LSM1303 Animal Behaviour

Giant Ichneumon Wasps

Ichneumon wasps are insects that could inspire a horror movie! It picks a victim, usually a caterpillar, and injects her eggs into the host’s body. Often she also injects a poison that paralyzes the victim without killing it. Then, it eats the caterpillar but it keeps the victim alive as long as possible by eating its fatty deposits and digestive organs first and saving the heart and central nervous system for last. 

Ichneumon wasp species are highly diverse – ranging from 3 mm (1/8-inch) to 13 cm (5 inches) long. Most are slender, with the females of many species having an extremely long ovipositor for laying eggs. Despite looking formidable, the ovipositor does not deliver a sting like many wasps or bees. It can be used by the wasps to bore into and lay eggs inside rotten wood.

She will tap the wood with her antennae, “listening” for the vibrations of her prey target: a larvae of the horntail wasps, which live inside cells in the wood. After locating her target, she will drill her ovipositor through the wood, into the defenseless prey. When the wasp senses the tip of the ovipositor in contact with the host larva, she injects the egg through the hollow tube. Upon hatching, the larval ichneumon feeds either externally or internally, killing the host when they themselves are ready to pupate.

Ants and such wasps are deadly enemies! 

The ants are duped by chemicals into accepting, nurturing, and protecting the butterfly caterpillar as one of their own. But when the wasp detects a caterpillar hiding inside an ant colony, it uses its own clever chemical trickery to sow confusion in the ranks of the ants, allowing it to gain access to the caterpillar.

The intruding wasp, by secreting a cocktail of compounds called pheromones, throws the ants into such a frenzy that they attack and even kill one another. In the chaos, the wasp slips unnoticed through the ant nest and preys on the unguarded caterpillar.

Pheromones have long been considered for use in controlling ants, said Graham W. Elmes of the Natural Environmental Research Council’s Centre for Ecology and Hydrology in Dorset, U.K. New pheromones he and his colleagues in Britain and Japan have recently discovered last longer than most such chemicals, making them particularly promising candidates for insect control.

Time could be running out, however. In recent years, the endangered wasps that produce the chemicals have been found in just four alpine meadows—two in southern France, two in northern Spain. None of the sites are protected from agricultural development.

All the same, it’s the caterpillar the wasp is really after. Female parasitic wasps lay their eggs on the caterpillars. As the caterpillar matures, the wasp eggs develop into larvae and eat their way through the caterpillar, killing it. To do that, though, the wasp must get by the ants, which naively protect the caterpillar as if it were one of their own.

Sounds like a gruesome murder indeed!

References:

http://www.2spare.com/item_55014.aspx
http://en.wikipedia.org/wiki/Ichneumon_wasp
http://www.cirrusimage.com/hymenoptera_ichneumon_megarhyssa_fem.htm
http://insects.tamu.edu/fieldguide/cimg327.html
http://news.nationalgeographic.com/news/2002/05/0530_020530_ants.html

The blue whale is the largest mammal ever to have existed, measuring up to 27 metres or more in length and 150 tons or more in weight. The haunting call of the blue whale is the most intense of any animal alive. The deep rhythmic pulses and moans are loud enough to travel across entire oceans, yet are totally inaudible to human ears due to low frequency. Blue whale calls are between 10 and 40 Hz, usually lasting between 10 and 30 seconds. (Song tracks)

Aerial view of blue whale (Wolcott Henry)

Richardson et al (1995) deduced 6 possible reasons of blue whale calls:

1. Maintenance of inter-individual distance

2. Species and individual recognition

3. Contextual information transmission (e.g. feeding, courtship, alarm)

4. Maintenance of social organization(e.g. contact calls between males and females)

5. Location of topograhic features

6. Location of prey resources

In recent years, reseachers discovered that the blue whale song is getting deeper as their population slowly recovers after nearly facing extinction. In 1962, the calls were at frequency of around 22Hz. In 2007, they decreased to around 15Hz. When their population increases, the blue whales communicate over shorter distances and do not need to be as loud. Hence, songs become deeper.

Until today, the exact purpose of blue whale calls still remains a mystery. Marine biologists believe that the blue whale songs could assist in conserving the endangered species. However, some research suggests that anthropogenic noise such as noice made by sonar, underwater gas and exploration, and commercial shipping effectively reduce the range of blue whale calls by 90%.

For the survival of blue whales, let their voices be heard.

References:

Gray, R. (2008, June 23). Blue whale song is getting deeper. Retrieved April 5, 2009, from Telegraph: http://www.telegraph.co.uk/earth/3345084/Blue-whale-song-is-getting-deeper.html 

John Pickrell. (2004, February 6). Uncovering Secrets of Blue Whale’s Song. Retrieved April 5, 2009, from National Geographic News: http://news.nationalgeographic.com/news/2004/02/0206_040206_bluewhalecam.html

National Geographic. (n.d.). Kingdom of the Blue Whale. Retrieved April 5, 2009, from National Geographic Channel: http://channel.nationalgeographic.com/channel/content/kingdom-of-the-blue-whale-3302/blue-whale-facts/#/compare/length

Richarson, W., Greene, C., Malme, C., & Thomson, D. (1995). Marine mammals and noise. San Diego, CA: Academic Press, Inc. 

Studies has discovered that mosquitofish can count to 4

Fishes are never known for their intellectual ability and are believed to have such short term memory that every round in the fish bowl seems like it’s a new place. However, recent studies done by study lead author Christian Agrillo, a psychologist at the University of Padova in Italy has shown that these small North and Central American fresh water fish, mosquitofish can actually count!

“Being able to count may require more brainpower than simply judging numbers based on size. But counting might sometimes be necessary as the fish seek safety in numbers to shield themselves from predators.”  - Christian Agrillo

They trained the social mosquitofish to relate number of geometric shapes to lead them to the correct ‘door’ to join the rest of the group. In order to ensure that the fish isn’t relating size to numbers, the set are randomly reset keeping only the number of shapes on the door constant and see if the fish will swim through the correct door.

There is however, a limitation to their ability. It is discovered that they can only count till 4. A second set of test carried out discovered that the fish prefers to join the group of fishes that has one more fish than the other. It is able to differentiate between 3 fish or 4 fish or less. It’s stump though when faced with a group of 12 and 8. They do attempt to count using size, but when faced with such close number, they could only stare.

Even though their maths grade not allow them to pass pre-school, the mosquitofish still joins the elite group of animals such as monkeys, humans and ferrets, that has the ability to count.

References:

Dell’Amore, C. (2009, March 31). Fish Can Count, Study Finds. Retrieved April 11, 2009, from National Geographic News: http://news.nationalgeographic.com/news/2009/03/090331-fish-count.html

Agrillo, C., Dadda, M., Serena, G., & Bisazza, A. (2009). Use of Number by Fish. Retrieved April 11, 2009, from PLoS One: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0004786

Clover, C. (2009, February 26). Fish can count to four – but no higher. Retrieved April 11, 2009, from Telegraph.co.uk: http://www.telegraph.co.uk/earth/earthnews/3326801/Fish-can-count-to-four—but-no-higher.html

Photo by Christian Agrillo/University of Padova

Male chimp offering his catch

Photograph by Cristina M. Gome

Amongst chimpanzees, mating behavior is largely based on female choice. A recent study on some Chimps in Ivory Coast have shed light on one of the techniques that male chimpanzees have up their sleeves, metaphorically speaking.

Male chimpanzees have been seen sharing meat with female chimpanzees, and this increases the likelihood of females mating with them. The study has shown that female chimpanzees were more likely to mate with the males who shared their meat with them than those who did not. Such behaviour has not only been observed occurring between males and estrous females, but also between males and female chimpanzees which were not in heat. By doing so, it is evident that the meat-for-sex trade is not an immediate exchange. This is an indicator that male chimpanzees possess the cognitive ability to plan ahead, and is capable of “investing” in their future.

“This is a long-term exchange, so males continue to share their catch with females when they are not fertile, copulating with them when they are.” (BBC News)

Such a phenomenon leads one to ponder just exactly why humans think we are the superior ones, when animals, like these chimpanzees appear to be rather capable of successfully winning over a girl’s heart as well. Perhaps men should take lessons from these chimps – and consider the benefits of planning ahead.

References:

Gill, V. (2009, April 7). BBC News | Science & Environment | Chimpanzees exchange meat for sex. Retrieved April 10, 2009, from BBC News: http://news.bbc.co.uk/2/hi/science/nature/7988169.stm

Gomes, C. M., & Boesch, C. (2009). Wild Chimpanzees Exchange Meat for Sex on a Long-Term Basis. PLoS ONE . http://www.plosone.org/article/info:doi/10.1371/journal.pone.0005116

While out in the field at night, one occasionally can notice a gecko without its tail. This rather strange looking individual has autotomised its tail (which is part of its body part) and this process is scientifically known as autotomy.

Autotomy is defined as the ability to voluntarily shed a body part, typically along a predetermined breakage plane (Wasson et.al., 2002). This unusual behaviour is relatively widespread in certain animal groups and has been observed in rodents, salamanders, lizards, crabs, spiders and sea stars (Juanes and Smith, 1995). As different groups of animals have developed and maintained this behaviour, this implies that there must be strong selective benefits to it.

Spider with missing leg

Why do animals choose to autotomise their limbs or body part? Several reasons have been proposed. Firstly, autotomy enables the animal to reduce injury to body parts. For example, certain species of crabs are known to break off their injured limbs. Secondly, this allows the animal to distract a predator and enable it to get away without being eaten. For example, certain lizards will often drop their tail when grasped in order to escape from predators.

Lizard missing part of the tail

However, losing a limb or a body part does not come without any cost and the animal may be at a disadvantage when its limb is temporarily absent. Firstly, the animal may suffer from a reduced ability to forage or defend. For example, when a crab loses a cheliped, it will be less capable in feeding and defending against potential predators. Secondly, the animal will also have to expend precious resources to regenerate the lost body part. This will come at the expense of growth and reproduction.

In conclusion, autotomy can be beneficial to the animal and may be important for survival in certain animals. However, it is not without any negative impacts to the animal.

Literature Cited

Juanes, F. & L. D., Smith, 1995. The ecological consequences of limb damage and loss in decapod crustaceans: a review and prospectus. Journal of experimental marine biology and ecology 193: 197-223.

Wasson, K., B. E., Lyon  & M. Knope, 2002. Hair-trigger autotomy in porcelain crabs is a highly effective escape strategy. Behavioral Ecology, 13, 481–486.