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No one hazarded a guess on the puzzle posted last week. It’s an interesting animal I found most curious. Here is the puzzle again.
The animal this refers to is often referred to as a bearcat or occasionally bearweasel, although it is neither a bear, nor a cat, nor a weasel. Of the three, it is most closely related to the cats. What I am talking about is the binturong, aka Arctictis binturong.
Binturongs live in the tropical rain forests of southeast Asia and are viverids, along with civets, linsangs, and genets. If you’re like most people, you may have a vague recollection of what a civet might be and no idea at all what linsangs and genets are. Fortunately, Toni Llobet has very helpfully illustrated them for the Handbook of the Mammals of the World, Vo1. 1: Carnivora, in 2009. He’s done a huge number of excellent illustrations for that text. If you are at all interested in mammal diversity, it is worth checking out.
Binturongs look tough and surly, with bushy black or brown fur with whitish or rust-colored highlights giving them a grumpy old man kind of look. They are in the Order Carnivora, so that would seem to fit, but in reality they tend to spend their days sleeping and their nights ambling around the trees looking for fruit. While fruit is their favorite, they aren’t too picky, and will pretty much anything they come across that doesn’t run away fast enough, which doesn’t have to be that fast because the binturong isn’t going to bother chasing down a meal when pretty much everything qualifies as a potential meal.
Many mammals use scent to mark their territory and to advertise and often have particular glands to make oils that carry the scent. Binturongs have an unusually distinctive smell. It is said they smell like buttered popcorn. The San Diego Zoo has a nice web page about them (which served as the main reference for the last two paragraphs) if you want to read more about them.
I said earlier that Binturongs are often referred to as bearcats, and occasionally as bear weasels. This is one of the things I find interesting about them because, other than all of them being in the Order Carnivora, none of those four are related. There is some debate as to the precise relationships within the carnivorans, but all the hypotheses put these animals in separate clades, or groups.
Before I get into this, there are a couple of things I want to clarify for the non-phylogenetically trained readers. A species can also be called by a more general term called a taxon. A taxon (plural taxa) is simply a species or group of related species. Mammalia is a taxon that contains all the mammalian taxa. If a researcher uses a method called cladistics, which almost everyone these days does, every taxon above species can also be called a clade. This was done to get rid of trying to come up with names for all the different ranks. When you got really detailed, it got kind of ridiculous having Sub-infra-super-supra-mega-gigantor-gonzo-teenytiny…attached onto everything. The number of prefixes could get absurd. It also gave people the false sense that things like Families or Orders actually meant comparable things when in reality they meant nothing at all, yet people still insisted on comparing them as if they meant the same things. A family of insects has little evolutionary similarity with a family within mammals and should not be compared. Taking away ridiculous names lessened (but sadly did not stop) the proclivities of people to do silly things like that. All these relationships can be mapped onto what is called cladograms or phylogenetic “trees”.
Now that everyone understands all that, it is important to understand that when scientists talk about carnivores and carnivorans, they are talking about two entirely different things, which, I know, is stupidly confusing and the scientists who are responsible for this should be slapped soundly and I humbly apologize. Carnivores refers to animals that eat meat as their primary diet. It has nothing to do with their relationships to one another and this is the way most people think about the term carnivores. Wolves are carnivores, just as are sharks, even though one would have to go very, very, very far back to find a common ancestor. Carnivorans, on the other hand, are those animals within the the Clade Carnivora. These animals include all animals more closely related to cats and dogs than anything else, including hyaenas, bears, seals, pandas, weasels, raccoons, skunks, and many other animals, including viverids. Carnivora is based on relationships, not diet. Thus, not all carnivorans are carnivores.
Now that I have gone through all that, binturongs are omnivorous, not carnivorous, carnivorans. As I stated earlier, they belong to the clade Viverridae. How do they relate to bears (Ursidae), cats (Felidae), or weasels (Mustelidae)? It is a bit of a debate, but they are closer to cats than the others. The first thing to know is that clade Carnivora is generally split into two major groups: Feliformia, the cat-like animals, and Caniformia, the dog-like animals. Here is a supertree published in 2012. A supertree is basically a compilation showing the consensus of a whole bunch of published trees of different parts. Each species that is added to the list increases the number of possible relationships exponentially, so trying to make a tree that shows all the species of carnivorans gets mathematically hideously complex. So people study their favorite group within Carnivora and then a supertree is put together with all of them together.
Nyatura and Bininda-Emonds chose to make their tree in a circular format, which is popular for including a large number of species, but is unfortunately the most difficult format for people to understand. It works just the same as all the other trees, it is just bent around and following the lines connecting the groups may be difficult for some.
At any rate, all the clades making up Caniformia are above the dotted line, which I added to hopefully make this easier to read, and all the clades in Feliformia are below the line. Viverrids, including our friend the biturong, is in purple at the bottom, most closely associated with groups like the Hyaenidae (hyaenas), Herpestids and Eupleridae (mongoose, fossa, and meerkats), and then of course, less closely, the felids. The bears and weasels are both in Caniformia and quite far removed from the biturong.
Here is another view of the data in a much simpler format to understand, published by Blaire Van Valkenburgh et al. in 2014.
Other phylogenies may differ slightly by placing the viverrids a bit closer to the prionodontids and felids than hyaenids, but most everyone agrees that is the general area they belong. From this it is quite clear that viverrids are their own thing and only superficially resemble any of the animals they are often referred to as, but evolutionarily, they share a much closer common ancestor with cats than they do with either bears of weasels. So they aren’t bear-like cats, or cat-like bears, or weasel-like, bear-like cats. We humans just like to say it’s like this crossed with that to fit it into our neat categories of memory. If we really wanted to be accurate, we would call them mongoosecats or hyaenacats, or maybe even more accurately cat-like mongoose.
I haven’t done an animal cross game in a while, so when I ran across this animal, I thought it time to do another one. I was not familiar with this whiskery creature, but found it fascinating as soon as I saw it. I’m sure you will too, if you can figure out what it is. The animal is a living animal and as you can probably expect, a mammal. It is also on the endangered species list as a vulnerable species.
Put your guesses in the comments or join the conversation on Facebook and we’ll see if anyone can figure it out before I reveal the answer.
Chase, from Odyssey of Time (nice blog, check it out), guessed the answer for this puzzle. See below for what amazing animal this picture represents.
If one thinks about cliff-diving geese, nothing fits the bill better than barnacle geese, also known as Branta leucopsis. They live in the North Atlantic and can be found along the coasts and islands around Greenland, the United Kingdom, and most recently in the Baltic Sea around some of the Nordic countries.
The day they are born they face a daunting task. To protect the eggs from predators, the adults make their nest high up on cliff faces, oftentimes 400 feet (150m) above the base of the cliff. Unfortunately, the food is at the bottom of the cliff and the parents do not bring food to the chicks. So what is a hungry newborn to do? They jump.
It’s a rough life. Between the dangers of the fall, the predatory birds above, and the foxes below. they are fortunate is half of the chicks survive their first day. Personally, I don’t see how any of them survive. The fall is just brutal. Listen carefully to the video and you can hear the chick squeak as it hits the rocks repeatedly on the way down. Amazingly, the chick just brushes itself off and carries on, a little dazed, but seemingly no worse for wear.
Sir John Mandeville, in the 14th century, had an interesting view of them. According to Sir Mandeville, “in our country were trees that bear a fruit that become birds flying, and those that fell in the water live, and they that fall on the earth die anon, and they be right good to man’s meat. And hereof had they as great marvel, that some of them trowed it were an impossible thing to be.”
Last week I posed this challenge. What real animal combines traits from the kiwi, anteater, and hedgehog. Chase and Herman Diaz came up with the correct answer.
The animal that has the traits of these three animals is the echidna, also known as the spiny anteater. Named for the “mother of all monsters” in Greek mythology, the real echidna looks like a combination of other animals, much like the mythical Echidna herself, who was part woman, part snake.
When people think of weird mammals, echidnas are very often at the top of people’s lists. It has several traits that are commonly mentioned. First, it is a monotreme, a group of mammals that lay eggs. Today, monotremes consist only of echidnas and platypuses, but in there were several others in the distant past. Platypuses are so strange that people at first thought it was a fraud. Who would believe an egg-laying mammal with the face of a duck?
Second is their fur, which has numerous sharp spines, similar to that of a hedgehog. Because these spines are modified hairs, they have limited control of them. Just like other mammals can make their hair stand up (humans know this chiefly as “goosebumps”), the echidna can make its spines stand up, although they can’t shoot their spines like some people would have you believe.
That fact the echidnas lay eggs makes their reproductive system rather different from almost all other mammals. Internet sites always want more people to click on their site, so echidna reproduction gets a lot of discussion. An internet search will immediately turn up comments and pictures of the four-headed penis of the males and the fact that the females have no nipples, instead feeding their young (called puggles) through glands in their pouches (yes, they have pouches like marsupials) which secrete the milk that the young lap up. You can even find talk of the mating trains echidnas can form during mating season, in which the males form a line behind the female and follow her around for upwards of six weeks until she finally decides to mate. Then they dig a trench around her, jump in and try to push each other out like some sort of bizarre sumo contest. The last male still in the trench wins the right to breed first.
Much like many reptiles, which have what is termed a hemipenis (a two-headed penis), the male echidna only uses half of its penis at a time. In the echidna’s case, that means that they use two out of the four heads at any one time, which is good, because the female echidna has two uteruses. We’re still not done with the weirdness. Because the female may mate with several males, the sperm joins into one large mass, a super-sperm if you will, that together, can swim faster and stronger than any of them separately.
There are several traits that the echidna shares with the platypus, in addition to laying eggs. The echidna is edentulous, meaning it has no teeth. It does, however, have an incredibly fast tongue; able to slurp up the ants, termites, and other insects at the rate of 100 licks/minute; thus its name Tachyglossus, which means “swift tongue”. It also has a very sensitive beak that is electroreceptive, meaning it can detect the tiny bioelectrical signals given off by the insects for which it forages. Additionally, echidnas have a spur on its hind legs, although unlike the platypus, it is not venomous.
So what does it mean to be a monotreme? The Tree of Life web project has an excellent and clear summary of what a monotreme is scientifically. Evolutionarily, the monotremes are the oldest true mammalian lineage, splitting off the line that led to placental mammals sometime around 200 million years ago (as a point of reference, the oldest known dinosaur was found in rocks dating to 230 million years ago). Much of what we consider to be mammalian had yet to evolve by this point, so there were still several traits monotremes shared with reptiles that were derived from the common ancestor of both the reptiles and mammals. This split was so early in fact, that the middle ear bones developed independently from other mammals.
My personal favorite of all the strange things about the echidna is its thermoregulation. When people think of mammals, besides for milk glands and fur, they think of “warm-bloodedness”. Thermoregulation is far more complex than most people realize. There is much more than “warm- or “cold-bloodedness”. Better descriptions of thermoregulation are endothermy (temperature controlled internally)/homeothermy (maintains constant temperature) and ectothermic (temperature strongly influenced by environment)/poikilothermic (temperature fluctuates). But these are just endpoints on a spectrum. Perhaps no other animal illustrates the variation better than the echidna.
The echidna does it all. At various times, the echidna displays endothermy, ectothermy, homeothermy, and poikilothermy. It hibernates, it goes into torpor on a regular basis. The echidna is also a eurytherm, meaning that it can operate just fine at a variety of temperatures without loss of function or activity levels. Whereas most mammals would lose function and coordination if their bodies cooled even a couple of degrees and would completely shut down if they cooled ten or more degrees, the echidna gets along just find even when its body cools to 20 C (that is 68 F for those in the US, a temperature at which we would be long dead).
Needless to say, it is a heterothermic animal. Heterothermy is when an animal lets its body temperatures fluctuate. While it is a broad term that includes poikilothermy, it is typically distinguished from poikilotherms by being under the control of the animal and/or by being regional, meaning that different parts of its body have different temperatures. The classic example of this is the deer, in which the legs are allowed to get cold while the body stays warm. African elephants do this somewhat in reverse, shunting blood to their ears allowing them to heat up, thereby dumping heat from their core body to their ears, which can then cool off more readily due to their large surface area. Of course, few mammals can beat the camel, allowing their temperatures to vary as much as 7 C throughout the course of a day.
Anyway, back to the echidna. Check out this graph. In this study, the researchers measured the body temperatures of a female echidna for 13 years. The graph shows temperature ranges for one year. Another study found that the echidna typically maintained temperatures when active at around 32-33 C (as compared to our 37 C) and dropped to 27-28 at night when it was inactive, although it could drop to as low as 4.7 C and still get up and have normal activity during the day. This variability not only allows it to use less energy, but it also allows it to tolerate temperatures as high as 42 C. Starting the day cold allows it to absorb more heat during the day without overheating. And it is not just its temperature that it allows to vary. The echidna can vary its metabolic rate while still maintaining its normal activity levels. Of course, when it needs a stable body temperature, like for instance, when it is incubating an egg, it can do that too.
All told, the echidna is a pretty amazing animal. It is also about as close as we are going to get in a living animal to see what our mammalian forebears were like in the early years of mammalian existence.
The natural world can be a very strange place. WTF evolution?! is a great site that takes a humorous look at some of nature’s weird turns. Today I am going to celebrate some of nature’s curiosities by playing a game. Some animals are so weird they look like combinations of other animals. For instance, the platypus is often said to look like a cross between a duck and a beaver. I will provide a fictional cross between a set of animals. See if you can guess what real animal it might be. Then come back later to see what animal it is and description of what makes it such a curious animal.
For today’s cross, what might you get if you cross a kiwi (the bird, not the fruit) with an anteater and a hedgehog? I will give you a hint. It is an extant animal, so you can rule out any fossil animals.