Lyes of attraction

Except for the occasional white lie here and there, most of us try to avoid deceiving our families and friends and dislike being lied to by others. Lying is not considered a positive trait and people who tell fibs too often are mistrusted and usually find that they have fewer friends than they thought they did.

As you undoubtedly know, lying is a particularly huge issue in relationships and has probably broken up more couples over human history than we can record. This comes as no surprise and dumped liars rarely receive sympathy as we all know that it's their own fault. What is odd though, is that not all animals share our views on lying and for one species in particular, the Australian lyrebird, the better an individual can lie the more popular they are!

Lyrebirds are among the most esteemed of Australia's native animals and are famous for their impressive prowess of 'lying'.  There are just 2 species of lyrebird: the superb lyrebird (Menura novaehollandiae) that is pictured above and Albert's lyrebird (Menura alberti), which belong to their own unique genus.

In fact, being able to lie well is much more important than simply for making an individual popular - it is an essential skill that a male bird must master if he wants to attract a mate! Lyrebirds, you see, have one of the most sophisticated courtship rituals in nature, which involves splaying their luxurious tail feathers (in much the same way as a peacock), and mimicking as many noises as they possibly can. These sounds, which can be imitations of anything, such as other bird calls, car alarms and even chainsaws felling trees, are then incorporated into an elaborate song that the male may sing for up to 4 hours a day during breeding season (June to August)!

It appears that the more complex the courtship song, the more successful the male bird is in attracting a mate. Once a male lyrebird has successfully mated with a female bird, she lays a single egg in a nest that she's made on the ground, and incubates it as the sole parent for nearly 2 months.

Analysis of the songs made by courting lyrebirds has found that they are usually split into 7 clearly distinct sections, where about 80% of the entire song is made from mimicry. Male and female lyrebirds both become sexually mature before they are 10 years old, although it should be noted that females mature a few years earlier than males do. Due to this, male birds don't actually start singing properly until they are almost a decade old. Before then, males are believed to practise 'lying' where they learn to modulate their highly developed voice box so that it can mimic almost any sound they hear.

Thus, the ability to lie and produce a whole host of sounds that are not normally made by lyrebirds is a huge part of their culture and has made the passerine (song) birds one of the most noted birds in Australia, and maybe even in the world.

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...

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.

Reference

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.

Spit: the smell of survival

The Australian outback can reach blistering temperatures as high as 50 degrees Celsius during the day and its landscape often lacks trees, making it is hard to find shade. This makes it extremely difficult for animals to survive in, mainly due to the dangers of dehydration and overheating. Overheating damages enzymes, which are important for digestion and many key biological processes, causing them to denature (lose their specific structure) and become non-functional; meaning that the animal may die.

In order to survive in such hostile conditions, the species that live in the outback have evolved many physiological and behavioural adaptations that allow them to cope with high temperatures and often, limited access to water. The most obvious behavioural adaptations are restricting activity to the night (nocturnal) or to the twilight (crepuscular) hours, when the temperature is much cooler. Most physiological adaptations are designed to increase the amount of heat energy lost by an organism and a striking example of this is having extremely large ears. Although this may look comical to us, it is actually a very clever way of cooling down since large ears have a very high surface area, from which the body's excess heat energy can be lost and are very thin. This high surface area to volume ratio makes them perfect for losing heat energy and they contain many blood vessels, which continuously carry the hot blood from the animals core to their ears. Thus, losing heat energy via the ears is extremely efficient and makes it possible for them to remain cool enough to survive. In addition, it also improves their hearing as large ears can 'collect' more sound waves than smaller ones, helping them stay alert for the sounds of predators or prey, respectively.

A bilby in Australia. Its large ears lose a lot of heat energy, helping it to survive in the extremely hot conditions of the Australian outback.

Controlling the times of activity and possessing adaptations like large ears are fine for smaller animals, such as biblies, but kangaroos are large and very active. A particular problem they have is that hopping, their main method of locomotion, is very energy expensive and produces lots of waste heat energy. Thus, these common methods of controlling body temperature would be inadequate to allow kangaroos to survive in such extreme conditions by themselves. So, to increase the amount of heat energy they lose, kangaroos use a novel behavioural trait - they lick the insides of their forearms. Although this may seem strange, it is highly efficient at losing heat energy and works by the same principles as sweating, which makes sense since kangaroos, like many mammals, are unable to sweat and rely on panting as a method of water loss instead. The process loses heat because the water on the skin absorbs heat energy, which it uses to evaporate. As the water leaves the skin, it carries the energy it has absorbed with it, cooling the skin down. Therefore, kangaroos can lose an enormous amount of heat energy via 'spit bathing' as it is called, helping them to stay cool

The importance that spit bathing plays for the survival of kangaroos is indicated by the highly developed salivary glands in their mouth. Of particular importance is the the parotid salivary glands, which are very large and are twice as heavy in relation to a kangaroo's body size than in other ruminants, such as sheep. They also have an extremely large number of serous-type secretary cells that constantly produce saliva, which is unusual because in most animals they are mainly active when food is actually being eaten. Thus, kangaroos can constantly produce large quantities of saliva.

A red kangaroo lounging in a hole that it has dug in the shade beneath a tree. Note its large ears and long thin forearms, perfect for losing heat energy.

However, there is a major problem with using saliva to cool themselves down - it wastes valuable water in an environment where it is already scarce. How then do kangaroos manage to keep enough water to maintain their blood pressure, whilst using enough to cool down? Firstly, kangaroos are able to concentrate their urine by absorbing much more water back from the filtrate in their kidneys than humans are able to do, which reduces the volume of urine that they produce and thereby, limits water loss. Secondly, they slow down their metabolism during the hottest parts of the day so that their body uses up less water in respiration.

Thus, kangaroos are able to survive in the hot, arid conditions of the Australian outback, despite their large size and active lifestyle.