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I'm watching Shark Week—of course—and my ear just snagged on a term I've heard a lot in the past few decades. Great White sharks are, I'm told, "opportunistic feeders", and therefore they'll adjust their tactics in order to take advantage of different kinds of prey available.
Now for the first time I pause to wonder: If "opportunistic" means that it'll eat anything that comes along (anything within its range, of course; a shark won't eat plants and a bear won't eat rocks), then by that definition what isn't an opportunistic feeder? Does the word mean anything useful? This is a complaint only if the answer is No; if I'm misunderstanding something then it's a real question.
My guess of what it means:
Lions theoretically could eat grass and plants to supplement their protein needs, but they don't. Bears, on the other hand look out for opportunities to survive on berries, roots, honey, etc, besides fish and meat.
White sharks, though strictly carnivorous, develop specialized tactics to catch different sea and land animals. Their opposite number would be whales that only open up and take in whatever plankton and small fishes that come along.
So opportunistic means looking out for a wide range of food sources.
One misunderstanding could be this: hyenas singling out the weak or sick individuals in a herd, which can be called opportunistic too, but not in the sense of 'opportunistic feeder.'
That's my best guess, claiming no authority at all.
"The fox knows many things, but the hedgehog knows one big thing."
An opportunistic feeder is an animal that is a generalist, when it comes to eating. Many animals specialize, creating a smaller niche for themselves, but one with less competition.
Bears and raccoons are good examples of opportunistic feeders--they will eat many varieties of foods, and they have many skills for discovering or acquiring those foods. They eat whatever they find, wherever they may find it. They are not picky. Plants, animals, whatever--if they can digest it, they will most certainly try to. Super bright creatures--they can open anything anywhere if there's food involved.
Pandas--which are closely related to both bears and raccoons--are NOT opportunistic feeders. They eat bamboo. They eat lots of bamboo. They are very good at stripping the tasty shoots right out of the bamboo. They are the undisputed kings of bamboo-eating.
They suck at every other kind of foraging.
I can buy this narrower version of "opportunistic", but maybe there are better examples. A bear is, simply, an omnivore; this is not a statement about his habits, but of his digestion, ie what he's capable of eating. A raccoon, the same. A shark is a meat eater, even I suppose such as the basking and Greenland sharks. A panda eats only bamboo because that's all he can eat. (Or am I mistaken? Maybe I've just been assuming all this time.)
If "opportunistic" means only that an organism is capable of digesting a relatively large variety of items....Well, that doesn't seem to be the sense in which it's used. My impression is that when these folks use the term, they mean the beast eats whatever it happens across (so long, as always, that it's within the range of what it can digest). If a koala can eat other vegetation beside eucalyptus leaves, then it would not be opportunistic in this sense. But can it? Can anyone name an animal that can eat a wide variety of foods but chooses to eat only a few of them?
Cattles feeds are mixtures that include bones, meat, and just about **anything**
You never know that lions do not have omnivorous stomach like cattles.
Is human an 'opportunistic feeder'? Not the modern one, who mostly simply takes whatever plastics and tins available in the supper market.
You are confusing physiology with behavior.
"Herbivore" and "Carnivore" (and similar words) are about what foods an animal can digest.
"Opportunism" and "Specialism" are about what behaviors an animal is capable of--and therefore what foods an animal can acquire.
An opportunist is able to take advantage of a wide variety of food sources. Its behavior is flexible. Although pandas mostly eat bamboo, they are physically capable of eating other things, including meat. But they aren't behaviorally capable of adapting to rapidly changing food availability. They don't know how to hunt. They don't know how to forage for anything but bamboo. They get lucky and stumble across other stuff sometimes. Black bears, however, routinely forage for a wide variety of foods, using a wide variety of foraging behaviors.
Let's look at another example: raptors. All raptors have specific physical adaptations--such as talons--for hunting live prey. They all must eat meat. But their behavior is radically different.
A red-tailed hawk patrols the sky, looking for any small mammal, lizard, large insect, frog--whatever animal it can find, wherever it can find it, and can adapt its behavior according to what is available. It looks in more places for more things. It is behaviorally capable of taking advantage of abundance in whatever form it finds it. This is opportunism.
An osprey MUST dive for fish. A peregrine MUST impact other flying birds and knock them unconscious out of the sky. These two raptors are specialists and cannot use other behaviors in hunting. Their skills are specialized and limited; therefore, they can only take advantage of a few prey species. They're very good at those tasks, but unable to adapt to other food sources. Put a lizard on a rock in front of either of these animals, and neither would know how to hunt it, though either one could digest it.
EmmettRedd said
I do not eat liver. And, since 1973-4, I do not eat much chicken. I do not eat pretzels. I also do not risk the stomache chocolate might cause.Some snakes will go for months (I am sure they are passing up opportunities) after a large meal.
Emmett
Emmet was saying that he passes up many foods that he is capable of eating and using for nourishment so to answer your original question, Bob, "What isn't an opportunistic feeder?" Emmet isn't.
Bob Bridges said
You have the advantage of me: You understood my question, but I don't yet understand the answer. Do you mean that "opportunistic feeder" does, or does not, mean something other than "feeder"?
Dick got it. The snake and I are both predators (from your question in the topic title) but will pass on 'opportunities'.
Emmett
BTW, horses are herbivores which are opportunistic. They will eat so much of a feed nutritionally higher than grass that they will founder.
Correct me if I'm wrong, but cattle wouldn't eat meat products and bone unless we tricked them into it. If that is the case, such are not part of their natural diet even under extreme circumstances. When grass becomes sparse, cows don't start feeding on each other: man brought it about for cows to be cannibalistic.
Perhaps it is less confusing when the discussion is restricted to the diets that would occur in nature under both common and extreme circumstances.
Again--opportunism is not about diet. It is about behavior.
When an animal is perfectly capable of eating something, physiologically, but it does not because it lacks the behaviors necessary to acquire it, that is specialism.
When an animal has a broad range of behaviors for acquiring food, and displays flexibility in its behavior so that it can adapt to rapidly changing conditions, that is opportunism.
Has not one thing to do with meat vs. plants, or common vs. extreme circumstances. It only refers to adaptability of feeding behavior.
Here's an example among humans:
George eats hamburgers every day for lunch.
George eats hamburgers every day for dinner.
George is physiologically capable of eating other foods, but he has a thing for hamburgers.
Even when pizza is on sale, he still eats only hamburgers.
He is unwilling to change his behavior to adapt to the weekly sales. He has his routine, and that's what he does.
It saves him time at the store because his shopping list is so specific.
George is a specialist.
Harry goes to the grocery store and buys whatever is on sale that week.
This week grapes and ham are on sale, so he buys grapes and ham.
Last week oranges and frozen pizzas were on sale, so he bought oranges and frozen pizzas.
Next week apples and fish sticks will be on sale, so he will buy apples and fish sticks.
It takes Harry longer to shop, but he saves money.
Harry also has a backyard garden and grows some of his own foods.
He also attends pot lucks and shares his bounty with others, enjoying what they offer in return.
Harry also visits the bakery sometimes for day-old bread. He gets a lot of it at a great price.
He adapts to changing availability, and he always has his eye open for a bargain.
Harry is a generalist.
Harry and George are both capable of eating the same foods, but their behaviors are radically different. George is efficient and can find his food quickly. Harry is not as efficient, but he is just fine when the store runs out of ground beef. George goes hungry when the store runs out of ground beef.
George is an interesting character but a bit out of this world, and not only on account of his feeding habit, because who in America shops for burgers in a store, and uses shopping list too? Some Walmarts have a McDonald concession, but people just grab a burger there, not shop. But George would be truly out of this world if he as said to do will bear going hungry if burgers run out.
In any case individuals do not seem to inspire insights into behavior of whole species, least of all humans, weird creatures practically aliens on this earth.
Glenn said
"
...
When an animal has a broad range of behaviors for acquiring food, and displays flexibility in its behavior so that it can adapt to rapidly changing conditions, that is opportunism
...
"I got it. And that is my point. Cows lack the behaviors for acquiring beef for food.
However, cows eat the placenta after giving birth.
That is something this beef loving omnivore will NOT take the opportunity to eat.
Emmett
Emmett, placenta sounds ummy next to other things that cycle round and round the American food chains, opportunistic or no as long as you are urban carnivore:
Just take a look at what's being fed to the animals you eat.
Same Species Meat
Diseased Animals
Feathers, Hair, Skin, Hooves, and Blood
Manure and Other Animal Waste
Plastics
Drugs and Chemicals
Unhealthy Amounts of Grains
RobertB,
I was simply responding with a non-human-forced, natural-cow behavior which did have them eating a beef product.
I have not read your website; its topic seems a little too far off. However, if at least two members request a discussion of how I raise my cattle (including the ones I eat), I will read it and respond (likely in another thread). Members can contact me via personal message (PM in the message header) if they do not want to clutter this thread.
Emmett
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