1Good afternoon everyone.
2Well, with some of you about to go out on field work
3it's timely that in this afternoon's session I'll be sharing some ideas about the reasons why groups of whales and dolphins
4sometimes swim ashore from the sea right onto the beach and...
5most often, die in what are known as 'mass strandings'.
6Unfortunately, this type of event is a frequent occurrence in some of the locations that you'll be travelling to,
7where sometimes the tide goes out suddenly, confusing the animals.
8However, there are many other theories about the causes of mass strandings.
9The first is that the behaviour is linked to parasites.
10It's often found that stranded animals were infested with large numbers of parasites.
11For instance, a type of worm is commonly found in the ears of dead whales.
12Since marine animals rely heavily on their hearing to navigate,
13this type of infestation has the potential to be very harmful.
14Another theory is related to toxins, or poisons.
15These have also been found to contribute to the death of many marine animals.
16Many toxins, as I'm sure you're aware, originate from plants, or animals.
17The whale ingests these toxins in its normal feeding behaviour
18but whether these poisons directly or indirectly lead to stranding and death
19seems to depend upon the toxin involved.
20In 1988, for example,
2114 humpback whales examined after stranding along the beaches of Cape Cod
22were found to have been poisoned after eating tuna that contained saxitoxin,
23the same toxin that can be fatal in humans.
24Alternatively, it has also been suggested that some animals strand accidentally by following their prey ashore in the confusion of the chase.
25In 1995, David Thurston monitored pilot whales that beached after following squid ashore.
26However, this idea does not seem to hold true for the majority of mass strandings
27because examination of the animals' stomach contents reveal that most had not been feeding as they stranded.
28There are also some new theories which link strandings to humans.
29A growing concern is that loud noises in the ocean cause strandings.
30Noises such as those caused by military exercises are of particular concern
31and have been pinpointed as the cause of some strandings of late.
32One of these, a mass stranding of whales in 2000 in the Bahamas
33coincided closely with experiments using a new submarine detection system.
34There were several factors that made this stranding stand out as different from previous strandings.
35This led researchers to look for a new cause.
36For one, all the stranded animals were healthy.
37In addition, the animals were spread out along 38 kilometres of coast,
38whereas it's more common for the animals to be found in a group when mass strandings occur.
39A final theory is related to group behaviour,
40and suggests that sea mammals cannot distinguish between sick and healthy leaders
41and will follow sick leaders, even to an inevitable death.
42This is a particularly interesting theory
43since the whales that are thought to be most social - the toothed whales -
44are the group that strand the most frequently.
45The theory is also supported by evidence from a dolphin stranding in 1994.
46Examination of the dead animals revealed that apart from the leader,
47all the others had been healthy at the time of their death.
48Without one consistent theory however,
49it is very hard for us to do anything about this phenomenon
50except to assist animals where and when we can.
51Stranding networks have been established around the world
52to aid in rescuing animals and collecting samples from those that could not be helped.
53I recommend John Connor's Marine Mammals Ashore as an excellent starting point
54if you're interested in finding out more about these networks, or establishing one yourself.