It’s summertime and you’re sweating from the heat and humidity. You jump in the pool and feel a rush of relief as you suddenly feel cooler. The water might not be colder than the air, but it sure feels like it, and it does a great job of relieving you from the heat. We’re all familiar with this, but did you know it may also explain why whales are so big?

Almost 4 years ago, I began my PhD studies at Stanford University. I was interested in how changes in the environment impact biodiversity through time. I first decided to tackle the question of how transitions from land to water impact body size. Mammals are a well-studied group of animals, and they’ve made this transition multiple independent times. There’s also lots of data on their body size, of species in the modern and the fossil record, so they seemed like a great place to start to answer this question. The original goal was just to test whether aquatic mammals are bigger than we expect by chance, but I was really surprised by what we discovered about the drivers of their evolution.

We did (unsurprisingly) find that aquatic mammals are bigger than expected, but also noticed that, despite each group of aquatic mammals evolving from differently sized terrestrial ancestors, they all evolved to the same size of about 500 kg! Even stranger, we found that aquatic mammals are much more constrained in their body size than their terrestrial counterparts! This goes against almost all the reasons why people believe aquatic mammals are big. Once you’re in the water, the idea goes, you should be able to get as big as you want without being hindered by the limitations of gravity and food shortages. Rather, we found that aquatic mammals must get bigger.

After hitting the books, I was shocked that I was able to develop a simple mathematical model that explained the minimum, maximum, and average sizes that we were seeing in aquatic mammals. The minimum constraint in the model shows that these mammals need to produce more energy in their bodies and lose less of that energy, relatively speaking, to the water, to have any energy left over for reproduction and growth. Otters are the one exception to this trend: we’re thinking that this is because they only spend part of their lives in the water or are more efficient at conserving their body heat with their thick fur, although we haven’t been able to test either of those hypotheses yet.

Through developing the model, I also discovered that there’s a maximum limitation on size too. At a certain point, aquatic mammals just can’t eat enough food, no matter how much there is, to sustain larger sizes. For toothed mammals, it appears that this maximum is about the size of a sperm whale. However, baleen whales have figured out a way to eat more efficiently than their toothed cousins, in which they filter entire schools of krill at once from large gulps of water. This feeding strategy seems to allow them to exceed this maximum limit and achieve superwhale sizes.

Long story short, if you want to be a mammal and live in the water for your entire life, you need to get a lot bigger, but you also need to be careful, because you can’t get too much bigger. It’s a tricky balance that aquatic mammals have amazingly mastered at least three times! I’ll stick to my occasional dips in the pool, thank you very much!

The post So, You Want to Live in the Water? A Tale of Why Aquatic Mammals are So Big first appeared on Deep Sea News.

I am reminded that with great repetition, scientists have found in areas of land and ocean with more oxygen, animals are larger.  In 2001, my Ph.D. advisor Mike Rex and I found that snails in the deep ocean were much larger in parts of the abyss where oxygen was higher.  In one species, one of my favorite deep-sea snails (yes I have a favorite deep-sea snail) Benthomangelia antonia, size doubled across the Atlantic Ocean due to a relatively small increase in oxygen concentration.  A couple of years earlier, the duo of Chapelle and Peck compared 1,853 species of amphipods crustaceans from the poles to equator in both marine and freshwater areas.  They too found when there was more oxygen animals were bigger.  Alligators, fruit flies, domestic chickens, trout, rats, red-bellied turtles, mealworms, and garter snakes, when grown in low oxygen environments obtain smaller sizes.  Even humans living in lower oxygen concentrations at higher elevations, as seen in the high altitude dwelling Peruvians and Tibetans, reach smaller adult sizes.

This pattern of large animals in higher oxygen regions and vice versa also translates across the history of life as well.  Animals were larger during geologic times when oxygen concentrations were greater.  Enter the massive dragonflies of the genus Meganeura that occurred during the Carboniferous, approximately 300 million years ago.  With wingspans of up to 65 centimeters (25.6 inches), Meganeura was one of the larges known flying insects to have lived on Earth.  Their existence and large sizes occurs during a time with atmospheric oxygen was at high.  This high oxygen era led to a lot more than just large dragonflies.  The land and oceans were teeming with giants ranging from arthropods, bryozoans, urchins, brachiopods, and corals. Moreover, the sizes of the largest arthropods, mollusks, and chordates all decline from the Carboniferous to the lower oxygen Permian.

In 2009, my friend and colleague Jon Payne at Stanford university lead a team (myself included) documenting changes in the maximum size of life throughout the history of life (see above plot).  During this 3.5 billion year span, life increased over 16 orders of magnitude in body size.  However, a great majority of this increase occurred in two discrete steps one at 1.9 billion years ago and the second approximately 0.5 billion years.  The steps corresponded with evolution from prokaryotic to eukaryotic cells and from single cell to multicelluar organisms.  Most interestingly, these steps also coincide, or slightly postdate, major increase of oxygen in the atmosphere.  Major shifts in size and the complexity of life appears to have required more oxygen.

But why this pattern?  Simply, cells require oxygen to make cellular energy in the form of ATP.  The more cells that come with bigger body sizes require even larger quantities of oxygen.  But the whole story is more complicated than just this.  Oxygen uptake by an organism is limited by the amount of surface area available for diffusion whether it be the surface area of the gills, lungs, or body surface.  But how much oxygen an organism needs is governed by its mass.  With increasing size, mass increases quicker than surface area, thus demand increases more quickly than supply.  For any given shape there will be a critical size in which oxygen cannot supply demand.  This constraint is exacerbated by low oxygen concentrations.  This is also why gills and lungs have evolved to increase their surface areas through branching, invagination, and folding.

Despite my continued frustration with this whole scuba scenario, I try to remember I am simply the modern day equivalent of the massive dragonflies of the Carboniferous. We are creatures bound by physics and biology.

The post I’m the modern day equivalent of a massive Carboniferous dragonfly first appeared on Deep Sea News.

I am not sure when this obsession with both small and large things began. One of the earliest photographs of me is in a giant rocking chair. With a big smile on my face, I am dwarfed by the colossal piece of furniture. Sadly, in researching this post I discovered this rocking chair is not the largest. That title is bestowed to a towering rocking chair, a 56.5 feet tall behemoth in Casey, Illinois, not only the world’s largest rocking chair but also the largest chair in all of America. I will of course need to visit, and photograph, myself next to the massive chair. Another photograph to add to my photo collection of myself with oversized objects. The world’s largest Adirondack chair and me…got it. Largest chest of drawers…done. Largest frying pan…visited. Giant 6-foot tall cheese grater…photographed and almost bought. I could go on and on.

I never realized I could get paid for my obsession. I did not at some point in high school realize or declare I wanted a vocation focused on extreme sizes. Nor was such a trajectory flagged as a possibility on those mandated vocational tests. I got flagged for being perfect for cake decorating. No joke. Nothing about decorating tiny or giant cakes. Of course, who would even think you could make a career out of a passion for size, except maybe Guinness World Records? No, I came by it all by accident.

As an undergraduate, I applied for a summer program to conduct research with a biologist. Knowing at the time I wanted to be a marine biologist, I applied to do summer research counting fish on the coral reefs of St. Croix. An unshockingly, popular choice among undergraduates, I did not get the position. My second and third choices were the only other ocean-based projects in the program. When the scientist involved with my second choice project called to invite me to work with him that summer, I didn’t even remember what the project was. I wasn’t really concerned with the specifics of the other projects because how could I not be selected for my first choice, St. Croix, dream project. Opposed to the beautiful tropical beaches of the Caribbean, my destiny would be to work in a windowless lab all summer in Boston. The project didn’t exceedingly interest me at the time as I wanted to be a field scientist and microscopy in the lab sounded…well dull. But working in an air-conditioned lab in the big city sounded better than living with my parents in rural Arkansas working in the intense Southern heat sweating in a factory. So off to Boston I went. Within a few hours of the first day, I fell in love with the project. So much so I asked that scientist, a preeminent deep-sea biologist and expert on the body size of marine invertebrates, if I could pursue a doctorate with him.

In the biological world, size is more than a novelty. How an organism relates to the world around it is determined by its size, and understanding what influences size is key to understanding the diversity of life itself.  That summer I measured the size of 100’s of tiny snails and when I returned to pursue my Ph.D. I measured thousands more. In total I measured 14,278 deep-sea snails. The largest no bigger than Abraham Lincoln’s head on the face of the penny. The smallest the size of his nose. Those snails I measured were collected from off the coast of New England from depths of over 600 feet to well over 18,000 feet, from the shallows of the New England continental shelf to the abyssal plains.

Why would anyone measure close to 15,000 snails? In the late 1800’s Henry Nottidge Mosely wrote: “Some animals appear to be dwarfed by deep- sea conditions.” By the 1970s, Hjalmar Thiel of Universität Hamburg observed that the deep sea is a “small organism habitat.” Increased depth typically translates into less food in the oceans with the deep-sea being a very food poor environment. As you might expect this has profound effects on the body size of deep-sea animals. Thiel’s seminal 1975 work demonstrated that with increased depth, smaller organisms became more dominant. At depths greater than 4 kilometers on the vast abyssal plains where food is extremely limited, you find some of the most diminutive sizes. In a particularly striking example of this, my doctoral advisor Michael Rex and I calculated those nearly 15,000 deep-sea snails I measured could fit completely inside a single Busycon carica, a fist-sized New England knobbed whelk found along the coast. But by measuring all those snails, Mike and I were able to document exactly how size in these snails changes over a 3.5 mile increase in depth. That study was the first of its kind and remains the largest number of deep-sea animals ever individually measured.

But to say that all creatures of the deep are miniaturized overlooks the complexity of size evolution in the deep sea. Some taxa actually become giants. The Giant Isopod, a roly-poly the size of very large men’s shoe, and sea-spiders the size of dinner plates, quickly dispel the Lilliputian view of the deep sea. Although all those deep-sea snails are smaller than their shallow-water relatives, shockingly Mike and I also found that they actually increase in size with greater depth and presumed lower food availability. To further confound the situation, other scientists have reported the exact opposite pattern in other types of snails, whose size decreases with depth. The same appeared to be true in other taxa, such as crustaceans. How can the deep-sea be both a habitat of dwarfs and giants?

To answer that, I turned from the Earth’s largest habitat to one of its smallest—islands. On islands both giants and dwarfs exist. The diminished kiwi and the enormous Moa of New Zealand, the colossal Komodo dragon on the island of Komodo, the extinct pygmy elephants on the islands of the Mediterranean, the ant-sized frog of the Seychelles, the giant hissing cockroach of Madagascar and the giant tortoise of the Galapagos represent just a few of the multitudes of size extremes on islands. In 1964, J. Bristol Foster of the University of East Africa demonstrated that large mammals became miniaturized over time on islands. Conversely, small mammals tended toward gigantism. This occurs with such frequency that scientists refer to it as “Foster’s rule” or the “Island rule.” Big animals getting small and small animals getting large.

My colleagues and I discovered a similar pattern in 2006 between shallow and deep seas. As shallow-water gastropods evolved into deep-sea dwellers, small species became larger and large species became smaller. Interestingly, size did not shift in a parallel manner. Larger taxa became disproportionately smaller sized—that is, both converged on a size somewhat smaller than medium. I’ve since observed this pattern in radically different taxa, such as bivalves, sharks, and cephalopods.

The fact that islands and the deep sea have so little in common represents a wonderful opportunity that allows elimination of several hypotheses. Of course, what the deep sea lacks is food. The absence of sunlight precludes plants.   Thus, for the majority of organisms living there, the food chain starts with plankton, dead organisms and other organic debris descending from the ocean’s surface. Less than five per cent of the total food available drifts to the sea floor, leading to an extremely food-limited environment. On islands, less food is available because the small land areas support fewer plants at the base of the food chain.

In either case, island and deep-sea animals need to be efficient and creative in their acquisition of food. In both habitats, there may not be enough total food to support populations of giants only. Unable to travel long distances to search for food or to store large fat reserves to fast through periods of food scarcity, smaller organisms are also at a disadvantage. If these contrasting evolutionary pressures were equal, size would be driven to an intermediate. However, the selection against larger sizes is greater, leading toward an evolutionary convergence that is slightly smaller than the intermediate size. Thus, differential responses to food reduction by different- sized organisms may resolve the outstanding paradox of divergent size patterns in the deep. In the interests of reaching this ‘golden medium’, some species become giant while others miniaturized.

In that summer of 1996, as a clueless undergraduate, I started my scientific adventure that fueled my obsession with size. Two decades later, I still am excited by the body size of animals. Much of my research, and the students who work with me, is dedicated to understanding how the expansive variety of sizes on Earth from bacteria to blue whales emerged. Did I mention the great selfie I took recently with a giant whale vertebra the size of coffee table?

The post Craig With Big Things (and Small Things) first appeared on Deep Sea News.

Further out from the venting fluid is the ‘B’ group, a mixture of medium size males and females. This coed party can be in the 100’s per meter squared. The majority of the females here possess ripe ovaries suggesting they are receptive to the sexual inquiries of the males. Further out again from the venting fluids is an additional coed party, ‘C’ group, and despite only being attended by the smallest of females and males densities reaches over 4,000 per meter squared. This area smells a lot like stale beer and hormones, is illuminated by glow sticks, and all overlaid with rhythmic pounding of the latest pop hit club remix. There ain’t party like a C group party because a C group party never stops.

At the very periphery, far from the venting fluids and at the coldest temperatures, is a transition zone. Here, juveniles are in search of the venting fluids to sustain their harry bacteria. In addition, brooding females find refuge here for their young from the environmental extremes of the vent and potential damage from lusty crabs crawling all over each other.

In the video above an ‘A’ Group (00:41–01:05) A ‘B’ Group (left) adjacent to an ‘A’ group (right) at the “Black & White” chimney (00:41–01:05).

In short, males are driven by sex and food as you might expect from a crab with luxuriant chest ‘hair’. The females add the additional priority of actually carrying and caring about the young.

Marsh, L., Copley, J., Tyler, P., & Thatje, S. (2015). In hot and cold water: differential life-history traits are key to success in contrasting thermal deep-sea environments Journal of Animal Ecology DOI: 10.1111/1365-2656.12337

The post For Hoff Yeti Crabs Food, Sex, and Birth Determine Living Space At Vents   first appeared on Deep Sea News.

Recently a 2003 video went viral on the internet.  The video is a story of a 3 meter Great White Shark that was tagged.  That electronic tag eventually washed up on a beach.  The data from the tag seem to suggest, at least to the narrator and some others on the internet, that a massive ocean monster ate the shark.  The main line of evidence for this is that the tag recorded a temperature of 78˚F.

a temperature that can only be achieved inside the belly of another living animal

• At an undescribed location on the Australian Coast a female 3 meter shark was tagged.
• The female, called Shark Alpha, was observed to be healthy and the tag was perfectly placed.
• Four months later the tag was found by a beach comber 2.5 miles from where Shark Alpha was originally tagged.
• Data from the tag indicated that at 4:00 am on Christmas Eve, the tag went quickly to a depth 580 meters (1903 feet) on the continental shelf.
• The tag detected at 580 meters a temperature shift from 46˚F to 78˚F
• The recorded temperature of 78˚F lasted for eight days while the tag moved from a depth of 330 feet to the surface.

The narrator of the video, the “researcher” in the video, and others on the internet suggest these facts are consistent with Shark Alpha being eaten by a much larger mysterious predator.

Australian researchers are hunting for what they call a “mystery sea monster” that devoured a 9-foot-long great white shark.-CNN

Multiple news agencies are thankfully pointing out that there really is no mystery here.  Well of course there is the mystery of why Scienotainment TV Channels keep spreading the story of a magical ocean full of mermaids, sea monsters, and the long extinct megalodon, but I digress.

As reported at NBC

“I don’t know this story,” R. Dean Grubbs, a shark researcher at the Florida State University Coastal and Marine Laboratory, told NBC News in an email, “but it doesn’t take some mysterious giant shark to eat a 9-foot white shark.” Grubbs said he’s had more than one 10- to 12-foot-long tagged shark eaten by other sharks. “Two 10- to 12-foot sixgill sharks were eaten by what we believe, based on the vertical tracks, were larger tiger sharks,” he wrote. “And one 10-foot tiger shark was eaten by what we are pretty certain was a larger sixgill shark. I have also caught multiple sharks that would have been over 10 feet, but only the head remained.”

One possibility raised is a cannibalistic and larger Great White ate Shark Alpha.  Well that is certainly reasonable although not nearly as entertaining.  Work by my student as part of thier work for Sizing Ocean Giants is presented below.  In terms of all Great Whites ever measured, and where we could access the size measurements, Shark Alpha is not very big. Indeed, 75% of the approximately 800 Great White Sharks we have measurements for are larger than 3 meters.

When I was undergraduate I learned a great principle that I continuously apply in my career as a scientist.  KISS. Keep It Simple Stupid.  In other words, the simplest explanation is likely the correct one.  No need to make up a super predator when 75% of measured Great Whites are larger than the focal shark.

But of course I suppose that doesn’t make for good ratings.  So in an attempt to get massive hittage on DSN, I propose a wereshark ate Shark Alpha.

The post What ate a 3 meter long Great White? Probably a Wereshark first appeared on Deep Sea News.

This increase in size within a group animals through time, i.e. larger species and larger species are constantly showing up on the evolutionary state, is a well known rule of biology.  We refer to this pattern as Cope’s Rule, named after an American paleontologist Edward Drinker Cope.  At broad levels, Cope’s Rule is definitely true.  The start of life on this planet was microscopic and now we have whales and redwoods. However, a mixed bag of patterns of increasing, decreasing, and no change is body size is seen in organism as diverse as molluscs and mammals.  Even within a single group like mammals, some groups like rodents show little change with time, while whales get larger with time, and horses get both bigger and smaller.

Godzilla appears to be following Cope’s Rule.  So how big will Godzilla be in 2050?  Rhett Allain at Dot Physics calculates this to be 170 meters.  But I, as nerds debating meaningless things will, disagree.  Allain appears to use multiple dates for each iteration of Godzilla.  For example, the 50 meter Godzilla occurs in movies from 1954-1975 and again in 2001.  In Allain’s plots, 50 meter Godzilla occurs in 1954, 1960, 1970, and 1991.  This artificially weights the analysis and treats separate iterations, i.e. species, of Godzilla the same as a single individual of the same species of Godzilla.  To restate, different sightings, e.g. different movies, of the same individual of Godzilla are put into the analysis multiple times even though they are presumably the same individual. I prefer to use a standard paleontological method, specifically the size at first occurrence.

So redoing the analysis, I first find no actual statistical increase in size with time.  That is because the second smallest Godzilla, 55 meters, did not appear until 1999 (purple dot in the graph), the regression between size and time is not significant with this point included.  I am also not sure why the artist of the plot decided to place the 55 meter purple Godzilla out of temporal order. If purple Godzilla is thrown out of the analysis we get the equation

Log 10 Height = -13.94 + 0.008 Year

So in 2050, I calculate that Godzilla would be 288.4 meters not 170 meters.

So why is Godzilla obtaining ever larger sizes with time?  Skyscrapers.  Skyscraper height has increased dramatically over the last century.  For Godzilla to continue to plow through buildings in major metropolises, a more formidable size is needed.  Of course this size change can only be evolutionarily adaptive if it changes the fitness of Godzilla, i.e. in the simplest case the number of offspring passed to the next generation.  If Godzilla is able to topple buildings this might allow for greater acquisition of resources in this case food in the form of people. This would increase the lifespan of Godzilla allow for more reproduction or allow for greater amount of energy to be passed to the offspring increasing their rate of survival  Or perhaps toppling buildings is a sexual display that sexual partners cue on.  Sexual selection!

Of course the real problem of a 55,000 ton Godzilla is the urine production. Using the handy Kaiju post, we can quickly calculate that, 151,436,928 12,921,400 gallons per day.  That is about 1.8 about quarter of the hold of the largest production oil tankers.

The post The Ever Increasing Size of Godzilla: Implications for Sexual Selection and Urine Production first appeared on Deep Sea News.

In the Japanese pygmy squid, Idiosepius paradoxus, mating includes neither a pleasant courtship nor aggressive behavior. Males copulate freely with females. Pygmy squid males will dart toward a female, grasp hold of her, and attach a capsule (the spermatangia) contain sperm to the base of her arms. However, females will often remove the spermatangia. Females will stretch out their buccal mass (mouth and pharynx) to search for the spermatangia at the base of the arms. Once picking up these spermatangia with their beaks, females with either eat them or blowing them away from water from the funnel.

So when does a pygmy squid female choose to keep or discard spermatangia? In a recent study, Sata et al. found the elongation of the buccal mass of females post copulation was predicted by the length of the male partner and the duration of the copulation. Males who were longer than 8-9mm or lasted longer than 3 seconds faired poorer than their shorter, in every possible way, male competition. Why small males and quickies? Both of these may be a evolutionary result decrease risk from predators. Shorter pygmy squid males may stay hidden more easily amongst seagrass. Likewise, mating can make squid pairs more conspicuous to predators and quickies would be favored or long tromps.

And because the females does this all post coitus, the males are none the wiser.

Noriyosi Sato, Takashi Kasugai, & Hiroyuki Munehara (2013). Sperm transfer or spermatangia removal: postcopulatory
behaviour of picking up spermatangium by female
Japanese pygmy squid Marine Biology, 160, 553-561 : 10.1007/s00227-012-2112-5

Noriyosi Sato, Takashi Kasugai, & Hiroyuki Munehara (2013). Female Pygmy Squid Cryptically Favour Small Males and Fast Copulation as Observed by Removal of Spermatangia Evolutionary Biology : 10.1007/s11692-013-9261-4

The post Pygmy Squids Females Favor Small Males and Fast Copulation first appeared on Deep Sea News.

Recently, Quarks to Quasar’s on Facebook published an illustration (above) of how massive a Colossal Squid can reach.  The Facebook post was liked by 3,300 people and shared 1,150 times (they have 351k followers).  I am excited that the Colossal Squid is loved by this many people. One problem. The illustration is wrong.  Really wrong.  Although the Colossal Squid can reach, well, colossal proportions, the length of this big squid is grossly exaggerated in the above illustration.

Steve O’Shea one of the world’s leading experts on Big Ass Squids has this to say,

On April 1, 2003 the popular press was first alerted to the Colossal Squid, a.k.a. Mesonychoteuthis hamiltoni, although this species has been known to the scientific community since 1925, after it was described from two arm (brachial) crowns recovered from sperm whale stomachs (Robson 1925). We have located 11 further reports in which adult and subadult specimens have been described, and are aware of at least 7 further, similarly sized specimens that have yet to be reported. Juveniles of this species are not uncommon from surface waters to ~1000m depth….This species attains the greatest weight, but not necessarily greatest length of all squid species, and is known to attain a mantle length of at least 2.5m.

A newer specimen caught since Steve wrote the above is the Te Papa Museum Museum tank specimen that I’ve seen in person. It measures in at an actual total length of 5.4 meters (17.7 feet).

So more realistic would be

No doubt you have also seen the Amazing Ocean Facts circulating around the web. Overall, I love the concept.  Humor, cartoons, ocean creatures, and some science. Yes more please!  However, I have to speak out against both because I take size seriously.

In the above cartoon the Colossal Squid is stated to be twice the length of school bus.  The average length of your standard school bus is around 45 feet long.  So according to this comic a Colossal Squid is 90 feet long. I mentioned in my other post about the sizes of Giant Squids that the longest recorded specimen was 42 feet long, 3 feet shy of a single school bus.  Now here is the kicker.  Giant Squids are longer than Colossal Squids.

Why does this all matter?

Hat tip to Steve Haddock from the Monterey Bay Aquarium Research Institute who brought this to my attention. Make sure you check out his page on Facebook Jellywatch.

The post How Big Is A Colossal Squid Really? first appeared on Deep Sea News.

For background, biologists know that much of an animal’s biology, everything from limb length, heart volume, lung capacity, territorial range, and urine production, all scale with body size. We use an equation, based on data from lots of animals, to calculate all of these. The equation usually takes the form of Variable of interest = a (mass)^b. a the intercept usually varies among groups like birds, mammals, frogs, carnivores, nocturnal, carnivores, etc.. b the slope can as well but usually scales as a multiple of 0.25.

By knowing the mass of an animal, we can gain some insights even in the absence of direct observation, like how many people a day a Kaiju would consume.

Many people questioned basing my equations on Komodo Dragons, arguing that Kaiju were more like mammals, other reptiles, birds, fish, or crustaceans. A commenter also noted that the weights of each Kaiju are known.

So with actual weights and assuming that Kaiju are like different types of organisms in their physiology, the number of people per day needed to sustain a Kaiju is

Of course I assumed that the tons were not metric tons but long tons. At least one commenter disagreed. If we use metric tons instead

A commenter also suggested that digestive efficiency would not be 100%, i.e. a that all the energy of human would not be accessible to a Kaiju. Perhaps Kaiju are complete crap at digesting bone or their guts are just designed really poorly. Assuming they have an efficiency of 50% and long tons

So if Kaiju are essentially mammals, complete rubbish at digestion, and assuming long tons, then the largest Kaiju, Slattern at 6,750 tons, would require 314.2 people per day. In 61.7 years it could eat its way through Hong Kong, assuming of course there were no births and no other non-Kaiju related deaths. Who has time for sex when they’re running from a 6750 ton alien?

But what about other aspects of Kaiju biology?

In the table above, I calculate different biological features of the largest Kaiju, Slattern, based on different animals (mammals, birds, frogs, fish, etc.). Slattern’s heart beat would be an order of magnitude slower than most humans, beating less than 5 times per minute. The heart would be anywhere from 2 tons upwards of 30.5 tons. Based on either birds or mammals, it wouldn’t even be able to even muster a single offspring per birthing event. On the other hand if Kaiju are reptilian, we are all severely screwed. Lifespan would be measured in 100’s of years.

Piss…how much would it produce? Every day a Kaiju, if mammalian, would produce about 40 barrels worth of urine. If Kaiju are like frogs, then Slattern would produce 92 Olympic swimming pools worth of urine per day (roughly 0.8% of flow rate of the River Thames).

With the scariness of that settling in, the density of Slatterns supported on Earth could be alarming. At the smallest this would still top out over 20,000. It strikes me that Kaiju are probably territorial. Why else would they always be so damn angry and smashing things all the time? If this is true then the numbers drop radically. If they are avian or mammalian, then Earth could support one, like beta fish in an aquarium. If on the other hand they are like hunting primates or lizards, we are looking at thousands.

McNab, B.K. (2009) Resources and energetics determined dinosaur maximal size. PNAS 106:12184-12188

Nagy, K.A., Girand, I.A., and Brown, T.K. (1999) Energetics of free-ranging mammals, reptiles, and birds. Annu. Rev. Nutr. 19:247-277

Peters, R.J. (1983) The ecological implications of body size. Cambridge University Press.

The post How much urine can a Kaiju produce? And other fun information first appeared on Deep Sea News.

 The short answer is not as many as you think.

I spent Saturday watching Pacific Rim.  The movie has everything I want in a flick—big-ass sea monsters, big-ass robots, and big-ass robots fighting big-ass sea monsters.  Pacific Rim is undoubtedly the no-holds-bar-over-the-top-action-flick-who-gives-damn-about-plot-or-character-development-o-yeah-it-has-Ron-Motherf’n-Perlman kind of movie we all need.  My wife disagrees but I still love her.

The stars of Pacific Rim are the Kaiju (怪獣) a Japanese word that literally translates to “strange creature”.  Kaiju films are a staple of Japanese cinematography with Kaijuu, like Godzilla, Mothra, or Rodan, attacking each other or better yet a whole city.

Being the complete nerd I am, I waited patiently until I heard the magical words I needed to hear during the move. “That Kaiju weighed 2500 tons.” At 2500 tons and a puny category 3, this monster didn’t even top the scales as the largest.

Kaiju are creatures of a highly toxic nature and have been categorized on the “Serizawa Scale”. Each Kaiju is classified under five different categories. Categories 1 through 2 represent the weakest of the Kaiju, while Categories 3 through 5 are the strongest. The Serizawa Scale measures water displacement, toxicity and ambient radiation levels given off by their bodies when they pass through the breach.

Knowing a Kaiju’s weight I can tell you a lot about Kaiju biology, like how many humans they need to eat per day to survive.

First we need to calculate what is the field energy expenditure, i.e. the number of joules per day to survive, for a Kaiju.  During the film the “scientist” states the Kaiju are related to the dinosaurs.  A previous paper suggests the equation for dinosaurs should be based on those for Komodo Dragons, i.e. active carnivorous lizards.  So

2500 tons = 2,267,961,850 grams

The equation is

FFE=1.07(mass)^0.735

FFE=8.05*10^6 kJ/day

Given the 2500 ton size of the Kaiju, you might be surprised this doesn’t come close the energy demand, 10.14*10^6 kJ/day, for a blue whale at a mere 160 tons.  The Kaiju estimate is just a single order of magnitude higher than that of elephants and rhinos, 5.36*10^5 and 7.10*10^6 kJ/day.

So what’s going on? The FFE is higher for carnivores than herbivore. More energy is required to chase and subdue prey.  That constant search for prey may also require muscle structure for endurance [pdf], increasing muscle mitochondria density, and requiring more energy.  But we accounted for that by using the total bad us flesh munching, bone crushing Komodo Dragon equation.

The real reason? Lizards don’t run as hot as mammals, i.e. they don’t regulate their internal temperature. Komodo Dragons, an active carnivorous lizard, actually do heat up bit, but still don’t suck energy like a mammal.  Keeping the body warm is energetically expensive to maintain, as exampled by heating bills in Boston to keep my Southern butt warm.

So real question is how many humans would a Kaiju need to eat daily to survive?  The human body contains, depending on athleticism, anywhere from 600,000 to 750,000 kilojoules of energy.  Per day the Kaiju would need to eat anywhere between 10.7 to 13.4 humans.  This would mean that it would take a Kaiju, at the quick side, 1,472 years to to eat through the population of Hong Kong, home of the Shatterdome base.

If we assume a Category 5 Kaiju weighs 5,000 tons, then it would only need 17.9 humans per day, taking it 1,102 years to eat its way through Hong Kong.  Perhaps we shouldn’t be so worried about them.

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