Friday, January 2, 2015

How do you find a hyena?

Jambo Fisi Lovers!

Some of you may have noticed that a few of our hyenas are sporting an extra piece of jewelry. The GPS and VHF collars that these chosen few wear around their necks aids us tremendously in locating them and gives us information on their travel patterns throughout the day.  The criteria for choosing which hyenas to collar tend to vary with the current research projects in the field. We are currently focused on collaring males who are ready to disperse for a male dispersal project that is being conducted by one of our grad students Tracy. These collars become our eyes when we are unable to follow the hyenas in the field.

Navajo, our oldest hyena sporting her collar along with a bloody face.

As mentioned in my previous blog, we have two types of collars: GPS and VHF. VHF collars transmit a radio signal that is picked up by a receiver that is linked to an antenna. Our cars are equipped with two types of antennas. One antenna receives signals from all directions and the other from one direction. Once we pick up a signal we switch from the multi-directional antenna to the unidirectional one. While switched to the unidirectional antennae we drive the car around in a circle and listen to the pulses being sent through the receiver. Once the circle is complete we drive in the direction that emitted the loudest pulse. The loudest direction should lead you to the hyena. Tracking however can be made difficult in areas with lots of shrubs and bushes (the signal can bounce off of these bushes making it difficult to determine the correct location).

We wear these headphones during observation sessions to hear the pulses being sent through the receiver.  They aren’t the most comfortable piece of equipment but they get the job done!

GPS collars are a bit more sophisticated and about 10 times more expensive than the VHF collars. The GPS collars are equipped with battery packs, a VHF component that emits radio pulses for tracking, a memory for storing location information, and a GPS system.  We are also able to download “points” (GPS coordinates) from the collars using a computer. If we are curious as to where a hyena spends most of its time these points provide the answers to our questions.

Although the GPS collar is more technologically advance, the VHF collar has a longer battery life. The VHF collar lasts about 3 years and the GPS collar 2 years.

Along with letting us know where a collared hyena can be found the collars are also capable of letting us know when a hyena has not moved for a long period of time. Each collar has its own way of sending out what is known as a mortality signal. A mortality signal is sent when the hyena has not moved for a certain number of hours. In order to send a mortality signal the VHF collars transmit a fast paced signal to the receiver, which can be heard through the headphones, while the GPS collars send a message via text or email informing us that the collar is stationary.

In the end the collars help us significantly in the field. Now that you know all about our collars….
Do you think you’re ready to track hyenas now?


dee said...

Grest post Ashlei. What are you learning so far about the dispersing males?

Anonymous said...

How long do the collars have to be stationary for the 'dead' signal? More than a day?

Anonymous said...

How heavy are the collars, and are collars bitten off or damaged during aggressive interactions?

Michigan State University | College of Natural Science