215 Beep-beep! Radio Signals Track Fish and Wildlife - webapps8

Beep-beep!Radio SignalsTrack Fishand WildlifeTelemetry enables biologists to follow mammals,birds, and fish. Aim: To understand how thesecreatures live in the wildWilliam E. Berg and Robert F. StrandHETEARLY autumn day on LeechLake was warm and overcast,the kind that drives muskies to bite.Sure enough, in one boat an angler'srod bowed and his reel sang fromthe run of a large fish.Finally, the angler netted atrophy muskie, about 28 pounds,but there was no picture taking, noproud display of the fish. Instead,the fisherman donned surgicalgloves, placed the muskie on a specialtable, and quickly made an incisioninto the body cavity. Carefully,he inserted a silicone-sealed, miniatureradio transmitter into the fish,closed the incision, and returnedthe giant to the water — all within 30minutes.About 50 miles east of LeechLake, a trapper checked his sets. Ashe cautiously approached a trapsite,a coyote — held uninjured butfirmly in a foothold trap — lungedfrom the grass. Rather than kill theAuthor Strand, above, holds antennato track muskie. Battery and transmitter,right, weigh 68 grams, butto fish in water less than one ounce.SEPTEMBER-OCTOBER 1985 27

Radio-tracking Wildlifecoyote for its pelt, the trapper removeda sterile syringe from hispack, filled it with tranquilizer, anddrugged the coyote. Then heclipped a number tag onto each earand placed a radio collar around thecoyote's neck. After recovering fromthe drug, the coyote scamperedaway.A strange way to fish and trap?Not really. The fisherman and trapperwere both Department of NaturalResources biologists learningmore about Minnesota's fish andwildlife through a technique calledradio-telemetry.Miniature Transmitter. Radiotelemetryhas been used worldwideby fish and wildlife researchers fornearly 30 years.The technique is rather simple. Aradio transmitter is placed on or inthe animal. Each transmitter is aminiature radio station, with its ownbattery, antenna, and frequency.The beep-beep from the transmittercannot be heard by the animal, butonly by a biologist using a specialreceiver and antenna.Wildlife telemetry has made dramatictechnological advances sincethe 1950s, due mainly to solid-stateelectronics and the development ofmercury, nickel-cadmium, and nowlithium batteries.Transmitters must not inhibit theanimal's normal habits and canweigh no more than 2-5 percent ofthe animal's weight, or I-IV4 percentof a fish's weight. The smallest 1transmitters are jelly-bean-size, butmost are larger. Battery-poweredtransmitters operate for one to fiveyears, and those using solar powercan operate almost indefinitely.To aid biologists in their studies,dozens of animals and fish in recentyears have been equipped withtransmitters. Examples of mammals:moose, deer, wolf, bear,coyote, red fox, bobcat, Canadalynx, pine marten, cottontail rabbit,beaver, and pocket gopher.Birds include ruffed, sharptailed,and spruce grouse, great grayowl, eagle, sandhill crane, wild turkey,and several species of ducksand geese. Radioed fish includemuskie, trout in Lake Superior,sunfish, perch, walleye, and paddlefish.Most transmitters are placed on28 Collar with transmitter, above, will allow fawn's neck to grow. Largeanimals, like bear and moose, right, are tranquilized before transmitteris attached. Bright collar aids in sighting animal in dense woods.

Radio-tracking WildlifeBattery-powered radioreceivers track animalsin field. Farleft: Biologist holdsportable antenna ashe homes in on subject.Left: Antenna ismounted on roof oftruck. Compass cardprovides directionof subject.mammals as neck collars. However,they may be clipped to an ear of adeer or moose, or sewn into thecheek of a pocket gopher. Thetransmitter is surgically implantedinto the body cavity of fish andaquatic mammals like mink andotter.Birds usually carry transmitterson their backs, held with a harnessof surgical tubing. On a turtle, thetransmitter is epoxied to the shell.Telemetry Studies. Telemetry -—transmitting audio or visual radiosignals over a distance — is the biologist'sonly method for locating ananimal without seeing or otherwisedisturbing it. Telemetry has enabledDNR fish and wildlife biologists tostudy their subjects in many ways:• In northwestern Minnesota, themoose's dependence on willow habitatwas substantiated• Behavior, movements, and dispersalpatterns of timber wolves,coyotes, bear, and deer over muchof northern Minnesota have beendocumented• Radio-collared whitetail fawnsin southeastern Minnesota led biologiststo favored doe-fawn habitats• Telemetry of wild turkeys in thesoutheast indicated causes of mortalityand led to our first turkeyhunting season• Preferred nesting and broodrearinghabitat were identified forseveral species of waterfowl• Transmitters on the rare greatgray owl located existing habitatsand demonstrated the bird's abilityto fly great distances into Manitobaand Ontario in search of prey• Implants in Lake Superior troutpermitted following their movementsin the big lake• Implanted transmitters in muskiespinpointed spawning groundsin Leech Lake and spawning time.This led to a delay in our muskieseason until the first Saturday inJune, and enabled the DNR to obtainspawn to propagate the Leech30 THE MINNESOTA VOLUNTEER

Lake (Mississippi) strain muskie.Telemetry Versatility. In radiotelemetry,tracking is most oftendone from a vehicle, aircraft, boat,or tower to determine an animal'slocation. But telemetry's other applicationsare limited only by thebiologist's imagination. Examples:• Activity sensors in transmittersreveal if an animal is dead or alive,feeding, or resting• Physiologic transmitter implantsbroadcast an animal s bodytemperature, heartbeat, and bloodpressure• Temperature-sensitive thermistortransmitters inside a dummyduck egg reveal the temperature ofincubation, when a hen is present,and when the egg is turned. Thermistorsalso indicate the water temperaturesought by fish, a coldbloodedanimal• Fisheries managers place transmittersin test nets far out in Lake ofthe Woods to locate nets quickly• Conservation Officers implanttransmitters in illegally taken fishand wildlife to apprehend game-lawviolators.Technological innovations arefurther advancing telemetry. Satellitesreceive some transmitter signalsand relay them to an earthboundbiologist, or to an automaticrecorder, which then transfers theinformation to computer tape. Atransmitter equipped with a tranquilizerdart can drug a radioequippedanimal at the push of abutton when the animal needs a newtransmitter. A tiny transmitter in atranquilizer dart leads researchersto drugged animals which otherwisecouldn't be found.Wildlife telemetry techniqueshave spread to other fields. Wideranginghunting dogs may carry atransmitter collar so their masterscan locate them. Habitual wanderersfrom nursing homes mayhave a transmitter sewn into theircoats so they can be located if lost.And law enforcement officers nowuse telemetry to apprehend pursesnatchers, heavy equipmentthieves, and drug smugglers.As transmitters become smallerand more sophisticated, there's essentiallyno limit to fish and wildlifetelemetry applications in the studyof our fish and wildlife. •William E. Berg is a research biologistwith the DNR Forest WildlifePopulations and Research Group.Grand Rapids. He wrote "MountainLions in MinnesotaP in the May—June 1984 Volunteer. Robert F.Strand is a fisheries biologist. DNR.Bemidji.Who Owns the LandP"THE LAND belongs to the future. . . . We come and go, hut the land is alwayshere. And the people who love it and understand it are the people whoown it — for a little while. — Willa Gather. () PioneersSEPTEMBER-OCTOBER 1985 31