True or Poo?

The Definitive Field Guide to Filthy Animal Facts and Falsehoods


By Nick Caruso

By Dani Rabaiotti

Read by Joe Hempel

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  1. Audiobook Download (Unabridged)
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  3. Hardcover $16.00 $21.00 CAD

This item is a preorder. Your payment method will be charged immediately, and the product is expected to ship on or around October 23, 2018. This date is subject to change due to shipping delays beyond our control.

From the scientist duo behind the New York Times bestselling sensation Does It Fart? comes a new illustrated compendium of animal facts and falsehoods, from the head-scratching to the repulsive!

After Does It Fart? comes Number Two…a fully illustrated compendium of animal facts and falsehoods — the more repulsive the better.

Do komodo dragons have toxic slobber? Is it true that a scorpion that sheds its tail dies of constipation? Speaking of poo, do rabbits really have a habit of, err, eating their own? And can you really get high from licking toads, or is that…fake newts?

The answers to all these questions and more can be found in True or Poo?, a manual for disgusting and one-upping your friends and enemies for years to come.



Myths about animals are as old as time. For example, salamanders were once believed to be born from fire or even immune to it, because people observed salamanders emerging from logs that they were burning to keep warm. In reality, these salamanders make their homes inside logs and are very sensitive to rising temperatures. When their homes begin to heat up, the salamanders quickly evacuate. Another common myth is that ostriches bury their heads in the sand to “hide” from predators. (Both of these myths as well as others throughout this book can be traced back to the naturalist and philosopher, Pliny the Elder.) In reality, however, observations of ostriches “burying” their heads was likely them lowering their head into their nests, which consist of holes in the ground, to turn their eggs, or potentially just moving their head to the ground to feed.

These myths, however, can’t compete with some of the weird and wild things that animals actually do every day. Animals and their evolutionary adaptations are amazing, we don’t need made-up facts about them. For example, did you know that salamanders can regenerate their tails as well as their arms and legs? And ostriches can run at speed of over 70 kmph? While it may seem innocuous to believe these animal myths, often it can lead to an underappreciation of how truly great the natural world is or, worse, needless harm toward certain species that have obtained a bad reputation as a result of this “fake gnus.”

As zoologists, we have had the privilege to get up close and personal with a wide variety of animal species, as well as reading thousands (and we seriously mean thousands) of papers on animal-related topics throughout our careers. On top of this, we hang out with a lot of other people who study and work closely with various animal species, who have many weird and wild animal tales to tell. It turns out, in fact, that nature is pretty gross—the Victorians may have had some very ingrained ideas about the beauty of nature, but in reality animals do a lot of really, really disgusting stuff.

In this book you will find a mixture of bizarre myths that many people believe about the animal kingdom, along with some absolutely unbelievable facts. They cover topics from mating and parenting to feeding and digestion and strange names, and the peculiar places animals call home. All with a gruesome and gross slant, of course. Can you guess whether they are True… or just a bunch of Poo?


In order to persist, species need to reproduce. However, reproduction in the animal kingdom is incredibly variable—one animal’s stink might be another’s kink! There is so much that needs to happen in order for reproduction to be successful. First, animals need to find and attract a mate; this is the courtship stage. Typically, males compete to win over females and this can involve elaborate displays with a healthy dose of swagger which can often relate information about the male’s reproductive fitness to the females. For example, a bright, colorful, and long tail in peacocks signals to the female, known as a peahen, that the male is in good health and quality, because he can acquire abundant resources to devote to his plumage and still escape predation while being very clearly visible. But sometimes a physical encounter between males is needed for the female to decide who should sire her offspring. As always in the animal kingdom, though, there are exceptions, and in some animals, such as the Jacana—a genus of large-footed wading bird—the females are the ones that fight to secure the best mate around.

During mating, gametes, which are the reproductive cells that contain half of the DNA of each parent, unite to form a zygote. In humans, development of the zygote, known as gestation, on average lasts 280 days and occurs within the female, but this is by no means a constant throughout the animal kingdom. After an offspring is born or hatched, some species are content to let their progeny fend for themselves, but it might surprise you to know that there are also some attentive and dedicated animal parents. Some animals work together to raise their young, but sometimes one parent does all the heavy lifting—often this is the female, although males do occasionally lend a helping hand, fin, or claw.

In this section you will find the answers to questions about all the weird and wonderful ways by which animals reproduce—from courtship displays through mating and finally to parenting. What do hooded seal courtship and children’s birthday parties have in common? (See here.) Do some species really find urine attractive? (See here.) Which animals use their genitalia in a way that resembles Olympic sports? (See here and here.) Are birds really as romantic as they seem? (See here.) Or will they abandon their young if something is amiss? (See here.) What really happens to male clownfish when their female partner meets a terrible fate? (See here.) What is so special about the Surinam toad? (See here.) What do infant—mammals get up to when they are born—apart from being adorable? (See here.)

The next few pages will also highlight just how far animal parents will go to raise their young. Are females the only ones that practice parental care? (See here.) Just how big a ball of poo can a dung beetle push? (See here.) Will they eat their offspring’s waste (see here) or let their offspring eat them (see here and here)?



When humans think of balloons, they might think of birthday parties, but when a female hooded seal (Cystophora cristata) sees a balloon, she is more likely to think of mating. Hooded seals are so-named because of the presence of a “hood”—an inflatable bladder between the eyes and upper lip, found on males. Males inflate their “balloons” to make themselves appear larger and more threatening toward other males, in the hope of exerting their dominance. But that’s not all, male hooded seals also have an inflatable nasal membrane that appears bright red or pink when inflated. If the display fails to intimidate, males may resort to fighting to decide on their social standing. But his work isn’t done yet—he also presents his balloon to a female, hoping to impress her enough that she will agree to mate with him. Given this rather strange mating ritual, we do not recommend that you invite hooded seals to a child’s birthday party.



Humans generally start walking a year after they are born, but giraffes, elephants, and other hoofed mammals accomplish this “feet” within minutes. This doesn’t mean that humans are worse parents than other mammals, but rather it has to do with our brains. Humans have large brains for our size and subsequently a large cranium, or skull. For our species’ existence this is a very good thing; we can use tools, solve complex problems, communicate, and even write books about farts and poo. But those large skulls need to be able to fit through the birth canal, so our brains are relatively underdeveloped at birth, which means that a good portion of our development happens afterwards. The brains of hoofed mammals, on the other hand, are relatively more advanced than humans’ by the time they’re born. Their gestation—the time between conception and birth—is typically longer, at around 14 months for a giraffe and as long as 22 months for an elephant. In fact, scientists have found that the time it takes for a given species of mammal to walk from conception (including gestation) is well predicted by the average size of that species’ brain.



There are numerous similarities between humans and other primates, including our genetic makeup, our use of tools and our propensity to socialize with other members of our species. Likewise, we can find similarities between humans and capuchin monkeys (subfamily Cebinae), which can be found in forested areas in Central and South America. To get a male’s attention, female capuchins will often grab or pull his tail or may even throw rocks at him; behaviors that are reminiscent of schoolyard children. However, one behavior that capuchins and (most) humans do not share is that male capuchins will urinate into their hands and then rub it into their fur. It may seem gross, but there’s a good reason for this urine wash. Studies have found that females are able to detect testosterone levels in the urine, which allows them to identify sexually mature males and differentiate potential mates based on their social status. At this point, we are unaware of a similar ability in humans to use the scent of urine to distinguish potential mates, so we advise against using a urine-based aftershave.



The interactions between species can often be described as an “evolutionary arms race,” in which evolutionary adaptations in one species are eventually countered by adaptations in another. For example, rough-skinned newts (Taricha granulosa) have evolved the secretion of a toxin that can cause paralysis and death, but some garter snakes (Thamnophis sirtalis), which eat newts, are resistant to it. But for many species, like flatworms (phylum Platyhelminthes), an ongoing evolutionary arms race is happening within a species.

Hermaphroditic flatworms, where each individual is equipped with both egg- and sperm-producing organs, will fence each other with their penises, which are extendable and sharp—the longer and sharper the better. The winner will then stab the loser and inject them with their sperm. This is known as traumatic insemination, and it can be observed throughout the animal kingdom in species such as rotifers, gastropod snails, nematodes, and the giant squid. Traumatic insemination has evolved in species that had pretty gross mating behavior in the first place, like males that glue the female’s reproductive tract closed, or block it with their own reproductive organs in the hope of preventing other males reproducing with her. By piercing and injecting the female with their hypodermic genitalia, competing males can then sidestep this barrier.



What would you do if the female of your species was five times your size and could strangle and eat you when you attempted to mate with her? If you answered “detach your penis and throw it at her,” you might just be an argonaut (genus Argonauta). Argonauts are a genus of octopuses that can be found in the open ocean, and they are distinguished from other octopuses in that they produce their own shell. The male argonaut’s “penis” is actually a modified arm, known as a hectocotylus, that contains sperm. When removed from the male’s body, this appendage continues to swim toward the female, attaches to her mantle (the structure behind their head where you can find their organs), and can be stored in her mantle cavity. Unfortunately for the male, he dies shortly afterwards (so would you, if you ripped one of your arms off and floated off into the ocean), so he only gets one shot at siring offspring. Females, on the other hand, can store sperm and fertilize her eggs from multiple males.

While it might seem to be a rather unfortunate fate for the male argonaut, the alternative is being eaten without the chance to pass along his genes to the next generation, which is even less ideal.



This awesome superfamily of insects—the scarab beetles or dung beetles, Scarabaeoidea—all feed partly or exclusively on feces. It may not sound very appetizing, but they do an incredibly important job of recycling nutrients—without them there would be poo all over the place! And that would lead to an increased spread of disease and poor soil quality. There are three types of dung beetle: dwellers, who just hang out in the dung where they find it; burrowers, who tunnel under the dung and bury it; and rollers, which form the dung into balls before rolling it away to their burrows and breeding chambers. This third group go to some extreme lengths to get this poopy food ready for their babies to eat. The male shapes the feces into a huge ball and starts rolling it toward soft ground. If the female likes what she sees (and who wouldn’t?), she will climb onto and ride the ball—adding her own weight to what he is pushing (helpful!). Once they get to a good spot, they both bury the ball and prepare it for brooding, then the female lays her eggs in it. One species in particular, Onthophagus taurus, is particularly good at pushing around big balls of poo—males can push up to 1142 times their own weight. That would be the equivalent of a human rolling a ball the weight of a sperm whale. Talk about a strong father figure!



For all 54 known species of seahorses (genus Hippocampus), the male is observed giving birth to the young, but does that mean the male gets pregnant? While we have rated this statement as “true,” male seahorses don’t become pregnant in the manner in which most people are familiar—they aren’t actually producing eggs. Male seahorses are equipped with a brood pouch on their abdomen, and after successfully courting the female with a dance, she will deposit eggs into this pouch. While scientists don’t know the exact cause for this parental role reversal, it is possible that this trait evolved because it allowed females to produce more eggs; handing over the reins to the male means more time for her to devote to producing the next batch. After being fertilized by the male, the eggs will develop within this pouch and eventually he will give birth to the young–which are fully formed, tiny versions of the adults.

Male seahorses, however, contribute more than just a pouch for developing embryos, studies have shown that they provide nutrients, remove waste and even protect their young from infection. Interestingly, the genes that are expressed during a male seahorse’s pregnancy are similar to those found in pregnant mammalian females. However, unlike mammals, seahorse young can develop outside of the brood pouch, although this process typically takes longer, and fewer offspring survive.




  • "A very necessary book."—New York Post
  • "A book everyone can enjoy."—Cheezburger
  • "Appropriately titled."—BuzzFeed
  • "The only book on animal flatulence you'll ever need."—The Telegraph (UK)
  • "Answers the important questions."—Popular Mechanics
  • "It's time to embrace both your scientific curiosity and your inner 10-year-old."—CNet
  • "The book is jam-packed with Fart Facts, giving time to the farters, the non-farters, and those where the fart-jury is still out.... Does It Fart? is the sort of book that reaches everyone."—
  • "The topic of flatulence is richer and more varied than readers might expect.... Cheeky illustrations by Ethan Kocak add to the book's general irreverence... The book now occupies a place of honor in my house, next to the toilet, where it is always on call to satisfy the curiosity of my lucky guests when they need a bit of bathroom reading."—Katie L. Burke, American Scientist
  • "Does It Fart? clearly makes the perfect gift for animal lovers, science geeks, and fart-obsessed teenage boys. Sniff one out for the special stinker in your life now."—
  • "This breezy read will give you numerous unexpected insights into the animal kingdom.... With whimsical illustrations and an entire section on animal digestion and excretion, it's an educational book for the whole family."—Mental Floss

On Sale
Oct 23, 2018
Hachette Audio

Nick Caruso

About the Author

Nick Caruso is a postdoctoral associate in the Department of Fish and Wildlife Conservation at Virginia Tech.

Learn more about this author

Dani Rabaiotti

About the Author

Dani Rabaiotti is a PhD candidate and a zoologist at the Zoological Society of London.

Learn more about this author