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Gary Corda, Telemetry Solutions, 1630 North Main Street #303, Walnut Creek, CA 94596 USA

Advantage: Biologists will be able to accurately determine how long their study animal has been dead. The implications of this advancement are up to the imagination of the biologist. By knowing when a particular animal has died, the biologist may be able to correlate the death with weather events, temperature changes, ovulation cycles, daytime versus nighttime factors, and even seasonal factors.

Typical Mortality Transmitters: The mortality feature on radio transmitters enables biologists to determine if their study animal has died. It does this by increasing the pulse rate of the transmitter after there has been no movement of the transmitter for a predetermined period of time, typically 4 hr. The normal (live) pulse rate is usually 60 beats per minute (bpm) and the mortality pulse rate is 100 bpm*. The limitation with the typical mortality feature is that it only lets the biologist know if the animal has died, not when it died.

Time-in-Mortality Transmitters: Recently, a radio transmitter manufacturer has incorporated a microprocessor and tiny timing crystal (similar to that in a wristwatch) into its design. Two advantages of using microprocessors with timing crystals are: 1) increased transmitter reliability and 2) precise pulsing characteristics of the transmitters. While the transmitters are manufactured, the microprocessors are computer-programmed to change the transmitter's pulse rate so that the longer the animal has been dead (motionless) the faster the pulse rate. Additionally, once the Time-in-Mortality mode activates, movement does not affect pulse rate. This means that even if a scavenger moves the study animal, the transmitter will remain in the mortality mode.**

For example, a biologist wants a transmitter with a live pulse rate of 60 bpm and an initial mortality rate of 100 bpm. She also decides that she would like the pulse rate to increase by 5 bpm every 4 hr that the animal is dead. If the biologist receives a transmitter signal of 115 bpm, she can determine that the animal has been dead from between 16 and 20 hr (4 hr to go into mortality mode to increase the pulse rate to 100 bpm + 12 hr to increase the pulse rate from 100 to 115). By monitoring the pulse rate and determining how long it takes to go to 120 bpm, she can subtract this time from the 20 hr to know exactly when movement stopped.

While one biologist may check his animals several times a day, another will check less frequently, perhaps once every week or two. To optimize his or her study, the following parameters can all be customized by the biologist: normal pulse rate, time to onset of mortality, initial mortality pulse rate, and the rate and size of increase of the mortality pulse rate. Therefore, one biologist may want a transmitter with pulsing characteristics of: 60 bpm normal, 4-hr delay, 100 bpm initial mortality, and pulse rate increasing 5 bpm every 4 hr. Another biologist can customize his transmitters to have a normal pulse rate of 40 bpm, 12-hr delay, 75 bpm initial mortality, and pulse rate increasing 2 bpm every 3 days. The choices are limitless and up to the biologist.

* Depending on manufacturer and/or the biologist's preference, the normal/mortality pulse rates may be set at rates other than 60/100 bpm.
** Transmitters may be reset to the live mode by placing a magnet on the transmitter's on/off switch.
***At this point, the transmitter is still operating in the "live" mode.