34 MinnesotaConservationVolunteer

How can timber wolves travel across hundreds of miles of forests, swamps, lakes, and rivers without getting lost?

How can steelhead trout navigate the big waters of Lake Superior and find the North Shore stream where they hatched as baby trout?

How can hummingbirds make incredibly long and dangerous journeys for migration every spring and fall?

W ithoutmaps,compasses,orothernavigationaltools,Minnesotawildanimalstravelhundredsoreven

thousandsofmiles.Toguidetheirway,theymightreadweatherandsunlight.Theymightfollowrivers,mountainranges,orotherlandmarks.Inaddition,theymightrelyonspecialadaptations(bodychangesthatevolvedovertimetohelpthemlivebetterintheirenvironment)andinstincts(automaticresponsesthatarenatural,notlearned).

By Tom Anderson

Who’s That

Navigator?

September–October2007 35Gray wolf by stan tekiela; steelhead trout by scott ripley, windiGo imaGes; ruby-throated humminGbird by michael furtman

September–October2007 37

Champion NavigatorsBirdsarechampionnavigators.Manyspeciestravelacrossentirecontinents.Forexample,bobolinks,Baltimoreorioles,andruby-throatedhummingbirdsareNeotropicalmigrantsthatwinterinthetropicsandmigratetoNorthAmericatonestinspring.Thesebirdsmakethisjourneybecausetheirfavoriteandnecessaryfoodsbecomescarceorunavailableasseasonschange.Forexample,ruby-throatedhummingbirdsdependonnectarfromflowers.WhenflowersstopbloominginMinnesota,theyflysouth.SomeflyalongtheMexicancoast.OthersflyacrosstheGulfofMexico—upto20hoursnonstop—toCostaRica,Nicaragua,andothercountriesinCentralAmerica.

Dangerous FlightsManyofthemillionsofbirdsthatmigrateeachyeardieduringtheirmigration.Theirjourneyssometimestakethemthroughstrongwinds,heavyrains,thunder,lightning,andevensnowstorms.Theymightencountervariouspredators,fromhawkstohousecats.Tallbuildingsandwiresfromradioandtelevisiontowerscanbedeadlyforbirdsthatnavigateatnight.

A male ruby-throated hummingbird sips nectar.

Forhundredsofyears,ornithologistsandnaturalistshavebeeninvestigatingthemysteriesofbirdmigration.Theyhavelearnedthatbirdsuselandmarkssuchascoastlines,rivers,mountainranges,andothergeographicalfeaturestosteeracourse.Formanybirds,thesunanditspositionintheskyaidnavigation.Birdsthatmigrateatnightsteerbythestarsandplanets.ScientistshavelongtheorizedthatbirdsuseEarth’smagneticfieldtohelpthemmigrate,buttheydon’tknowexactlyhow.Someevidencesuggests

Ace Pilots

top

left

: sta

n t

ekie

la, r

iGh

t: il

lust

rati

on

by

bill

rey

no

lds

36 MinnesotaConservationVolunteer

thatmicroscopicparticlesofironintheupperbeakofsomebirdspeciesactlikeamagneticcompassneedle.Otherstudiesshowthebird’sinternalcompassismorecomplicated,workingthroughchemicalreactionsatthemolecularlevel.

Migration Routes

Bobolink

Ruby-throated Hummingbird

Argentina

Costa Rica

38 MinnesotaConservationVolunteer September–October2007 39

SalmonandsteelheadtroutperformamazingannualfeatsofnavigationbetweenLakeSuperioranditstributarystreams.

Steelhead,amigratoryformofrainbowtrout,hatchupstreamfromthelakeintheshallow,gravelyareasofmanyriversinMinnesota,Wisconsin,Michigan,andCanada.Aftertwoyearsinmoststreams,theyoungfish(calledsmolts) thenmigrateintoLakeSuperioranddisperse.

Afterlivingandgrowinginthelakeforaboutthreeyears,thesteelheadreturntotheirhomestreamstospawn.StandingatthemouthofaNorthShorestreaminspring,youmightbeluckyenoughtospotseveraloftheselargefishintheshallows.Alittlefartherupstream,youmightseeasteelheadleapupasmallwaterfall.

Water PilotsTonavigatetothestreamswheretheyhatched,migratoryfishuse

avarietyofhomingmechanisms.Somefishusethepositionofthesuntofindtheshorewiththemouthoftheirhomestream.Fishinthesalmonfamilycontainmicroscopicparticlesofironintheirbrain.Theironactslikethemagneticneedleinacompass,enablingthesalmontoorientitselfbyadjustingtoEarth’smagneticfield.

Asenseofsmellhelpssomefishsniffouthome.Whatsmellsfromyourchildhoodwillyoualwaysremember?Steelheadandsalmonrememberthesmellofthestreamwheretheylivedasyoungfish.

Eachstreamhasasignatureofsmellsinitswaterchemistry.It’sacollectionofblendedchemicalsfromthesurroundingland,likeacidsfromdecayingleavesinthestream.Justasyoumightfollowyournosefromonepartofyourhousetowardatemptingaromacomingfromthekitchen,anadultfishsmellsitswayfromthelaketothestream.

Migratory Fish

Steelhead trout, a type

of rainbow trout, migrate

from streams into Lake

Superior and back.

top

left

: e.r

. deG

Gin

Ger

, dem

bin

sky

pho

to a

sso

ciat

es; r

iGh

t: il

lust

rati

on

by

bill

rey

no

lds

Duluth French River

Knife River

Gooseberry River

Baptism River

Temperance River

Brule River

40 MinnesotaConservationVolunteer September–October2007 41

ThelargestmemberofthewilddogfamilyinMinnesotaisthegraywolf,ortimberwolf.Wolvesliveinpacksanddonotmigrate,buttheirhometerritoriessometimescoverhundredsofsquaremiles.Justasyoulearnyourwayaroundyourneighborhood,wolveslearnhowtogetaroundtheirvasthomegroundtofindfoodandshelter.

WolvesinMinnesotafollowmooseorwhite-taileddeertohuntthem.Thenthewolvessomehowfindtheirwaybackhome.Theyreturnhomebyinstinct,orbya

senseofhomethatispartofthebrainandnervoussystem.

Good NosesWolvesdependontheirsenseofsmelltofindtheboundariesoftheirlargehomeranges.Likeyourpetdog,thewolfurinatestomarkitsscentonstumps,rocks,orshrubs.Otherwolvespassbyand“read”thesescentposts—theyfindoutwhoclaimstheterritory.Wolveshowltocommunicatewithinapack.Ifawolfgetsseparatedfromitspack,howlingcanhelpitreunitewiththepackanditshometerritory.

Wolf Ways

A gray wolf crosses the Kettle River near Sandstone.

top

left

: sta

n t

ekie

la, r

iGh

t: il

lust

rati

on

by

bill

rey

no

lds

Duluth

Fort Ripley

Bemidji

Wolf range

A few wolf territories as mapped by DNR wolf biologists.

42 MinnesotaConservationVolunteer

Imagineyouare,likeawolf,travelingandtryingtofindyourwaybacktoyourhometerritory.Youknowthatyoumusttravelnorth,butyouhavenocompass.Hereareafewnaturaltricksforfindingnorth,south,east,andwestinthewild.

Find Your Direction

1FindtheNorthStaronaclearnight.FirstfindtheBigDipper,thedipper-shapedgroupofstarsintheconstellationUrsaMajor.Thenfindthetwostarsontheoutsideofthedipper’scup.ImaginealineconnectingthosetwostarsandfollowituptothebrightstarknownastheNorthStar,orPolaris,whichalwaysappearsinthenorth.

2Lookformossgrowinghighonthetrees.Mosspreferstogrowwheremoisturelingers,soittendstogrowhighestonthenorthsideofthetrunkwhereitisshadedfromthesun.

3 Compareplantsonasouth-facinghillsidetoplantsonanorth-facinghill.Southernslopeswithconstantexposuretothehot,dryingsunhavefardifferentvegetation.

4Notethepositionofthesunonaclearday.Itrisesintheeast

andsetsinthewest.InwinterinMinnesota,thesunstaysinthesouthernskythroughouttheday.

5 Studyathatch-buildingantmoundinsummer. Totakeadvantageofthesun’swarmth,red-and-blackthatchantsusuallyworkmoreonthesouthsideoftheirmound.Theykeepthissidefreeofvegetation.Becauseitreceivesmoreanttraffic,thesouthsidealsoslopesmorethanthenorthsidedoes. nV

Special offer to teacherS

Sign up for free classroom subscriptions to Minnesota Conservation Volunteer. Thanks to a generous gift from Dale L. Charbonneau, Minnesota teachers and students may subscribe free for the 2007–2008 school year. Go to www.mndnr.gov/young_naturalists.

Also online, find free teachers guides to this and other Young Naturalists stories.

September–October2007 43

illu

stra

tio

n b

y bi

ll r

eyn

old

s

North Star

Little Dipper

Big Dipper