Frequently Asked Questions
What happens to the Life History Transmitter if the host animal was killed by a shark and eaten (if the body was consumed)?
Three things could happen: most predators like sharks and killer whales do not swallow large prey such as sea lions whole. Instead, they tear them apart and eat the bits and pieces one at a time. There is a good chance the LHX tags will come flying out of the killed sea lion’s body as the predator tears it apart. The tags are designed to remain ‘free-floating’: they have a special coating that prevents connective tissue from sticking to the tag. This makes it more likely the tags will come flying out and won’t get swallowed by the predator. However, it is also possible that a predator will swallow an LHX tag. In that case, it will likely pass through the digestive tract of the predator and be passed out with other excrements or it may be thrown up. In this case the tag would eventually still end up outside floating on the water from where it would begin transmissions. There is of course a slight possibility that the predator just happens to bite down on a tag, and it may crush it. In that case, the tag is destroyed, and we won’t hear from it.
What would happen to the temperature profile and light sensor data inside the stomach of a predator?
This depends on whether the predator is warm-blooded (homeotherm) or cold-blooded (poikilotherm). In homoeothermic mammals like killer whales, the tag would register the temperature of its new host (around 37 degrees Celsius or 98 degrees Fahrenheit). The light sensor would continue to sense darkness because the tag would be inside the whale's stomach. Therefore, the tag would not register any changes in any of its sensors. Only after the tag passes out of the whale's body, it would cool rapidly to the temperature of seawater and begin registering light. If the tag is exposed to air, it can send its information on to the satellite. The rapid cooling would still make this appear as a predation event, though the exact time of the event would be delayed. The researchers are working on additional sensors that can detect when a tag is inside of the stomach of a predator so that they can properly deal with this time offset.
If a shark ate a tag, it would sense a very rapid temperature drop to about that of seawater since they are cold-blooded poikilotherms. However, the light sensor would remain dark while the tag would be inside the shark's digestive tract. Once the tag passed out of the shark's body, there would be little temperature change, but the tag would immediately sense light and begin to transmit.
In either case (ingestion by shark or killer whale) the data would still show a predation event. Darkness and an abrupt drop in temperature would indicate a shark ate the tag, whereas an abrupt drop and light would indicate a killer whale ate the tag.
How does the ARGOS satellite work?
http://www.argos-system.org/html/system/how_it_works_en.html
