Tag: mice

Posted in Science & Nature

Grasshopper Mouse

Posted on by Jinavie

Grasshopper mice are a species of New World mice found in deserts throughout North America. They are small-to-medium sized, growing up to 13cm in size and weighing around 40-50g.

Despite their cute appearances, they are carnivorous, ferocious hunters. They feast on various insects, but are also known to hunt other mice.

Grasshopper mice have interesting adaptations that make them seem more like a miniature wolf or mongoose rather than a mouse. For example, they stalk their prey like a cat before pouncing. They hunt highly venomous insects such as scorpions and centipedes because they have evolved to convert the deadly toxins of a scorpion sting into harmless chemicals.

An interesting feature of the grasshopper mouse is that they often howl like a wolf to ward off competitors and to communicate with each other. It has been nicknamed the werewolf mouse because they are known to howl in the night with their heads thrown back, communicating over the vast desert with a high-pitched howl.

Posted in Science & Nature

Shared Bodily Warmth

Posted on by Jinavie

Body heat is a vital condition that animals need to survive. It is so vital that when you are hypothermic, your body will override almost everything else to conserve heat as much as possible. Without enough heat, the chemical reactions that fuel your cells will grind to a halt and you will die. To solve the issue of getting heat, nature came up with two answers: endotherms and ectotherms.
Endotherms are organisms that produce their own heat (e.g. mammals) by trapping the heat produced by metabolism and through extra mechanisms such as shivering. Ectotherms rely on absorbing environmental heat (e.g. reptiles), usually through the sun. Because of this, ectotherms suffer a much greater range in body temperature. This means that animals such as lizards will be slower and more sluggish when it is cold.

Being in a cold environment quickens the process of heat loss, robbing you of the precious heat you generate. A solution to this is shared bodily warmth. Also known as kleptothermy, this is a common thermoregulation strategy where a group of animals huddle together to share the heat generated by each other. This increases the efficiency of heat generation (thermogenesis) and the group as a whole can stay warmer for longer. This behaviour is commonly seen in communal animals such as mice, who huddle together even when they are newborns (newborns lose heat much quicker than adults due to the difference in weight to surface area ratio). Some ectotherms such as snakes and lizards also engage in kleptothermy, where by huddling together they increase their effective mass and reduce heat loss.

An interesting case of kleptothermy is seen in Canadian red-sided garter snakes, where the heat is not shared, but stolen. A male snake will sometimes emerge from hibernation and begin to produce fake pheromones to attract other males as if it were a female. Other males are fooled into thinking that the snake is female and approach it to mate. Through this strange process, the snake is able to steal the heat from its rival males and use the extra energy to mate with an actual female (or lose it to an even more cunning male snake).

Posted in Psychology & Medicine

Overpopulation

Posted on by Jinavie

In 1972, John B. Calhoun designed a very specific mice cage called Universe 25, also known as the Mortality-Inhibiting Environment for Mice. Universe 25 was designed as a practical utopia for mice. It was constantly replenished with food and water, each wall had an intricate grid of nesting boxes connected by mesh tunnels and stairwells (like an apartment) and the cage was cleaned periodically. There were no predators, the temperature was set at a comfortable level and all mice resident were disease-free. In all ways, Universe 25 was an idyllic home for the mice.

Calhoun’s aim of this experiment was the same as the countless experiments before Universe 25: to see the effects of abundance on a population, and the consequences of that. Biologically speaking, a population only grows to the point that the environment can sustain it and then plateaus. So if the environment is completely abundant, the population will grow and grow without limitations (other than space). Thus, Calhoun’s main focus was overpopulation in societies. What did he find?

At the start of the experiment, four breeding pairs of mice were introduced to Universe 25. They began reproducing after 104 days of familiarisation and the population increased exponentially. The mice flourished in the prosperous environment. Around day 315, population growth slowed. By this stage, the mice population had grown to over 600, which made Universe 25 very crowded. Although there were still plenty of resources, the problem of overpopulation still remained. As the population grew and space became limited, male mice found it too difficult to defend their territory and eventually gave up doing so. The mice began losing their ability to form social bonds and these mice (“failures”) began congregating at the centre of the cage. This group of mice gave up on all normal social behaviour, leading to constant violence. The violence soon spread throughout the cage, with the mice society descending into chaos. The females, stressed and confused by the violence, attacked and cannibalised their own young, after which they retreated to the highest nest boxes where they isolated themselves. Certain males (termed “the beautiful ones” by Calhoun) did not show violence or any interest in females, choosing only to eat, sleep and groom themselves, wrapped in narcissistic introspection. Because of these two isolated groups, procreation slumped and population growth slowed. Elsewhere, in the “inner city” group at the middle of the cage, cannibalism, pansexualism and violence became common. The entire society had collapsed.

On day 560, the population ceased to grow at a peak population of 2200. After this, the number of pregnancies dwindled to nothing and no young survived past infancy. Adult mice were also affected, with mortality rates skyrocketing at all ages and increased rates of diseases. It was clear that the population was headed towards extinction. Even after the population dwindled down to a much more sustainable number, the mice were incapable of (or chose not to) reproducing to regenerate the population. Not only did mice society die, but the mice themselves met a grim fate as well.

This result was repeated in all of Calhoun’s experiments, conclusively showing that overpopulation leads to the demise of a society. Calhoun described this as “crowding into the behavioural sink”. He explained that the mice served as a warning to what human societies are headed towards if we do not solve the problem of overpopulation. We can already see the effect overpopulation has on societies. It is a known fact that people living in the inner areas of a city are more prone to poverty, crime, violence and a lower quality of life. However, Calhoun was not a nihilist. Instead of saying “humanity is doomed”, he explored different ways of resolving the problem. The most effective idea he came up with was space colonisation.

Posted in Science & Nature

Belling The Cat

Posted on by Jinavie

There once lived a community of mice in the attic of a house. The mice would sneak into kitchens, gnaw holes in the walls and run about freely. The owners were so fed up that they brought in a cat, causing the mice to all hide in fear. The terrified mice eventually held a meeting to discuss how they would sneak around the house without getting caught by the cat. One mouse suggested: “What if we put a bell around the neck of the cat? Then we can hear it coming and run away.”. The mice unanimously agreed that it was a brilliant idea. However, when they came to decide who would bell the cat, no mouse was brave enough to step forward and the plan was never carried out.

What would actually happen if a cat was belled? Without a doubt, the cat would take it as a cruel, cruel punishment. Not because it cannot catch mice, but because the sound of the bell ringing every time it moves will be extremely loud for the cat. A cat’s hearing is six times better than a human’s. With this excellent hearing, the constant sound of bells attacking its eardrums would be physical torture for the cat.

Furthermore, a cat can hear frequencies as high as 40,000Hz. A person can only hear up to 20,000Hz, meaning a cat hears over twice the range of sounds we can. This combined with the boosted volume results in the cat living in a very noisy world. Ergo, putting a bell around a cat’s neck is an extremely atrocious thing to do.

Posted in Psychology & Medicine

Toxoplasmosis

Posted on by Jinavie

There is a protozoan parasite called Toxoplasma gondii. This parasite infects many animals through an interesting route. 
The first victim is a mouse. An infected mouse loses its fear of cats, leading it to play fearlessly in front of one until it gets caught and eaten (was Jerry a mouse with toxoplasmosis?). It is unclear how it controls a more advanced animal’s brain, but thanks to this effect, Toxoplasma gondii can infect its intermediate host – a cat.
An infected cat starts excreting parasite eggs with its faeces. If a person forgets to wash their hands or eats food contaminated with cat faeces, they can be infected and become the final host for the parasite.

Usually, Toxoplasma gondii cannot overcome the healthy immune system, but it can infect those with a weaker immune system such as the elderly or pregnant women. Furthermore, it is part of the TORCH complex (toxoplasmosis, rubella, cytomegalovirus, herpes) – a group of infections that commonly cross over from the mother to the fetus in utero. Symptoms are normally flu-like, but if more severe it can cause dysfunction of the eyes, brain and other vital organs. Sometimes it lies dormant until the person’s immune system is weakened, whence it becomes active. Toxoplasmosis is also a possible cause of a miscarriage or infertility.

One fascinating symptom of toxoplasmosis is psychiatric disorders. Because Toxoplasma gondii can infiltrate the brain, it is known to cause depression or even schizophrenia. As cats are the most common intermediate host, cat owners are more susceptible to toxoplasmosis. Because of this, there is a theory that “crazy old cat ladies” are in fact toxoplasmosis patients.