Discussion:Killer whale

Notes:

Spatial and behavior Structure: During hunting the group disperses in a huge area. We so here can see that orcas are very organize. During hunting they communicate a lot. The hall herd searches for food, they disperse into different groups and try to find food. This makes that the animal disperse and so cover a much wider area as if they stayed all together.

Reconnaissance: Natural marking that we can find on the animal dorsal fins or marks all around the body

Identification

Searchers mostly identifiy orcas by observing specific characteristic on one individu]]. Some of these specific characteristic are natural marking that we can find on the animal dorsal fins or marks all around the body. This identification is the most used as it is the easiest technic to recognise an individu.

During years the searchers noticed, by looking in orca’s stomach and by observation that there was really two different groups defined by their nutrition. The first one, inshore, eat 89.7% marin mammals, 7.1% squid and 3.2% fish. These groups are consisted of 10 to 15 individuals. Their number is in taken account of their hunting strategy. This group is consisted of the most dangerous predator, as it can even attack blue whales and hunt a human thinking it is a seal. The offshore orcas eat 98.5% fishes, 1.1% squid and finally 0.4% marine mammals.

First discussion

There exist in everything mixtures of different kind of toxins. One toxins can produce or can be different type of compounds having for origin the first one. PCB can so, when dissolve create different kinds of toxin, which bases is PCB. As for DDT they can be bioacumalte and so cause the same process as DDT in the chain food. Researcher have calculated that the northern residential orcas are will be at risk of this toxin until 2030, while southern will be until 2060. The explanation of this difference is caused by the different distribution of the two groups. In fact this is also the case for other toxins, southern residential orcas are always mostly polluted because they are exactly in the area where there is human activity, while northern, which are more in the north of B.C, are in areas where there is less human population. PCB:

Cancer: has been a lot of studies on the effects of PCB's on animals and human health to show their carcinogenicity. It was shown that PCB's causes cancer in animals. Has been proven that the mixture of PCB's that bioaccumulates in fish is the most carcinogens. Tested were made on an organ beeing exposed to PCB's which created the development of a malignant melanomas in it. Immune effects: It has been proven that PCB's creates a deficient in the immunes system of animals and humans. There has been found any amount of PCB that do not create immune problems.

• diminution of the size of the thymus gland which is a very important gland for the immune system
• reduction of the response of the immune system
• dicrease of resistance to different kind of disease => have more change to develop pneumonia or a viral infection

There also has been research with seals and it has been observed that PCBs can cause weaken the immune system, physiologiy disturbance, skin disorder and reproductive problems. It has aslo been found tumors, skeletal abnormalities, reproductive problems and diseases in belugas from the st Lawrance. Moreover orcas are even 4 to 6 times more contaminated than these belugas. It has been notice that reproductively females have less PCBs in their body than the others. The answer of this is the same as DDTs. In fact the mother releases the toxins through her milk, which is drink by her calf. reproductive system nervous system endocrine system other health problems

http://www.greenfacts.org/en/pcbs/l-2/7-risks-exposure.htm

http://www.epa.gov/waste/hazard/tsd/pcbs/pubs/effects.htm#Endocrine http://extoxnet.orst.edu/faqs/foodcon/pcb.htm

http://environmentalchemistry.com/yogi/environmental/200601pcbsinfood.html

http://www.sciencedaily.com/releases/2007/09/070910094122.htm

!!!!!!!!!!!!!! PBDEs are doubling every 4 years in marine mammals," researchers added.!!!!!!!!!!!