing the physiology and measurements of less aquatic populations to more aquatic ones and see if this otter hypothesis holds up.
02-25-2020, 06:55 AM
( This post was last modified: 02-25-2020, 06:51 PM by BlakeW39
Edit Reason: source
)
Thanks @Shadow for letting me back in.
So sorry for the late, late reply. Hope I can add something. @Pckts , Cool video :) We're definitely in agreement that jaguars are aquatic compared to other cats. Especially in the Pantanal and other floodplains habitats. Big cats adapt to their habitats and available prey base -- and thus populations of big cats vary at the specific and subspecific levels. It should stand to reason, then, that jaguar populations would vary to a degree based on adaptations to their indigenous environments. This is what we indeed see; jaguars, like all big cats, vary in morphology (i.e. size, etc.) and behavior based upon their environments. This variance, however, is only slight -- all the populations of a big cat share a similar ecological goal, but are adaptable to do so under differing circumstances. Jaguars in wetlands have adapted to their habitat physically by developing proportionally shorter limbs with large paws, a larger skull presumably for increased predation on reptiles, and larger size. But these differences aren't extreme, and don't indicate intense specialization that would lead to speciation of a semi-aquatic 'otter-like' felid. Before I adress a second point, I want to say that livestock, like cattle, aren't really comparable wild ungulata. Livestock are easy prey in comparison and should be classified separately, from my humble perspective :) On jaguar predation and prey preferences: jaguars, as I have stated numerous times, are the most generalist of the big cats. Jaguars are highly generalistic. Jaguars, unlike other big cats, seem not to be very selective or specialized in their predation; in the study of over 3,000 jaguar hunts from across their range, they were seen to have not selected prey based upon morphology at all, but rather upon 'socio-ecological and behavioral traits' -- they hunt prey based upon its abundance. The result was that jaguars showed no preference of predation upon large ungulata, as is the case in every other extant large cat. They also took small prey relative to their body size -- on average, prey taken was only half the jaguar's body mass, which is a contrast to other large felids, who usually take prey comparable to or a bit greater than their own respective size. So, jaguars are the most generalized predators of the big cats, and they aren't selective in their prey preferences based on morphology to a significant extent. If jaguars are so generalistic, and take prey based on its abundance and availability, it would stand to reason that they would prey on mostly caiman and capybara where they are most common, or anteater where they are common, and so on. Likewise, they take relatively small prey relative to their size and tapirs indeed fell outside of their preferred prey across their range. Jaguars were the only pantherines to have survived the Quarternary extinctions, and the only very large big cat to survive. Why is this? While other big cats specialized in hunting megafauna that was quickly disappearing, the jaguar was able to adapt its diet to feeding on a variety of generally smaller prey, and correspondingly downsize the process -- which implies it was less specialized in these large herbivores to begin with. Afterall, South America lost ~87% of its megafauna, much more than any other region aside from the Sahul (Australasia). If the jaguar depended greatly upon it, it should have gone extinct. Perhaps the jaguar specialized less in large mammals because unlike on other continents, ungulata weren't as dominant and notoungulates and xenarthrans were present as well, and so because there were more forms, specialization was less advantageous..? Only a theory. A good study which supports these claims: https://www.frontiersin.org/articles/10....00148/full
@BlakeW39
That's actually the study I quoted as well. I think we agree for the most part, but again with Tapir it has to do with abundance but obviously they are not an easy task, just like all Boar type animals that can be double the size of the big cat hunting them. But in general, I don't think anything you wrote takes away from Jaguar prey preference. Like you stated, all Big cats prey on animals available, Jaguars not having as many large herbivores as options chose to prey on most abundant large prey available *Caiman and Capybara* But correlating the Jaguars ability to survive the extinction of large mammals in S. America to them not being specialized in hunting large herbivores seems to be misleading. All big cats have adapted to the prey available and they show morphological differences from that. Lastly, while I agree that Cattle should be classified in it's own category, this doesn't change the fact that Jaguars prey on them often when available and this shows that Jaguars prefer larger prey when abundant. If this has to do with cattle being more docile than other animals is up for debate. But any bovine of that size can be dangerous to it's attacker, arguably more dangerous than a Tapir IMO.
@Pckts ,
I didn't catch the study you quotes haha. Well, the study we've both reviewed takes into consideration over 3,000 jaguar kills; of this >3,000, it is found that all species of tapir were significantly avoided, with lowland tapir being very rarely predated on and the baird's tapid not being hunted one single time (out of 3,000). Tapirs are difficult prey -- they are very strong and robust animals -- but are they this difficult? I'd think not, as tigers for instance are able to reliably take on prey up to 4-5x their body mass, whereas a female tapir is only 1.3x the size of a jaguar. It's very clear to me that jaguars not predating on tapirs is not an issue of abundance, as they overlap in a number of spots all across the respective ranges of both animals, but rather it is very clear that tapirs are avoided prey. We must remember that the jaguar was not always an apex carnivore, but in the Pleistocene likely often was a mesocarnivore. This could explain their diet, as them being more akin to a leopard or puma in many cases than to a tiger. Jaguars, as we have established, have unusually diverse and generalized diets compared to the other big cats. Jaguars in the past likely would have taken larger prey, but they weren't dependent upon it -- if they were, they would not have survived. It's apparent that the other big cats of the Pleistocene Americas (aside from the puma) were dependent on larger prey, and as their prey died out, so did they. Jaguars were able to adapt to the Holocene because they didn't rely so much on the prey that was lost. I don't think it's at all misleading to say this. Also, while livestock are large, they lack defenaive capabilities similar to their wild counterparts, not even just physically, but that they lack the appropriate response to predators which a wild prey animal would have. |
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