Magazine Article 1998 – Ecologists have 30 years’ experience in wildlife research and welfare

Ecologists have 30 years’ experience in wildlife research and welfare

Sirtrack has over 30 years’ experience designing, building and packaging radio tracking and telemetry equipment for wildlife research.

”We are dedicated to excellence in the manufacture of our products because we, as ecologists, know that you must have quality and reliability in such equipment, ” says manager Dave Ward.

Sirtrack transmitters are constructed using both hybrid thick-film techniques and printed circuit boards to achieve maximum reliability and minimum weight.

All its transmitter packages are custom-built to meet the individual needs of clients. Pulse rate, pulse width, battery type, power output, collar materials, housings, coatings, antenna type, colour and labelling are all completed to give the best possible product for every specific requirement. Each package is fitted with a reed switch, so the transmitter can be turned on and off with an external magnet.

Single stage transmitters are designed for use with small birds, reptiles and small mammals such as bats and in any situation where weight is at a premium.

These are controlled by a microchip, which gives the circuit inherent reliability and stability. It is being used successfully in many countries on a wide range of lightweight species, including 10g bats and New Zealand’s giant weta. Without a battery it weighs just 0.4g and is only 6.8 x 5.7 x 4.9mm.

The range depends on its aerial, the environment and the quality of the receiving equipment. With a good whip aerial and line of sight, ground to ground ranges in the order of 1km are typical. However, Sirtrack says it has successfully located these transmitters from over 15km away when tracking from the top of a 300m hill and from a light aircraft.

With a minimal addition of weight a thermistor can be added to the circuitry, to measure temperature.

Two-stage transmitters are used on species as light as 100g right through to the heavyweights of wildlife.

A highpowered transmitter can be developed by modifying the two-stage transmitter to operate on higher voltages, when extra power and range are required. Ranges in excess of 100km are regularly achieved when these units are tracked from light aircraft.

A long-life transmitter will run for twice as long as the standard unit, yet can still have 70% of the range, with no increase in weight or size. It is very useful when working with species which are difficult to capture or when handling must be kept to a minimum.

Transmitter sensing options

Mercury tilt switches can be added to a transmitter to change its pulse rate as it moves through different predetermined angles. This technique is used to determine animal posture and behaviour.

The pulse rate of the mortality transmitter (eg determining when an animal is dead) will double or halve (user specified) if it is not moved for a pre-set period of time. The circuit can be configured to return to the normal pulse rate if movement is resumed, but more typically it will latch onto the new pulse regardless of subsequent movement. A microcontroller in this unit can help give a more accurate time of death.

With two electrodes in place the heart rate monitor emits a pulse every time the subject’s heart beats. It is based on the two stage transmitter and has particular application in studies of animal responses, stress and hibernation.

An audio transmitter is another company-made device. A tiny transducer microphone detects the sounds made by an animal as it pursues its activities. Feeding, grooming, snoring, calling and other sounds are transmitted with good fidelity and add a useful dimension to studies of animal activity and behaviour.

The transmitter is usually carried around the animal’s neck, but it may also be used to monitor activity in the den or nest. It does not emit a tracking signal, so it can only be located when the animal is generating sound. If the animal is large enough an additional tracking transmitter can be incorporated.

A trap transmitter operates in a failsafe mode, running continuously at a slow base pulse rate, but running twice as fast when the trap is triggered. Some clients use these, with the high powered transmitters, to monitor gates on catching pens many kilometres away.

Receivers

Sirtrack is having its own receiver designed at present. In the meantime, it has distributor and agency agreements with a number of overseas manufacturers.

These receivers are made by Telonics Inc, Custom Electronics, Televilt, AVM Instruments and Advanced Telemetry Systems.

Some receivers are more suited for laboratory than field work; some are better than others in noisy environments like helicopters; they vary in the number of channels they have, from three to 400; and there is a choice of channel spacing.

Antennas

Sirtrack designs and makes a range of tracking antennas. Its hand-held 3-element yagi antenna is popular with researchers and is in use in many parts of the world.

It conveniently folds up in seconds for travelling or working in difficult country. Robust and light, it comes in all the VHF frequency bands commonly used for tracking.

Multi-element yagi arrays give increased range and accuracy. These are usually mounted on a mast and operated from a fixed position or carried on a vehicle.

The company has extensive experience at tracking from light aircraft. It supplies brackets for mounting yagi antennae onto Cessna [Cessna] 1 72 wing struts. They’re approved by the Civil Aviation & Safety Authority of Australia, while approval is currently being sought from the Civil Aviation Authority of New Zealand.

Temperature and marking

Sirtrack offers two systems for the remote measurement of temperature. Both are used in a wide range of applications and differing environments.

It also has a personal radio marker, designed for emergency position indicating under rugged conditions. It is small, lightweight and easily carried in the pocket, in a pack, on a life jacket or left at base camp and used as a homing beacon. It is waterproof and tested to 20m. It has ground to ground line of sight range of 15- 20km and in excess of 100km when tracked from the air.

Sirtrack says it is the only manufacturer of wildlife radio-tracking equipment with ISO9002 certification.

Caption – He relates the story of a particular opossum in the Rimutakas which would go from trap to trap, eating the apple baits. “We’d just free it from one trap and it would go up the line to the next trap, enter and eat the apple and then wait for us to free it, so it could continue up the line,” recalls Ward. That was one smart ’possum able – to recognise the difference between scientists and fur or bounty trappers.

Photo caption – Tuku the Tamrin collared by Sirtrack at the Auckland zoo