Manatee v Alligator?

March 8, 2007 12:43 PM

Why don't alligators eat manatees?

It seems like alligators are pretty bad-ass predators, and manatees seem to get pushed around pretty easily. They are slow and do not seem to have many natural defenses, yet there are no known predators in nature besides us. For an alligator (and their habitats seem to overlap, if not match), it seems like manatees would be easy pickings, especially the young ones, and a good source of protein. Resulting in no manatees left.

I have not found a good explanation for this.

posted by Danf to science & nature (25 answers total)

Just a guess - Manatees are big and round, probably well able to defend themselves. Why go after something that big when smaller game is less effort?
posted by Egg Go Boom at 12:51 PM on March 8, 2007

Because Manatees are huge? Even the young ones? My guess is that alligators want to eat things they can get their jaws around. I think the first thing to figure out is "what's the biggest thing an alligator will attack as prey", and compare that to the size of a young manatee.

Also, manatees can swim pretty darn fast when they want to.

Anecdotally (heard from my Belizean snorkel guide on the way to diving with these beasts), manatees can flex their skin when alarmed and make themselves more or less impervious to puncture.
posted by mcstayinskool at 12:54 PM on March 8, 2007

The "manatees are too big for gators to eat" hypothesis seems to be supported by this page, which was the first result when I googled the terms "manatees" and "alligators".
posted by Greg Nog at 12:57 PM on March 8, 2007

Although defenseless, manatees' sheer size is a pretty good defense against gators. They can't chew their food, so they have to eat what they can swallow whole either by gulping it down in its entirety or else by ripping off chunks by violently shaking their head. Manatees are have extremely thick hides (they can be cut by boat propellors and still survive; in fact, I have never seen an adult manatee without shockingly deep propellor scars). It would likely be impossible for a gator to clamp onto its hide and rip anything loose other than perhaps a tail. A newborn baby manatee could conceivably be swallowed whole by an extremely large gator, but even a baby would have such thick skin that it seems like it would be a digestive nightmare. Plus, even the babies are pretty freakin' huge.
posted by gatorae at 1:05 PM on March 8, 2007

But it seems like a baby manatee would be very appealing to a gator. Mind, I am not trying to give anyone ideas, but if an alligator can drag a deer into the water, it could wreak a bunch of other havoc.
posted by Danf at 1:06 PM on March 8, 2007

American alligators are a freshwater species: they would not normally encounter a manatee. American crocodiles are a fresh- and brackish-water species, so I suppose they theoretically might encounter one another, but I bet not often; they also mainly predate on fish, so a manatee is, well, outside the search pattern. And big. Not recognized as food, in other words.
posted by mcwetboy at 1:18 PM on March 8, 2007

From the Mythbusters episode it seemed that Alligators are not very bad ass predators (they could barely get one to chase them). Alligators tended to sit around and wait to ambush it's prey.

Between that and the manatee's size I'd say it's just too much damn work for a gator to try to take down.
posted by bitdamaged at 1:21 PM on March 8, 2007

Some alligator attacks on manatees reported here, and manatee calves are at risk from alligators. Personally, I think the largest factor is that their habitats don't overlap as much as you think -- even when they're in the same area, manatees prefer saltier, deeper water than the alligator, which probably is a poor predator in open water.
posted by dhartung at 1:34 PM on March 8, 2007

The only thing I read was that "alligators don't eat manatees; the lummoxes are just too thick for their jaws"
posted by coryjojobob at 1:38 PM on March 8, 2007

McWetboy, many (if not most) manatees spend all winter in freshwater rivers and springheads. Additionally, alligators are common sights in brackish and salty estuaries and tidal rivers, as well as the Intercoastal Waterway and even occasionally the beach.
posted by saladin at 1:41 PM on March 8, 2007

A different point: alligators don't eat all that often. 6 or 7 big kills (or 20 small kills) per year is plenty. (Big snakes are the same way: an anaconda can get by just fine on one monkey or large parrot per month.)
posted by Steven C. Den Beste at 2:27 PM on March 8, 2007

gatorae says: They can't chew their food, so they have to eat what they can swallow whole either by gulping it down in its entirety or else by ripping off chunks by violently shaking their head.

I've heard that when gators/crocs grab something big like a person or a deer, once they do the barrel rolls and drown it they like to wedge it someplace underwater so it can rot and become easy to rip chunks off of.

Don't see why they can't do this with a manatee. Maybe manatees are good at holding their breaths and the croc gives up on trying to drown it.
posted by MonkeySaltedNuts at 3:55 PM on March 8, 2007

Try taking a bit out of a watermelon.
posted by monju_bosatsu at 4:04 PM on March 8, 2007

It's not that alligators don't try to off a manatee now and again. It's just that it's so damn easy to sit and wait several hours for a duck to wander by.

Alligators are cold-blooded, so they're not going to get all worked up and motivated to go after a large mammal with an even larger parent nearby. No, just sit. And wait. And wait some more. Low metabolism. Low caloric needs. Wait for it. Wait. Waaaait. Duck! SNATCH! Dinner! Yum.

Wait. Wait. Waaaait...
posted by frogan at 7:00 PM on March 8, 2007 [1 favorite]

Pretty weird you brought that up, cuz if my memory is correct, Crocodiles don't eat cute baby hippos. Those adorable big-nosed sancks just hang around, rolling on, and even tugging the tails of the crocs. I think I saw an animal planet show that showed baby hippos even teething on the annoyed but unresponsive crocs. Probably because said crocs don't want a wuppin' from momma hippo.

Ok, not an answer, and no link, but perhaps within the African counterpart to the Alligator/ manatee situation lies your answer. Good luck.
posted by conch soup at 8:51 PM on March 8, 2007

It's just that it's so damn easy to sit and wait several hours for a duck to wander by.

...or several weeks. Because they don't need to eat very often, they don't actively hunt. They lurk, and wait for prey to come to them, even if it takes weeks.

A full-grown Nile crocodile can, if absolutely necessary, survive for three years without eating.
posted by Steven C. Den Beste at 6:40 AM on March 9, 2007

Maybe manatees are good at holding their breaths and the croc gives up on trying to drown it.

Some quick googling brought up many references saying that manatees typically come up for air every 3-5 minutes, but can hold their breath for 20 minutes or more if necessary. I would imagine that even 3-5 minutes of death-rolling would be a lot of work for an alligator trying to drown something as big as (even a baby) manatee. So yeah, like others said, the effort just isn't worth it when there are easier meals available.
posted by vytae at 7:16 AM on March 9, 2007

Well, I guess the real question is, How long can an alligator (and Crocodile for curiosity) do a death roll? Some sites seem to imply that it can go on quite long, which to me would seem to make the baby manatees very appropriate prey. I'd bet a baby manatee's ability to hold it's breath is significantly less than the adult 3-5 with a max of 20 minutes. And the disorientation of a death rolll would probably be very exhausting, so I don't think time is that big a factor, even with alligators'/ crocs' slow metabolism. Those guys can go like 30mph when they have to.

Gosh, I'm getting hungry.
posted by conch soup at 9:51 AM on March 9, 2007

Those guys can go like 30mph when they have to.

But they can't sustain it.

The 100 meter dash is different from any other running event because it's so short. The runners breath hard while they're running, but in fact all the energy they're using is anaerobic. The race lasts 9 seconds, maybe, and it takes longer than that for the runner's aerobic metabolism to kick in, and increased oxygen flow to reach the relevant muscle cells.

The first step breakdown of glucose doesn't require oxygen in order to produce ATP. The rest of the steps in the Citric Acid cycle do require oxygen, but it's that first step which is used to power sudden bursts of activity, including sprinting in humans.

And that's how it is in crocs, too. They are capable of sudden bursts of great activity, but unlike us their systems cannot deliver oxygen to their tissues at high enough rates to sustain high level activity for long periods of time. It's because their hearts and lungs are different than ours.

By the way, the ability of crocodilians (and snakes and tortoises) to survive for very long periods of time on almost no food is almost certainly the reason why they came through the Cretaceous-Tertiary catastrophe so well. Since they rely so heavily on solar power, the multi-month cloud cover after the asteroid strike would have left them torpid that entire time, reducing their food requirement even further.
posted by Steven C. Den Beste at 12:51 PM on March 9, 2007

True True- the 30mph thing is only burst speed. Still, can a baby manatee hold it's breath longer than an alligator can death roll? There's a celebrity death match or great youtube post in here somewhere.

no baby manatees were harmed in the answering of this askmefi thread
posted by conch soup at 2:52 PM on March 9, 2007

conch soup: Crocodiles don't eat cute baby hippos.

Mama hippos can easily fit their jaws around a croc and kill it.
posted by MonkeySaltedNuts at 9:56 AM on March 10, 2007

We're wandering rather wide of the mark here, but hippos are extremely dangerous. Hippos kill more people in Africa per year than any other wild animal, including lions and crocs.
posted by Steven C. Den Beste at 1:23 PM on March 10, 2007

Steven C. Den Beste: Hippos kill more people in Africa per year than any other wild animal

That claim may be a jungle legend. This Smithsonian article says:

Although accurate numbers are hard to come by, lore has it that hippos kill more people each year than lions, elephants, leopards, buffaloes and rhinos combined.

Anyway I think a main reason hippos have such enormous tusks (up to 1.5 feet) is for killing crocs that bother them and their offspring. Manatees seem to have no aggressive defence against gators/crocs so maybe their main defense is holding their breath and waiting for the reptile to give up on drowning them.

And as long as we are pointing out trivia, I would like to note that manatees/dugongs are very closely related to elephants while whales are very closely related to hippos.
posted by MonkeySaltedNuts at 11:27 PM on March 11, 2007 [1 favorite]

Wow. 23 comments, and an interesting discussion over three days, and yet I'm not sure there's actually an answer in here. The alligator-manatee-crocodile-hippos-whale-elephant thread that wouldn't die.
posted by conch soup at 11:57 PM on March 11, 2007

Anyway I think a main reason hippos have such enormous tusks ...

...is for fighting other hippos in territoriality and mating disputes.
posted by frogan at 9:46 AM on March 12, 2007