The Devil You Know, the Devil You Don’t

(Via: Wikimedia Commons)
(Via: Wikimedia Commons)

Common Name: The Tasmanian Devil

A.K.A.Sarcophilus harrisii (Family Dasyuridae)

Vital Stats:

  • Latin name translates to “Harris’s Meat Lover” after naturalist George Harris
  • Weigh 6-13kg (13-29lbs.), around the size of a small dog
  • Largest carnivorous marsupials in the world after the extinction of the thylacine in 1936
  • Live up to five years in the wild; fully grown at two years of age

Found: On the Australian island-state of Tasmania

Devil Map

It Does What?!

Spins around in circles and chases talking rabbits, if the cartoons are to be believed. But Tasmanian devils have suffered from some bad press over the years. While they’re often portrayed as incurably vicious, dangerous creatures, this isn’t really the whole truth. Yes, they can scream like a person getting dismembered. And yes, they’re good little hunters that can take down prey larger than themselves, partly thanks to having the strongest bite per unit body mass of any living mammal. (Crunching through large bones is not a tall order for a Tasmanian devil.) But they just as often scavenge carrion killed by other causes, frequently in the form of roadkill. They don’t tend to attack humans, either (unless that human happens to be dead already). Faced with live humans, devils will usually just hold still and hope you don’t see them, sometimes trembling nervously as they do so. Doesn’t exactly strike fear into your heart, does it?

caption(Via:)
How many newborn devils CAN you fit on a 20 cent piece?
(Via: 500 Questions)

In fact, more than anything, devils deserve a bit of sympathy (just ask the ‘Stones)… life is tough for them right from the word ‘go.’ You see, Tasmanian devils are marsupial, meaning the young are born very under-developed and must crawl from the birth canal into their mother’s pouch to find a nipple to latch onto while they finish baking. The problem here is, devils give birth to between twenty and thirty babies, but possess only four nipples, which aren’t shared. In fact, they’re effectively stuck in the infant’s mouth from the time they latch on, preventing them from falling out of the mother’s pouch. So as newborn babies, fresh from the womb, they already have as much as an 87% chance of immediate death. That is some harsh selection right there. Somewhat tellingly, the babies can’t open their eyes until three months after their birth, yet come out of the womb with a full (if small) set of claws. You can see where evolution’s priorities were here.

But it doesn’t get much easier for the four that win the nipple race. Tasmanian devils are already working with a rather restricted range, having been hunted to local extinction on mainland Australia around 3000 years ago (probably by dingoes, which aren’t found in Tasmania). Nevertheless, they were doing pretty well in keeping their numbers up and had a healthy population until the mid-90s, when disaster struck.

caption(Via: Wikimedia Commons)
Don’t image-search this disease… it gets so much worse.
(Via: Wikimedia Commons)

Because the entire Tasmanian population of devils was originally based on only a few individuals, they’ve experienced a ‘Founder Effect,’ which basically means that the genetic diversity from one animal to the next is quite low. In terms of disease, they’re all susceptible to the same things. So when a form of transmissible cancer known as Devil Facial Tumour Disease (DFTD) suddenly popped up in 1996, it spread like wildfire from one devil to the next, mostly via their tendency to bite one another during sex and mealtimes.

An infected devil quickly develops tumours on its face and inside its mouth. This eventually makes it difficult to eat, leading to starvation within a year of contracting the disease. DFTD is estimated to have already killed up to 50% of all devils, rushing them from a healthy population to an endangered species in record time. While the government has taken the step of building up a healthy, captive population which will be isolated from the disease, in the long term, this will have the effect of reducing the species genetic diversity even further. As a small glimmer of hope, researchers are now reported to have found a few individuals with at least partial immunity to the disease, and hope to try to build a cure based on their physiology.

caption(Via:)
Bitey the Devil picks a fight.
(Via: TravelerFolio)

Fun Facts:

  • Tasmanian devils store fat reserves in their tails… a fat-tailed devil is a healthy devil.
  • See the white spots on the devil pictured above? All bite marks. Each scar leaves a patch of white fur. The natural white streak on the devil’s thick-skinned chest is thought to draw attacks away from more sensitive areas.
  • Unlike most other marsupials, the devil’s pouch opens to the rear of her body rather than the front (like a kangaroo), making it impossible for her to interact with her babies while they’re nursing there.
  • Devils tend to try to eat whatever’s available when they’re hungry. The following have been found in their droppings: steel wool pot scrapers, tea towels, parts of leather shoes, blue jeans, plastic fragments, dog collars (minus the unfortunate dog that had been in it), and echidna spines.
  • The only other known form of non-viral, transmissible cancer is a type of venereal disease that occurs in dogs.

Says Who?

  • Attard et al. (2011) Journal of Zoology 285: 292-300
  • Coghlan (2012) “’Immortal’ Tasmanian devil brings vaccine hope” New Scientist, 17 February
  • Grzelewski (2002) Smithsonian 68: February
  • Hamede et al. (2013) Journal of Animal Ecology 82: 182-190
  • Hesterman et al. (2008) Journal of Zoology 275: 130-138
  • Marshall (2011) “Tasmanian devils were sitting ducks for deadly cancer” New Scientist, 27 June
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Randomly Assembled and Surprisingly Dangerous: The Platypus

(Via: National Geographic)

Common Name: The Duck-Billed Platypus

A.K.A.: Ornithorhynchus anatinus

Vital Stats:

  • Only species of Family Ornithorhynchidae
  • Males average 50cm (20”) long, females 43cm (17”)
  • Weigh between 0.7 and 2.4kg (1.5 – 5.3lbs.)
  • Body temperature of 32 degrees Celcius; five degrees lower than placental mammals
  • Live up to 17 years in captivity
  • Eat freshwater crustaceans, worms, and insect larvae

Found: Eastern Australia and Tasmania

It Does What?!

Besides looking like it was assembled from spare parts? We’ve all seen pictures of platypuses (yes, “platypuses”, not “platypi”) before, and everyone knows what total oddities they are: the duck-like bill, the beaver-esque tail, the fact that they lay eggs, despite being mammals; but behind these weird traits lie… even more weird traits! So let’s take a moment to appreciate the lesser-known eccentricities of the platypus, shall we?

First off, these cuddly looking freaks are actually dangerous. Male platypuses have a spur on each hind foot which is filled with a venom powerful enough to kill a large dog. While it isn’t enough to take out a human, it does cause severe, incapacitating pain whose after-effects can last for months. One of only a very few venomous mammals, the male’s venom production increases during the breeding season, suggesting its purpose may lie in competition with other males.

Why your dog and your platypus shouldn’t play together.
(By Jason Edwards, via: How Stuff Works)

And speaking of breeding, reproduction in platypuses isn’t exactly ‘mammal standard’, either. Unlike all other mammals, which have two sex chromosomes (X and Y; XX for females, XY for males, with rare exceptions), the platypus has ten. Talk about evolutionary overkill. A male platypus has the pattern XYXYXYXYXY, while a female has ten Xs. Researchers have found that the actual genetic structure of these sex chromosomes is actually more similar to birds than mammals, although 80% of platypus genes are common to other mammals.

After this alphabet soup of chromosomes arranges itself, up to three fertilised eggs mature in utero for about four weeks; much longer than in most other egg-laying species (in birds, this may be only a day or two). Once laid, the eggs are only about the size of a thumbnail, and hatch in around ten days. While platypuses produce milk, they don’t actually have proper teats to suckle their babies- the fluid is released from pores in the skin. A small channel on the mother’s abdomen collects the milk, which is then lapped up by the young. Strangely, the babies are actually born with teeth, but lose them before adulthood. Such is the impracticality of platypus design…

Adorably impractical.
(Via: noahbrier.com)

Finally, let’s explore platypus hunting methods. Platypuses are the only mammals with the sixth sense of electroreception. Those leathery duck bills of theirs are actually precision receptors that can detect the electric fields created in the water by the contractions of muscles in their prey. Considering the prey in question is largely worms and insect larvae, we’re talking big-time sensitivity here. The bill is also very receptive to changes in pressure, so a movement in still water can be picked up in this way as well. Researchers have suggested that by interpreting the difference in arrival time of the pressure and electrical signals, the hunter may even be able to determine the distance of the prey. This would be especially useful, given that platypuses close both their eyes and ears when hunting. In fact, they won’t even eat underwater; captured food is stored in cheek pouches and brought to land to be consumed.

So there you have it. The platypus: even weirder than you thought.

[Fun Fact:The female platypus has two ovaries, but only the left one works.]

Intelligent Design’s Worst Nightmare
(Via: Animal Planet)

Says Who?

  • Brown (2008) Nature 453: 138-139
  • Grant & Fanning (2007) Platypus. CSIRO Publishing.
  • Graves (2008) Annual Review of Genetics 42: 565-586
  • Moyal (2002) Platypus: The Extraordinary Story of How a Curious Creature Baffled the World. Smithsonian Press.