So I was talking to my wife about the whole sperm whale vs. giant squid thing, and I got to wondering: if the sperm whale population has been drastically culled by centuries of whaling, doesn’t that mean that the giant squid population will go up? (I’m assuming that the whales are the only predators of the giant squid.)
Is my reasoning correct?
-Ben
I’m not sure whales eat anything that big on a regular basis, from what I understand they mostly eat plankton and heards of fish in big gulps.
— G. Raven
According to the Discovery Channel’s home page here, it does seem you are correct. The sightings/findings of giant squid does seem to be somewhat on the rise.
Roughly 200 have turned up over the past century stranded on beaches, and they are common enough that in 30
separate incidents over the past 10 years giant squid have come to the surface in deep-water fishing nets.
If those pesky buggers would pop up to the surface more often, we could properly conduct a census.
Your reasoning is correct for the predator to prey part; however there are many other factors that could contribute to an animals abundance. First, are the stocks of the squid’s food still strong, or have they been fished out too? There are also long-term cycles in ocean temperatures/currents and other qualities that do affect reproductive and survial rates of sea-creatures (coho salmon on the west coast are a good example of this). Conditions have to be good to grow baby giant squid too. We know pathetically little about giant squid life-histories, so it would be difficult to determine what the population is doing. Are sightings on the rise now that there are more people out on the water looking and fishing deeper and further out? Hard to say…
So what the heck do giant squid eat?
Aside from unwary sailors, of course. 
Morrison’s Lament, while most of the large whales feed on plankton and small fish, the Sperm Whale feeds on giant squid. Exclusively so, I believe. In fact, I seem to recall that ambergris, the waxy substance for which sperm whales were once hunted (and which is used in the making of perfume, of all things), is the digestive remant of the beaks of the squid. I may be wrong about that detail.
AFAIK, sperm whales don’t seem to be able to digest the beaks, spoke-. At least, according to the National Geographic special on giant squids and sperm whales I watched the other night on PBS. They were always finding a bunch of squid beaks in the stomachs of these whales. I guess that doesn’t mean that they can digest some beaks, or that it doesn’t take a long time.
As far as what giant squid eat, I have no clue, but if they’re anything like other squid, which I assume they are, they eat at least fish, and each other.
A good read on the giant squid is Richard Ellis’ “The Search for the Giant Squid” (Penguin Books, 1998).
Not much is known about their [giant squid] diet, but smaller squids eat just about anything they can, including (in one report) garbage from ships; plant material like bannanas were found in squid stomachs).
According to Ellis’ book, most giant squids have been so battered and decomposed by the time they’re found that the stomach contents were hardly indentifiable. One report from 1969 identified a parasite in squid muscle whose natural hosts are bony fishes and sharks. Pretty general. But in 1995, 3 male squids found off Ireland were found to have the “remains of various fishes, prawns, octopuses, and other squids” in their stomachs (pps. 40-41).
Clyde Roper of the Smithsonian is the leading researcher; one could look in his recent published articles to find something more definitive if there’ve been new findings.
Actually ‘Spoke’ Sperm Whales do not eat the giant squid exclusively, as a matter of fact they eat regular sized fish and squid. The Sperm Whale belongs to the Subfamily Physeterinae. The commonly catch their food by blowing air-bubbles in huge circles around school fish, and they in turn swim up the middle of the “circle of bubbles” and start eating. The Giant squid would most likely be their “treat” if you will. The common diet of Sperm Whales consists of ocopus, cod, rock fish, skates, angler fish, and most varieties of eels. They do eat a lot of Squid, and the beaks that are being found in their stomachs and intestinal tracks are not just one huge beak from a giant squid, but many small beaks and undigestable calcium by-products.
Sperm Whales belong to a group of predatory cetaceans. They are hunters. And I do not think that an animal of that size could live solely on one form of food source. Granted Blue whales live off mostly krill, but krill are found in schools of millions upon millions, they are in no short demand.
As for the Giant squid, I think that their populations may or may not be on the rise, but then again we may be finding more and more of them because we have been fishing deeper and deeper than we ever had in the past.
I’ve heard of humpbacks using the circle of bubbles trick to concentrate and catch krill, but I’ve never heard of sperm whales using it. Mostly, they do eat squid (according to various reference sources), although not necessarily all giant squid; they do eat various fish as well, including the occasional shark.
From the Columbia Encyclopedia:
Kind of like a cross between pearls and whale puke.
It is my understanding (please correct me if I am wrong) that the sperm whale population was never depleted as much as other species such as the blue whale and humpbacked whales. It was also my understanding that sperm whales had staged a pretty vigorous comeback in the last decade. (I am not trying to support whaling or anything like that, just suggesting that the population of sperm whales may never have been depleted to the point where the giant squid went hog wild).
I haven’t found any numbers on humpback/blue versus sperm whale depletion, but I did find some staggering info on sperm whales alone. Taken from this site
*Although most often associated with the harvest that occurred in the days of wooden sailing ships before the
turn of the century, the sperm whale endured even greater whaling pressure from the 1950s to the 1980s,
when modern factory ships removed over 200,000 whales from the ocean between Hawaii and the North
American west coast. Sperm whales were listed as endangered under the federal Endangered Species Act
in 1972. * The sperm whale population itself is estimated today at anywhere between 200,000 and 2,000,000 as opposed to pre-whaling estimates of about 2,459,00 (this from a lot of sperm whale sites-to numerous to mention). They do indeed seem to be back on the rise, but it seems the problem was most whalers went after adult male sperm whales for purely economic reasons (they’re bigger). Also, almost no cultures actually eat the meat of sperm whales they were primarily hunted for spermaceti and ambergris, which is damned shame. This site has oodles of info on what sperm whales were hunted for. According to this site, “Southern hemisphere ‘Division 5’ animals (90–130°E, i.e. including animals caught off Albany, WA)estimated, in 1980, to have declined by 91% (males >20 years) and 26% (females >13 years) between 1947 (taken as the start of major 20th century sperm whaling) and 1979. Concerns over excessive reduction of breeding males were a contributing factor to cessation of whaling in 1978.”
Sorry for the history lesson, but it’s a crying shame that our/my (whatever you deem to call them,) hunted these creatures for lubricant, perfume, oil and lotions. And targeted the bull males, almost assuring the demise of this magestic beast. I’m going to bow out and return to my previously scheduled drinking now, rather than search humpbacks, right’s or blue whales and suffer more heartbreak.