Killer Whale Hunting Strategies

The first thing that comes to mind for me when someone talks about orcas is Shamu. Although they look beautiful and majestic, these are not animals that you would want to get in the water with; they have the name "killer whales" for a reason. I knew a little about these animals and how they hunted in pods, but not much, so I decided to do some research on this topic

Research was done for a few years at Punta Norte on the east coast of Argentina, that primarily focused on the social dynamics of killer whales, Orcinus orca, when hunting marine mammals. These predators help to show association patterns and foraging behaviors, and paint a pattern to understanding hunting efficiencies. In general, killer whales are rather smart and clever when it comes to hunting their prey. It has been documented that a pod of these predators will swim in a line towards an ice floe that a seal is sitting on. They will create a large enough wave to tip the ice floe or flip it entirely and through the seal into the water for the whales to eat. Another strategy that has been used is when they attack an animal that is much larger than themselves. An example of this is a large number of the orcas ganging up on a baleen whale and attacking it from all sides.

The researchers for this study identified 13 different killer whales by recognizable features on their dorsal fins. The objective was to study the details of predator and prey interaction and foraging strategy of the whale population of Punta Norte. This allowed the researchers to observe the behavior of prey and predator directly, and to gain data over a span of two years. All of this data helped to indicate that the killer whales at Punta Norte hunt preferentially in the most productive areas and pursue the prey-type that is the easiest target. It was also found that whales within the same pod share food, and that one whale within each pod will do most of the hunting.

The hunting area of the orcas was divided up into 12 quadrants, each roughly 580m wide. Behavior was classified into categories consistent with earlier studies that had been done. Each time a whale would surface, it's behavior, position, and direction of travel was recorded. During 'patrol' behavior a whale would travel just beyond the surf zone parallel to the coast for roughly 20m or more. 'Hunting' was defined as nearshore intentional scanning, pursuits, close approaches and/or standing in the presence of potential prey.

A total of 13 whales were identified in three separate pods. The pod that was seen the most was made of two adult males (B-pod). The pod that was seen the second most was named A-pod and consisted of two adult females and five subadults. The third pod (C-pod) was made up of one adult male, one adult female, and two subadults. This C-pod was seen the least. This whales were seen over a two year time span and a total of 468 hours.

In general for all the pods, most of the hunting took place in quadrant 10, which had a deep channel in the middle that was surrounded by reefs. Of the attacks that were recorded, approximately 97% were directed towards southern sea lions, 2.4% were directed towards southern elephant seals, and 0.6% were directed towards birds. Of the attacks directed towards southern sea lions, the majority (65.5%) were directed towards the pups, which helps to indicate that the whales tend to go for the easier catch.

When the whales would catch a sea lion pup, it was held by an appendage and swung back and forth so that it would hit it's head on either side of the whale's head. It could also have been shaken very violently. The pup would then be taken off shore and was either not observed again, or was released and then pursued in open water by all the whales present. This helps to show that the killer whales tend to share the food with the rest of the pod.

After this study, there are several things that are now certain. These killer whales hunt in very specific locations with specific strategies, the cost of competing over high quality sites could be very high, and whales within the same pod will work together to get the prey, and then will share the food.

Source:
http://link.springer.com/article/10.1007/BF00166401

Singing about Science

                In sixth grade, I went on a three-day field trip to Cuyahoga Valley National Park.  While the trip was loads of fun and we learned a lot about the environment, the thing that stuck with me the most was this annoying song about watersheds.  Naturally, when we started talking about watersheds and estuaries in class, the song came to mind (and wouldn’t get out of it).  So I’ll share some new discoveries about estuarine populations while I’m humming.

                As we progress to larger species in class, I find myself disregarding the smaller marine organisms, but the health of zooplankton is significant in estuaries.  Research was conducted by David and eleven other researchers last year to determine if the unique habitat of estuaries caused a particular structure in zooplankton populations.  Water samples were taken from the Gironde Estuary in southwest France to be analyzed.  They found that the upstream-downstream gradient of the estuary related to the distribution of species while abundance within a set species had a trend with estuarine depth – subtidal versus intertidal.  The intertidal zone is especially attractive to zooplankton due to food availability.  With the numerous challenges to estuaries in mind, disruptions to these populations of zooplankton in the intertidal zone or the availability of food in this zone could have significant implications along the trophic cascade. 

                While considering the changes that estuaries undergo due to the challenges that they face, a bit of research about the adaptive abilities of Olympia oysters (Ostrea lurida) caught my attention.  Low salinity concentrations is linked to climate change, so this was the major aspect of change in the ocean water that they considered.  Bible and Sanford designed a fascinating study.  They collected oyster offspring from the Tomales Bay and San Francisco Bay estuaries and raised them in the laboratory.  A population of these lab-raised oysters were then placed in the bay they originated from and a second population was placed in the opposite bay.  This was completed at three different sites, and at two of the three sites the “local population” oysters survived better, indicating estuary-specific adaptation.  A similar experiment was completed with second-generation lab-raised oysters, and the results showed that the oysters descending from the estuary with the lowest salinity survived low salinity challenges in the lab more often than the other oysters.  I found this research to be well designed.  I hadn’t thought about this idea before, but this shows that we need to evaluate how populations are adapting to the challenges that their estuarine home is facing before we take extreme measures to restore the estuary to its original condition.

                That’s all for now!  If that wasn’t interesting enough, tune in next time for a song about something else.

Sources:

Bible, J.M., Sanford, E.  (2016).  Local adaptation in an estuarine foundation species: Implications for restoration.  Biological Conservation.  193, 95-102.  <http://www.sciencedirect.com/science/article/pii/S0006320715301634>.

David, V. et. al.  (2016).  Estuarine habitats structure zooplankton communities: Implications for the pelagic trophic pathways.  Estuarine, Coastal, and Shelf Science.  Published online.  <http://www.sciencedirect.com/science/article/pii/S0272771416300221>.

Tetrodotoxin (TTX)

Tetrodotoxin (TTX) is a poison that is produced by most commonly puffer fish as well as many other organisms. It is a virulent poison that acts by blocking the impulses of nerves along axon terminals. Which ultimately can lead a victim to die from paralysis. The specific channels that this toxin blocks is the sodium ion channels. TTX is larger than sodium, which is why it blocks the channels so easily. To give some perspective, sodium binds in the channels in nanoseconds whereas TTX is bound for tens of seconds in the channels.

There are a couple different ways for humans to get harmful doses of TTX one of the common ways of receiving a lethal dose of TTX is by digestion. In Japan puffer fish is a delicacy call fugu. Chefs prepare this dish with special certifications by the government so they do not prepare toxic flesh, liver, and gonads. But despite the precautions many cases of TTX poisoning are from people ingesting fugu (puffer fish).  Another way to get TTX poisoning is by coming into contact with the skin of Atelopid frogs, and certain newts, sea slugs, as well as being bitten by a certain gastropod mollusks. It has been verified that 1-2 mg of purified TTX can be lethal to a human.

Pufferfish or Tetraodontidae is a carnivore that contains the TTX toxin as mentioned above which makes the fish foul tasting and often is deadly to the predator that ate the pufferfish. To humans, pufferfish are approximately 1,200 times more poisonous than cyanide. And there is approximately enough TTX toxins in one pufferfish to kill about 30 humans. There is no known antidote for TTX poisoning only symptoms including numbing of the mouth and its surrounding areas, nausea and numbness.

I find that animals that are extremely toxic to any organisms are extremely interesting and I would like to find out more about this specific toxin and as to why they are in specific animals. In my presentation I would like to discuss more of the animal groups that the Tetrodotoxin occurs in.

http://emedicine.medscape.com/article/818763-overview

http://animals.nationalgeographic.com/animals/fish/pufferfish/

http://www.life.umd.edu/grad/mlfsc/zctsim/ionchannel.html 

http://www.thecephalopodpage.org/bluering2.php