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

How Do Springbok Keep Cool?

www.ultimate-africa.com

Springbok (Antidorcas marsupialus) live in South Africa which, obviously, can get very hot during the day. Many animals that live in Africa tend to try and stay in the shade during the day to keep cool but there are also those that store heat in their body during the day and then let their body temperature decrease rapidly during the night so that the next day they can do the same again. This technique is called adaptive heterothermy and has been seen in often in captive animals. Fuller et al (2005) carried out a study to see whether this technique was also found in wild animals and decided to investigate a free ranging herd of Springbok.

For this study some very impressive technology was used to save time and also to make the results more accurate. Small data recorders where implanted inside each animal and these measured the body temperature of the animals every 30 minutes for a year. If this technology had not been used then the Springbok would have had to have been captured every 30 minutes, every day for a year. Not only would this be very time consuming, it would also affect the results of the study because the animals would likely be stressed about being caught all the time. While the animals were doing their own thing for a year, the team measured the temperature of the air, the wind speed and the humidity so that at the end of the year the body temperature could be compared with the weather.

If the Springbok used the technique described above then the body temperature would be expected to change often with very wide swings. They actually found that the opposite happened. No matter what the weather was like, the body temperature of the animals hardly changed. This technique is called homeothermy and it was a very surprising find. Even stressful events like giving birth did not affect the body temperature a great amount.

This study highlighted a very important point to consider when carrying out experiments on body temperature. When animals are roaming free in their natural environment they often use behavioural mechanisms to change body temperature instead of using physiological mechanisms such as adaptive heterothermy. Behavioural mechanisms like this include huddling together when it is cold or finding a shady area when it is too warm. Fuller and team made a mistake in this study because they did not watch the behaviour of the animals, they only took physiological measurements. Hopefully further studies will be carried out that will learn from this mistake!

References

Fuller, A., Kamerman, P. R., Maloney, S. K., Matthee, A., Mitchell, G. and Mitchell, D. (2005). A year in the thermal life of a free-ranging herd of springbok Antidorcas marsupialis. J. Exp. Biol. 208, 2855-2864.

A Decade Long Marine Census Comes To An End

Yeti Crab - Census of Marine Life

The Census of Marine Life which started in 2000 has finally been completed. It is estimated that during the census 20,000 new species have been discovered, bringing the number of known species to nearly 250,000. The decade long project cost £413m and aimed to find out what lived, lives and will live in the oceans. It involved more than 540 expeditions with over 2,700 researchers and used many new types of technology. Fish were tagged and seals were fitted with monitors to record when they dived. Acoustic systems were used to measure fish populations.

Dr Ian Poiner, the chairman of the project’s scientific steering committee, told the BBC “All surface life depends on life inside and beneath the oceans”. This is literally true because we know that life evolved from the oceans and the very first life forms were aquatic organisms. Back then the atmosphere did not have everything they needed to survive but the water did. It was a while before the air contained the nutrients that were needed but eventually life began to evolve on earth. It is thought that there could still be many undiscovered species in the oceans and there could be at least a million of them in total.

Many wonderful species have been discovered during this census, including a Jurassic Shrimp that has thought to have been extinct for at least 50 million years and a crab which has been named the Yeti Crab (see the picture at the top of this post). However, it wasn’t just large organisms that Dr Poiner’s project looked for. The census included trying to tell tiny microbes apart using genetic sequencing. If you thought that a million organisms was a lot then you will be surprised at how many different types of microbes are thought to be in the water – one billion. Hopefully the Census of Marine Life will serve as a base for us to build on to try and preserve marine life.

Source - MSN News

A New Species of Giant Elephant Shrew?

An elephant shrew in an undated photo released September 21, 2010.
Credit: REUTERS/Zoological Society of London/ Handout

Researchers in a remote Kenyan forest, the Boni-Dodori forest, think they may have discovered a new species of Giant Elephant Shrew (Macroscelidea). Further genetic analysis will be carried out by the Zoological Society of London and the Kenya Wildlife Services (KWS) to determine whether this is actually a new species or whether it is a new variety of a current species.

Interestingly, the Giant Elephant Shrew is more closely related to elephants than shrews. Unlike many small mammals, these Shrews are only active during the day. They use their long snout to search under leaf litter where their food source, invertebrates, can be found and eaten with their extremely long tongue. It is the long snout that originally gave the Elephant Shrew their name.

Scientists launch many expeditions a year to research biodiversity around the world and this is especially needed now that forests take up a much smaller area of the world than they did 40 years ago. This is particularly dangerous as loss of habitats can cause animals to become endangered and even extinct, especially if they are not as widespread as some animals. The Giant Elephant Shrew are among the list of endangered animals and the discovery of a new species is a very significant discovery. Elephant Shrews tend to be more adapted to areas where water and food is available all year round, such as coastal forests, and destruction of the forests can be drastically dangerous for the survival of these species.

References:

The African Wildlife Foundation (AWF)

http://www.reuters.com/article/idUSTRE68K2SX20100922

Thanks to fellow zoologist Nicola for pointing this story out to me!

Why Do Lions Roar While Cats Meow?

If you don’t already know (and why would you?), cats are my favourite animals. I love small cats and large and my favourite cat is the Tiger. I was therefore very interested when I saw this article on the BBC website. In it, Ella Davies explains why bigger cats, like Lions and Tigers, roar and Wildcats meow. I have wondered this for a while and find it very interesting so I thought I would tell you all about it.

In a recent study, two scientists from the Alexander Koenig Zoological Research museum in Germany analysed the calls of 27 different species of cat and investigated whether they were affected by the habitat that the cat lived in and the size of the cat. While previous research found that it was the cat’s size that influenced the pitch of its calls, this study showed that cats living in open areas (e.g. lions, servals and cheetahs) had deeper calls than those living in dense habitats such as forests (e.g. marbled cats, wildcats and clouded leopards).

Previous research has shown that high pitch calls can be disrupted by dense vegetation and low pit calls are disrupted by air turbulence in more open spaces. Other scientists believe that the reason is actually because big cats can produce sounds at a lower frequency and this is why lions roar while cats meow. However, this study investigated this theory and found that body weight had no effect on how deep the call was.

I have found the published works of this study and plan to read through it for some more information. I will get back to you! You can find the article at the BBC here.

Kin Selection and Evolutionary Stable Strategies in Vampire Bats

This morning I have been reading about evolutionary stable strategies and one of the examples given in this week’s lecture was reciprocal food sharing in Vampire Bats so I have done some reading on it. I think it is really interesting how these bats behave so I’m going to tell you a bit about it from what I have learnt! First we need a definition of what an evolutionary stable strategy actually is. If most members of a population adopt the same strategy and this cannot be bettered by any other strategy then it can be defined as an evolutionary stable strategy (or an ESS). These are frequency dependent and this is because the successfulness of the strategy depends on what the organisms around you are doing. It can also depend on whether there are “cheats” around as these can take advantage of the ESS and lead to its downfall.

The research I read this morning was done by Gerald S. Wilkinson in 1984 and it is an example of an evolutionary stable strategy in the Vampire Bat (Desmodus rotundus). Vampire bats who do not manage to get a blood meal during the night often beg blood from successful individuals in the roost during the day. The successful individual may regurgitate some blood for the other bat to take in and therefore increase its chance of survival. Wilkinson investigated how this behaviour was an evolutionary stable strategy and came up with three conditions that need to be fulfilled in order for it to be considered an ESS. These were:

1. There must be enough repeated regurgitations between pairs of bats so that they each get a chance to regurgitate and receive blood
2. The benefit of receiving the blood must be greater than the cost of donating
3. Donors need to be able to recognise and not feed previous bats that have not reciprocated

When doing a census of the roost, it was found that the main social unit is the female group. This is because males tend to leave their natal group when they become one year old. Female bats tend to stay in their maternal groups and this means that female groups are usually made up of close relatives with only a few exceptions.  Most of the regurgitation of blood occurs between a mother and her offspring and any others tend to be between animals that are frequent roost mates. Blood is donated preferentially to individuals that are likely to die in the next 24 hours if they are not fed. This shows that the giving of blood is to increase the chances of a survival of a related bat. If the bat survives to adulthood it is more likely to reproduce and pass on the family genes. This is called Kin Selection and is quite common in the animal kingdom.

References

Wilkinson, G.S., 1984, Reciprocal food sharing in the vampire bat, Nature, Vol 308, pp 181-185