VHF Eartag Transmitting Subsystems

Introduction

Eartag units have been used as an attachment method on animals with changing neck girth (i.e. juveniles, buck deer, and some bears) where a collar may not be suitable. These eartag units are constructed using a high impact plastic housing that supersedes the water resistance of older designs using epoxy and acrylic resins as a moisture barrier.

Two basic designs, employing two different form factors, are available.

The ET-5 and ET-6 are designed as a "button" and the antenna penetrates the ear pinnae and exists out the back of the ear. This design approach uses an electrically foreshortened antenna that avoids the longer "droopy" antenna used in some other designs. The button design allows the transmitter to rotate freely, again minimizing irritation and infection at the attachment site. These eartags were originally designed for use on polar bears, but the design is suitable for use on other species of bear, and on ungulates.

A more classical approach in the design is used in the ET-7 and ET-8 configurations. In this design approach the electronics unit is attached to a standard eartag used extensively throughout the livestock industry. This approach allows for rotation of the eartag about a single attachment point, but in general the weight of the electronics package keeps that part of the configuration near the base of the ear and the antenna up and away from the animal's eye. This design approach is often favored for attachment to ungulate species. A classical whip antenna design is employed and attachment is accomplished quickly in the field.

Eartag configurations that have exposed antennas may have the damaged due to by other animals or mechanically damaged when the animal lives is in thick cover. Antenna breakage can occur and result in reduced range performance over time.

As a note both designs require special attachment tools which can be purchased separately.

Key Features

- Offers an alternative to other attachments such as collars.
- Used on juvenile animals during periods of rapid growth.
- Programmable duty cycling can extend the operational life of the unit.
- Specialized attachment tools are available for applying the tag.
- Numerous sensor options i.e. mortality sensing are available.
- Excellent range performance with the selection of various power level options.

How to use this table: The information contained in the following table is provided in a manner to allow comparison of models. To sort by model attributes i.e. weight, CLICK ON THE COLUMN HEADING. To obtain more specific information for a model, CLICK ON THE MODEL NUMBER.

Specifications for Transmitter Electronics

MK8 Transmitter General Specifications
MK9 Transmitter General Specifications

Conventional Control Options

Mortality (S6A, S6B) and activity (S9) sensors are available with all eartag configurations.

MK8 Microprocessor Control Options

An increased operational life may be achieved with the use of a microprocessor to establish a transmitting duty cycle. Microprocessor controlled transmitters provide capabilities beyond those offered by any other conventional VHF transmitter designed for tracking and/or wildlife monitoring. These new capabilities include MDC duty cycling (turning transmitters on and off at predetermined intervals), and MA transmission of activity indices. More traditional options such as MS6 mortality sensing and MS9 activity sensing remain available, but with increased flexibility.

MK8 Microprocessor Control Options

Opt. MDC MK8 Duty Cycles. Transmitters can be programmed to cycle through up to eight sequential time periods or "duty cycles" in order to extend transmitter life. Within each duty cycle, the transmitter can either be "on" or "off". Pulse rates can be uniquely defined for each "on" duty cycle. Each duty cycle can be defined from eight seconds to approximately 50 months in length. Duty Cycle timing begins at the moment the magnet is removed to initialize the transmitter. Upon completion of the last programmed Duty Cycle Period, the transmitter begins again at the first duty cycle.

Opt. MA Activity Sensor. Varies the pulse period depending on the relative activity level of the animal. A motion-sensitive switch detects animal movements and the microprocessor monitors changes in the state of the switch (open vs. closed). A user-defined evaluation time is established and the number of switch state changes is recorded by the microprocessor. The maximum number of state changes is limited to one per second by the software. The transmitter pulse period varies between two user-defined pulse periods. One pulse period corresponds to "no activity" and the other corresponds to a user-defined "maximum activity level". A graph supplied with the transmitter correlates activity level and pulse period.

Opt. MS4 Temperature Sensor. Monitors body temperature in proximity to the collar on the animal (pulse period varies with temperature). User may define the desired pulse period vs temperature characteristic of the transmitter (contact factory for details). Standard temperature resolution is approximately 0.4°C. Optional high-resolution circuitry provides approximately 0.1° C resolution.
The MS4 temperature sensor circuitry provides accurate temperature measurements, even when the transmitter cannot be recovered and recalibrated after period of data collection. This virtually eliminates calibration drifts due to aging and battery voltage changes over time.

Opt. MS5 Temperature-Triggered Mortality Sensor. This option determines a mortality event in an endothermic animal with a stable body temperature. Faster (mortality) pulse rate is triggered when body temperature drops below a user specified temperature. Note:
Pulse rate is returned to original rate if temperature rises back above the specified temperature. Consideration of the ambient temperature is a consideration in selection of the transition threshold. For example, temperature-controlled sensors would probably not be suitable in areas where high ambient temperatures would prevent rapid cooling of body after death. This option is often used in monitoring waterfowl mortality events where motion sensitive mortality sensors may not be applicable (e.g. where the body may continue to be rocked by waves on the surface of a lake). Available in all implant configurations. Please contact the laboratory to discuss implementation of this sensor before ordering.

Opt. MS6 Mortality-Motion Sensor. Provides "active or alive" or "inactive or dead" pulse period depending on activity state of the study animal. A motion-sensitive switch is incorporated in the unit to detect animal movements. The microprocessor continuously monitors the motion switch to determine when motion occurs. Once per second, the microprocessor increments an "activity counter" if motion was detected during the preceding one-second time period. This "activity counter" keeps a running total of the number of times motion was detected over a user-defined mortality evaluation time (8 sec to 6 days). The active pulse period is maintained as long as the number of switch closures in the mortality evaluation time is greater than the mortality threshold. If the number of switch closures falls below the established threshold, the unit produces the inactive period. A separate resurrection threshold allows the unit to return to the active pulse period if the number of activity counts during the mortality evaluation time exceeds the resurrection threshold. Note:
The microprocessor updates the active/inactive pulse period at intervals of 1/16th of the evaluation time. This means that after the "resurrection" threshold criterion is met, there will be a delay of up to 6.25% of the evaluation time before the transmitter reverts to the "active" pulse period. The same is true with the transition between "active" and "inactive" pulse periods. The actual time between cessation of motion and initiation of the "inactive/dead" pulse period can be up to 6.25% longer than the evaluation time.

Opt. MS9 Tip Switch Sensor. Transmits one of two different pulse rates depending on orientation of the transmitter. Usually designed to switch pulse rates as it passes through an angle of 0° (parallel to horizontal). Other switching angles may be selected with some configurations (factory set within 10°).** Typical uses include monitoring "head up" and "head down" positions.

MK9 Microprocessor Control Options

Opt. MDC MK9 Duty Cycles. Transmitters can be programmed for up to eight sequential time periods or "seasons", generally used to extend transmitter life. During each season, the transmitter may be "enabled" or "disabled". Timing is controlled by a Real-Time-Clock, allowing seasons to start and end on any desired calendar date and time, regardless of when the transmitter is initialized. Once the transmitter enters the last programmed "season", it continues to operate under the last season's parameters for the duration of the transmitter's lifetime.
Within each season, the transmitter may be programmed with an on/off "duty cycle" to further extend transmitter lifetime. Each on/off cycle can be defined in one hour increments from 1 hour to 255 hours (about 10.6 days).

Opt. MS6 Mortality-Motion Sensor. Provides "active or alive" or "inactive or dead" pulse period depending on activity state of the study animal. A motion-sensitive switch is incorporated in the unit to detect animal movements. The microprocessor continuously monitors the motion switch to determine when motion occurs. Once per second, the microprocessor increments an "activity counter" if motion was detected during the preceding one-second time period. This "activity counter" keeps a running total of the number of times motion was detected over a user-programmable mortality evaluation time (128 sec to 6 days). The active pulse period is maintained as long as the number of switch closures in the mortality evaluation time is greater than the mortality threshold. If the number of switch closures falls below the established threshold, the unit produces the inactive period. A separate resurrection threshold allows the unit to return to the active pulse period. If the number of activity counts during the evaluation interval exceeds the resurrection threshold, the unit will immediately assume the active pulse period. Notes:
The microprocessor updates the "inactive" pulse period at intervals of 1/16th of the evaluation interval. This means that the actual time between cessation of motion and initiation of the "inactive/dead" pulse period could be up to 6.25% longer than the evaluation period.

Opt. MS9 Tip Switch Sensor. Transmits one of two different pulse rates depending on orientation of transmitter. Usually designed to switch pulse rates as it passes through an angle of 0° (parallel to horizontal). Other switching angles may be selected with some configurations (factory set within 10°).** Typical uses include monitoring "head "up" and "head down" positions. Note:
The MK9 transmitter integrates the time spent "head up" vs "head down" with ~0.5sec time constant. If the transmitter position changes rapidly with respect to the integration time constant, the resulting pulse period will be between the "head up" and "head down" pulse period, providing an indication of the average amount of time the transmitter spent in the two positions.

Eartag Attachment Tools