27 June 2012

Watching from the waters

The Nile crocodile, Crocodylus niloticus, is one of the most feared animals in the world and is undisputedly the most dangerous species of crocodilian to humans - being estimated to kill around 200 people each year. This is mainly due to its close proximity to our settlements and its indiscriminate diet - with it hunting anything that moves! Growing as long as 16 feet (5 metres) and weighing up to 225kg (500lb), the Nile crocodile can be found through central and south-east Africa and on the western shores of Madagascar. 

This is believed to be one of the largest specimens of Nile crocodile ever caught! Its huge size makes it no wonder why many Ancient Egyptians incorporated the beast into their belief system and worshipped Sobek, the crocodile god that lived in Crocodilopolis - a great city of crocodiles!

Probably one of the main reasons that the crocodile is such a proficient predator and is so lethal to humans is because it is a silent ambush predator - its flat body allows it to remain completely submerged, even in the shallow waters by river banks; and it has slightly raised nostrils and eyes that can be poked above the surface while keeping everything else hidden underwater, allowing it to see and breath virtually unnoticed. This allows the crocodile to get within yards of its prey (including humans), completely unnoticed and once it is ready, it lunges out of the water. Once the crocodile has lunged it is normally too late for its victim due to the speed of the attack and the animal is then crushed in the crocodile's vice-like bite and dragged into the water. After it has bitten an animal, Nile crocodiles (as with most crocodilians), have an overwhelming instinct to role - this is commonly known as 'death rolling' and, by spinning like a corkscrew, the crocodiles tear huge chunks of flesh out of their prey. This helps to compensate for their ineffective teeth, which are unusually blunt for a predator.

A Nile crocodile that has caught a gazelle. Nile crocodiles can eat up to half their body weight at a time and their bite force has been measured to be as high as 5, 000 lbf (22N), which is like being hit by a very fast-moving truck! Like most crocodiles, N. niloticus has a primary and secondary bite where an individual bites its prey once and then re-bites it without relaxing their first bite, helping to drive its blunt teeth even further into the flesh of the animal.

Ambushing their prey in this manner means that they can remain motionless in the water for very long periods of time and so, can conserve enormous amounts of energy. Crocodilians can also reduce their energy expenditure even further by slowing down their breathing and reducing their metabolism using a sophisticated cardiac shunting system that diverts blood away from their heart. Although cardiac shunting mechanisms are found in many species of reptile none have one as advanced as crocodiles. This, along with the fact that they have the most advance heart physiology in the world, has led many scientists to believe that crocodiles were once endothermic (warm blooded) like mammals and birds! Such scientists believe that their warm blooded ancestors slowly evolved back into being ectotherms (cold blooded) when they began to ambush their prey from water since a cold blooded body-plan would be much more beneficial for such a strategy; mainly because it wastes much less energy than trying to maintain a body temperature that is hotter than the surrounding water - just think about how cold you get if you spend too long in a cool bath or pool!

Thus, crocodiles can remain even in fairly cool water for long periods of time and wait for a potential meal to come to them! This is usually when an animal ventures too close to the waters edge for a drink... Nile crocodiles don't even have to use their muscles to hold their head up so can save even more energy while they wait! Their lungs act as ballast tanks and when they are inflated with air, actually push the crocodiles snout and eyes up above the water level! In fact, crocodiles can slow down their energy expenditure so much that they can hold their breath underwater for up to 2 hours when they inactive; often, lying in little 'dens' that they've dug out of the riverbed with their arms.

Certain species of bird, such as the spur-winged plover (Vanelus spinosus), have been seen picking scraps of meat from between crocodile teeth. It is not known for certain whether the birds are merely 'running the gauntlet' to obtain food at great personal risk or whether crocodiles are allowing them to this; forming a mutualistic relationship where the birds are fed while keeping the crocodile's mouth and teeth clean.

Although Nile crocodiles often hunt via ambushing their prey, they can also hunt with a much more proactive and energetic approach - chasing after fish and eating them underwater. It is believed that Nile crocodiles prefer to eat larger terrestrial game that they hunt with surprise attacks preferentially and switch to smaller fish when they aren't available or during then night when their mammalian prey is less active. Nile crocodiles are thought to prefer to ambush mammals for two main reasons: firstly, since it is less energetically expensive as mentioned above; and secondly, because crocodiles are far-sighted underwater due to the closure of their protective nictitating, or 'third', eyelids. Closing their third eyelid helps to protect their eye from underwater debris but also bends the light that passes through it so that the lenses in their eye can't refract the light enough to focus on close-up objects. Obviously, this will severely reduce their ability to hunt underwater and hunting in such a manner would probably be impossible if they didn't have many sensory papillae around edge of their lower jaw. These papillae act a bit like whiskers in dogs and cats and are able to detect even very minute vibrations in the water, allowing the crocs to sense fish that are close to their mouth! Crocodiles use much more energy when hunting fish in such a manner and as a result, can only hold their breath underwater for about 15 minutes since their muscles require more oxygen.

Their ruthless ability to surprise their prey and the fact that they eat humans has undoubtedly earned the Nile crocodile a fearsome reputation as a heartless monster. Oddly however, this isn't true and Nile crocodiles are one of the few crocodilians that care for their young - with mothers watching over their nests from when they lay their eggs to when they hatch! Most crocodilians abandon their nests as soon as they have lain their eggs and leave their offspring to fend for themselves. Furthermore, many crocodilians are cannibalistic and will eat juvenile crocodiles so that they may actually kill their own young unknowingly...

The gender of crocodiles is determined by the temperature that the eggs are at during their incubation, with temperatures of 32 - 33C producing males. Anything warmer or cooler than this narrow temperature range produces females, which is of great concern to conservationist biologists since global warming may result in more females being born and less males! The small size of the baby crocodiles makes them very vulnerable to predation early in life, but as they grow bigger and, if all goes well, the crocodiles can live for up to 100 years!

The Nile crocodile then, is a brutal and ruthless predator that preferentially hunts by ambushing unsuspecting animals from water. It accomplishes this using a range of physiological and behavioural adaptations and techniques which allow them to get within yards of their prey, gliding through the water causing barely a ripple... Despite their danger to man and the polluting effects that our lifestyle has on the waters of their habitats, the Nile crocodile is thriving and is classified as being of 'Least Concern' by the IUCN. This is not surprising really, since crocodilians are ancient animals that even trod the world with the dinosaurs! Their famed resilience allowed them to survive through the catastrophe that killed off the once mighty dinosaurs; and maybe, will even mean that they will survive for long after man has disappeared...

25 June 2012

Save Peoples' Sight!

Hi everyone,

This weekend one of my friends is taking part in the Great Manchester Swim, hoping to raise money in support of the Royal National Institute for Blind People (RNIB). As you may or may not be aware, the RNIB is a charity that aims to prevent people from losing their sight unnecessarily and to support blind and partially sighted people so that they can live as independent lives as possible. Personally, I think that sight loss is one of the worst and most distressing ailments of man that sadly effects millions worldwide and any money that you could donate would be greatly appreciated by Charlotte and her brother, Malcolm, as well by the charity and the many individuals that it helps. If you are interested, more information is available on Charlotte's blog and you can sponsor their swim via their JustGiving page.

Obviously this is a very worthy cause and every penny counts! So please sponsor Charlotte and Malcolm for their efforts and help the RNIB to provide a better quality of life for many people less fortunate than ourselves.



20 June 2012

How effective are captive breeding programs?

One of the most amazing attributes that humans have is our unprecedented ability to alter our surrounding environment so that it is more suitable for our daily needs; with the most obvious of such alterations being the clearing of land to make room for housing and agricultural crops. Whilst we are not the only animals to alter our habitat (many other species such as beavers and termites also build large structures), we are the only species to build and destroy at such a large scale. The fact is that we have now spread onto every continent - even having science stations of Antarctica - and wherever we go, deforestation soon follows. The result of this is that there is very little true 'wilderness' left on Earth and many animals have lost their habitats due to our destructive ways and face imminent extinction in the near future as a result.

Picture taken by Neil Wade
'Slash and burn' agriculture is an ancient way of clearing land that dates back to our earliest endeavours of farming 12, 000 years ago and involves setting blaze to, sometimes, vast acres of forest. Obviously this technique is highly destructive and displaces all of the resident organisms that were previously living there, destroying their homes. The problem is made worse by the fact that land gained in such a way is very infertile so that farmers need to create new plots of land every year.

In fact, the problem is now so bad that research undertaken during the Millennium Ecosystem Assessment (MEA) has found that in the past 50 years humans have changed ecosystems more rapidly and extensively than at any other comparable time throughout our entire history! This has resulted in a huge and irreversible loss of Earth's biodiversity and the MEA found that we have already destroyed over half of the planet's forests, 20% of its coral reefs and 35% of its mangroves - all of which are essential ecosystems for providing habitats to animals, providing ecosystem services to us and in preserving the planet's future evolutionary potential. To make matters even worse, the MEA has predicted that the degradation of ecosystems is likely to get considerably worse during the first half of this century at the very least! This loss of habitat has had profound implications on the survival of many species, which are now already extinct or are endangered and this destructive human behaviour is unlikely to change any time soon. The question then, is whether or not we should try to preserve at least some of the species and ecosystems that we are threatening and of course, many people believe that we should. As the result of this, there are countless specialised conservation organisations across the globe like the WWF and the IUCN.

One of the methods that we can use to preserve endangered species then, is via captive breeding programs in which we take animals from the wild and breed them ex-situ in institutes such as zoos and aquariums. Captive breeding programs have been very successful in the past and have been sufficient to restore the natural populations of endangered species back to relatively 'safe' numbers. A good example of this is the black-footed ferret (Mustela nigripes), which has now made a remarkable recovery after its entire population was removed from the wild and bred in captivity, with reintroduction schemes running since the early 90's. In addition to breeding rare animals in an environment that is safe from illegal poaching, captive breeding programs also allow the animals to be studied by scientists; allow the public to see foreign and exotic animals in zoos, which is both interesting and may help to raise their awareness of the importance of conservation; and furthermore, helps to maintain a 'stock' population against unforeseeable events like natural disasters (which become a huge problem if all the individuals of a particular species are only found in one place!).

These elephant tusks were seized after an anti-poaching raid in Tanzania. Sadly, despite the great efforts to protect wild elephants, illegal poaching for their highly valuable ivory tusks still goes on as is very difficult to protect wild populations. Bringing endangered species, such as elephants, into captivity however makes this much easier.

However, even though captive breeding programs sound like a good idea at first glance and definitely have their good points, are they really feasible on a large scale? The IUCN has estimated that 2, 000 - 3, 000 species of terrestrial vertebrates will have to be captive bred in the near future in order to save them from extinction and sadly, the space and money that is available globally is nowhere near sufficient enough  to cope with such an epic undertaking. Thus, we may have to decide to save some species at the expense of others - decisions that would undoubtedly be both unpleasant and controversial: why is one species more important than another?

Obviously then some animals will be more suitable for captive breeding programs than others: mainly, small creatures that can be kept and maintained cheaply in small enclosures. Amphibians are a great example of such animals and furthermore, can be easily released back into the wild because they don't have any learnt behaviours that must be taught to them in order for them to survive. This is one of the main problems with reintroduction schemes, which is particularly evident in predators - without learning how to hunt and kill their prey, captive-bred animals cannot survive in the wild and thus depend on humans for their entire lives! The fact that amphibians make such good candidates for breeding in captivity is very fortunate, as over a half of all amphibians are now endangered due to the Chytid Fungus that is killing them in large numbers across the globe and due to their extreme susceptibility to anthropogenic environmental pollutants.

The endangered black-eyed tree frog, Agalychnis moreletti, is currently being bred in captivity in Chester Zoo. The zoo is participating in an international effort called the Amphibian Ark (AArk) program that aims to preserve amphibian life and safe-guard them against their global decline.

The lack of space that is available in zoos however, sadly makes the captive breeding of large animals much less feasible than programs that incorporate smaller species. This is particularly true for large predatory mammals such as lions and tigers, which need very large territories to thrive and do not respond well to being kept in captivity. In addition, they require so much space and cost so much to keep that zoos can only afford to keep relatively small numbers of them in captivity. This means that only a small number of individuals can be bred from so that the captive populations would become vulnerable to inbreeding depression and would suffer from low genetic diversity and have reduced fitness as a consequence. To explain this further, a small breeding population rapidly becomes inbred because simply put, there are no animals available for a individual to breed with that they are not related to. Over time the population becomes more and more inbred and deleterious alleles build up in individuals. Usually such maladaptive alleles are recessive and are masked in outbred individuals who have a 'normal' and healthy allele for the gene so that they don't suffer from its effects, even if they are carrying it. However inbreeding increases the chances of an individual having two copies of the deleterious allele (which are then are said to be homozygous for the allele) so that they suffer from its ill effects - a phenomenon known as inbreeding depression.

The lion, Panthera leo, is one of the most majestic predators in the world. Sadly however, captive lions usually have extremely low sperm counts and a very high percentage of what little sperm they do produce is abnormal. This problem, due to inbreeding depression, is very common in species of big cat and is exacerbated even further by the fact they they rarely even try to mate when in captivity! Problems that makes them very unsuitable for captive breeding programs.

As well as inbreeding depression, captive breeding programs have two other serious problems. The first is that keeping many animals of the same species in a small confined space that often has poorer than desirable hygiene means that the spread of infectious diseases becomes very likely (unless a vaccination against the disease is available). This can be disastrous for the recovery efforts of a species, which is highlighted in the case study of the before-mentioned black-footed ferrets where canine distemper killed all of the first ferrets that were taken into captivity! Sadly this could easily have led to the extinction of the species as more individuals had to be removed from the wild - an example that highlights the final disadvantage of captive breeding programs: removing individuals from an already dwindling population could actually push the species into extinction in the wild, as there may be too few left to breed successfully! Unfortunately, there is no way around this problem and all conservationist biologists can do is make a decision on what they think would be best for a species in its own specific case of circumstances and hope that it's the right one!

So in conclusion, captive breeding programs are undoubtedly very effective measures for preventing species from becoming extinct. However, due to the lack of space that is available and the unsuitability of some species for such schemes, they cannot be used to save every endangered species of animal so we must also take measures to preserve them in-situ in the wild. Often, this is accomplished by protecting animals from hunting under law and by setting up designated animal reserves or parks that specifically aim to protect them and conserve nature (click here for a recent example of a national park).

17 June 2012

Silence of the hunter

The killer whale, Orcinus orca, is one of few species of toothed-whale and is closely related to oceanic dolphins, which first appeared around 11 million years ago. Often being called 'the wolves of the sea', killer whales are highly intelligent and are extremely successful predators that can be found throughout the world's oceans; being able to feed off a wide range of prey species that they hunt using echolocation.

The main prey that a pod of killer whales hunts appears to be culturally specific and typically, pods hunt either mammals, sharks, fish or birds. Cultures of killer whales are highly specialised and efficient at hunting their specific type of prey and use a variety of advanced and sinister tactics. These tactics can be very different depending on what animals the whales are hunting, but usually rely on the stealth or the strength and speed of the whales. Furthermore, these tactics are usually highly coordinated and individual whales have been seen to be 'talking' with each other and adjusting their behaviour accordingly!

Killer whales living at the poles can break up through ice in order to reach the surface and breathe. In order to this they swim upwards like a battering ram and strike the ice with enormous force. The power of such strikes is staggering and was highlighted by the famous British Antarctic explorer Sir Ernest Shackleton, who recorded fragments of ice being scattered for 20 - 30 feet around their holes! This behaviour is also used to knock seals off an ice floe into the water where another whale finishes it off - a fact that was of great concern for Shackleton and his expedition while they were stranded in Antarctica for nearly 2 years!

However, this behaviour has long baffled scientists who study the pods of killer whales that hunt mammals such as seals and sea lions, since all marine mammals have excellent hearing and the whiskers of these animals can detect even very subtle vibrations in water. Judging by this then, it would be expected that their prey should hear the very vocal whales coming and flee the area or climb out of the water to safety. However this isn't the case and often, their prey doesn't even know that the whales are there. New research conducted in partnership between St. Andrews University in the UK and North Carolina State University in the USA has helped to shed some light on this, finding that when they are hunting, killer whales "go into silent mode" and neither speak to each other nor use their echolocation to help them find their prey.

Instead, the whales seem to use a very sophisticated 'search and destroy' method in order to hunt where the members of a pod spread out over great distances and then close in again. This is repeated in silence until an animal is found, whereupon the whales close in on the unfortunate animal and kill it - remarkably, still in complete silence! It is only after they have killed their prey that they begin to talk again, a behaviour that Dr. Deecke from St. Andrews relates to humans: "it's a bit like us in a dinner party - they communicate while they eat then gradually wander off and go quite again".

Killer whales have a highly complex social organisation that is comparable to that of elephants and even humans. At its most basic level, their society is made up of units of closely-related females called matrilines that typically consist of 5 or 6 individuals. These matrilines then form 'pods' with around 4 other matrilines, with which they regularly interact and spend time with. Multiple pods regularly mingle with other pods to form 'clans' and finally, multiple clans interact forming larger aggregations called 'communities', which can be spread over huge areas of ocean.

Exactly how killer whales manage to conduct this very sophisticated behaviour in silence isn't definitively known, but it is believed that they rehearse their hunting tactics beforehand so that an individual whale knows exactly where they are supposed to be and what they supposed to be doing, as well as where the rest of their pod is supposed to be. Scientists at the two universities plan to continue their research by fitting sound recording devices and satellite tracking tags to killers in order to follow their behaviour much more closely and it is hoped that by implementing such technologies into their research, that they can determine for certain whether or not the whales are hunting in set patterns and conduct 'practice' runs.

Legionnaires' outbreak claims its second life

As many of you may already be aware, there has been a sudden outbreak of Legionnaires' Disease in Edinburgh that has sadly claimed lives the lives of two men. The source of the outbreak is still unknown and although scientists doubt that they will ever be able to identify it definitively due to the large size of the industrial estate in the western district of the city, it is believed that the bacteria is spreading in the steam released from the cooling towers of certain factories. The outbreak already has 41 confirmed cases* and the number of suspected cases stands at 48*.

Although Legionnaires' Disease is caused by a range of bacteria from the genus Legionella, approximately 90% of cases are due to infection with Legionella pneumophila. L. pneumophila can cause a potentially fatal form of pneumonia in 'Legion Fever' or in some forms, can produce a milder illness that resembles the flu.

Named after an outbreak of pneumonia in a conference of the American Legion in the Bellevue-Stratford Hotel in 1977, Legionnaires' Disease is caused by small bacteria  from the genus Legionella and can be fatal in severe cases. The bacteria are found in water and are spread to people when they drink or wash in water from contaminated sources - a fact that can play havoc in hotels, apartment blocks and hotels as many individuals' in such buildings use water from the same source, meaning that infection can spread very rapidly. Legionnaires' Disease is rare in the UK however, due to the enforcement of strict regulations for the control and maintenance of water control systems (e.g. heating water to at least 60C) and as such, there was only 245 reported cases of the disease in England and Wales in 2009.

Poor maintenance of the cooling systems in the factory(s) involved is believed to have allowed the bacteria to build up and divide in the steam produced and then be disseminated over large areas of land in the airborne water vapour ejected from their cooling towers; infecting people who unknowingly come into contact with it and breathe in the droplets. Symptoms of the disease includes mild headaches, muscle pains, a persistent cough and occasionally vomiting and diarrhoea - anyone in south-west Edinburgh suffering from such symptoms should contact NHS Direct or their local GP if they are concerned (although the outbreak is believed to have already reached its peak). The disease is rarely fatal however and, as in the tragic cases of the two deaths earlier this week, is usually only so when it infects individuals who already have underlying health problems.

* as of publishing this post

13 June 2012

Parasites can cause schizophrenia?!

Everyone's heard of parasites, how can you not have? They are everywhere - infecting billions of animals, plants and bacteria worldwide and are found in almost every ecosystem imaginable. In fact, parasitism is the most successful form of life on the planet and countless species choose to live in this manner; having evolved over millions of years to take advantage of their hosts and to avoid their defensive capabilities.

Unfortunately parasites also exploit humans and tens of millions of individuals die each year as a result of parasites, with countless more suffering from chronic and debilitating diseases. Probably the most well-known deadly parasites of  man are those from the genus Plasmodium, which affect over half the world's population and are responsible for causing malaria - a disease that kills a person every 12 seconds and has killed more humans throughout our history than all of our wars combined! Of course many other parasites prey on man as well, with other fairly well-known examples including African sleeping sickness (which is caused by African trypanosomes) and the debilitating disease leishmaniasis (which is caused by Leishmania parasites).

A child suffering from leishmaniasis, a protozoan parasite that inhabits macrophages - the same type of white blood cell that the AIDS virus (HIV) lives in. Depending on the strain of the parasite this lesion will either disappear by itself or, without medical intervention, could continue to grow until the child's death.

However many of these diseases occur in hot and distant countries, such as Africa which is plagued by the examples mentioned above, and it is easy to forget that parasites regularly effect us here in Europe, the United Kingdom and the USA as well. In fact, anyone who's ever had an itch in a rather private place knows that we can catch 'worms' - intestinal nematode parasites that latch onto the walls of our gut and shed their eggs through our faeces. However, although unpleasant, catching 'worms' is rarely life threatening and can even help to alleviate the symptoms of asthma and other inflammatory diseases as the body shifts the dominance of its immune response away from the inflammatory causing Th1 response to a Th2 response, which is more suitable for killing worms in the gut! Cases such as this, where parasites can to help reduce the symptoms of 'modern diseases' that have only recently appeared in the civilised world, have led many scientists to believe that our hygiene and healthcare is now so good it it actually harming us in some ways as with less infection our leucocyctes (white blood cells) have nothing to fight and actually begin to harm our own bodies!

However, many of the parasites that can effect us in Europe are much more sinister and do not have such helpful side effects. One such parasite is Toxoplasma gondii, an intracellular protozoan that is arguably the most successful parasite in the world as it can effect almost any warm blooded animal (most parasites can only inhabit one or a very small number of specific species) and is found on every continent of the globe. The parasite is spread through cat  faeces, by ingesting under-cooked meat or across a mother's placenta to her unborn baby (which is known as congenital or 'vertical' transmission) and can affect up to 80% of human populations depending on where you live. For example, the incidence of T. gondii is about 16% in the UK where eating rare meat is unpopular; yet in France, where rare meat and blue meats are in high demand, 8 in every 10 people are infected by the parasite!

While all felids can contract T. gondii and pass sporolating oocysts (which are essentially just 'bags' of membrane that contains multiple parasites) with their faeces, is the domestic cat (Felis catus) that mainly transmits them to humans. This is usually when their owner has changed their litter or stroked them near to their tail and then prepared food without first washing their hands.

It may be confusing then, why so few people have heard of T. gondii or about toxoplasmosis (the disease that it causes) and even more so, why we do not have a vaccine against the parasite. The answer however, is fairly mundane - it is because the parasite does not cause any symptoms in individuals with a normally functioning immune system meaning that healthcare organisations around the world largely ignore the parasite. In fact, healthcare institutions only bother worrying about the parasites in patients in a state of  immunodeficiency, such as AIDS or chemotherapy patients; and during pregnancy, as congenital infection can result in the baby being born  blind, deformed or even in a miscarriage (don't worry - the parasite is checked for during routine baby checks throughout pregnancy and can be killed safely by the antibiotic Spiramycin, which builds up and persists for long periods of time in placental tissue).

The lack of symptoms that T. gondii parasites cause has led many scientists to believe for years that the parasite is safe and doesn't merit further study, despite the parasite forming life-long cysts in our brains that contain bradyzoites (parasites that become active by turning into tachyzoites when the cyst is eaten by another organism. Obviously, this is a 'dead end' for the parasites in humans since we are only rarely eaten). However, recent research suggests that the parasites are in fact harmful to us - slowing down our reaction times, altering our behaviour and inducing many psychotic diseases like the infamous schizophrenia (which despite popular belief, is NOT a split-personality disorder!).

Toxoplasma gondii tachyzoites can be seen here, after absorbing an intracellular blue/purple dye. The parasites can enter almost any nucleated cell and illicit a strong Th1 immune response. Oddly, they want this response from their host and even promote it by secreting their own chemicals! These chemicals can also be beneficial for their host in other ways, helping them to overcome long-established intestinal worm infections and even develop immunity to Leishmania parasites!

It is still not clear exactly how the parasites alter our behaviour, with the outcome appearing to be dependent on gender and personality-type in humans but the changes are believed to be similar to those altered in rodents, where the animals become more likely to take risks; have delayed reaction times; become less able to learn; spend more time in open spaces; and lose their fear of cats - one of their major natural predators! Amazingly, the behavioural changes are so profound that infected mice have been seen to start running in circles with their eyes closed whenever they see a cat! It is believed that these changes are induced in rodent behaviour to increase the changes of them being eaten by a felid - a fact that is highly beneficial to the parasite as T. gondii can only enter the sexual stage of its life cycle inside a cat! Thus, cats are its definitive host and the parasites effectively spend their entire lives trying to get inside a cat. The changes in human behaviour are not believed to be aimed at us directly, but are thought to take place due to the similarities that our brains have to those of rodents.

Research has found that individuals infected with T. gondii are 2.65 times more likely to be involved in a car crash. This is not surprising really, given that the parasites slow down our reaction times and make us more likely to take risks.

Although inducing changes in our behaviour is undesirable and no-one wants to think that they are being manipulated by a parasite so that they get eaten by a cat, it may not really matter in the grand scheme of things - are most of us ever going to be in a position where a cat could eat us? The most worrying problem that is caused by T. gondii then, is the fact that they alter our brain chemistry. Studies have found that the parasite increases the production of the neurotransmitter dopamine in our brains and that this in turn, can lead to schizophrenia - a debilitating disease that is characterised by a range of symptoms including social withdrawal, delusions, self neglect, hallucinations and altered perception and thinking patterns. Schizophrenia is the ninth most prevalent cause of disability worldwide and frequently leaves its sufferers unable to function normally in society. Furthermore, the parasites have been found to be positively correlated with the risk of having a stroke, developing Alzheimer's disease, epilepsy and depression!

Thus, catching and living with T. gondii may not be as unproblematic as previously thought, especially because once you've been infected with the parasites, you will unfortunately have them for the rest of your life. To further complicate matters, it is unlikely that a drug can be developed against T. gondii parasites because once they switch to bradyzoites and form cysts throughout brain and muscle tissue, killing them becomes more trouble than its worth - killing that many parasites at once could release huge amounts of toxins into the host's bloodstream, causing them to die very rapidly from anaphylactic shock. Therefore, the only real protection against T. gondii is to prevent yourself from catching it in the first place. The easiest way you can do this is to ensure that you cook all meat thoroughly at temperatures above 65C for a least 10 minutes, even if the meat has been frozen as the parasites can survive for very long periods of time in temperatures as low as -12C!

11 June 2012

Top 10 fastest animals

One of the simplest ways for a predator to hunt its prey or for a preyed upon animal to escape a predator is to be very fast. This fact has not gone unnoticed in the Animal Kingdom and many different species rely on this attribute for their very survival. As a result of this there has been fierce competition in the natural world to become ever faster and faster - meaning that many animals have evolved over time so that they can now move at completely ridiculous speeds! Using the fastest speed recorded for each species, this post looks at the top 10 fastest animals on Earth and includes terrestrial animals, birds and fish...

10: Sailfish - 68mph/109kph


Sailfish, Istiophorus spp., are prized game fish that are found throughout the warmer oceans of the world.

Growing as big as 3 metres in length and weighing to be 90 kilograms, sailfish are top predators in many ocean ecosystems that mainly hunt fish and squid near to the ocean surface. The extravagant sail that gives the species its name is normally kept down when the fish is swimming, but is raised when it feels excited or threatened.

9: Eider duck - 70mph/113kph


The eider duck, Somateria mollissima., is the UK's heaviest and fastest species of duck.

Eider ducks are found throughout the northern hemisphere and inhabit coastal regions, rarely venturing too far inland. This is mainly because their main source of food is molluscs, which are exposed on beaches during low tides.

8: Canvasback duck - 72mph/116kph


The canvasback duck, Aythya valisineria, is characterised by its long thin neck that it uses when diving to help it forage for underwater plants.

Canvasback ducks are found in North America, growing up to 22 inches long and weighing around 3.5 pounds. The ducks build their nests from mud and moss in the Lower Mississippi Alluvial Valley in the summer, which are then abandoned during the winter as they migrate to the coasts of California.

7: Cheetah - 75mph/121kph


The cheetah, Acinonyx jubatus, is the world's fastest terrestrial animal and is found in most of Africa and some parts of the middle east.

The fact that the cheetah can run so fast on land has long baffled scientists until recently. This is mainly because cheetahs are cats and the most efficient skeleton that has evolved for running is the design employed by canines. Therefore, it makes sense that a dog should be the fastest land animal. Recent studies however have helped to explain this, showing that the cheetah actually has a skeletal structure that is more like that of dog than a cat - a fact that allows the animal to produce extreme bursts of speed. These sprints cannot be maintained for much further than 500 metres however, due to the huge rise in the animals core body temperature that they cause.

6: White-rumped swift  - 77mph/124kph


The white-rumped swift, Apus caffer, can be easily identified by its white rump that is of stark contrast to the rest of its plumage.


Like all swifts, the birds feed off medium to large aerial insects and are particularly active during the late afternoon when the activity of their insect prey is at its highest. The birds are migratory, spending their summers in Northern Europe and Britain and winters in sub-Saharan Africa.

5: Red-breasted merganser - 80mph/129kph


The red-breasted merganser, Mergus serrator, is a diving bird that is in the same family as sawbills.


Red-breasted mergansers can be most easily seen in the UK around coastal regions during the winter. The birds can live in freshwater as well and their tenancy to eat salmon and trout have brought them into conflict with game and industrial fisherman alike.

4: Spur-winged goose - 88mph/142kph


The spur-winged goose, Plectropterus gambensis, can have a wing span as large as 2 meters and can be found throughout sub-Saharan Africa.

Despite its name, the spur-winged goose is not a true goose and is in fact, only distantly related to the animals that give it its name. The spur-winged goose has a few physiological differences to its cousins and is Africa's biggest species of wildfowl.

3: Frigate bird - 95mph/153kph


There are 5 different species of frigate bird, which belong to the genus Fregata. During spring male frigate birds inflate the gular pouch on their neck, exposing their stunning red skin in the hopes of attracting a mate.

Frigate birds are seabirds that are related to pelicans and are sometimes called 'Man of War Birds' or 'Pirate Birds'. The birds primarily eat fish from deep water (in the pelagic zone) although they have also been seen to steal food from the nests of other sea birds, which makes it no surprise that they are so fast!

2: Spine-tailed swift - 106mph/171kmp


The spine-tailed swift, Hirundapus caudacutus, is a migratory bird that spends its winters in Australia and breeds during the spring mainly in Asia and Siberia, but have been found as far north-west as Great Britain!


The spine-tailed swift, also called the white-throated needletail,  is a small bird from the swift family. With its short legs, the bird cannot take off from the ground so they nest high up in cliffs or more recently, in high human buildings. When they wish to fly, the birds simply jump off the cliff and gain control during their free-fall by opening their wings. Once in flight the birds hunt aerial insects and are in fact, the fastest bird in flapping flight as the Peregrine falcon is only faster during its dives!

1: Peregrine falcon - 242mph/389kph


The Peregrine falcon, Falco peregrinus, is one of the most wide-spread birds of prey and can be found across every continent that is not covered by ice.

The Peregrine is a large falcon that is about the size of a crow. The bird is a fearsome aerial predator and is renowned for its agility and unique method of hunting called stooping. The extreme speed of the bird has made it very popular as a show-bird among falconers.

6 June 2012

Paralysed rats walk again!

An interesting new study has revealed that it has been successful in enabling artificially paralysed rats to regain motor function and walk again! These findings have exciting implications for helping humans to recover from spinal damage and Dr. Vissel from the Garvan Institute of Medical Research in Sidney has said that: "we are on the edge of a truly profound advance in modern medicine - the prospect of repairing the spinal cord after injury".

Much of the physiology of the common rat (Rattus norvegicus) is very similar to that of humans, which makes the animal extremely useful for scientific study.

The study, carried out by researchers at the Swiss Federal Institute of Technology (EPFL), involved severing the spinal cord of rats in two separate places at their 7th and 10th thoracic vertebrae (which form the section of your spine behind your ribs). This was sufficient to completely disrupt their voluntary muscle control; leaving the rats paralysed and unable to move. The researchers then injected their spinal cords with a solution of various electrolytes such as serotonin and dopamine receptor agonists, which increased the activity levels of the nerves and stimulated the rats' nerves even further using electricity (at 40Hz if anyone's interested...) by attaching diodes to various segments of their spines near their base.

By supporting the movement of the rats in a robotic harness, researchers found that they were eventually able to walk, run and even climb stairs when their spine was being stimulated! This behaviour was gradually 'built up' however, as the rats appeared to have had to relearn how to move so the research doesn't suggest that there is an 'instant fix' to spinal damage; rather that it is possible with extensive physiotherapy in conjunction with modern medical techniques, such as those used in this experiment.

"It is completely unexpected to see this level of recovery." Professor Courtine (EPFL)

Thus, this exciting experiment suggests that recovery after spinal damage is perfectly possible for humans and that such individuals will eventually be able to live normal and independent lives. Experts point out however that although this technique has worked well in rats, it may not work in humans. 'Real life' injuries to the spine are much more complicated than those that were artificially introduced in this experiment and humans are much larger, more complicated organisms than rats. The study does provide hope however, and, as stated by Dr. Bacon (the director of research at Spinal Research): "this is a robust demonstration that medical research is moving in the right direction and restoring function after paralysis can no longer be dismissed as a pipedream".


van den Brand R., Heutschi J., Barraud Q., DiGiovanna J., Bartholdi K., Huerlimann M., Friedli L., Vollenweider I., Moraud E. M., Duis S., Dominici N., Micera S., Musienko P. & Courtine G. (2012). Restoring Voluntary Control of Locomotion after Paralyzing Spinal Cord Injury. Science 336, 1182-1185.

5 June 2012

Tragedy of the commons? Don't be so melodramatic...

The 'tragedy of the commons' is a fairly well known ecological dilemma, which arises from the fact that people will exploit a shared resource to exhaustion before they will deplete a resource that they own themselves. This concept was first described by the ecologist Garrett Hardin in 1968 and is often used to help plan for sustainable development in an area.

The basic principle underlying the tragedy of the commons is this: an individual who uses their own resources for a service gets the benefit of that resource, but at a cost - they have had to use up resources that they personally own and consequently, cannot use them again. However, an individual who uses a shared resource for a service still gets that all of the benefits that this entails, but they are not using up their own resources. Thus, the individual gets all of the benefits from a service, but at no personal cost. So using common resources seems like a good idea, right? And yes, it is for an individual at their own personal level. The problem is however, that many individuals will have worked out that they can use the resource at no cost to themselves and as such, the common ground will be over used and will be exploited until it is completely depleted and becomes useless. This fact led Hardin to coin the phenomenon of the 'tragedy of the commons': multiple individuals that are acting rationally and in their own personal best interests (as they usually are) will ultimately deplete a shared resource, even when it's clear that this is not always in the best interests for the resource for them to do so.

Note how most of the sheep in this photo have red paint sprayed onto them with one (left), instead having yellow paint. This tactic is often used by farmers to mark their own livestock when grazing them on shared resources so that they can identify their own animals later.

The classic example for the tragedy of the commons and the one used by Hardin to first describe it, is medieval land tenure by European herders. A group of herders all have their own land on which to graze their animals, which by using, they will benefit by having their livestock fed and healthy. However, by feeding their animals off their land they are using up their own grass and without grass, the land's soil is washed away and it may eventually become useless. Knowing this, herders take their livestock to the village or town common instead - land which none of them own and allow their livestock to graze here. Therefore, their animals are still fed but they are not degrading the quality of their own land so that the herders, on a personal level, are in a 'win-win' situation. But, although this is good for a single herder, there is a major problem with this as you've no doubt realised. The problem is that while a single herder may have for example, 10 sheep, which would take a very long time to use up and deplete a field, multiple herders are using the field at the same time. Hence, if 10 herders use it who all have 10 sheep, then 100 sheep are all feeding off the same field - meaning that its resources will quickly be depleted. This rapidly degrades the quality of the common, meaning that soon it will not be able to support livestock and, with poor muddy ground, cannot really be used for recreation either (the purpose for which it was made available to everyone).

This photograph shows the heavy land use of grazing cows. It is unlikely that a single farmer owns so may cows so this is probably a shared resource - a resource which is clearly being overexploited. Even though this overgrazing will rapidly degrade the quality of the land, it allows farmers to feed their cattle at no personal cost to themselves so that they will be inclined to use it until it has been exhausted.

The tragedy of the commons can be applied to all common resources and modern-day examples include overfishing in the world's oceans and industrial logging in the world's rainforests: such resources are either not privately owned or are too big for that ownership to be enforced effectively, so that they are overexploited by multiple groups and as a result, are being rapidly degraded.

The tragedy of the commons is frequently used in arguments that support sustainable development programmes, allowing such programmes to satisfy both conservation and economic entities by encompassing economic growth and environmental protection. Furthermore, it is regularly used as a warning against the implementation of policies that restrict the use of private property or espouse the expansion of public land - factors that may drive individuals into exploiting shared resources! The tragedy of the commons is also used to argue for the privatisation of resources in order to protect them and although desirable, this is often impractical. How, for example, can you privatise the ozone layer or honeybees? To complicate things even further some areas, such as the Amazon Rainforest, are just too big - even it was completely privately owned it is unlikely that it could be protected in its entirety and therefore it is unlikely that illegal logging could be effectively prevented!

Therefore the tragedy of the commons is an issue of logic, where any rationally acting individual will first exploit a shared resource before using their own because this is in their best interests. This means that it is very hard to prevent and in order to combat it, policies must be put into place to control overexploitation and where possible, encourage individuals to use their own resources preferentially to shared ones.

3 June 2012

Extinct bee is re-introduced into the UK

The short-haired bumblebee has been extinct in the United Kingdom since 1988, where its numbers declined as the result of the dramatic increase in farming that followed World War II. This extensive farming was needed to fuel Britain's rapid population growth and sadly, about 97% of the bees wildflower-rich grasslands have now been lost. 

The short-haired bumblebee, Bombus subterraneus. Bees vision is at the ultraviolet end of the electromagnetic spectrum so the insects see blues and purples very prominently, as well as light that our eyes cannot see. As a result, they seem to prefer blue and purple flowers to those that are red or yellow.

However, the loss of their habitat hasn't phased conservationists in the Royal Society for the Protection of Birds (RSPB) in their reserve at Dungeness, Kent (one of the larger counties in the UK). The team have spent the last three years planting as many many wildflowers as possible and have created lush meadows that are already benefiting other species of endangered bee that are still endemic in the UK, such as the shrill carder bee, and the RSPB now thinks that they are ready for the short-haired bumblebee to make its return.

"There will be a really good chance that it [the short-haired bumblebee] will establish, it will  become self sustainable and spread." Nikki Gammons from the Short-haired Bumblebee Project.

The generosity of the Swedish government has made the bee's return possible, who have given scientists permission to go and collect up to 100 new queens from their countryside. The short-haired bee is still common in Sweden and removing a small number of queens such as this shouldn't have an impact on their populations there. Once in the UK, 20 - 30% of the queens are expected to survive their hibernation over their first winter here (which is very high odds for the survival rates of an introduced species) and the colonies that they form are expected to be able to survive fairly well in RSPB Dungeness, persisting there long-term.

Many local farmers are also involved in the project, which also been funded by Natural England and the Bumblebee Conservation Trust (in addition to that of the RSPB), who are planning to leave the edges of their fields untouched. These wild strips, or 'corridors', will contain many of the flowers that the bees need to survive and will help the short-haired bumblebee to spread across its ancient endemic ranges throughout southern England.

Want to help the bees?

Although the re-introduction of the short-haired bee into the UK will hopefully be a success, it doesn't change the fact that bee numbers are crashing worldwide. There are various reasons for this - some are due to man and some are not; but regardless, their loss will have profound implications to us. Bees are estimated to be involved in the production of around a third of all human food by pollinating our crops and represent US$40 billion in terms of the services that they provide to the human agricultural industry - in the UK alone, bees contribute more than £400 million a year to our economy by pollinating crops and medicinal plants!

The production and use of highly toxic neonicotinoid pesticides is one of the major contributors to the demise of bees, a fact that AVAAZ is trying to remedy. By signing their petition you can support AVAAZ when they confront Bayer (one of the major producers of the pesticides) and try to get the company to stop their production. Please consider spending a few seconds to sign this petition - bees are crucial organisms for global ecosystems and need our help!

2 June 2012

Death of the giant eagle

700 years ago the largest bird of prey and one of the largest aerial predators that has ever lived hunted in the skies over New Zealand's South Island - Harpagornis moorei, more commonly known as Haast's Eagle. The bird, weighing up to 15kg (which is very heavy for a bird as they have hollow bones), had a wingspan of 3m and was the top predator in its ecosystem - hunting the moa (Dinornis novaezealandiae), a 12 foot high flightless bird that weighed in at almost 230kg!

Haast's Eagle was a specialist predator and almost exclusively hunted moa, soaring at high altitude before dropping out of the sky at speeds that are estimated to be as fast as 50mph, striking the flightless bird with enormous force! Wounds on the bones of moa suggest that once the eagle was within striking distance of the hapless bird, it grabbed its prey's pelvis with one talon and the crushed the back of its neck with the other. It is believed that the eagle then landed on top of the moa and, if it was still alive, quickly finished it off using its very large and razor sharp beak. Unlike many modern-day predators that have to compete with scavengers for their kill, the isolated island habitat of New Zealand did not have such animals, which enabled H. moorei to have consumed all of its kill by itself, returning to the carcass for up to a week after it was killed! The fact that the eagle could utilise the vast majority of its kill is believed to be one of the reasons that the species evolved to be so large.

An artists impression of Haast's Eagle hunting moa. Despite the eagle's very large size, which is pushing the boundaries of body mass for powered flight, it had a very short wing span. This is believed to be an adaptation for hunting over the scrubland and forests of New Zealand because it allowed them to hunt in dense vegetation.

The other reason that the eagle grew to such an impressive size is believed to be due to a phenomenon called 'island gigantism', which is likely the main driving force behind the evolution of its growth. Island gigantism is a relatively common biological trait where species that live on isolated islands with no contact to the mainlands grow to be unusually large. This may seem strange, but makes sense biologically as these isolated islands often develop their own unique ecosystems due to the fact that the more abundant species that live on mainlands cannot get across to them. As a consequence of this, there are relatively few species inhabiting the island so that such animals are under little competition for resources. Thus, animals on isolated islands are able to fuel large body growth and often evolve to be unusually large. The isolated nature of such islands also means that many of the species that live there have evolved independently from those on the continent so that many of the organisms found on cut-off islands are unique, being found nowhere else. A good example of such novel species are the strange species of marsupials that are found in Australia, which broke away from Africa 184 million years ago. These marsupials have therefore, evolved independently from continental species for a very long period of time.

Growing to lengths of 3 metres the Komodo dragon, Varanus komodensis, is the world's largest species of lizard and the world's biggest poisonous animal. The lizard is found spread across certain islands in Indonesia and is an excellent example of island gigantism, with its large size being attributed to a lack of competition over prey as there are no other species that fill its niche on the islands.

Bizarrely, phylogenetic analysis of the DNA of H. moorei has found that the eagle is not related to other large species of predatory eagle as you might expect, but is instead most closely related to the Little Eagle, Hieraaetus morphnoides. This rather small bird of prey is about the same size as a Peregrine Falcon, weighing a mere 815g! Although it is slightly odd that the ancestor of the Little Eagle remained at such a diminutive size while one of its cousins became one of the most massive aerial predators ever, it in fact supports the idea that island gigantism fuelled the evolution of the colossal size of H. moorei: a small number of the ancestors of the two eagles were trapped in New Zealand after it separated from Antarctica between 130 and 85 million years ago, whilst others remained over the larger continent. Those over the continent had greater competition for resources so could not fuel the growth needed to reach such huge sizes and consequently, evolved into the Little Eagle. Those trapped in New Zealand however, had an abundance of food and evolved into the giant Haast's Eagle.

This shows the foot of H. moorei (left) compared with that of a Little Eagle (right). It has been calculated that the massive eagle's talons could have pierced and crushed bone up to 6mm thick under 50mm of skin and flesh!

Although the large size of the eagle is very impressive it also, rather unfortunately, led to its downfall. Unsurprisingly its extinction was due to the arrival of man to New Zealand, as one of the main characteristics of human invasion into a new environment is the extinction of its endemic megafauna - such large animals provide excellent sources of food and are typically very vulnerable to the alterations that humans make to their habitat. In this case however, humans did not hunt and kill Haast's Eagle directly; instead killing it by wiping out the moa, leaving the eagle with nothing to eat. Obviously, a 12 foot flightless bird was easy pickings for the early Maori settlers (who came from Hawaii) and they exploited the bird, hunting it mercilessly. This over-hunting would have wiped the moa out eventually, but the problem was made even worse because moa eggs were also considered as a delicacy and were raided from the birds nests. This was a huge factor in the moa's rapid extinction because they only laid a few eggs every year; meaning that there were nowhere near enough young moa to replace the adults that were being killed by humans for meat!

Once the moa became extinct it was only a matter of time before Haast's Eagle followed it into the abyss,  mainly because it had evolved to a specialist predator that hunted moa almost exclusively. However even if H. moorei knew how to have hunted the other animals resident to New Zealand, none of them were large enough to have fed it for long so the birds would have eventually starved to death anyway. Although such an end to a species is not uncommon and has happened many times in the past, it is still a sad and rather undignified end for such a majestic species and Haast's Eagles have not soared above the far-flung islands of New Zealand for over 600 years...