The Etruscan Shrew

Etruscan Shrew (Suncus etruscus)

Alright, this is a little bit of a stretch for Etruscan week, but the Etruscan shrew (Suncus etruscus) is fascinating! It is the smallest mammal by mass weighing an average of only 1.8 grams (0.063 oz) (although there are certain bats with smaller skulls). The tiny creature does indeed live in what was once Etruria…although it admittedly also lives around the Mediterranean, throughout the Middle East, North Africa, Asia Minor, across Southeast Asia, and down into Malaysia.  There are also invasive colonies in Nigeria (though goodness knows how they got there).

Etruscan Shrew Range

The shrew has a fierce metabolism: its little heart beats 1511 times per minute (25 beats a second). It must eat up to twice its own body weight every day to stoke its internal fires. I like food–but I would wear down fast eating a thousand hamburgers a day. Once I watched a documentary about the top ten super predators—and shrews weighed in at number one. They only eat live food which they catch—and they catch between 20 and 30 prey animals a day. This becomes all the more impressive when one considers that they eat insects (which have wings and are sometimes bigger than the shrew) as well as spiders and myriapods which are armed with terrible stings and venoms. Additionally the shrew dines on immature amphibians, baby rodents, worms, and larvae.

Etruscan Shrew with Snail

Etruscan shrews are largely nocturnal and crepuscular. Because of their poor eyesight, they have acute hearing, highly sensitive whiskers, and an amazing sense of smell: indeed, their long tin noses are mobile and can move about quite sinuously. In winter their fur grows long and they sometimes undergo periods of temporary hibernation when their body temperature drops down to 12 °C (54 °F). They are only social during mating season when a pair will live together through the 27-28 day gestation and until the cubs are independent (which is when they are three to four weeks of age). Litters range from two to six cubs. Because they are so small (and so widespread), Etruscan shrews are preyed on by all manner of snakes, cats, lizards, birds, and other predators. Their particular bane seems to be owls. Naturally, none of these predators are as dangerous to the overall species as humankind is. Etruscan shrews now have a non-contiguous range because of agriculture and habitat loss (although they seem to enjoy human ruins). They live to two years of age in captivity—although owls usually prevent death from old age in the wild.

The Etruscan Shrew is cute in its own way…

If we were not so jaded, we would recognize how remarkable and intense the Etruscan shrew is. Just writing about it, I feel like I have been describing an alien lifeform—a clever cunning creature which fits in a teaspoon. Except when it hibernates, it must endlessly devour. We will return to the art and society of ancient Etruria tomorrow, but right now spare a moment to reflect on the extraordinary nature of our strange mammal kin!

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Naked Mole Rats

Naked Mole Rat Queen with Offspring

Naked Mole Rats (Heterocephalus glaber) are unique among mammals in that they are eusocial (well actually Damaraland mole rats might be eusocial too, but they are in the same family, the Bathyergidae).  Like bees or ants, mole rats live in a hive society: only one naked mole rat female is fertile and she gives birth to sterile workers who maintain and protect the underground burrows where the colony lives.  A queen breeds with 3 or 4 male naked mole rats and she jealously guards her reproductive monopoly.  If other female naked mole rats begin to produce sexual hormones or behave in a queenlike manner, the queen will viciously attack them.  When the old queen dies, violent battles can break out to become the new queen.  Once a victor emerges, the spaces between her vertebrae expand and she becomes longer and larger. Mole rats breed all year and they can produce a litter of three to twelve pups every 80 days.

Naked Mole Rat (Heterocephalus glaber)

Naked mole rats live in the arid parts of Kenya, Somalia, and Ethiopia.  They feed on huge tubers which weigh as much as all the mole rats in a colony.  The mole rats eat the tubers slowly from the inside, which give the roots time to regrow.  Additionally mole rats can efficiently recycle food, so newly weaned mole rats are fed feces (which can also provide sustenance for adults).    Naked mole rats have huge sharp incisors for tunneling.   Their lips close in such a way that the incisors always remain outside their mouth–so the mole rats can tunnel indefinitely without getting dirt in their mouths.   Worker mole rats are 8 to 10 cm (3 to 4 in) long and weigh 30 to 35 grams (1.1 to 1.2 oz), although the queen grows much larger.  Naked mole rats have weak eyes and tiny skinny legs.  In effect they are pale pink wrinkled tubes with a few long sensitive whisker-like hairs sprouting from their bodies.  They move equally quickly forwards and backwards through their elaborate tunnels (which can measure up to 5 kilometers (3 miles) in total length).

Mole rats are unusual among mammals in other significant ways as well.  Naked mole rats do not maintain same thermal homeostasis as other mammals.  Their body temperatures are much closer to the ambient temperature in their burrows.  If they become unduly cold, they move to the top tunnels of their burrows and huddle together.  If they become hot, the naked mole rats retreat into the bottom levels where the temperatures are cooler.

Oxygen is a precious commodity in the underground tunnels of mole rats, so the fossorial roents have evolved extremely efficient blood and lungs in order to maximize oxygen uptake.   Additionally mole rats have very low metabolic rates compared to other (non-hibernating) mammals.  Their hearts beat slowly:  they breathe shallowly and eat little. In times of drought or famine, they are capable of going into a survival mode where their already slow metabolisms drop another 25 percent.  Naked Mole rats lack a critical neural transmitter which would allow them to feel certain sorts of pain sensations (such as pain caused by acid or hot pepper).  It is believed that the mole rats lost the ability to feel such sensations because the high carbon dioxide levels in their tunnels lead to extremely acidic conditions (mole rats are also surprisingly acid resistant, although I shudder to think of how we know this).

Mole rats live a long time—some captive mole rats are in their early thirties—and they do not age like other mammals but remain young and fit throughout their lives.  Additionally mole rats are untroubled by cancers.  It seems the underlying cause of this remarkable cancer-free long life is a certain hyaluronan (HMW-HA), a gooey peptide which fills up gaps between cells.  The fact that cells do not grow closely together prevents tumors from ever forming.  Hyaluronans exist in all other mammals (and in other animals).  The complex sugars are part of our joints and cartilage.  However the hyaluronan found in naked mole rats is much larger and more complicated.

Thanks to their ant-like colonial life and bizarre appearances, naked mole rats might seem quite alien, but they are near cousins to humans (primates and rodents are close relatives—which will surprise nobody who has ever known a businessperson).  They even come from the same part of Africa as us. The naked mole rats are social animals and they care deeply for one another over their decades of life.  Additionally our kinship with the wrinkly pink rats could provide other benefits.  Humans suffer greatly from aging and cancers.  Mole rats–with their remarkable hyaluronans–could provide workable insights into how to alleviate cancer and aging.

Family Portrait?

Otters

Adult Asian Small-clawed otters (Aonyx cinerea)

Otters (subfamily Lutrinae) are the aquatic branch of the splendid Mustelidae family which includes all sorts of highly successful predators like weasels, ferrets, polecats, otters, fishers, and wolverines.  We have already described the giant river otter of the Amazon, a magnificent apex predator which lives on anacondas and piranhas but there are also 12 other species of otters living throughout the Americas, Eurasia, and North Africa (and in the ocean).

European Otter (Lutra lutra)

All of the otters partake of the tremendous strength (and weakness) of the Mustelidae family.  They are ridiculously fast, powerful, and agile, but in order to keep up their swift lifestyles they have huge metabolic intake.  This means they must eat all of the time, and as predators their life is one endless hectic hunt.  Northern otters are at a particular disadvantage since they live in freezing rivers, lakes, and oceans.  In cold weather, European river otters have to eat 15% of their weight every day, while Sea otters must daily down an incredible 25% of their mass.  Fortunately a fast metabolism brings its own incredible reward: otters (like weasels and ferrets) seem to be effortlessly moving while everything else is standing still.

A group of sea otters (Enhydra lutris)

Otters eat a startling variety of prey.  Although fish is the staple of their diet they also opportunistically eat snakes, frogs, lizards, birds, eggs, small mammals, mollusks, crustaceans, and sundry other invertebrates.  Their need for calories keeps them from being too picky.  Despite their speedy metabolisms, otters live as long as dogs (and can survive even longer in captivity).  Different otters have different levels of sociability—the Oriental small clawed otters and the river otters are quite clannish and live in big playful groups.

Baby Asian Small-clawed otters (Aonyx cinerea)

In addition to being great hunters (and eaters) otters are famous for playing.  Their frolicksome antics are a joy to behold, so I found some video on Youtube, but be warned: the sound on my computer is broken so I have no idea what the narrator/soundtrack/music is like.  It might be slidewhistles or it might be 2 minutes and 56 second of the foulest curse words.  Maybe you should watch it on mute.

 

 

Perhaps because otters seem to appreciate life, people have a reverence for them (not that reverence stopped furriers from nearly driving several species extinct during the course of the past three centuries).  In the  the shapeshifting dwarf Otr prefers to spend his time as an otter until he is killed by the malicious trickster god Loki.  Loki is forced to cover the otter skin with treasure, but one whisker remains uncovered and so Loki was forced to part with his magic ring of power (which went on to wreak havoc, as magic ring inevitably do).  To Zoroastrians, the otter was reckoned to be truly pure–and thus sacred to Ahura Mazda, the uncreated god who represents the apogee of wisdom, light, and goodness in their pantheon.  So if, by bad luck, the evil dragon Ahriman happens to burn his way into this world and begins to destroy existence you might want to go be near some otters.  You know, even without the evil dragon, you should go spend time watching otters.  They’re just great animals.

The North American river otter (Lontra canadensis)