Your comments are true to a point, but highly oversimplified. Predators kill commonly kill other predatory species out of instinct.
I wasn't speaking of just the Florida ecosystem when I mentioned larger predators displacing smaller ones. I was talking of most of the middle latitudes of N.A. The prey of all predators I mentioned overlaps at least one step up and down the chain:
-Foxes, bobcats, and coyotes all prey on rabbit sized prey as well as birds so they compete with each other.
-Bobcats, cougars, coyotes, and wolves all prey on deer sized animals so they compete with each other.
-Cougars, bear, and wolves all prey on elk sized animals so they compete with each other.
I was completely ignoring fighting over carcasses. They simply kill each other on sight if they have the advantage; with the exception of bears. Bears do need a little provocation and in turn, not many other of the others are bold enough to provoke a bear.
I really can't speak for North America, as I don't know the specifics. Also I can't really speak for situations complicated by the action of humans or on the specific instances you know of, of one predator species killing another.
I can only speak generally because I only studied speciation and evolution generally.
At a gross oversimplification - but still relevant.
Imagine an island, it is 100 square miles of identical ecosystem.
Now imagine looking at 10 square miles of that ecosystem.
What is often found is a variation of the following, going from top to bottom, from Apex predator down through the heirarchy to prey species.
1 x A predator.
10 x B predator.
100 x C predator/prey.
1000 x D prey.
10,000 x E prey.
The actual numbers aren't important and neither are the number of levels in the system or the specific interactions.
The important thing to note is that the relative numbers of each species will be the same over the entire island and over time.
Generally we have reached a stable system with how many of each species are sustainable at each level.
This is because each species has a particular ecological niche, they are not in 'direct competition' as I mean it because although the two main predator species may hunt prey species D there are more than enough of prey species D to sustain both predator species. This has to be true because if there weren't then whichever species was best would survive and the predator species that was worse would not, or the prey species would go extinct (closely followed by the two predator species)
Obviously in a real situation there would be other interactions.
Predator A's diet may be 1% predator B, 9% predator/prey C, 70% prey D and 20% prey E.
Predator B's diet may be 5% predator C 25% prey D and 70% prey E.
Predator A will mainly hunt prey D, but will take other species as and when they become available.
Predator B will mainly hunt prey E, but will take other species if they can.
Also obviously the actual system is dynamic and can become infinitely more complex.
In the short term there can be fluctuations in numbers at particular levels that will have knock on effects on other levels. But because the system is stable these are only fluctuations and the system will end up becoming balanced once again.
What I've said can be taken as true for ecosystems in general. Unfortunately in real life things are often complicated by the actions of man.
Man can end up arbitrarily changing the numbers of different species or the ecosystem itself which can cause the system to be unbalanced or even fail.
(The video about wolves in yellowstone is a great example.)
Again I can't comment on specifics you know about or have witnessed but what you have termed 'displacement' is in my mind far more likely to be caused through 'unnatural' external pressures on the system by man. Or perhaps more likely is one of the mechanisms by which the stable system is maintained.
That is when you have seen (or know of) a predator species killing another it is in response to local and short term changes.
From the grossly oversimplified example above if Predator B species has a particularly good year and there are now 20 individuals in a particular 10 square miles then they are going to come into more contact with Predator species A. Therefore the natural instinct of predator A kicks in and it kills predator B individuals when it comes across them. Soon the number of predator B approaches 10, predator A no longer comes into contact with predator B and so the populations remain stable.
Anyway I hope I have explained myself more clearly. I don't think you're wrong and am not trying to discount what you've said.
In fact I think we're just looking at the system from two different vantage points, myself from the general from text books and lectures, whereas you clearly have a lot more experience of the specifics in real time on the ground. Obviously I make assumptions to simplify the system so I can better understand it and come at it from a completely different perspective to yourself.
