The Effects of Stress on Animals

It's ironic that I'm about to talk to you about the effects of stress on animals because I currently look like this:

On a more serious note.. stress can be a very important measure of animal welfare. Stress can potentially show that there is a problem with the animal's welfare, particularly in captive environments. For example in a zoo with a monorail going over an enclosure, if an animal becomes stressed every time the monorail goes over it can indicate that the monorail is having a significant detrimental effect on their welfare.Stress is an important process as it allows the body to adapt to change. The stress response is triggered by a threat such as a decrease in temperature. This causes the hypothalamus in the brain to release corticotropin-releasing hormone (CRF) which travels to the anterior pituitary. CRF controls the release of adrenocorticotropic hormone which stimulates the adrenal cortex to secrete cortisol.

Cortisol is responsible for the body's response to stress. The cells which are not needed for what we call the "fight or flight" response are stimulated by cortisol so that they decrease their use of blood glucose and start using fats and proteins for energy instead. Processes such as immune system reactions are also turned off as they are not needed to cope with the stress. Metabolic rate is therefore increased and life-sustaining processes have more energy. Cortisol is a type of Corticosteroid which are used in stressful circumstances. Corticosteroids stimulate glucose production from fat (as mentioned above), break down the tissue protein, increase the sensitivity of the blood vessels to adrenaline (to allow fight or flight), increase the rate of urine formation, make muscles function for longer, affect brain excitability, increase gastric acid and pepsin secretion, act as an anti-inflammatory and suppress the immune system (as mentioned above). Once the stress response has served its purpose cortisol effects the cells of the brain which causes a decrease in the release of CRF in a negative feedback loop.

The effect of stress on the body has three different stages depending on the length of time the stress is present. The first stage is called the Alarm Stage. This is when the body first reacts to the stress and it's response is in a state of alarm. At this point adrenaline is produced so that the fight or flight response can be used. There is also some activation of the HPA axis, producing cortisol. If the stressor persists then the body begins to adapt to the change and this is called the Adaptation Stage. However, if the stressor persists for too long then the body enters the Exhaustion Stage and it's resources become depleted. This can cause long term damage to the individual with effects such as ulcers, depression, diabetes or cardiovascular problems and it must therefore be avoided at all costs.

The physiological processes which occur when an organism is stressed allow us to measure welfare effectively by taking measurements of cortisol or other corticosteroids. This allows for improvements to be made to a captive animals environment using enrichment. It can also be combined with behavioural welfare assessments to get a better result.

Animal Welfare

Animals have had a bad run of it haven't they? I'm deep in revision at the moment so you will probably get lots of posts from me while I'm doing my extra reading. Yesterday I was revising a lecture about Animal Welfare in general and Legislation. I decided to look up the history of animal welfare and some other bits and I thought they'd make an interesting blog post.

The first ideas on the moral status of animals probably came from the bible. Indeed, in Genesis (1:20-28) you can read about how Adam was given "dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth". Other religions at this time did respect animals, an example of this was in buddhism where not only was there are deep respect for the animal kingdom but there was also a belief in reincarnation which was often not in human form. However, focussing on the Christian view of animals it is probably unsurprising that people such as the philosopher René Descartes (1596-1650) had the view that animals had no souls, mind or reason and therefore could not suffer pain. Nicolas Malebranche (1638-1715) had a similar view and was quoted as saying "animals eat without pleasure, cry without pain, grow without knowing it; they desire nothing, fear nothing, know nothing". Thankfully as time wore on people such as Jeremy Bentham and Jean-Jacques Rousseau argued for animal rights. In the 18th century Rousseau argued that animals were sentiant and Bentham argued that it was the ability to suffer, not to reason, which should influence the decision on whether animals had rights. In the 20th century the situation detiorated rapidly as the second world war came to an end and the industrialisation of farming meant that more animals were being killed for meat than ever before.

Now animal welfare is in the spotlight all the time and there are a huge variety of legislations and laws which can be read about on the DEFRA website. However the definition of welfare is still discussed and debated over. The most popular definitions are that welfare is "the state of an animal as it attempts to cope with its environment (Fraser & Broom, 1990) and "animal welfare is a state of physical and psychological harmony between the animal with itself and its surroundings". In spite of this the five freedoms from the UK Animal Welfare Council (FAWC) are widely accepted and list as follows:

1. Freedom from thirst, hunger and malnutrition
2. Freedom from discomfort
3. Freedom from pain, injury and disease
4. Freedom from fear and distress
5. Freedom to express normal behaviour

 Extrinsic and intrinsic values of animals have a large effect on how people percieve animal welfare. Verhoog (1992) argues that scientists percieve animals as "analytic" beings rather than "naturalistic" like most people and that this may cloud their judgement when they are considering whether an animal's welfare is compromised. As well as this, it could be argued that scientists only take an interest in the welfare of an animal if they think its welfare should be respected. I know from experience that there is much less objection to the dissection of a locust than there is to that of a rat. Resistance to certain areas of animal research, such as genetic engineering, is often found to be for intrinsic reasons (such as it's not fair on the animal) rather than extrinsic reasons (such as risks of the experiment to the animal). Because of this, Rollin (1986) proposed the zoocentric bioethical theory which says that only higher animals with some form of consciousness are morally relevent and should be protected. Sentient animals have more intrinsic value to people as feelings of happiness are considered to be of value to the animals.

References
www.defra.gov.uk
Fraser, D. & Broom, D.B. 1990. Farm animal behaviour and welfare. CAB International, Wallingford, Oxon
Rollin, B.E. 1986. "The Frankenstein Thing": the moral impact of genetic engineering of animals, In: Verhoog, H. 2007. The tension between common sense and scientific perception of animals: recent developments in research on animal integrity. NJAS. 54(4) 361-373
Verhoog, H. 2007. The tension between common sense and scientific perception of animals: recent developments in research on animal integrity. NJAS. 54(4) 361-373

Amphibians and Reptiles are disappearing

The European Adder (from Wikipedia)

The Amphibian and Reptile Conservation (ARC) Trust have released a worrying report naming the species that are becoming rarer in the UK. The population of adders which are native to this country is declining rapidly and the populations of slow worms, common lizards, grass snakes,common toads, common frogs and great crested newts are also becoming more rare. Some of the endangered species already have high levels of protection but this does not apply to some of the species that are considered more common. The plight of the adder is one which must be looked at. While this species was once very common in the UK, it is now one of the rarest widespread reptiles and is in need of serious conservation attention.

The only good news given by the report is of the palmate newt which is actually increasing its range and becoming more common.This is thought to indicate changes in the quality of Britain's ponds as palmate newts prefer acidic pools which are now common from acid rain fall and agricultural run off which are major problems associated with pollution. However the main problem which is thought to be effecting the populations of amphibians and reptiles is habitat fragmentation.

Elephants Know About Cooperation

A new study has suggested that elephants know when they need help from another. The study, led by Dr Joshua Plotnik from the University of Cambridge, tested Asian Elephants (Elephas maximus) using a table with food on which was attached to two pieces of rope. The elephants quickly learned that pulling on the piece of rope without a helper caused the rope to fall on the floor and therefore the table was not pulled closer. This advanced grasp of the need to work together indicates that elephants belong to an "elite group of intelligent animals". Studies such as this one can be really helpful in developing conservation programs for endangered animals such as these. Read more on this story here.

Zombie Ants

Picture from The Guardian website

Fungi have been discovered in Brazilian jungles which infect ants, take over their bodies and ensure that they die in a place that is a perfect position for the fungus to grow and breed. This leaves "zombie" ant corpses, like the one above, with their mandibles attached to leaf veins which are the perfect place for spores to be released. Victims of this fungus (named Ophiocordyceps) have been found from up to 150 years ago but the mechanism involved has only just been discovered. Ants either find the spores on the floor of the forest or they fall on the ants from above. In seven days the fungus grows and releases chemicals which make the ant wander off and bite onto a leaf vein, usually in a place which is perfect for fungal growth. The ant dies moments after, leaving behind a vessel from which the fungus shoots is spores during the night.

Just another example of the marvellous ways in which fungi spread their spores (remember the glow in the dark fungi?).

Tagging May Be Harmful to Penguins

From BBC

There are many problems which must be overcome when carrying out studies on wild animals. For example when studying captive animals it is relatively easy to keep track of the animals. When carrying out studies on wild animals, especially over a long period of time, there are a few ways to make sure the same animals are used each time you sample. One of these methods involves putting a band around the flipper of a penguin and has been widely used up to now. It allows scientists to study specific individuals without having to catch them and cause them unneeded stress. The study of these animals is as important as ever, especially with the effects that climate change is having on their habitat. However, it has now been suggested that the use of these bands could actually be harmful to the animals.

When swimming, penguins use only their flippers to propel themselves forward and this is the reason that many scientists have questioned the use of these bands. Saraux and colleagues have now found that the use of these bands causes the survival rate in adult King Penguins to decrease significantly compared to the survival rate of non-banded individuals.As well as this, the breeding rate for those that survived was also significantly lowered. Finally, their study showed that banded penguins were more negatively effected by climate change than non-banded penguins as they arrived late to breed and therefore missed out on opportunities to create offspring. This study was a decade long and therefore longer than most other studies on this subject. Other methods of tagging are now going to have to be considered such as transponders under the skin of the individuals. As well as the effect these bands have on the survival rate of the animals, with the change in behaviour also considered the results of any past or future studies using these bands may be deemed insignificant and may have to be carried out again.

Reference
Saraux, C., Le Bohec, C., Durant, J.M., Viblanc, V.A., Gauthier-Clerc, M., Beaune, D., Park, Y., Yoccoz, N.G., Stenseth, N.C., Le Maho, Y., 2011. Reliability of flipper-banded penguins as indicators of climate change. Nature 469, 203-208

Glowing Mushrooms and Fireflies

I've been neglecting you dear Zoology blog. I am very sorry and I am going to try and post on here at least once a week to keep on top of my extra reading. This evening I would like to talk to you about a very interesting subject I had a lecture on this week, bioluminescence. Many of us will have seen examples of bioluminescence (without knowing the fancy word for it) in fireflies and some people may also have seen glow worms. The majority of bioluminescence however is found in the oceans.

animals.nationalgeographic.com

As you would expect, it is very hard to see when you live in a deep sea habitat. The photo above is a Anglerfish which lives in very deep regions of the ocean and looks very much like a scary alien from a sci-fi movie! As you can see, the Anglerfish has a lure which has a light on the end. If you have ever seen Finding Nemo you will know that it uses this lure to attract smaller fish for it to eat. Dragonfish have a similar lure which goes underneath them rather than over their mouth. Dragonfish also have a light next to their eye which is a wavelength that only they can see. This is a pretty nifty way of being able to see both predators and prey without them seeing you.

tech.ca.msn.com

Bioluminescence is also helpful for marine organisms avoiding predators. The Hawaiian Bobtail Squid uses a bacterium (Vibrio fischeri) to create light which it reflects from its body in the same direction as the moonlight and therefore obscures its silhouette in the water and makes it difficult for predators to see them. The image above is the deep sea octopus (Stauroteuthis syrtensis) which is one of the very few bioluminescent octopuses. Strangely, it is the suckers on this octopus which light up and the function of this is not yet known but could be to either attract prey or for communication. The bioluminescence shown in ocean species is generally either blue or green as these are the colours that travel the furthest. In terrestrial organisms the colours can vary greatly.

animals.nationalgeographic.com

As I mentioned earlier, fireflies are a well known example of bioluminescence and are one of the few terrestrial examples. Since fireflies are usually seen as little glowing dots I thought I would give you a close up picture of one. Different species of firefly use different colours of light depending on the time of day they use their light and the ability of that particular species to see different colours. Many species emit red light but we only see yellow or green light due to our eyes. These organisms use their light to attract mates so they can reproduce, which is very different from the marine organisms we have already talked about.

Wikipedia

Finally I would like to talk to you about bioluminescent mushrooms. That's right, glowing mushrooms. The picture above shows a tropical fungus which is often found on decaying matter such as wood or leaves. When conditions, such as temperature and water content of the soil are right, these fungi glow. At night insects are attracted to the fungi and carry away spores which are then dropped somewhere nearby. This allows maximum growth of the spores due to the good conditions.

Bioluminescence is a very interesting subject that is still being researched. It is unknown why many organisms spend so much energy on producing light and studies are currently going on to help us discover more about this fascinating subject. The animals I have mentioned about are only a few of the many examples of this phenomenon and many are still being discovered.

References:

•  Deheyn, D.D., Latz, M.I., 2007, Bioluminescence characteristics of a tropical terrestrial fungus (Basidiomycetes), Luminescence, Voll 22, pp 462-467
• Dehingia, N., Baruah, D., Siam, C., Gohain Barua, A., Baruah, G.D., 2010, Purkinje effect and bioluminescence of fireflies, Current Science, Vol 99 (10), pp 1425-1429
• Johnsen, S., Balser, E.J., Widder, E.A., 1998, Light emitting suckers in an octopus, Nature, Vol 398, p113
• Nyholm, S.V., McFall-Ngai, M.J., 2004, The winnowing: establishing the squid-vibrio symbosis, Nature, Vol 2, pp 632-643