29 April 2012

The amazing acid-proof ant

Most terrestrial insects actively avoid liquids, particularly water, because they are too small to escape from its surface if they fall in, owing to the strong hold that the liquids surface tension holds over them. Even larger insects are no different and dislike water, even though some of the bigger species may be able to paddle around to some degree and eventually escape (if they are not eaten by a bird or a fish first).

The diver ant, Camponotus schmitzi, however is a species of carpenter ant that goes against the insect social norm and actually depends on water to survive. Well, depends on acid that is; not water... The fearless ant lives in an exclusive mutualistic relationship with Nepenthes bicalcarata, a species of  carnivorous pitcher plant that lives in Borneo, where it actually dives into the plants digestive juices in order to scavenge for its prey!

A small group of diver ants waiting underneath the lip of N. bicalarata until a insect drops into the acid pool at its base. The ants will then 'liberate' the plant of its meal, eating it themselves. Although this action robs the plant of its meal initially, the ants mainly scavenge large insects and throw back what they don't eat. This also helps to remove debris from the acid pool, keeping it fresher and therefore more attractive to potential prey animals; meaning the ants also benefit the pitcher plant.

If you've never heard of pitcher plants before then you may be confused as to why they have a pool of acid in their base, but it's actually fairly simple - pitcher plants, like the more famous Venus Fly Trap, are carnivores that live by feeding off insects that they have lured into their trap. Whereas species of Venus Fly Trap clamp insects that have landed on their surface and then actively secrete acid to digest them, pitcher plants use a 'pitfall trap' mechanism. This involves a small hole in their top that their prey must climb into to reach the attractive-smelling puddle of liquid in their base. However, this liquid is actually a mixture of a powerful acid and other digestive juices and once the prey species has crawled inside, it is prevented from escaping by tough downward-pointing spines. Unfortunately, the hapless animal then faces a slow and grisly death where it is digested alive.

Nepenthes sumatrana, a species of pitcher plant that can be found throughout the Phillippines. Its bright colouration and sweet smell help to attract its prey. Some of the larger species of pitcher plant, like those found in the Amazon Rainforest, can even attract and eat mice or frogs as prey!

The observation of diver ants has found that they spend most of their time hidden under the lip of N. bicalarata and run down into the base of the plant when an insect falls into its deadly pool of acid and digestive juices. Amazingly, the ants then dive head-first into the acid and work together to pull out the now dead arthropod and begin to eat it in safety on the shore of the pool. Therefore, the ants still get a meat meal but do not have the same risk of injury that most predators face while killing their prey.

Or do they? This strange hunting method seems to have a major and very deadly risk - obviously, the pitcher plants acid should also kill the ants! Scientists are still baffled by why it doesn't and it is thought that the short exposure time of the ants to the digestive juices allows them to survive, along with some other physiological adaptation that helps provide them with some immunity to the corrosive effects of the acid.

One physiological adaptation that has been identified however, is that the ants have a fluid on their outer cuticle (layer of skin) that makes them less water-repellent and therefore, helps to negate the action of surface tension. This allows the ants to dive underwater and leave the acid pool freely and without this chemical surfactant, they would be trapped on the surface of the acid pool like other insects; eventually dying.

A unit of C. schmitzi workers dragging a dead insect (either a grasshopper or cricket) from the pitcher plant's deadly digestive juices.

What is also interesting, is that the ants appear to sprint through the acid rather than swim; using the same tripod sequence as when they move on land - they move the first and last legs on their left side along with the middle leg on their right side and then the front and last leg of their right side with the middle of their left. This simple method of swimming suggests that the ants have evolved fairly recently, since the ancient and truly aquatic insects have all developed much more complex patterns of swimming than this.

Thus, the ingenuity and unique adaptations of diver ants allow them survive in a very hostile organism that by all rights, should kill the ants; turning them into its next meal...

25 April 2012

Should wolves be re-introducted into Scotland?

Farmers have been at war with wolves for thousands of years, desperately trying to protect their livestock from being killed and eaten by the wild animals. This war has led to many familiar jobs to protect livestock, such as shepherding and even to the creation of certain breeds of dog! A fairly obvious example being German Shepherds... Since the advent of guns and their ready availability to farmers however, the war tipped in favour of humans and wolves have since been eradicated from much of their historical ranges across Europe and North America.

The United Kingdom is no different from these countries and has also eradicated the endemic populations of the grey wolf, Canis lupus, that once lived here; with the species being officially extinct in the UK in 1769. Over the past few decades  however, the interest in the re-introduction of wolves has been increasing in many countries, partly due to a better understanding of their ecological importance in pest control and partly due to the aesthetics of seeing them in the wild (many people just like knowing that they're out there). The re-introduction of grey wolves in the USA (such as in Yellowstone National Park) and in many countries throughout  Europe has been a great success and in such countries, the re-introduction of wolves has even been economically beneficial! (Despite the belief that they will cost a country money by killing farmers livestock.)

The grey wolf, Canis lupus, once roamed freely throughout much of Europe, Asia and North America until the heavy hunting by farmers and loss of their habitat due to human activity led to a huge decrease in their numbers - completely wiping them out in many areas. Thankfully, efforts have been made to restore the species and its numbers have greatly increased; with it now being classified as being of 'Least Concern' by the IUCN.

The UK's interest in re-introducing grey wolves is also increasing, particularly in releasing them back into Scotland, which still has much of their natural habitat left throughout the Scottish Highlands, so is the most suitable location for them to live in. In addition, much of the Scottish Highlands are unoccupied and are relatively unused by humans, which will help to reduce the contact between wolves and man - a factor that is essential for the re-introduction scheme to be a success; mainly due to the problems that wolves can cause farmers via eating their livestock - sheep in particular.

The Cuillin Mountains in the Scottish Highlands offer as much of an untouched environment for the re-introduction of grey wolves as now exists in the United Kingdom.

However, the re-introduction of wolves into Scotland has met with opposition and not everyone is as eager to see wolves return to the wild as conservation biologists. These people, predominantly farmers, believe that they will lose out if wolves once again roam the wilderness since the wolves will kill their livestock. Obviously, this represents a significant monetary loss for farmers who are unable to sell the sheep, for example, or use it for breeding. Farmers would have also invested a fair amount of money for the maintenance of the sheep via food costs, vets bills and its general care - money that will not be returned as the farmer cannot sell the animal! However, this has rarely been a problem in countries where grey wolves have been re-introduced and many of the governments in such countries subsidise the cost of anti-wolf devices, such as effective fencing; throat-protection (that make it harder for wolves to kill sheep) and anti-wolf collars; auditory and visual alarm systems; guard dogs; and non-lethal projectiles for farmers that help to reduce attacks. Furthermore, many governments now compensate farmers for the loss of a sheep to a wolf pack, meaning that farmers are reimbursed for the value of the sheep and the cost for maintaining it.

Large breeds of dog, such as the German Shepherd, are very effective at deterring wolves from attacking sheep and other livestock. The German Shepherd (or Alsatian) is a relatively new breed of dog, with its origins dating back to the late 1800s and itself, possesses a large amount of wolf DNA.

Thus, the presence of grey wolves in Scotland shouldn't hinder the efforts of farmers so long as we put some sort of scheme(s) in place to minimise the loss of their livestock and the related damage that it causes to them, meaning that the negative aspects of their reintroduction can be controlled for. This means that the only effects that the re-introduction of wolves will have overall, should be positive. Obviously, an endemic wolf population may well boost tourism to Scotland as many people would like to see wild wolves, helping to raise money that can boost our economy and possibly be used to aid various conservation efforts. Also, many jobs would be created (at least at first) when they are released into and established in the Scottish Highlands, both for the care of the wolves and in the scientific study of the process (such as how wolves adapt to a new environment).

However, these benefits of releasing wolves into Scotland are only secondary and the main positive influence that they would have is in helping to control the populations of the red deer, one of their main sources of prey. Since wiping out wolves from Scotland (and from the UK in general), the populations of red deer, among other prey species, have risen dramatically as they no longer have any natural predators. Their high numbers makes them very damaging to their environment due to the over-exploitation of its resources and their extensive overgrazing can destroy large areas of vegetation. This therefore, reduces the resources that are available to other woodland animals and the overall biodiversity of our woodlands has fallen in such areas; with many species of insects, birds and small mammals being unable to survive there!

The population size of the red deer, Cervus elaphus, has increased dramatically due to the eradication of grey wolves and its other natural predators from the UK. Trophy and meat hunting by humans is not extensive enough to keep their population in check by itself and as a result, their unnaturally large numbers can be very destructive to ecosystems.

As well as being detrimental for the health of ecosystems and to conservation efforts overall, this destruction of ecosystems by deer can itself damage farmers livelihoods, as red deer may eat many of the berries, apples and pears for example, that farmers sell over the summer. Furthermore, large numbers of deer can also be harmful to our health as they carry the potentially fatal Lyme disease, a blood-bourne infection that is spread from to deer to humans via ticks! Thus, in order to control the pesky red deer populations and to help ecosystems to remain balanced (there still needs to be some deer in the environment for it to remain healthy), the UK's government must periodically spend large sums of money to cull the populations of red deer once they become too large to be sustained by their environment, with the Deer Commission for Scotland aiming to maintain a population density of 6 deer per square kilometre.

Obviously, such measures are extreme and are highly unpopular as nobody wants to know about a deer massacre (however necessary). The re-introduction of wolves into Scotland however, can provide a natural alternative to this by regulating red deer populations via predation, which is both cheaper and more desirable. In addition, the abundance of red deer also means that it is unlikely that wolves will attack farmers livestock since wolves are 'creatures of habit' and have preferred species of prey. Much of the research into the behaviour of grey wolves has found that if their preferred prey (which varies between populations and packs) is present in an area, then the wolves rarely hunt other game! Obviously this has implications for farmers, meaning that re-introduced wolves may not attack their livestock at all!

However, the critics that oppose wolf re-introduction have one last argument against unleashing wolves into Scotland: wolves are highly mobile and have very expansive territorial ranges. This means that wolves are unlikely to stay solely in the areas where they've been released and could quite easily move into more heavily farmed areas than what is seen in the Scottish Highlands, where deer numbers are smaller so that the wolves would be more likely to attack livestock. Furthermore, grey wolves could quite easily spread south into England and eventually even into Wales, which are much more heavily urbanised and therefore, much less suitable for endemic wolf populations. Other than rebuilding Hadrian's Wall, it would hard to stop this migration - a fact that is of great concern to both critics and re-introduction policy makers alike; sadly, helping to make their re-introduction less likely...

Hadrian's Wall, spanning from the west to the east coast of Great Britain, was build on the order of the Roman emperor Hadrian on the border between Scotland and England in AD 122. Whereas it is disputed whether the wall was to defend the edge of the Roman Empire from the Scots or was built merely to mark the boundary of the Roman Empire, rebuilding the wall would undoubtedly help to keep wolves out of England...

Sadly, due to the problems that re-introducing wolves back into the UK would have and the long-held negative perceptions towards wolves held by farmers, their re-introduction looks unlikely at the moment even despite the many benefits that it would have. However, the will to re-introduce grey wolves is still here and maybe, after seeing how successful the new populations of wolves have been in Europe and North America, the eerie howls of wolves will one day in the future, once again drift across the Scottish Highlands...

21 April 2012

The burning weight of coins

The Royal Mint (UK) is currently planning to change the composition of '5p' and '10p' coins from the silver-based alloy cupronickel, to a new alloy that is based on steel and nickel. Changing the materials of the coins is expected to save the save the Mint an estimated £8 million (nearly US$13 million) and on a side-note, will make the coins slightly thicker and heavier.

The new 10p coins, which have dimensions more like a £1 coin than the previous styles of 10p.

However despite being good from an economic perspective, the new coins (made from steel galvanised with nickel) may cause dermatitis in members of our population with nickel allergies, which unfortunately is the most common contact allergy in the UK. Worryingly, dermatologists from St. John's Institute of Dermatology, London have said that there has been no assessment to the health risks that these new coins pose and the Central Bank of Sweden has decided that it will not be manufacturing the new coins, after a lengthy debate; with a spokesperson saying that "nickel poses unacceptable risks to health".

However, there may not be cause for alarm since the Treasury claims to have carried out a competent risk assessment over the possible health issues and a spokesman for the Royal Mint has said that "the new nickel-plated 5p and 10p coins have no additional potential to cause adverse effects on people with allergic contact dermatitis and hand dermatitis".

Thus, despite the concerns about the potential health risks that the new coins could cause, it is still unclear whether or not they will have adverse effects on some peoples' health and more research into the matter should be carried out; even if the Treasury and Royal Mint already believe the new coins to be safe and the research is just carried out to put public concerns at ease.

20 April 2012

Land of the Leopard: Russia provides hope for Amur leopards & Siberian tigers

The Amur leopard is a subspecies of leopard that is resident to the south-western Primorye region of Russia and has been classified as 'Critically Endangered' by the IUCN since 1996. It is estimated that as few as 30 individuals may remain in the wild, occupying a tiny area of land. Therefore, the Russian government has just announced that they are creating a 1, 011 square mile big cat reserve called the 'Land of the Leopard National Park' in order to try and save the cat.

The 'Critically Endangered' Amur leopard, Panthera pardus orientalis, which the Land of the Leopard National Park hopes to conserve.

The reserve, declared on the 9th April 2012, aims to safeguard Amur leopards, along with Amur (Siberian) tigers, by protecting them from illegal poaching and hunting by farmers. The Wildlife Conservation Society, which has supported the Russian government in conserving big cats since 1996, has heralded the new reserve saying that: 

"it will provide a critical refuge for some of the most endangered big cats on the planet" (Dale Miquelle, Russian programme director). 

The Land of the Leopard National Park combines three already protected areas: Kedrovaya Pad Reserve, Barsovy Federal Wildlife Refuge and Borisovkoe Plateau Regional Wildlife Refuge (partly to make them easier to manage), with a large expanse of previously unprotected land along the Chinese boarder. Migration between wild leopards and tigers between the reserve into China and vice versa is essential for the conservation of the species since it allows genes to 'flow' between the remaining populations, helping to avoid the negative effects of inbreeding (inbreeding depression) that often occurs in small, protected populations.

Although some conservationists are sceptical that the reserve will help to save the leopard, saying that is too little, too late (to use a cliché), they agree that it is a huge step in the right direction and will definitely be of help in the recovery efforts of Siberian tigers. However, there is still hope for the recovery of the Amur leopard, as many species have recovered successfully from such a dwindling population sizes in the past and the Land of the Leopard may be enough to save the cat, particularly if poaching can be successfully prevented.

The Amur (or Siberian) tiger, Panthera tigris altaica, which is classified as endangered by the IUCN. Numbers of Amur tiger have increased dramatically since its protection in the 1930's and there are now an estimated 500 of the tigers remaining in the wild.

19 April 2012

Mouse plagues: the terror of Australia

In 1993, south Australia was assaulted with a plague of mice. Sounds ridiculous doesn't it? But when half a billion field mice rise up in the spring to destroy your crops and eat your livestock alive, then no-one's laughing... And this is exactly what happened.

The common field mouse, Apodemus sylvaticus, is the culprit of the regular mouse plagues in Australia. The mouse, originating in Asia, was spread around the world as a stow-a-way on-board merchant trading ships.

The 1993 assault was Australia's largest recorded mouse plague and an estimated 500, 000 tons of wheat was destroyed by the rodents over the plague's 6 month duration, which is enough to feed the entire state of Utah (USA) for 4 years! The mental trauma of the plague and the loss in the livelihood of farmers was enough to drive at least 6 people to suicide and many farmers chose to abandon their livelihood and leave the at-risk areas in the south, for good.

Surprisingly, mouse plagues are fairly common in Australia and on average, happen about once a decade. (Australia suffered its most recent mouse plague last year, although it was nowhere near as large as the one in 1993). They typically erupt after a period of very wet weather that causes a 'bumper' harvest, which provides enough food for the mice to allow their populations to grow to enormous sizes. This, coupled with the fact that field mice living in Australia have very few natural predators, suffer from only a handful of the diseases that are endemic to their European cousins and have a very rampant sex life, means that their populations can grow to ridiculous sizes in a very short space of time. In fact, it has been estimated than one mouse and all of her offspring can produce 3, 000 new mice in a single year: a single pair can have babies every 3 weeks, producing an estimated 500 young in 5 months; babies that can then breed themselves at just 5 weeks old!

A pile of field mice that were poisoned by Australian farmers during the mouse plague of 1917. Although mice plagues are rare elsewhere in the world now, evidence suggests that have blighted humans throughout our history. Aristotle wrote about them 2, 351 years ago and they have even been mentioned in the Bible, in the First Book of Samuel.

As previously said, such large populations of mice are extremely destructive and consequently, farmers go to huge lengths to eradicate them in order to protect their crops and livestock. These techniques range from many simple (but not very effective) 'old-school' traps such as drowning mice in troughs full of water and leaving tarpaulins tied to the ground. During the day, field mice will hide beneath these tarpaulins, a fact that farmers have traditionally taken advantage of, using many inhumane methods like crushing and fire to kill the pests. Poisons are another, much more effective way to kill mice and are now laced over grain during mouse plagues. Poisons are usually sufficient to end mouse plagues, turning previously swarming land into killing fields. In 1993, 35 million mice were killed in just 1 month after poison was used (which reportedly hardly even dented their numbers) and one farmer claimed to be removing 70, 000 dead mice a day from his property.

Even without poisoning the plagues would eventually burn themselves out anyway, as such incredibly high numbers of field mice means that diseases spread throughout their populations like wildfire and they will eventually use up all of their available resources, meaning that they will starve to death. However, this won't be before they cause billions of dollars worth of loss to the Australian economy, so their government must still invest in expensive poisons (which also kill other native wildlife so are a last-resort weapon) in order to control the situation.

Despite being a fairly common occurrence in Australia, mice plagues cause huge amounts of damage and are very hard to control for in advance, mainly due to their unpredictability. They are incredibly damaging to the country's economy, to individual farmers' livelihoods and to local peoples' mental health! So all-in-all, are a real menace. Fortunately though, mouse plagues can be controlled and after human intervention their populations crash, with only an estimated 2 mice out of every 1, 000 surviving the cull...

17 April 2012

"Starry, starry... mole?"

The star-nosed mole, Condylura cristata, is the only member of the genus Condylura and can be found in the wet lowlands of eastern Canada and in the north-eastern states of the USA, typically near to lakes, rivers and streams. The mole is small, with adults being no longer than 20cm and weighing up to a maximum of 55g; and are are instantly identifiable by the tentacle appendages protruding from their nose.

The 22 fleshy tentacles of the star-nosed mole give the species its name and are believed by some scientists to be able to detect the electrical currents emanating from their prey. However, many scientists doubt this as there is little empirical evidence to support this idea.

Unlike other species of mole, which are able to see (albeit with only limited success), star-nosed moles are completely blind. Therefore, they rely exclusively on their nose tentacles in order to detect food, such as worms, insects and crustaceans; and to navigate their way around dark tunnels and other environments. As such, their tentacles are extremely sensitive to touch stimuli and odorants and possess around 25, 000 Eimer's organs per cubic centimetre. This is much higher than in any other species of mole and their tentacles' star-shaped arrangement appears to be an adaptation that allows them to keep soil from entering their nose and to eat very small prey quickly. In fact, they are able to eat prey extremely quickly and are the fastest foragers in the animal world, taking on average of 227 milliseconds to decide whether an item is edible and to consume it. This decision making and response ability is so fast that it is at the limits of the speed of neuronal conduction!

Like other species of mole, the star-nosed mole digs shallow tunnels through the earth when foraging, which helps them to evade their predators, which include owls and hawks and to find many subterranean species of prey, such as worms. Their tunnels can be as long as 270 metres and often exit underwater, with the mole being a surprisingly good swimmer; being able to forage along the beds of rivers, lakes and streams. Interesting, star-nosed moles are also able to smell underwater, which they accomplish by breathing bubbles of air onto objects that they are interested in and then by inhaling these bubbles to carry the scents back through their nose.

Little else is known about the shy species of mole, except that it shows no preference to day, night or twilight activity (which is unusual) and remains active throughout the winter. It is also believe that star-nosed moles live in colonies, as many are frequently seen fairly close together.

14 April 2012

Ensnared by a fungus

A single gram of soil can contain millions of different micro-organisms, including large amounts of fungi, protozoans, bacteria and nematodes (tiny, non-segmented worms). As would be expected, all of these different organisms interact with each other in complex food chains, which are often go unnoticed due to their small size and apparent insignificance. However, these interactions are in fact very important and have large effects on the decomposition of dead biological material and therefore, in the ecological recycling of nutrients.

Probably the most important fungi in recycling nutrients are the saprobic, wood-rotting species (see the earlier post 'Fungi: rotting civilisation from its very foundations' for more information), which are essential in allowing larger ecosystems, such as forests, to exist. However, they are not entirely responsible for recycling carbon and predatory fungi, belonging to the phyla Ascomycota, Basidiomycota and Mucoromycotina are also key contributors, by recycling the carbon from the micro-organisms that they kill.

The very rare predatory fungus Anthurus archeri.

There are over 200 identified species of predatory fungi and they can feed on a wide-range of micro-organisms including bacteria and other types of fungi, but predominantly feed off nematodes or other types of microscopic worm. Although it is not disputed that fungi can predate nematode worms, the finding was initially surprising as how can a relatively immobile fungus catch and eat an active worm?

Fungi have evolved many different techniques that enable them to do this, using both passive and active methods. Passive methods are fairly simple and such fungi produce a network of hyphae that permeates the surrounding soil. The hyphae act a bit like spider webs and have droplets of glue or hooks at regular intervals along their length. Upon contact with the glue or hook, a nematode becomes snared and cannot escape. The hyphae then 'blooms', extending hyphal tendrils that pierce the skin of the hapless worm and grow inside it. Once inside, the worm is digested and its nutrients are absorbed by the same tendrils and carried back to the central body (mycelium) of the fungus.

These passive methods are relatively simple methods of capture, probably being the first techniques to evolve as they are easy to produce, but are not the most efficient way of ensnaring prey. Thus, many predatory species have evolved more active methods of capturing prey that involved motion-triggered traps. These traps include the hour-glass shaped clamps of Nematoctonus, which latch onto unsuspecting nematodes as they swim past and hold them in a vice-like grip as the fungus extends its penetrative, invasive hyphae towards them; and the spectacular inflatable collar seen in Arthrobotrys species. The collar consists of 3 cells that inflate rapidly when a nematode swims through them, closing in less than 1/10th of a second that traps the nematode as would a clamp. The struggling worm often traps its tail in another collar, which are regularly spaced along the length of the hyphae, when thrashing around and becomes completely immobilised. As with the other species of predatory fungi, invasive hyphae bloom from these collars and penetrate the nematode; typically digesting it in 12-24 hours.

Active methods of capture: the hour-glass shaped clamps of the Basidiomycete Nematoctonus (left) and a nematode trapped in the inflating collar of the predatory fungus Arthrobotrys anchonia (right).

The presence of predatory fungi is significant for increasing the rate of carbon turnover in the biological Carbon Cycle and they also help to control the population size of nematodes, which can be damaging pests or parasites of plants, fungi and bacteria; all of which are ecologically important organisms.

11 April 2012

Fatal white-nose syndrome spreads through the USA

White-nose syndrome is a fungal disease that has killed more than 5.5 million bats in Northern America, with the infection being fatal  in almost every case. The disease was first recorded in New York in 2006 and despite the extensive efforts to control the disease since then, it has spread through 20 states in the USA and 4 Canadian provinces.

White-nose syndrome, caused by the fungus Geomyces destructans, is characterised by a white growth on a bats nose, ears, wings and tail. Other symptoms include weight loss and abnormal behaviour, such as diurnal activity.

The disease is caused by a common European fungus that oddly, doesn't kill bats in Europe. This has led scientists to believe that the fungus has either changed somehow in America, which gives it its fatal effects or that bats in Europe have a local immunity to the fungus that is not found in American populations, which protects them from the disease. It is hoped that if European bats have immunity to the fungus, it can lead to the formation of a vaccine for their cousins in America, helping to reduce the fatal effects of white-nose syndrome.

The main problem with the fungus is that it prefers to grow in dark, damp climates such as those found in caves. Obviously then, it easily spreads to any bats that are living in an infected cave and the fungus can wipe out entire colonies at a time. Catching the disease is particularly likely over winter when the bats are hibernating and sadly, many die in their sleep without even knowing that they were ever infected.

Recent studies in America have found that at least half of their bat species are at critical risk from the disease and face being wiped out. This is of great concern to the USA since resident bat populations are great controllers of pests and keep the populations of crop-damaging insects down, saving the US agriculture industry an estimated US$3.7 billion a year!

Thus, efforts to eradicate or mitigate the effects of the disease are underway and the US government plans to puts procedures in place in airports and in logistics companies that will hopefully slow or stop the spread of the disease, buying scientists more time to deal with it.

10 April 2012

Shark Bay gangland

Many species of mammal live in complex social groups of close kin, where they work together in defending against predators and sometimes, in gathering food resources. This is particularly obvious in the more intelligent mammals, such as primates and many large carnivores like wolves and lions. Social groups such as these are usually made up of sisters, or closely related females, with one (or a small number) of unrelated males that they mate with. This type of social relationship is called a 'semi-closed group' and normally, the population of a species in a certain area is split up into small groups, where each group holds a specific territory and acts with hostility towards invading and neighbouring groups. 

There are a few species of mammal that have even more sophisticated social networks than this, where each individual group may form co-beneficial affiliations with neighbouring groups for their mutual benefit. Such socialites are called 'open social networks' and are characteristic of the intellectual elite species of mammal, including humans, many of the higher primates, elephants, whales and dolphins. 

Indo-Pacific bottlenose dolphins (hereby referred to simply as dolphins) in Shark Bay, Western Australia, are known to live in open social networks. Recent research however, has found that this is not the full extent of their social domestication and that the dolphins in Shark Bay display social behaviour that is not only unique among mammals, but is unique even amongst other dolphins!

A school of Indo-Pacific bottlenose dolphins (Tursiops species) in Shark bay, Australia. Bottlenose dolphins are top predators within their ecosytem and the upper vertebrae in their neck are fused to prevent their head from moving side-to-side, allowing their spine withstand the extreme speeds that they often reach whilst hunting. 

Dolphins resident of Shark Bay live in a form of fission-fusion grouping, where the bottlenose population are under the control of groups of male dolphins that show closer bonds between other male individuals than in male-female or female-female dolphin relationships. This is highly unusual within the animal world, where males are usually in competition with each other for females and typically, form a social hierarchy where only the head male (or alpha) is allowed to mate. Females on-the-other-hand, often form tight-knit groups for their own protection and protection for their young.

The groups of males form three orders of nested alliances. First-order alliances consist of of 2 or 3 males that cooperate with each other to capture and control groups of females, all of which are allowed to mate and usually act aggressively to protect their group's mating right. First-order groups have often been seen to form second-order alliances, where teams of 10 to 14 males cooperate to defend themselves against attacks from other alliances and to mount their own assaults. Second-order alliances are the core unit of social organisation in Shark Bay and can remain intact for decades! Finally, some second-order alliances merge with others in the second-order to form third-order alliances, which are concerned solely with the possession and acquisition of females. Such groups have been seen to mount large-scale assaults on other other alliances to steal their female members and fiercely guard their own against theft.

It is thought that this strange method of social bonding between male dolphins living in Shark bay has arisen because the affects of kinship, which is the basis of most social grouping, is diluted in their population. Females only give birth to a single calf at a time and have babies infrequently, meaning that the likelihood of a male dolphin having a brother of a similar age is low. This, along with the fact that dolphins leave their mothers at an early age, means that they cannot consistently rely on close kin for allies; and as a consequence, have evolved strong social bonds between other males.

Randic S., Connor R., Sherwin W. B. & Krutzen M. (2012). A novel mammalian social structure in Indo-Pacific bottlenose dolphins (Tursiops sp.): complex male alliances in an open social network. Proceedings of the Royal Society B published online on 28 March 2012.

5 April 2012

Life's so short so I'm so fast

The Peregrine Falcon is a large, crow-sized bird of prey that is renown for its exceptional in-flight capabilities: the bird is incredibly agile and is the fastest known animal, entering dives of over 200mph whilst hunting! The Peregrine is also the world's most widespread raptor, being found on every ice-free landmass except New Zealand and can flourish in almost every ecosystem other than extreme polar regions, very high mountain ranges and areas of dense vegetation such as in tropical rainforests.

Peregrine Falcons have long, broad wings that end in points, the physics of which allows the bird great manoeuvrability, whilst simultaneously allowing them to reach very high speeds. Their wing-span can be a large as 47 inches and their typical body length is between 13-23 inches. Like many birds of prey, Peregrines show reverse sexual dimorphism and female falcons can be as much as 30 times more massive than males. Peregrines become sexually mature when they are a year old and mate with one partner for their entire life (unless their partner is killed), which is usually around 15 years. The falcons also use the same scrape nest for many years, which unfortunately means that their breeding habits are easily disrupted by anthropogenic activities and if their nest is disturbed, it may be a few years before the pair breeds again.

The Pergrine Falcon, Falco peregrinus. This photo shows the characteristic black 'moustache' of the bird that descends either side of its beak. Their moustache is often used by birdwatchers to quickly identify the bird. The Peregrines upper beak is notches near to its tip, which is an adaptation that allows them to kill prey by severing their spinal column at their neck.

Peregrines predominately eat medium-sized birds such as pigeons and small ducks, but will also occasionally hunt small mammals, reptiles and even insects when their preferred food sources are scarce. Like all falcons, Peregrines specialise in hunting prey whilst it is in-flight, which is where their manoeuvrability becomes useful as well as their extreme speed. When hunting, the falcons will soar to an extreme height until they locate a potential meal. Once they have locked onto a bird they enter a ridiculously steep dive, called a hunting stoop, where they reach incredible speeds of over 200mph. To-date, the fastest recorded dive of a Peregrine is 242mph! Dropping like a missile, the falcon aims to clip one of the wings of its prey, the force of which often kills the unlucky bird outright. Even if the bird does survive the impact however, its fragile wing will be shattered and it will fall to its death. The Peregrine then simply finds where the bird has landed and tucks in...

A Peregrine Falcon entering its hunting stoop. The bird pulls its wings in tightly against its body and will drop at an almost vertical trajectory. Third eyelids, called nictitating eyelids, shut during the dive to protect the bird's eyes and specialised bony tubercles on its nostrils prevent much of the airflow from entering its lungs, preventing them from bursting due to the high-pressure air that is flowing into them.

The speed and spectacular hunting techniques of the Peregrine Falcon has long made the bird of interest to humans and the bird has historically been associated with aggression and martial powers. In Europe for example, Peregrines were the hierarchical bird of prey associated with princes, just below the Gyrfalcon that was used by kings, and princes often used the falcon for hunting and as a display of status. Native American Indians also used the raptor as a symbol of status, along with various other birds of prey, as a representation of celestial power and men of high status were often buried in costumes of such birds.

Man's interest in the Peregrine has also meant that it has been heavily sought after for falconry for more than 3, 000 years and the bird is frequently used in shows and by experienced falconers due to the high speeds of its dives.

A Peregrine Falcon featured on the quarter for the state of Idaho, USA.

Unfortunately, the high human interest in the bird has meant that historically, it was vulnerable to egg poaching. This, along with their persecution by farmers and their susceptibility to many pesticides such as DDT, meant that the numbers of Peregrines decreased dramatically throughout the mid- to late- 20th Century and bird was once classified as an endangered species by the IUCN. However, although the interest of humans in the Peregrine was part of its downfall, it is also the bird's saving grace and the recovery of the bird has been very successful. This is mainly due to the large numbers of the bird that were kept in captivity for their use in falconry, which enabled conservation biologists to mount a large-scale breeding program and the species has responded well, with an increase in Peregrine populations worldwide. There are now an estimated 1, 400 breeding pairs of Peregrine Falcons in the UK and in 1999, the bird was removed from the US Endangered Species List.

2 April 2012

"I spy with my HUGE eye, something beginning with w..."

One of last months posts, 'Hunting in the depths', featured sperm whales and talked about how they dove down into the depths of the oceans to hunt their main source of food, giant squid.

Obviously, giant squid want to avoid being eaten by sperm whales and are extremely vulnerable to attack due to the whales' fearsome arsenal. One of the main defences that they have evolved against the whales is developing incredibly large eyes that can measure more than 11 inches across! The large size of these eyes has long confused scientists because they are very expensive to make and are virtually completely useless in the deep oceans, where there is no light. This means that their eyes should have disappeared over the course of their evolution, like in many other species of deep cave-dwelling organism.

A sperm whale hunting a giant squid. Note the giant squids enormous eye, which works via a lens refracting light in the same way as a human eye does.

The fact that they possess such highly developed eyes, which can have lenses that are bigger than the entire human eye, means that this can't be the case. New research into giant squid by Professor Nilsson from Lund University, Sweden  has helped to 'shed light' onto the function of these eyes and explain why evolution has favoured their development rather than their loss.

The depths of the ocean are filled with bioluminescent organisms, which when disturbed, flash and glow. Thus, diving sperm whales agitate these organisms as they swim past and giant squid are able to see the light from this disturbance. The squid are able to gage the size of the organism and the direction that it is travelling in from this light and consequently, can determine whether or not the shape is a sperm whale to either ready itself against an attack or flee.

Therefore, the large eyes of giant squid have direct implications to the animal's survival so that in the past, individuals with biggest and best eyes survived for the longest and could breed the most. This meant that large eyes were under a strong selection pressure in giant squid, despite being useless for seeing anything else, so that today the species has abnormally large eyes.

1 April 2012

Is evolution in danger of extinction?

Everyone is familiar with the concept of extinction. Sometimes species are lost forever, whether it is due to natural and unavoidable catastrophes like a large asteroid hitting our planet, which many scientists believe wiped out the dinosaurs, or due the activities of humans. The extinction of a species is sad, but the brutal fact is that it is not all bad and the death of one species allows the evolution of another to occur and fill the now empty niche. A good example is that the mass extinction of the dinosaurs allowed the previously oppressed group of mammals to evolve and become one of the most dominant forms of life on the planet, which has worked out pretty well for us... These events are called extinction spasms and follow all mass extinction events, with the 'bounce-back' time of species taking millions of years. For example, it took 20 million years after the Cretaceous Tertiary Extinction Event for the surviving marine invertebrates to establish as many new families of organisms as they'd lost.

The Barringer Crater in Arizona is 1 mile wide and 570 feet deep. It is believed to be the crash site of the city-sized KT asteroid that hit the Earth 65 million years ago with the force of million nuclear bombs, wiping out half the life-forms on the planet, including the dinosaurs.

Therefore, life has always recovered after mass extinction events and many new species have appeared after them. This is mainly because the past five mass extinction events have left many of the key environments for evolution intact, such as rainforests and underwater environments. Such environments are sometimes called 'evolutionary powerhouses' and are critical for the development of new species, having produced substantially more new species of organism than any other environment, including almost every major group of vertebrate.

The planet is currently undergoing its sixth and largest mass extinction event, which is due to the destructive activities of humans. The most damaging of our activities are mainly mass hunting and deforestation, which have resulted in many species already falling extinct. The problem with this mass extinction however, which sets it apart from the others, is that we are destroying the powerhouse environments and are killing every other category of animal at the same time, rather than just certain ones. This is resulting in a rapid loss of the planet's overall genetic diversity - diversity that is essential for life to recover after we wake up, stop destroying the planet and take steps to halt the extinction event.

An aerial view of the border between Haiti (left) and the Dominican Republic (right). The heavy logging in Haiti for the charcoal and firewood industries has resulted in mass deforestation and as a result, only 3% of Haiti's forests now remain.

As according to Charles Darwin, evolution works when a gene randomly mutates and that this mutation gives the individual an advantage over others of its species, helping it to survive for longer. Thus, the individual can breed more because it is around for a greater length of time and gradually, the mutated allele (which is naturally selected for), increases in frequency throughout the population of the species. Once a species has gone however, its genes are lost and cannot change or be passed on so their potential for evolving into a new species is also gone. New species usually evolve when separate populations of a particular species live in different environmental conditions and cannot breed with each other. Therefore, the different populations will be under different selection pressures for new genes and will undergo speciation, slowly becoming different subspecies and eventually, different species altogether.

Thus, the recovery of life after a mass extinction event depends upon the species that survive it and the genes that remain - genes cannot just appear from nowhere! Therefore the rapid loss of forested habitats, which have survived remarkably well in past mass extinctions, is greatly reducing the planet's genetic 'resource base' and is pushing even more species extinct. Worryingly, it is looking more and more likely that the process of evolution will become severely limited in its capacity to create new species of life and ultimately, may fail and become extinct itself. If this should happen life on Earth will die (eventually humans will die out as well as we'll have no food) and will not be replaced, leaving the planet as just another barren and lifeless rock drifting through space...