Cuckoos: Outsourcing Childcare, Hogging the Bed

(Via: Batsby)

Common Name: Parasitic Cuckoos

A.K.A.: Subfamily Cuculinae (Family Cuculidae)

Vital Stats:

  • Range in length from 15-63cm (6-25”) and weigh between 17g (0.6oz.) and 630g (1.4lbs.)
  • The majority of cuckoos are not parasites, but around 60sp. are (about 56 in the Old World, and 3 in the New World)
  • Babies of brood parasites are initially coloured so as to resemble the young of the host species

Found: The cuckoo family is present throughout the temperate and tropical world, with the exceptions of southwest South America and regions of North Africa and the Middle East. Parasitic cuckoos occupy a subset of this range, principally in the Old World.

Cuckoo Map

It Does What?!

Parenting is tough… less sleep, less free time, all those all those hungry mouths to feed. What’s a busy mother to do? You know you need to perpetuate the species, but who has the time? Impressively, cuckoos have come up with the same answer that many humans have: outsourcing! Involuntary outsourcing, in this case.

One of these things is not like the others.(Via: Timothy H. Parker)
One of these things is not like the others.
(Via: Timothy H. Parker)

Once a female cuckoo has mated and is ready to lay the eggs, rather than build a nest and slog her way through childcare, she waits for another female with freshly laid eggs to take off for some food and just lays her egg there, spreading her clutch across several nests. In theory, when the duped female returns, she’ll just settle in and care for the new egg along with her own. Cuckoo eggs have a shorter incubation period than that of their host, so the foreign egg usually hatches first, at which point the baby cuckoo just gives the other eggs (or chicks, if the timing didn’t quite work out) a good shove, and enjoys having both a nest and a doting mother to itself. The cuckoo chick will tend to grow faster than its host species, so it keeps its adoptive parent busy with constant begging for food, having eliminated the competition.

But this wouldn’t be a fun evolutionary arms race if the host species just took it on the chin. Birds plagued by cuckoo eggs have worked out several ways to try to cope with the problem. First off, and not surprisingly, they’ve developed a burning hatred of cuckoos. Adult cuckoos seen in the area of the hosts’ nests will immediately be mobbed and run off by a group of angry mothers. The cuckoos, however, have learned to use this to their advantage by having the male of a pair tease and lure the angry mob away while the female lays her eggs in peace. Advantage: cuckoos.

And this, kids, is how you deal with those annoying younger siblings.(Via: M. Bán, PLoS ONE)
And this, kids, is how you deal with those annoying younger siblings.
(By: M. Bán, PLoS ONE)

A second strategy used by the parasitised birds is to learn to recognise foreign eggs and pre-emptively toss them out of the nest. Cuckoos responded to this in two ways. First, they slowly evolved eggs to match those of their host bird in colour and size (or, in the case of covered nests, very dark eggs which aren’t easily seen at all). Bird species with higher levels of egg rejection just end up with cuckoo eggs which look more and more similar to their own. Second, if a host does reject the foreign egg, the cuckoo who laid it will sometimes come and just destroy the entire nest, killing anything left inside it in an act of motherly vengeance. Advantage: cuckoos.

A third strategy, developed by the Superb Fairy Wren (not to be confused with the equally floridly named Splendid Fairy Wren) is a bit more clever. As soon as the host mother lays her eggs, she begins to sing to them in a very specific pattern. Now, in this case, the cuckoo egg will hatch around the same time as her own eggs, but was deposited there several days later than her own. This means that her own chicks have been sitting there, unborn, learning her song for a longer period of time than the cuckoo has. Once the eggs are hatched, only her own chicks will be able to properly replicate her calls. Can’t sing the song? No food for you. And if, prior to starving to death, the parasite chick does manage to push her chicks out of the nest, the mother will fail to hear the proper response at all and know to simply abandon the nest entirely. Advantage: Fairy Wren. Superb indeed.

Shrikes: don't try to outsmart a bird that kills mammals for sport.(Via:
Shrikes… don’t try to outsmart a bird that kills mammals for sport.

There is at least one known case of a former host species throwing off the yoke of cuckoo parasitism entirely. The red-backed shrike, aside from being particularly murderously aggressive toward adult cuckoos (and many other things), became very good at identifying cuckoo eggs, very quickly. So quickly, in fact, that researchers believe the cuckoos simply didn’t have time to adapt. In laboratory experiments, the shrikes correctly identified and rejected 93.3% of all cuckoo eggs placed in their nests. Pretty good pattern recognition for a brain the size of a pea. While cuckoo-red shrike parasitism has been known historically for some time, it hasn’t been seen in nature for the last 30-40 years.

Shrikes for the win.

Fun Facts:

  • Even typically non-parasitic cuckoos will sometimes lay their eggs in the nests of their own or other species, but will still help to feed the chicks (parental guilt, perhaps?).
  • The eggshells of parasitic cuckoos are unusually thick, helping prevent them from cracking as their mother drops them from above into the host nest.
  • Striped cuckoos, not content to just shove their adoptive siblings out of the nest, actually peck them to death with their beaks.
  • A few birds deal with homicidal cuckoo chicks by building steep-sided nests, making it difficult for any chick to be pushed out (and raising them as one big, happy family, I guess).

Says Who?

  • Colombelli-Négrel et al. (2012) Current Biology 22: 2155-2160
  • Feeney et al. (2012) Animal Behaviour 84: 3-12
  • Lovaszi & Moskat (2004) Behaviour 141(2): 245-262
  • Spottiswoode & Stevens (2012) American Naturalist 179(5): 633-648
  • Wang & Kimball (2012) Journal of Ornithology 153: 825-831

The Old Girls’ Club

(Photo by the Author)
(Photo by the Author)

Common Name: African Elephants, Asian Elephants

A.K.A.: Loxodonta africana, Elephas maximus

Vital Stats:

  • Comprise the entirety of Family Elephantidae and Order Proboscidea
  • African elephants are thought by some to be two species; the African Forest Elephant, and the African Bush Elephant
  • Can live for up to 70 years in the wild
  • The largest living terrestrial animals, reaching heights of up to 4m (13’) and weights of up to 7000kg (15,000lbs.)
  • Consume up to 150kg (330lbs.) of food daily

Found: Savannahs, bushlands, and forests in sub-Saharan Africa and Southeast Asia (but sparsely across these regions)

Elephant Map

It Does What?!

Everyone knows elephants are cool. And weird looking. What they don’t tend to get a lot of credit for is just what complex lives they live, and how well-adapted they are to their surroundings. Far from being the dim, bovine, eating machines they’re often depicted as, elephants have been found to have an intelligence and self-awareness ranking up around that of primates and cetaceans, with comparably nuanced societies.

Jumbo renounces vegetarianism.
(Via: One Big Photo)

Elephant herds are matriarchal, being led by the oldest female and consisting of her close female relatives and their young offspring. Males are given the boot around the time they reach sexual maturity during their teens (because even the most intelligent animals find teenage boys a trial) and live the rest of their lives either alone or with a small pack of other exiled males.

Good parenting and discipline (delivered by mom with a swat of the trunk) seem to be extremely important for young male elephants; when orphaned males were introduced to a game reserve in South Africa in the late ‘90s, they immediately began going on killing sprees, hunting down and violently killing over 30 (endangered) rhinos, a completely abnormal behaviour for an elephant. As soon as well-adjusted adult males were introduced, the aggression stopped. Everybody needs a good role-model, I guess.

You may have heard stories about so-called “elephant graveyards,” where elephants go to die and leave remains near those of their relatives. While these have now been found to be a myth, appearing due to large die-offs happening suddenly in times of drought, it’s true that elephants show an inordinate amount of interest in the carcasses and bones of other elephants. Presented with a set of bones, elephants will become highly agitated and touch the bones repeatedly with their trunks, especially the dead animal’s tusks. Researchers speculate that this is because the tusks feel the same as they did in life, and touching is such an important aspect of elephant society. They are the only known animal outside of humans to take a particular interest in the bones of their species.

Probably not what evolution intended.
(Via: The Road to Anywhere)

And what about their most obviously bizarre feature? How did a prehensile nose develop?! It’s hard to say for sure, but one interesting theory comes from the fact that elephants use their trunks as snorkels while swimming, sometimes crossing shallow lakes by simply walking across the bottom with only their noses above water. Given that manatees are one of elephants’ closest relatives, some scientists have speculated that elephants evolved from aquatic mammals, slowly becoming terrestrial, but never losing their once-important snorkel. (Or their internal testicles, another trait associated with an aquatic lifestyle.) Other scientists think those guys don’t know what they’re talking about and lack evidence to support this theory. So it goes in science.

Whatever their origin, elephants’ trunks have become enormously important in their lives, and are used in everything from eating to fighting to bonding with family members. Actually a fusion of the nose and upper lip, trunks have over 100,000 muscles and are sensitive enough to crack open a peanut shell and retrieve the seed from it. The ability to grasp comes from one or two (in Asian and African elephants, respectively) finger-like extensions at the trunk’s tip. These “fingers,” combined with the elephants’ high degree of intelligence, have allowed them to learn the use of several tools, including tree-branch fly-swatters, which they probably invented millions of years before we came up with the idea. Different priorities…

caption(Via: Wikimedia Commons)
Yeah, we definitely need a few more of these.
(Via: Wikimedia Commons)

And finally, let’s not forget the dearly departed cousins. While African and Asian elephants are the only remaining species of Proboscidea, the order containing both mammoths and mastodons, there were once over 160 of them, inhabiting every continent except Australia and Antarctica. Most of these persisted until the most recent ice age killed off nearly all of the largest mammals. Some systematists believe that Asian elephants are in fact more closely related to woolly mammoths than they are to African elephants, and it’s even been speculated that a cloned mammoth could some day be gestated in the womb of an Asian elephant. ‘Cause if we learned anything from Jurassic Park, it’s that reanimating extinct megafauna is a great idea.

Fun Facts:

  • Elephants use ‘seismic communication,’ transmitting messages via a low-pitched rumble, which is detected by distant elephants using the pads of their feet.
  • While they can move surprisingly quickly, elephants don’t technically “run,” due to the fact that their legs never all leave the ground simultaneously.
  • It’s a common myth that elephants get drunk eating fermented marula fruits which have fallen to the ground. Given the low level of alcohol which accumulates in rotting fruit, an animal the size of an elephant would have to eat an unrealistically huge amount in a short time to reach a high enough blood alcohol level. But they do seem to enjoy them as a snack.

Says Who?

  • Choi (2011) “Woolly Mammoths Could Be Cloned Someday, Scientist Says”. Live Science.
  • McComb et al. (2006) Biology Letters 2: 26-28
  • Morris et al. (2006) Physiological and Biochemical Zoology 79(2): 363-369
  • Shoshani (1998) TREE 13(12): 480-487
  • Shoshani & Tassy (2005) Quaternary International 126-128: 5-20
  • Shoshani et al. (2006) Brain Research Bulletin 70: 124-157
  • West (2002) Physiology 17: 47-50

The Life and Times of the Last Earthpig

(Via: National Geographic)

Common Name: The Aardvark

A.K.A.: Orycteropus afer, Family Orycteropodidae

Vital Stats:

  • Also referred to as the “antbear” or “earthpig”
  • Common name derives from Afrikaans words meaning ‘earth’ and ‘pig’
  • Habitats include savannas, grasslands, and woodlands
  • Weighs 40-65kg (88-140lbs.) and can grow up to 2.2m (7’3”) long
  • Can live up to 24 years in captivity
  • Nocturnal, feeding only during the evening and at night

Found: Sub-Saharan Africa

Aardvark Map

It Does What?!

Like the platypus and several other creatures we’ve looked at, aardvarks are considered “living fossils,” organisms which have changed little from the way they looked millions of years ago (around 20 million, in this case).

Aardvarks don’t look much like most mammals of today, other than a passing similarity to the South American anteater, to which it isn’t closely related. In fact, aardvarks aren’t particularly closely related to anything. Not only are they the sole species in their genus, but they have their own family and order as well. This is because everything else that used to inhabit these ranks has since become extinct. At one time, there were at least 14 different species in the aardvark family, spread over parts of Africa, Europe, and Asia; but today, there’s just our friend the earthpig. Strangely, among the aardvark’s closest living relatives are manatees and elephants (all part of the motley superorder, Afrotheria), which suggests just what distant cousins they must be.

Okay, so aside from having outlived its family members, what’s so interesting about these things? Well, one look at them will tell you they must have evolved to fit some unusual lifestyle. Aardvarks are myrmecophagous, meaning they specialise in eating ants and termites, and nearly everything about that odd little body is geared to this task. First, finding their insect food means digging into large anthills and termite mounds, so aardvarks have become prodigious diggers, tunnelling at rates of up to two feet in 15 seconds with their heavily clawed feet. They use this skill in creating their underground burrows as well, excavating tunnels up to 13m (43’) long and even changing their home’s layout from time to time. Because, you know, you get tired of the same old thing…

Clark the Aardvark, fresh from finishing his new ensuite bathroom with walk-in closet.
(By: Frans Lanting, Via: Posterlouge)

Moving further up, the aardvark’s narrow, elongated head and long, snake-like tongue are perfect for dipping into the minute passages made by ants and termites. They even have a special sticky saliva that adheres to ants at a touch. In a single night of feeding sessions lasting from five seconds to two minutes per stop, an aardvark can attack 200 hills, consuming as many as 50,000 insects. The ants and termites try to fight back, of course, but the aardvark has thick, tough skin and can seal its nostrils shut, making bites and stings ineffective.

There’s just one feature of the aardvark that doesn’t make a lot of sense for its insect-eating lifestyle, and that’s a set of back teeth. (In fact, they’re are born with front teeth as well, but lose them at maturity.) No other myrmecophage on Earth has a functional set of teeth… you just don’t need ‘em to eat ants. So why do aardvarks have them? A little thing called the Aardvark Cucumber!

In a bonus piece of evolutionary weirdness, aardvarks supplement their diet with a single type of fruit, a cucumber which has now become entirely reliant on hungry aardvarks for its continued existence. The plant flowers above ground – as plants do – but then pushes itself into the earth as it sets fruit, resulting in a subterranean fruit. These cucumbers are dug up by aardvarks and eaten as a source of moisture, while the seeds go undigested and are conveniently deposited elsewhere with a ready source of fertiliser for germination. Without the aardvark, seed dispersal would be impossible, and new plants would be unable to obtain enough water and nutrients to survive.

So there you have the life of the lonely aardvark… enemy of the ants, saviour of the cucumber, brother to no one.

“I laugh in the face of probable extinction… and nail clippers.”
(Via: Zooborns)

[Fun Fact: If pursued into its burrow, an aardvark will protect itself by sealing off the tunnel behind itself and digging further into the ground in the other direction.]

[Also… On their front feet, aardvarks have lost their equivalent to our thumb, retaining only four digits.]

Says Who?

  • Endo et al. (2003) Annals of Anatomy 185: 367-372
  • Lehmann et al. (2004) Journal of African Earth Sciences 40: 201-217
  • Lehmann (2008) Fossil Record 11(2): 67-81
  • Taylor et al. (2002) Journal of Arid Environments 50: 135-152
  • Taylor & Skinner (2003) Journal of the Zoological Society of London 261: 291-297

Living in Filth and Looking Up at the Stars

(Via: Wikimedia Commons)

Common Name: Dung Beetles

A.K.A.: Subfamily Scarabaeinae

Vital Stats:

  • Many subsist entirely on faeces, while others also consume fungi and decaying plant matter
  • Found in extremely diverse habitats, on all inhabited continents
  • Grow up to 6cm (2.4”) long, and can live for up to three years

Found: Across the temperate and tropical regions of the world

Dung Beetle Map

It Does What?!

Dung beetles… if you believe in reincarnation, these are why you try to stay on the straight and narrow. Otherwise, you might end up coming back as a creature whose life quite literally revolves around excrement. Dung beetles owe their entire existence to the fact that larger animals have inefficient digestive systems, consuming manure for its remaining nutrients and even laying their eggs inside it as food for their future young. Gross, yes, but once you get past the “ick” factor, it’s a pretty practical system.

Dung beetles come in three main varieties: rollers, tunnellers, and dwellers. Rollers, which are the type most people are familiar with, roll faeces into small balls which they roll away with them to consume and bury elsewhere. Tunnellers dig under the dung, burying it on site as an underground food source. Dwellers, the slackers of the dung beetle world, don’t bother with burying their treasure, preferring to simply live in it where it falls. I’ll focus on the rollers from here on in, as they’re the most bizarrely specialised of the bunch.

Dung beetles find their warm, fresh meals either through their excellent sense of smell or, in the case of some species, by simply riding around on their chosen food provider until the right time comes. Studies have shown that the beetles prefer omnivore or herbivore droppings to those of carnivores, perhaps for the more easily-digestible plant matter. One particularly intrepid group of researchers even determined that human faeces are favoured above those of most other large mammals. Good job, guys. Your funding agency must be proud.

It's a hot commodity... so to speak.(Via: Wikimedia Commons)
It’s a hot commodity… so to speak.
(Via: Wikimedia Commons)

Rollers immediately set to work on a new pile of droppings by shaping a dense little ball of up to ten times their weight (about TimBit sized, for you Canadians out there. Mmm!). Before rolling the ball away to be eaten/buried for later, the beetle will climb up on it and do a sort of dance, rotating around its top. Researchers also observed the beetles doing this dance if their rolling path was disturbed, or if another beetle stopped them to try to steal their ball.

So why the dance? As you might guess, it’s a means of getting their bearings, but what’s really fascinating is how they’re doing it. Dung beetles always roll their balls in a straight line directly away from its origin, probably as a means of reducing competition from other nearby beetles as quickly as possible. And they do this despite facing the ground as they roll the ball with their hind legs. During the day, this was fairly obviously accomplished by positioning themselves according to the direction of the sun, using their dorsal vision. However, they can also do it on a clear, moonless night. How?

Using a planetarium and a series of experiments which, hilariously, involved fitting the dung beetles with little cardboard hats to block their overhead vision, a South African researcher has determined that the beetles are actually using the light from the Milky Way to navigate. This is the only known instance of animals using an entire galaxy to orient themselves. Birds and seals have been known to use stars for positioning, but never the Milky Way itself. This from a tiny creature that cleans up piles of poop for a living… there’s probably an inspiring metaphor here somewhere.

Goes great with coffee!(Via: Wikimedia Commons)
Goes great with coffee!
(Via: Wikimedia Commons)

In the “But what does it do for me?” department, dung beetles are actually immensely useful to humans. Beyond restoring important soil nutrients, in areas of intense cattle-grazing, the beetles cart off and bury literally tonnes of manure that would otherwise host dangerous parasites and disease-carrying flies. Australia has intentionally introduced African dung beetles for this express purpose. Results have been much better than certain other introductions there.

The value of dung beetles has apparently been recognised for a very long time. Ever heard of the sacred scarab beetles of ancient Egypt? Yep… they’re dung beetles. One and the same. The beetles represented transformation and were linked with the god of the rising sun, who was believed to remake the sun and roll it across the sky each day, like the beetle with its ball. Something to think about next time you’re watching a beautiful sunrise.

[Fun Fact: Dung beetles in the African savanna use their dung balls as thermal refuges, periodically climbing up on them to moisten and cool their feet, which can increase in temperature by as much as ten degrees as they travel over the hot ground.]

Says Who?

  • Baird et al. (2012) PLoS ONE 7(1): e30211
  • Chamorro-Florescano (2011) Evolutionary Ecology 25: 277-289
  • Dacke et al. (2013) Current Biology 23: in press
  • Smolka et al. (2012) Current Biology 22(20): R863-R864
  • Whipple & Hoback (2012) Environmental Entomology 41(2): 238-244

Necessity is the Mother of Invention, or, How to Eat Like a Shrike

(By: Arthur Morris, Via: Livebooks Blog)

Common Name: The Shrike

A.K.A.: Family Laniidae

Vital Stats:

  • Family consists of three genera and around 30 species
  • Shrikes range in size from 17cm (6.5”) up to 50cm (20”) long
  • Feathers may be black and white, cream, grey, or brown

Found: Various species found in North America, Southern Africa, and Eurasia

It Does What?!

Sometimes a creature aspires to a spot a little higher on the food chain, but doesn’t quite have all the equipment to get there. Behold the shrike, the bird that wishes it were a raptor. Like birds of prey, shrikes have strong, hooked beaks, sharp eyes, and an appetite for meat, but they’re missing a couple of important features. First, and most important… no talons. Shrikes can’t grab a victim and tear it into pieces like a hawk or falcon could. And second, no crop (a sort of internal storage pouch), so they can’t eat a large quantity of meat in a single sitting.

Not to be deterred by their anatomical shortcomings, these inventive go-getters have come up with a single solution to both problems. Two birds with one stone, if you will. After dispatching their prey with a quick beak to the back of the neck, shrikes will carry the carcass to a nearby shrub and actually impale it on a short branch or thorn. Aside from looking incredibly badass, this serves to anchor the body in one place, allowing the shrike to use its beak to rip the meat into pieces. What’s more, the bird can just leave its leftovers hanging there for later, like the meat locker at a butcher shop. [Wondering what that looks like? Here’s a video, set to appropriately ominous music.]

And now they’re learning to use human technology…
(Via: Nature Saskatchewan)

What kind of prey are we talking about here? Anything from small insects right up to mice, frogs, lizards, and other birds. There’s even a record of one killing and impaling a good-sized bat. Impressively, shrikes have also hit on the value of ageing their food – one species hunts the toxic lubber grasshopper of the southern United States. The dead grasshoppers are then left hanging for several days to let the poison degrade before being eaten. Clever birds.

Shrikes are monogamous and share in parenting duties; when the female is sitting on eggs, it’s the male’s job to go out and kill something nutritious for two. Of course, this makes selecting a good hunter an important task for females during mate selection. When a single male wants to advertise his skills, he makes a conspicuous display of his biggest, most impressive kills for any prospective ladies. Once he’s gotten one’s attention, he performs a mating dance that mimics the action of impaling prey on branches and then feeds her from his assortment of carcasses. (Be sure to include this point next time you’re explaining ‘the birds and the bees’ to someone.)

The owner of this lizard is probably off getting lucky.
(Via: Wikimedia Commons)

I guess when you have only one major skill, you want to make the most of it, because aside from eating and attracting mates, shrikes also use their impaling trick for communication. Bonded pairs are territorial and will defend their terrain from others of their species. In a sort of macabre message to would-be trespassers, the couple will mount their kills around the borders of their land, perhaps in an effort to show others what could become of them if push came to shove. (Did I mention these things actually have a comic book monster named for them? Eat your heart out, Batman.) Unfortunately for them, researchers note that this action often resulted in the prey being snatched by opportunistic passers-by and having to be replaced. It’s so hard to look murderous when everybody keeps stealing your victims…

[Fun Fact: Shrikes with young chicks will often eat only the head of their prey, saving the bodies for the kids. ‘Cause that’s just good parenting.]

Says Who?

  • Keynan & Yosef (2010) Behavioural Processes 85: 47-51
  • Sarkozi & Brooks (2003) Southwestern Naturalist 48(2): 301-303
  • Smith (1973) Behaviour 44(1/2): 113-141
  • Yosef & Pinshow (2005) Behavioural Processes 69: 363-367
You’re next.
(Via: Tough Little Birds)

Nights of the Living Dead… Further Horrors of the Insect World

(By: Paul Nylander Via: The Tucson Citizen)

Common Name: The Tarantula Hawk

A.K.A.: Genera Pepsis and Hemipepsis

Vital Stats:

  • The two genera make up Tribe Pepsini in Family Pompilidae
  • Grow up to 5cm (2”) long
  • Stingers are up to 7mm (1/3”) long
  • Quite long lived for wasps, with lifespans of more than a year
  • Adults feed primarily on milkweed nectar

Found: Across much of the tropics and southern hemisphere

It Does What?!

Happy Halloween, readers! Today’s the day when we’re surrounded by images of zombies, witches, ghosts, and spiders- all creatures meant to scare us on some level. Of course, only one of these things is real. And spiders truly are a scary thing for many people. For all you arachnophobes out there who are feeling vaguely uncomfortable about the preponderance of fake spiders out there today, did you ever wonder what the spiders fear? What keeps tarantulas, the biggest, scariest arachnids of them all, awake at night? Tarantula hawks, that’s what. If spiders had Halloween, this is what they would dress up as.

A creature that can kill small rodents being outmatched by a nectar-sipping insect. Sad.
(Via: Wikimedia Commons)

Like any good mother, the female tarantula hawk wants to ensure that her baby has all the food it requires to grow up into a healthy adult wasp. Rather than bag a large piece of prey and have it spoil by the time her egg hatches, she has developed an ingenious system of keeping meat fresh.

Spying a tarantula from the air, she will attack, injecting the spider with her venom as it struggles to bite her. A particularly hard and slippery exoskeleton renders this counterattack ineffective; the fangs simply slip off her. Before long, the tarantula has succumbed to her venom and is alive, but completely paralysed. Once the prey has been neutralised, she sets out over land, dragging the spider up to 100m (quite a long way, considering the scale involved) back to the site of a burrow she has dug out. Here, our mom-to-be lays a single egg on the helpless spider’s abdomen, then proceeds to immure it in the burrow.

A hundred metres starts to look like a very long trip.
(By: Erin Zimmerman, taken during my field work in Guyana)

But this is only the beginning of the horror for the paralysed spider. Soon after, the egg hatches, and the hungry larva tunnels directly into the spider’s flesh, eating as it goes. The larva instinctively knows to avoid the tarantula’s vital organs as it eats, thereby keeping the prey alive for as long as possible. After several weeks of chowing down, the larva finishes off the job and emerges from the spider’s body, having now matured into a wasp. It then simply unseals the burrow and flies away, leaving the late tarantula in its ready-made grave.

Wondering what happens when a person gets stung by one of these? It’s an interesting question, because the answer is both “a lot” and “not much”. You see, the paralytic agent in the venom only works on invertebrates, and won’t actually do any real damage to human tissue. Before you go trying to catch one, though, know that, in terms of immediate reaction, tarantula hawks are considered to have the single most painful insect sting in the world. It’s best described by an entomologist who has actually experienced such a sting:

“Advice I have given in speaking engagements was to ‘lay down and scream’. The reasoning being that the pain is so debilitating and excruciating that the victim is at risk of further injury by tripping in a hole or over an object in the path and falling onto a cactus or into a barbed wire fence. Such is the pain, that few, if any, can maintain normal coordination or cognitive control to prevent accidental injury. Screaming is a satisfying expression that helps reduce attention to the pain of the sting itself.” [Schmidt 2004]

In short… don’t touch these.

A few words now on just how frighteningly well-adapted this wasp is. Not only is it covered in armour and full of incredibly painful venom, but at roughly the size of your little finger, it’s one of the largest wasps out there, and more of a fight than most insectivores want to deal with. It is essentially without predators. And lest any potential enemies forget why they’re not touching it, the tarantula hawk has both a distinct colour and a characteristic odour, meant to remind aggressors of the pain associated with any previous run-ins. Researchers have described tarantula hawks as being “among the best defended animals on earth” [Schmidt 2004]. And because success always spawns imitation, there are now several other creatures mimicking the appearance of the female tarantula hawk as a form of protection, including the more-or-less defenceless males of the same species.

So the next time you shudder at the thought of a tarantula stalking you in the wild, stop and remember what might be stalking it.

[Fun Fact: Despite its phenomenal pain-inducing qualities, tarantula hawk venom is only about 5% as lethal as honeybee venom, based on studies by people who inject white mice with horrible things for a living.]

Says Who?

  • Alcock & Kemp (2006) Ethology 112: 691-698
  • Kurczewski (2010) Northeastern Naturalist 17(1): 115-124
  • Schmidt (2004) Journal of the Kansas Entomological Society 77(4): 402-413
  • Schoeters et al. (1997) Canadian Journal of Zoology 75: 1014-1019

The Plant That Time Forgot (Welwitschia mirabilis)

(Via: Wikimedia Commons)

Common Name: Welwitschia mirabilis

A.K.A.: Welwitschia

Vital Stats:

  • Welwitschia is a gymnosperm, like pines or firs, and thus reproduces via male and female cones
  • Considered a “living fossil”
  • Named after one of its discoverers, Austrian botanist Friedrich Welwitsch
  • In mature specimens, the woody stem can grow up to one metre (3.3’) across

Found: In the Namib desert, along the west coast of Namibia and Angola

It Does What?!

Restricted to a tiny, arid swath of African desert, Welwitschia mirabilis represents the last remaining species of a very unusual lineage of plants. Close relatives met with extinction over the aeons, while welwitschia, tucked away in its remote and harsh desert range with little competition, just kept going. The fact that the species is alone, not just in its genus, but also in its family and order (the two ranks above genus in plant systematics), speaks to just how distantly related to any other living plant it is. For the sake of comparison, the Rosales, the order to which roses, apples, and pears belong, contains around 7700 species in 9 families and 260 genera. So original and captivating is welwitschia among plants that it has been the subject of more than 250 scientific articles since it was first described in 1863.

A mere infant. But probably still older than you are.

So what makes this thing so weird? Well, plants typically have what’s called an apical meristem at the tips of their stems and/or branches. You can think of this as a clump of stem cells that keeps dividing, throwing off new leaves and buds in its wake. If you cut off the apical meristem, the plant must either develop a new one elsewhere, or stop producing new tissue.

In welwitschia, this isn’t the case. At the beginning of the plant’s life, the apical meristem produces just two leaves, and then dies. The plant will never grow another leaf, which is much more surprising when you consider that it may well live for more than a thousand years. How do you get through a millennium with only two leaves?! The answer is, these aren’t ordinary leaves. Uniquely, welwitschia’s two strap-like leaves have a band of meristematic tissue built into their base, which means they can continue to elongate outward indefinitely. The leaves will continue to grow at a rate of around half a millimetre (0.02”) per day for as long as the plant lives. If you’re thinking that this must mean leaves that are several hundred metres long, unfortunately, no, they aren’t. The leaves are abraded away by sand storms and eaten by passing animals. Even in the best case scenario, the cells at the leaf tips have a maximum lifetime of about ten years (still pretty good for a leaf…). What’s more, the leaves tend to get frayed and split over time, and end up looking like a lot more than just two leaves. Despite all the punishment, though, each leaf can reach a length of up to four metres (13’), giving a mature welwitschia a width of up to eight metres (26’) across.

Welwitschia’s answer to the pinecone.
(Image by Friedrich A. Lohmuller)

As you might expect from a long-lived relic of the past, there aren’t a lot of these plants around. For once, this has less to do with human disturbance than natural circumstances. Over millions of years, the range where welwitschia grows has dried out considerably, and in fact continues to get drier even now. Today, the plant relies largely on fog to meet its water needs, restricting its range to a thin strip of desert coastline where fogs occur regularly. Unlike cactuses or succulents, welwitschia has never evolved the ability to store water. Also problematic is a fungus, Aspergillus niger, which frequently infects and destroys germinating seeds. These factors together can mean that a welwitschia colony can sometimes go many years without successfully reproducing.

And of course, no threatened species would be complete without some human interference. In recent decades, unscrupulous collectors have removed plants from already small breeding populations, making it even more difficult to sustain their numbers. Interestingly, it’s noted in Wikipedia that plants in Angola are actually better protected from collecting than those in Namibia due to the higher concentration of landmines there.

So… landmines: bad for humans, good for endangered plants.

You think you have problems with split ends?
(Via: Natural History Museum)

Says Who?

  • The Gymnosperm Database
  • Dilcher et al. (2005) American Journal of Botany 92(8):1294-1310
  • Henschel & Seely (2000) Plant Ecology 150:7-26
  • Jacobson & Lester (2003) Journal of Heredity 94(3):212-217
  • Rodin (1958) American Journal of Botany 45(2):96-103