2o06 columbia basin pygmy rabbit captive breeding ai{d genetic

2O06COLUMBIA BASIN PYGMY RABBIT CAPTIVE
BREEDING AI{D GENETIC MANAGEMENT PLAN
David Hays and Kenneth I. Warheit
'WildlifeProgram
WashingtonDepartmentof Fish andWildlife
600 CapitolWay N.
Olympia,V/A 9850i-1091
April2006
Acknowlcdgcmcnts
The 2006 captivebreedingand geneticsmanagementplan is an updateto the 2005 plan. This
plan summarizesinformation developedby a number of people involved with captivebreeding
and conservationof the ColumbiaBasin pygmy rabbit, including Kristin Mansfield,Jan Steele,
Tara Davilla, Becky Elias, Michael Illig, Lisa Shipley,Chris Warren,Rob'Westra,Lisa
Harrenstien,Rod Sayler,Nina Woodford, Rachel Lamson, and Cherril Bowman.
Introduction
Pygmy rabbits (Brachylagus idahoensrs),the smallestrabbits in North America, are found in
shrub-steppehabitat within the TemperateDesert Ecoregion in westernNorth America as
describedby Bailey (1998). This includesthe ColumbiaBasin of Washingtonand the Columbia
Plateauand GreatBasin of Oregon,Idaho,Montana,Wyoming, Utah, California,andNevadaof
the United States. The populationin Washingtonis confinedto the ColumbiaBasin of central
Washington,and is estimatedto havebeengeographicallyisolatedfrom otherpopulationsof the
speciesfor thousandsof years(Lyman 1991,Warheit 2001, Lyman 2004).
There are few historic accountsof pygmy rabbitsin the ColumbiaBasin. Taylor and Shaw
(1929)reportedthe pygmy rabbit as fairly commonin Adams County,while Booth (1947) and
Dalquest(1948)reportedthem as scarce.Pre- 1962museumspecimenswere collectedin four
counties:Adams, Grant,Douglas,and Lincoln (WDFW 1995). Therewere no verified pygmy
rabbit collectionsor reportsbetween1962 and 1979. Little was known aboutthe distributionand
statusof pygmy rabbitsin Washingtonuntil surveyswere conductedby'WashingtonDepartment
of Fish and Wildlife (V/DFW, formerly Departmentof Game)between1987and 1990(Dobler
andDixon 1990).
Pygmy rabbitswere known from six relativelysmall, isolatedpopulationsduring the 1990'sin
Washington. Populationsizeswere neverknown; relativenumbersof animalswere estimated
through counts of active burrows. Number of active burrows rangedfrom 10 - 590 at the six
sites. The pygmy rabbit was listed as a threatenedspeciesin Washingtonin 1990and was
reclassifiedto endangeredstatusin 1993 (WDFW 1993). A staterecoveryplan for the pygmy
rabbitwas writtenin 1995(V/DFW 1995).
(USDI2003). Populationswith the
Between1997-2001fiveof the six populationsdisappeared
fewestactiveburrows generallydisappearedfirst. Two populationsdramaticallydeclinedafter
fìre. By March 2007, rabbits remainedonly at SagebrushFlats, near Ephrata, and that
populationsuffereda suddenlarge declineduring the winter of 2000-2001. Reasonfor the
suddendeclineis not known.
WashingtonDepartmentof Fish and Wildlife, in cooperationwith PeggyBartels,a concerned
citizen,conductedgeneticanalysesof pygmy rabbitsin 2001. The resultsindicatedthat the
ColumbiaBasinpopulationof pygmy rabbitsis geneticallydistinct from all otherpopulationsof
pygmy rabbits in the United States,and appearsto have suffered from a reduction in genetic
diversityover the past 50 yearsto a relatively low level (Warheit2001).
Pygmy rabbitsof the ColumbiaBasinin Washingtonwere listed under emergencyprovisionsof
thc federalEndangeredSpeciesAct in November2001 by the U.S. Fish and Wildlifc Scrvice,
listing in March 2003 (USDI2003). Surveysin
with a fînal rule continuìngthe endangered
winter 2003 2004 at SagebrushFlats failed to locateactiveburrows (8. Patterson,WDFW,
pefs.comm.).
Natural history of the Columbia Basin pygmy rabbit
The mean adult weights of pygmy rabbitsrangefrom 375 to slightly over 500 grams(0.83 to 1.1
pounds),andlengthsfrom23.5 to 29.5cm (9.3 to 11.6in.) (On 1940;Janson1946;Wilde 1978;
Gahr 1993;WDFW 1995). Their overall color is slate-graytipped with brown, their legs,chest,
and nape are tawny cinnamon-brown;the entire edgesof their earsare pale buff. Their earsare
short, rounded, and thickly furred outside. Their tails are small, uniform in color, and nearly
unnoticeablein the wild (Orr 1940;Janson7946;WDFW 1995). The pygmy rabbit is
distinguishablefrom other leporidsby its small size,short ears,gray color, small hind legs,and
lack of white on the tail.
Pygmy rabbitsaretypically found in densestandsof sagebrush(Artemisidspp.),and arehighly
dependenton sagebrushto provide both food and shelterthroughout the year (Orr 1940; Green
and Flinders 1980;V/DFW 1995). The winter diet of pygmy rabbitsmay be comprisedof up to
99 percentsagebrush(Wilde I978), which is unique amongleporids(White et aL.1982).Pygmy
rabbits are known to climb amongthe upper branchesof sagebrush plants to forage (Green and
Flindersi 980),
The pygmy rabbit is the only rabbit in the United Statesthat digs its own burrows (Nelson 1909;
Greenand Flinders 1980;WDFW 1995). Pygmy rabbit burrows are typically found in deep,
loosesoils. Holever, pygrny rabbitsoccasionallymake use of burrows abandonedby other
(Marmotaflaviventris) or badger(Taxidea taxus)
species,such as the yellow-bellied marmot
'WDFW
1995).
(Wilde 1978;GreenandFlinders1980;
Pygmy rabbits,especiallyjuveniles,likely usetheir burrows as protectionfrom predatorsand
inclementweather(Bailey 1936;Bradfield 1974). The burrows frequentlyhavemultiple
entrances,some of which are concealedat the baseof larger sagebrushplants (V/DFW 1995).
Pygmy rabbits evadepredatorsby maneuveringthrough the densecover of their preferred
habitats,often along establishedtrails, or by escapinginto their burrows (Bailey 1936;Severaid
1950;Bradfield 1974). Burrows arerelatively simple and shallow,often no more than2 m (6,6
ft. in length and usuallylessthan 1 m (3.3 ft) deepwith no distinct chambers(Bradfield 1974;
Greenand Flinders 1980;Gahr 1993). The numberof activeburrowsmay not be directly related
to the number of individuals in a given area. Someindividual pygmy rabbits appearto maintain
multiple burrows,while someindividual burrowsareusedby multiple individuals(Gahr 1993;
WDFW 1995).
Pygmy rabbits begin breeding at age1 and breedingmay occur from Februarythrough July (L.
Shipley,WashingtonStateUniversity,pers.comm.2003). In somepartsof the species'range,
femalesmay haveup to threelitters per year and averagesix young per litter (Green1978;Wilde
1978). Recentinformationon captivepygmy rabbitsindicatesthat femalesmay excavate
specialized"natal" burrows for their litters in the vicinity of their regularburrows(P. Swenson,
OregonZoo, pers.comm. 2001;L. Shipley,V/ashingtonStateUniversity,pers.comm. 2001).
The gestationperiod of captive pygmy rabbits is approximately25 days and kits emergefrom
their natal hrtrrowsat roughly two weeksof age(L. Shipley,'WashingtonStateLlniversity,pers.
comm.2003).
Pygmy rabbits may be active at any time of the day or night and appearto be most active during
mid-morning(Bradfield 1974;Greenand Flindersl980; Gahr 1993). Remotevideo observation
of captive pygmy rabbits indicatesthat they are most active at night (L. Shipley, Washington
StateUnviersity,pers.comm).
History of the captive breeding program
In December,2000, 4 pygny rabbits were brought from the Lemhi Valley of Idaho and rearedat
the Oregon Zoo in Portland. Additional rabbits were capturedfrom Idaho in 2001 and 2002. ln
2002Idaho rabbits were moved to captive breeding facilities at Northwest Trek Wildlife Park
and Washington StateUniversity. Idaho rabbits were used to develophusbandrymethods,to
provide animals for experimentalreleases(back into Idaho), and to comparereproductiveresults
with Columbia Basin pygmy rabbits under similar captive environments.
To preventpossibleextinctionof the ColumbiaBasinpygmy rabbits,16 pygmy rabbitswere
trapped at SagebrushFlats, Washington from May 2001 through January2002, and transported
to captive breeding facilities at the Oregon Zoo andWashington StateUniversity. The captive
breedingprogramwas initiated in spring2002 with 18 animalsfrom the 16 founders. Captive
breedingof pygmy rabbitsis a cooperativeprojectbetweenWashingtonDepartmentof Fish and
Wildlife, U. S. Fish and Wildlife Service,the OregonZoo, WashingtonStateUniversity,and
NorthwestTrek Wildlife Park. A ScienceTeam,with membersfrom wildlife agencies,
universities,and zooswas formed to review and direct all aspectsof captivebreeding,
Populationgrowth of captiveColumbiaBasin pygmy rabbitshasbeenstaticto negative,and
only threecaptiveColumbiaBasin rabbitsremainin April 2006,down from 15 in April 2005.
Geneticdiversityof the ColumbiaBasin pygmy rabbitsis low, andreproductiveperformancehas
beenpoor comparedwith captiveIdahopygmy rabbits. Experimentalintercrossess
were
conductedin 2003 to determinewhether Columbia Basin and Idaho pygmy rabbits could
interbreed. Resultsindicated that they could interbreed,and reproductiveperformanceof
intercrossanimalswas superiorto the pure ColumbiaBasin stock. Recoveryof the Columbia
Basin pygmy rabbitswill requirethe introductionof non-ColumbiaBasinpygmy rabbitsinto the
captive breeding program to improve genetic diversity and reproductive success(USFWS 2004).
This approachwas usedfor the Florida pantherrecoveryprogram(Hedrick 1995).
This documentsummarizesresults of captive breeding activities in2002 - 2005, and outlines
goalsand recommendations
for the endangeredColumbiaBasinpygmy rabbit in the captive
breedingfacilitiesin Portland,Oregon(OregonZoo), Pullman,Washington(WashingtonState
Univerity) and Eatonville,'Washington(NorthwestTrek Wildlife Park). We review the current
geneticstatusof the captivepopulation,provide the geneticgoalsof the captive-breeding
program, and provide prescriptive recommendationsthat should guide the husbandryof
ColumbiaBasinpygmy rabbits. This documenthasbeendevelopedto supportthe Columbia
4
Basinpygmy rabbit recoveryteamin their developmentof a recoveryplan, and fulfills the
requirementsof FederalRecoveryPermit T8050644-3.
Captive Breeding Summary for 2001through 2005
Captivebreedingof Idahopygmy rabbitsoccurredduring 2001 - 2005,while ColumbiaBasin
pygmy rabbits were captively bred in2002 - 2005 and intercrossbreeding began in2003-, at
first (2003) on an experimentalbasis. Captivebreedingresultscontinuedto show strong
differencesbetweenbreedingsuccessof Idahopygmy rabbitsand ColumbiaBasinpygmy
rabbits. All of the breedingparametersinvestigatedshowedstatistically significant differences
betweenIdaho and ColumbiaBasinpygmy rabbits(Table 1). For all years,pregrrancysuccess
was 100% for Idaho females(whenpairedwith IdahomalesN : 20) and5lYo for Columbia
Basin females(when pairedwith ColumbiaBasin malesN : 35). Pregnancyrateswhen Idaho or
Columbia Basin femaleswere mated to produceintercrossoffspring were intermediate,
approximately 70Yo(N : 36). Perhapsmost import antly,Idahopygmy rabbitsproduced1'75
litters/ breeding female and 3 litters per breeding male, while Columbia Basin pygmy rabbits
produced0.66 litters per breedingfemale and0.79litters per breedingmales(Table 1). Number
òf yormgproducedper total numberof femaleswas 4.9 for Idaho rabbits and2.I for Columbia
Basin pygmy rabbits(Table 1; seeElias 2004).
Fourteenl0O%ColumbiaBasinpygmy rabbit kits lived to burrow emergencein 2002, 15 in
2003,12 in2004,but no l0O% kits lived to burrow emergencein 2005. Extensivepairingsof
lO0% ColumbiaBasinpygmy rabbits at all facilitieswere all eventuallyunsuccessfulin 2005.
and ColumbiaBasin(2002-2005)
Tabte1. Reproductiveperformanceof captiveIdaho (2001-2005)
pygmyrabbits.
Femalespregnant
Kits/Male
Young /Femalel
Pairings resulting in
confirmed pregnancy
Litters/BreedingFemale
ColumbiaBasin
5 1 %( N : 3 5 )
2 . 3 8( N : 2 e )
2 . 0 3( N : 3 4 )
1 8% ( N :121)
0.66(N:35)
Idaho
100% ( N:20)
8.7s( ì{ : 12)
5 . 3 5( N : 2 0 )
3 4% ( N : 3 4 )
1 . 7 s( N : 2 0 )
An experimentto determineif Columbia Basin and Idaho pygmy rabbits could interbreedwas
initiated in 2003,with the successfulbirth of 10 intercrossanimals. In2004 and 2005,intercross
animalswere successfullyableto backcrosswith ColumbiaBasinpygmy rabbits. In April 2006,
the captivepopulationconsistedof 9 rabbitsthat are 50% ColumbiaBasin, 3 rabbitsthat are
62.5% ColumbiaBasin, 47 thal are75%oColumbiaBasin, 6 that are87.5o/oColumbiaBasin as
well as the 3 that are700YoColumbiaBasinpygmy rabbits.
Reproductivebehavior was intensively monitored at Washington StateUniversity in 2003
ZOO+.Reproductivebehavior showedsignificant differencesbetween Columbia Basin and Idaho
pygmy rabbits. Although identifiedbehaviorswere similar, ColumbiaBasinpygmy rabbits
,p."t S times longer (averaging964minutes)than Idahopygmy rabbits(124 minutes)before
beginningreproductivebehavior. ColumbiaBasin pygmy rabbitsspent5 times longer
chasing/houronce reproductivebehavior began than Idaho rabbits, however both groupshad
equalnumbersof mountings(Elias 2004) In addition,in two yearsof breeding,ColumbiaBasin
pygmy rabbitsdid not successfullybreedafter April 12,while Idahopygmy rabbitssuccessfully
breclthroughMay anrlinto early June.
The poor reproductiveperformanceof Columbia Basin pygmy rabbits comparedto Idaho pygmy
rabbits endangersthe continued existenceof Columbia Basin pygmy rabbits in captivity, and has
preventedthe production of sufficient number of animalsto reintroduceback into the wild. The
size of the ColumbiaBasin captivepopulationto datehasbeendeclining. Projectionsusing
populationmodeling softwarePM 2000 indicatecontinueddeclinesin ColumbiaBasinpygmy
rabbits. Intercrossanimals,however,have markedlyincreasedfitness(as exhibitedby
reproductive success)over the Columbia Basin pygmy rabbits.
Medical Issues
Pygmy rabbitshavebeenmaintainedin captivity on soil. The two principal diseaseissuesof
both relatedto
concernfor captivepygmy rabbitshavebeencoccidiosisandmycobacteriosis,
soil relationship.Disseminatedmycobacteriosisdue to Mycobacteriumavium hasbeenthe most
commoncauseof deathof adult captivepygmy rabbits. Fatal disseminatedmycobacteriosisdue
to M. avium was diagnosedin 28 captivepygmy rabbitsbetweenJune2002and September2004,
with deathsoccurring at 2 of the 3 captive holding facilities. M. avium is a bacterium that
commonly existsin soil andwater, and can survivefor long periodsof time in soil. High
numbersof the bacteriumcanbe shedin feces. The incubationperiod of mycobacteriosiscanbe
weeksto months,and detectionof infectedindividualsis difficult. Treatmentcan take several
years and its efficacy in pygmy rabbits is unknown. There may be side-effectsof treatment,
including reduced reproductiveperformance. Currently, regular fecal cultures are done on
captiverabbitsin an attemptto detectsubclinicallyinfectedanimals.
Antemortem and postmortemmedical recordsfrom thesecaseswere evaluatedretrospectively
with the goalsof describingthe clinical behaviorof mycobacteriosisin pygmy rabbits
(Harrenstienet al, unpubl manuscript).V/e assessed
the relativevalue of physicalexamination
findings and diagnostictestresultsin the presumptiveor definitive diagnosisof mycobacteriosis
in pygmy rabbits,use of varioustreatmentprotocols,possiblerisk factorsfor the observedhigh
for preventionof mycobacteriosis.Partiallymortality, and developedrecommendations
ineffective cell-mediatedimmunity appearsto be the strongestreasonfor the high morbidity and
mortality of M. avium infections in pygmy rabbits.
Coccidiosisis causedby aprotozoanthat invadesthe intestinesand othertissuesof animals. A
new pathogenicspeciesof coccidian,Eimeria brachylagøshasbeenidentified from captive
pygmy rabbits (Duszynski et al. unpubl manuscript). Four captive-bornColumbia Basin pygmy
rabbit young and 3 captive-bornIdaho pygmy rabbit young died of intestinal coccidiosis during
the 2002 breedingseason.In 2003, four captive-bomColumbiaBasinpygmy rabbit young and
at least6 young Idahopygmy rabbitsdied of intestinalcoccidiosis.The speciesof coccidia
infectingpygmy rabbitsis under study,but has not beenpositively identified. Antibiotics have
beeneffectiveat decreasingparasiteloads. Sincethe deathsin spring 2002,coccidialevels are
now monitoredin captivepygmy rabbits. Animals with elevatedcoccidialevels are treatedwith
antibiotics.
6
The heavymycobacteriosislossesin the captiveColumbiaBasinpygmy rabbitshave causedthe
building of 30 experimentalnon-soil pensfor animalhusbandry.Animals will be kept off soil
until the breedingseason,unlesswe developsuccessfulreproductionoff-soil.
The high incidenceof myoobaotcriosisletl the OregonZoo to initiate an investigationinto the
rabbits cellular immune function. In collaborationwith researchersfrom the National Institutes
of Health,blood samplesfrom 14 Columbia Basinpygmy rabbitsand 9 Idahopygmy rabbits
were testedto determinethe responseof their immune systemcells to infection. In general,
Columbia Basin pygmy rabbits had a significantly poorer immune responsethan the Idaho
pygmy rabbits(K. Mansfield,WDFW, pers.comm.). While at this point it is not possibleto say
with certainty whether this hnding is related to the higher degreeof inbreeding in Columbia
Basin pygmy rabbits, a relationship betweendiminished geneticdiversity and higher
susceptibility to mycobacteriosishas been demonstratedfor a number of other species.
A new mortality factor emergedduring the summerof 2004. Approximately 14 pygmy rabbits
housedat Washington StateUniversity have died of an intestinal diseaseof unknown origin. A1l
geneticlines (ColumbiaBasin, Idaho, and intercross)havebeenaffected. Most caseshavebeen
young adults,althoughsomeyoung of the yearhave also died. As of March 1,2005, no cases
have been detectedat the other two captive breeding facilities, the OregonZoo andNorthwest
Trek. A decisionwas madeto suspendplansto move rabbitsbetweenfacilities. This suspension
will result in fewer desiredpairings than would have occurredwith animal exchange,but is being
taken to ensurethis diseasedoesnot spreadto other facilities.
GeneticManagement
Conservation Genetic Principles used in Captive Breeding Programs
Most captivebreedingprogramsfor endangeredspeciesaredesignedto maintaina specific
percentageof wild populations'geneticdiversity for a specifiedtime period. Souléet al (1986)
originally proposedthat there shouldbe an effort to retain90% of the wild population'sgenetic
diversity for a period of 200 years,althoughin practice,this goal hasbeenrelaxedto a lower
percentagefor a shorterperiod of time. Attempts to retain in captivity a certain percentageof the
wild population'sgeneticdiversity are groundedin Lwofuirdatnentalassumptions:(1) the wild
populationis still relativelylarge (e.g.,Ne feffectivepopulation]> 500, or N > 1000individuals)
and geneticallydiverse,and(2) the foundingpopulationfor the captiveprogramis a random
sampleof the wild population,and is large enoughto retainmost of the geneticdiversity
(measuredas allelic diversity or heterozygosity)of the wild populations(seeFrankhamet al.
2002 for discussionofspecific goals).
In orderto retain a signif,rcantproportionof the wild population'sgeneticdiversity,captivebreeding managersmust attemptto maximize the size of the captivepopulation, given the limits
imposedby the breedingfacilities. This is becausethe deteriorationof geneticdiversity as a
result ofgenetic drift (lossofalleles) and inbreeding(lossofheterozygosity)is reducedin larger
versussmallerpopulations. Thereis also a needto maximizeNe/N, in orderto maximize genetic
diversityper size of the breedingpopulation.
In addition to retaining geneticdiversity, captive breedingprogramsmust also attemptto avoid
inbreedingdepression(reductionin survival or reproductionas a result of inbreeding)or the
accumulationof deleteriousmutations(e.g.,producinghomozygousindividualsfor recessive
allelesthat will reducefitnessin its homozygousstate). Managersdesigningbreedingprograms
can minimize theseaffectsby pairing captiveincliviclualswith low kinship values. This will
potentially avoid the negativefactorsassociatedwith inbreedingdepressionand help maintain a
level of geneticdiversityby preservingheterozygositywithin the captivepopulation.
Summary of the population geneticsof the captive-bred Columbian Basin Pygmy Rabbits
Methods
Twelve microsatelliteloci developedfrom Europeanrabbit (Oryctolaguscuniculus)were
screenedfor amplificationand variability in pygmy rabbits. Of these12loci, nine were selected
for use in this analysis(Table 1). Eight of thesemicrosatelliteloci have di-nucleotiderepeat
sequences,
and one locushas a tetra-nucleotiderepeatsequence.PCR protocolsfor theseloci
were modihed from thosein the original publications(Table2) to facilitatemultiplexing and
amplificationin pygmy rabbits. Protocolsare availablefrom authorupon request. All PCR
amplificationswere conductedwith MJ ResearchPTC-200thermocyclersusing fluorescently
labeledprimers (oligonucleotideprimers synthesizedby IntegratedDNA Technologies,Inc.
UDTI or Applied Biosystems[ABU). DNA fragmentswere visualizedusing an Applied
BiosystemsABI Prism 377 sequenceror a 3100 Genetic Analyzer,and sizedusing an internal
lane/capillarysizestandard(Applied BiosystemsGeneScan500 - ROX), and ABI GeneScan3.7
'We
and ABI Genotyper3.7 softwarerunning on MS Windows NT/2000-basedcomputers.
calculatedallele frequencies,expectedheterozygosity,observedheterozygosity,allelic richness,
and othermeasuresof genotypicdiversityusing Fstat(Goudet2001), GDA (Lewis and Zaykin
2001),or Microsatellite Analyzer(MSA; Dieringer and Schlötterer2003).
Founders
SixteenColumbiaBasinpygmy rabbitswere trappedat SagebrushFlats,Washingtonand
transpoftedto captivebreedin$facilities at the OregonZoo (OZ) and WashingtonState
University (WSU) between};4ay7,2001 and January15,2002 (Figure 1). These16 rabbits
(Founders)representedan unknown but presumablysizeableportion of the then-existing
populationof ColumbiaBasinpygmy rabbits. No other ColumbiaBasin pygmy rabbitshave
been capturedsinceJanuary2002,despiterepeatedattempts.None of the original 16 rabbitsthat
formed the founding population are now alive, and unlessnew pygmy rabbit populations are
discovered,the ColumbiaBasinrabbitsmay now be extinct in the wild. Therefore,the genetic
diversity of the Founders,designatedas C82001 in Table 2, representsnot only the initial
genetic conditions for the captive breedingprogram, but also perhapsthe genetic diversity of the
entirepopulationof ColumbiaBasinpygmy rabbitsin 2001. We comparedthe geneticdiversity
of C82001 to that from a populationof Idahopygmy rabbitstrappedone year earlier(20 June
2000 through21 December2000) from Lemhi County,Idaho (IDWILD). For eachmeasureof
geneticdiversity (Table2) the Idahopopulationis approximatelytwo-timesas diverseas the
ColumbiaBasinpopulation(C82001), despitethe fact that the samplesizesareroughly equal
and the geographicextentfrom which the sampleswere drawn is the same(Figure2).
The geneticdiversity of the Founderscan alsobe comparedtemporallywith two historical
samplesfrom SagebrushFlats:a museumskin collectionfrom 1949 and 1950,and a blood
samplecollectedby Gahr (1993)in 1992. All threeColumbiaBasin samplesshow lower genetic
diversity than the Idaho samples,and there appearsto be a decline in geneticdiversity ftom 1949
to 2001 (Table 2). The captivebreedingprogramfor ColumbiaBasinpygmy rabbitswas
initiatedwith a populationthat showedthe lowest geneticdiversity of all wild populations
sampledthus far, antl frolr a population that appearsto have been declining in gcnctic diversity
for over 50 years. Becausewe brought all known Columbia Basin individuals into captivity, we
suspectwe capturedthe remaining geneticdiversity within the wild Columbia Basin pygmy
rabbits.
Captive Breeding
The founding population was split into two "subpopulations"one each at the Oregon Zoo (OZ)
and Washington StateUniversity (WSU), and was immediately augmentedby five kits from
Danae,who was bred in the wild (i.e., fatherof the kits is unknown;Figure 1). The nine
microsatellite genotypesfor eachof thesekits were identical and differed from Danaeat only
two of the 18 alleles,suggestingthat Danaebred with an individual with nearly the same
genotypeas her, possiblya closerelative. The survivorsfrom the Foundersand Danae's
offspring were the individuals that constitutedthe initial captivebreedingpopulation (C82002;
Table 2, Figure 1). We definedeachcaptivepopulationbasedon thosenamedindividualsalive
at the beginning of eachcalendaryear, and calculatedthe theoreticalrelatedness(sensuQueller
and Goodnight1989)betweeneachpairwise combinationof malesand females. Breedingpairs
were selectedinitially (2001-2004)basedon individualswith the lowestpairwiserelatedness,
rare alleles).
and priority was given to the most geneticallydiverseindividuals(i.e.,possessed
Beginningin 2005,we basedour breedingstrategyon the kinship valuescalculatedfrom the
actualpedigrees,using PM2000 (Pollak et a1.,2005).Although the captivepopulationexistsat
two localities(OZ and WSU) it is managedas a singlepopulation,with individual rabbitsbeing
moved betweenlocalitiesin orderto achievethe most optimal pairings.
Therehave beenfour captivebreedingseasonsfor the ColumbiaBasinpygmy rabbits. As
definedby FiguresI and2, and Table 2, the2002 populationproducedthe 2003 population,the
2003 populationproducedIhe 2004population,and so on, resultingin the current2006
population(C82006-mix; Table 2). Not includedin the 2003 ColumbiaBasin population,but
experimentin 2003 were
participatingin an experimentalColumbiaBasin- Idaho crossbreeding
(INEEL)
Laboratory
and
Environmental
two malesfrom the IdahoNational Engineering
population(Alder and Behlem),who are shownin Figure 2. Thepopulationthat includedall the
Columbia Basin individuals alive in January2004 andoffspring from the Columbia Basin
Idaho INEEL intercross(not including pure IDINEEL individuals)is representedas the C82004Mixed population(Table2). From this point forward (i.e.,2004-2006),we representpopulations
as eitherpure ColumbiaBasin (e.g.,CB2006-CB)or ColumbiaBasinplus intercrossindividuals
(e.g.,C82006-Mixed).For eachpopulationpair (e.g.,C82006-CBand C82006-Mixed),the
geneticdiversity is greaterfor the mixed population,and for most years,when consideringthe
mixed populations,therehasbeenan increasein geneticdiversityfrom 2003 to 2006 (Table2;
Figure4). This is oppositeto the 2003-2006trend when consideringthe pure ColumbiaBasin
populations(Table2;Figure 4).
Gene Diversity in the Captive Pygmy Rabbit Population
Table 3 providesa summaryof genediversity statisticsfor historicalwild populationsof
ColumbiaBasinpygmy rabbits,and for the two captivepopulationsof pygmy rabbits,as defined
above. The geneticgenediversity statisticis the expectedheterozygositycalculatedfrom the
nine microsatellitesloci. Thepedigreegenediversity statisticis from PM2000 andrepresents
the proportional changein genediversity from the founding population to the currentpopulation.
Although PM 2000 considersthis genediversityto be relatedto the expectedheterozygosity,it is
calculateddirectly from the pedigreeas 1-MK (MK : meankinship' of all nonfoundersin the
currentpopulation). The current genetic genediversity (expectedheterozygosity)for the
ColumbiaBasinpopulationis 0.27,which is a33Yo- 40% declinefrom the historicalexpected
heterozygosityat SagebrushFlats (SBF). The pedigreegenediversity (genediversity) for the
captivepure ColumbiaBasin populationequals85% of the founders'genediversity (Table 3);
this representsan increasein meankinship of I5o/oin just five years.
As expected,the genediversity of the non-Idaho or mixed population is greaterthan that for the
pure ColumbiaBasinrabbitsfor both the geneticand pedigreestatistics(Table 3). In fact, the
expectedheterozygosityfor the mixed population(0.56) is 24o/ogreaterthan the most diverse
historicalpopulationof ColumbiaBasin rabbits(SBF-1949),and nearly 107%greaterthan the
pure Columbia Basin rabbits in captivity (populationsare not independentin that the pure
ColumbiaBasinrabbitsare a major componentof the mixed population). The increasein
geneticdiversity is a function of the addition to the Columbia Basin captivebreedingprogram of
descendents
from sevenpure Idahopygmy rabbitsthroughthe intercrossmatings(seebelow).
Although the expectedheterozygosityhas increasedwith the addition of the intercrossrabbits,
genediversityis 0.9^1(Table 3) and thereforeindicatesan 9Yodeclinein gene
the pedigree-based
diversityfrom the foundingpopulation'. The reasonthe pedigree-based
statisticshowsa decline
in genediversity is becausethe effectivepopulationsize is lessthan the censuspopulationsize.
That is, not all adult individuals have bred with equal frequency,and the number of offspring
producedby thesebreedingadultsis not equal. Thesefactorsreducethe effectivepopulation
sizebelow that of the censuspopulationand thereforeincreasemeankinship amongthe
survivingindividualsin the population.
Founders Input to Captive Population
There area total of 15 foundersin the mixed population; eight foundersfrom Columbia Basin,
and sevenfrom Idaho,as discussedabove. Thesefoundershavenot contributedequallyto the
currentmixed population(Table4). The founders'input to the captivepopulationcanbe represented
using any one offour statistics:representation',contribution*,alleleretention',and
(calculatedin PM2000). We have also addeda fifth statistic(PCAl),
numberof descendants
which is the weightedlinear combinationof eachof the four PM2000 statisticsthat accountfor
the most total variancein the dataset (i.e., the first principle component,using a total correlation
matrix). Thesefive statisticsare shown in Table 4. Although three founderseachhave greater
'
It is important to differentiate "kinship" from relatedness.Kinship is the probability that two randomly chosen
alleles,one from eachoftwo individuals,are identicalby descent(Blouin, 2003),and can be calculateddirectly
from a pedigreewithout specificknowledgeof the any particularlocus. Relatedness
is the proportionof allelesin
two individualsthat are identicalby descent(Blouin, 2003). Relatedness
canbe calculatedfrom genotypicdataor
as 2 times kinship.
'Founding population
for the mixed populationincludesall the ColumbiaBasin Idaho founders
' The proportion of the alleles in the living
captive population that are derived from the founder. This is the
proportional founder contribution.
*
The numberof copiesof the founder'sgenomepresentnthe líving captivepopulation(e.g.,offspring: 0.50,
grand offspring : 0.25).
'
The probability that an allele presentin the founder exists in the living captive population.
10
hashad the greatest
the most amongall founders,Elymus (60 descendants)
than 60 descendants,
input into the captivepopulation, as measuredby PCAl, which summarizesthe other four
statistics. All foundersare now dead(Elymus died March 30,2006), and changesto their
contribution to the captivepopulation will be a function of breedingperformanceof their
descentlants.As cxpected,ColumbiaBasin input into thc mixcd captivepopulationis greater
than that of the Idaho founders,basedon all founder statistics. For example,there are total of 82
"genomes"presentin the living captive population (seeContribution), of which 75o/oate
from the 15 foundersin the
ColumbiaBasin genomes.Likewise,there are 519 descendants
rabbits. Among the Columbia
Basin
Columbia
from
or
76Yo
mixed captivepopulation,with 395
Basin rabbits, eachmale founder has averageda greaterinput to the living captivepopulation
comparedwith each female founder. Fifty nine percent of the Columbia Basin contribution, and
5i%oof theColumbia Basin descendantsare from male rabbits, and the allelic retention for males
greaterthan that for females..Among the Idahorabbits,Alder hasbeenmost successful,
is 43%o
and 10.75genomes(Contribution), His allelic retentionis as largerthan
leaving 50 descendants
all ColumbiaBasinrabbits,exceptBam Bam.
Genetic Goals for the Captive Population of Pygmy Rabbits
Over the past four years,the captivebreeding program for the pure Columbia Basin pygmy
rabbitshasmaintainedT3Yo- 95% of the geneticdiversity of the foundingpopulation(Table2).
However, the captivebreedingprogram of pure Columbia Basin pygmy rabbits is vulnerable
because(1) only threepure ColumbiaBasinpygmy rabbit remainalive, as of April 15,2006 (2)
the geneticdiversity of the ColumbiaBasin foundingpopulationwas low; (3) the effective
populationsize of the captivepopulationsis low (Ne : 5,7; populationon JanuaryI,2006 ) and
therefore geneticdrift may further decreasegenetìcdiversity, and (4) there are no known wild
ColumbiaBasin pygmy rabbitsavailableto geneticallyaugmentthe captivebreedingprogram
Thereforethe primary geneticgoalsof the ColumbiaBasin captivebreedingprogramare as
follows:
Increasethe effectivesize (Ne) of the populationby increasingthe numberof breeding
adults participating in the breedingprogram.
2 . Increasethe censussize of the captivepopulationby searchingfor and removing
additionalwild ColumbiaBasin pygmy rabbits.
J.
Infusenew geneticdiversityinto the ColumbiaBasinpopulationby continuingan
intercrossstrategyto reversethe negativeeffectsof geneticdrift andinbreeding.This action
will dramaticallyincreasethe level of geneticdiversitywithin the population(Table2,
Figure 4), andlessenthe affects of geneticdrift by increasingthe effective population
size.
I
2006 Management Priorities
Given the abovediscussion,the 2006 managementprioritiesfor the captivebreedingprogram
are:
a) Maintain geneticdiversityof ColumbiaBasin Pygmy rabbitsby matchingthe most
appropriatepure ColumbiaBasin malesand females(minimize loss of geneticdiversity),
b) Produceoffspringof pure-bredColumbiaBasinpygmy rabbits,
to produce87.5o/oColumbiaBasinpygmy rabbits
c) Conductintercrosses
to the Idahorabbit Alder(See
breedingof rabbitswith a high relatedness
d) De-emphasize
Table4).
1l
e) Conductintercrossesto produceT5%o
ColumbiaBasin pygmy rabbits
Ð Createno new Fl intercrosses(ColumbiaBasin/Idahointercrosses)and avoid pairingsto
produce62.5% ColumbiaBasinpygmy rabbits.
g) Conductbreedingexperimentsto compareresultsof largepen breedingto small pen
breeding
h) Conductexperimentaloff-soil breeding.
Objective Ã) Maintain genetic diversity of Columbiu Basín Pyg*y rqbbits by matching the
most appropriate Columbíø Basin møles and females (minimize loss of genetic diversity).
This objective is achievedthrough analysisof the rabbit pedigree,genotl,ping all individuals, and
prioritizing specificpairings. Geneticrelatedness,
both theoreticalbasedupon allelic diversity,
and kinship basedon the pedigreehavebeenusedto determinepairings. For 2006 we will
kinship valuescalculatedin PM2000, and founderstataisticsto prioritize breedingpairings.
Objective B) Produce offspring o.f100% Columbia Basin pygmy rabbits.
Pairingsof ColumbiaBasin pygmy rabbitswill be the highestpriority from March 1 through
April 15. This period includesall known datesof successfulColumbiaBasin pairingsfrom
2002 through2005 with a buffer of one additionalweek. However,in2006, we have few
healthyColumbiaBasin individualsto pair. The most importantindividual is Raphaelaat WSU,
and shewill be primarily pairedwith Heathfor this period. The other importantpairing will be
Lolo and Bryn at the OregonZoo.
Objective C) Conduct intercrossesbreedingto produce 87.5% or híglter Columbia Basin
pygnty røbbits.
Intercrossesthat are 75o/oor 87.5%ColumbiaBasinpygmy rabbitswill be bred with I00%
ColurnbiaBasinpygmy rabbits.
Objective D) De-emphasízebreeding of rabbits with a high kínslrip to the Idaho rqbbit Alder.
There are currently 28 animalsthat are in the captive breedingpool that have relatively high
kinship to the Idahorabbit Alder. To de-emphasize
Alder in the captivepoplationwe will take a
'We
numberof steps. First we will not breedthe F1 (50%) ColumbiaBasinmale Ivan.
will also
pygmy
rabbitsGretchen,'Wolfgang,and Inge with 100% Columbia
only breedthe 3 50% female
Basinmales. In addition,the 11 males('Watson,Crick, Starsky,Buckley, Pan,Orlando,Vigo,
Kerr, Periwinkle,O^yr, and Moore) that haverelativelyhigh kinship to Alder will be deemphasizedin the captivebreedingprogram. This de-emphasis
will be donein severaldifferent
ways. First they will not be bred in largepens,as we anticipatemalesin largepenscontributing
disproportionatelyto malesbred in small pens. Second,we will use one or more of thesemales
for non-soilbreedingexperiments.Third, we will attemptto reducethe numberof breeding
introductions(introducedpairings)of the remainingmaleswith high kinship to Alder through
carefulbreedingmanagement.This meansthat othermaleswill havepriority in breeding
pairingswhereverpossible.
T2
ObjectiveE) Conduct íntercrossesto produce 75% Columbia Bøsin pygmy rqbbits
with animalssignificantlyrelatedto Alder, we will emphasize
Consistentwith our de-emphasis
ColuurbiaBasinpygrìryrabbitsin 2006. This will be accomplishcdwith
the produ<;tionolT5o/o
pairingsof 100 and50o/oColumbiaBasin animals,T5Yowith75% ColumbiaBasin animals,and
87.5% wirh 62.5%ColumbiaBasinanimals.
Objective ß) Conduct research into srtifícíal inseminatíon.
The poor reproductiveperformanceof ColumbiaBasinpygmy rabbitsresultedin several
genetically important animals dying without passingon their genesto offspring. The purposeof
this researchis to deúelop artificial inseminationmethodsto maintain geneticdiversity within
the captive Columbia Basin pygmy rabbits through human intervention. In 2004 we attempted
on 4 separateoccasionswith 7 males(a11wereIdaho animals). Rabbitswere
electroejaculation
by inhalationof isofluranewith oxygenvia box induction. Males initially
anesthetized
respondedto electo-stimulationwith muscletension,hind limb extensionandpenile erection
howeverwe were unableto collect a viable semensampleduring any of theseattempts.Males
generallyshowedthe best responseat the onsetof stimulationor immediatelyfollowing rest
periodsandrapidly becamerefractoryto further stimulation.In one casewe did collect a small
volume of seminalfluid (-20 pl) which containeda few non-motilespermatozoa.We also
attemptedthis procedureon2 domesticrabbits(silver foxes weighing- 3.5 kg) and collected
viable semensamplesfrom both males. Differencesin anestheticdepthbetweenthe pygmy
rabbits andthe domesticsmay partly explaintheseresults. In the futurewe may wish to attempt
of pygmy rabbitsat a shalloweranestheticplaneor without generalanesthesia.
electroejaculation
was perfotmedby radioimmunoassay.Mean
extractionandmeasurement
Fecaltestosterone
betweenID and CB populationsfor
significantly
did
not
differ
levels
fecal
testosterone
weekly
However,2 out of the 4
the one month sampledduring the breedingseason(3128104-4128104).
levels compared
CB malessampleddid show significantlylower meanweekly fecai testosterone
(5124104-6125104),
to all othermalesfrom eitherpopulation.After the end of the breedingseason
levelsin eachof the 4 weeks
ID malesmaintainedsignificantlyhigher weekly fecal testosterone
the
breeding
seasonwas not
level
cluring
sampled. Individual, weekly fecal testosterone
correlatedwith breedingsuccessduring the entire2004 season(definedasthe ratio of litters
siredto pairings). Buck agewas a predictorof breedingsuccess(12:0.789). 2 yearold males
were more successfulthan either 1 or 3 year olds.
Objective G) Conduct Experimental off-soil breeding.
Principalmorlality factorsfor pygmy rabbitsin captivity havebeencoccidiosisand
mycobacteriosis.Both of thesemicro-organismsare containedin andpassedto pygmy rabbits
throughsoil. We built new pensfor pygmy rabbitswith concretefloors that could be adaptedto
either with soil or without soil. Four female Idaho rabbits and2 male Idaho rabbits were used
at WSU in2004 to testthe effectivenessof breedingpygmy rabbitsoff soil. Both malesand
femaleswere housedin penswith rubberflooring and a setof nestboxesfor housing. After each
pairing anotherset of nestboxesfilled with timothy hay were addedto the pen to encourage
nestingfor birth of the kits. Six of 9 (67%) of pairingsresultedin a pregnancy.Of these6
pregnancies,only 1 lead to a successfulweaningof any kits, but only afterthe femalewas
IJ
transfered to a soil pen to give birth. All other successfulpregnanciesresultedin the kits dying
within 4-5 daysafterbirth. A total of l0 kits were known to havebeenborn (carcasses
found;
other carcasses
were consumedby the dam), of which 2 survivedpastweaning. In 2006,we will
continue to experimentwith off-soil breeding and selectiveintroduction of soil into the breeding
process.
Capacity of Breeding Facilities During 2006
Currently, we have 70 permanentpens for pygmy rabbits betweenWashington StateUniversity,
the OregonZoo andNorthwestTrek Wildlife Park, 30 of theseavailablefor non-soil care. Each
pen holds one adult animalor one litter of kits (temporarily). We alsohave 7 largepensof 600
to 800 sq. ft. eachat Washington StateUniversity for experimentalbreed in large enclosures.
WashingtonStateUniversityhas a pre-releasepen that can be re-furbishedfor animalsto be
releasedto the wild. Smallerpensarelocatedat all threefacilities,including WSU's pre-release
pens.We cantemporarilyhold an additional30 - 50 animalsin theseareasfor approximatelysix
months. In 2006 we will build temporary pens at all three facilities to hold animalsthat will
likely be released.
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t4
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Teer¡ 1. Microsatellitedatausedin this analysis
Name
Speciesof Origin
RepeatSequence
Reference
satS
cuniculus
Oryctolagus
(TC)zsTTT (CT)s
Mougel,et al. (1997)
satT
Oryctolaguscuniculus
(TG)r+
M o u g e le, t a l .( 1 9 9 7 )
satS
Oryctolagus
cuniculus
(CT)r¿(GT)sTT (GT)5
Mougel,et al. (1997)
I6
satl2
cunlculus
Oryctolagus
(CTAT)10
et al.(1997)
Mougel,
sat16
oryctolaguscuiicutus
(TG)rs
et al.(1997)
Mougel,
sol03
cunículus
Oryctolagus
(TC)r¿(T)4(TC)16
Ricoet al, (r994)
sol08
cuniculus
Oryctolagus
(TG)rs(N)1s(TG)s
Ricoet al.(199a)
sol30
Aryctolaguscuniculus
(TC)r+(AIfi)4 fiC)s
Ricoet al. (199a)
sol44
cuniculus
Oryctolagus
(GT)rz
et al.(1997)
Surridge
t7
Teet-p2. Geneticdiversitymeasureslor 12 spatialor temporalpopulationsof pygmy rabbitsin
Idaho (ID) and Washington(ColumbiaBasin,CB). The IDWILD populationis from Lemhi
County, Idaho. All ColumbiaBasinpopulationsare from SagebrushFlats. The ColumbiaBasin
populationsiclentifieclas "-CB" inclucleonly pnre, I00% ColumbiaBasinrabbits,while those
populationsidentified as "-Mixed" includeliving rabbits> 50yoColumbiaBasin. Seetext.
Population
N
A
A Ri.hn"r,
H"
Ho
IDWILD
21.00
6.78
5.84
0.75
0.80
c81949
13.78
3.33
3.09
0.41
0.42
c81992
40.67
3.22
2.69
0.41
0.40
c82001
16.00
2.44
2.38
0.37
0.37
cB.2002
18.00
2 .4 4
2.24
0.33
0.36
c82003
2 0 .0 0
2.33
2.04
0.27
0.28
CB2OO4-CB
2 4 .0 0
2.33
2.05
0.28
0.34
C82004-Mixed 3 4 .0 0
4 .4 4
3.40
0.43
0.53
c82005-cB
17.00
2.22
2.06
0.29
0.37
C82005-Mixed 4 2 .8 9
5.33
3.79
0.52
0.63
c82006-cB
2.11
2.11
0.27
0.35
5.78
3.86
0.56
0.62
9.00
C82006-Mixed 8 2 .8 9
N = rneansarnplesize per locus
A : tneannumbel of allelesper locus
: allelic rjchness(meannumberof allelesper locus,standardizedaclcssall populationdue the sanrplewith the snrallest
Ani.nno"
sarnplesize (n=9; seeEl Mousadik and Petìt 1996)
H": GeneDiversity
H" : observedheternzygosity
18
ColumbiaBasin
Captive-Alive.Pure
Population
Captive-Alive.Non-ldaho
19
Tesrp 6. Statisticsfor the 15 foundersof the mixed populationof captivepygmy rabbits. Table
lists foundersin order of greatestto lowest input into the captivepopulations,asmeasuredby
PCA1. Under Origin, CB and ID indicateColumbiaBasin and ldaho rabbitsrespectively;and
Studbooklist the off,rcialStudbooknumber for eachfounder. Below the list of founders are
summary statisticsfor both the Columbia Basin and Idaho contribution to the captive population.
Contribution,and
For Allele Retentionthis statisticis a medianvalue. Representation,
Descendantsare sums. The first line underthe founderstatisticsindicatesthat variable's
contributionto the frrst principle component.PCA1 accountsfor a total of 94o/oof the total
variance among all founder statistics.
Representat¡onContribution AlleleRetent. Descendants PCAl
Studbook
Sex
Elymus
Alder
Bam Bam
Danae
Wild (Danae'smate)
10
22
P22
M
Randy
Maya
Clover
3
6
23
M
Behlen
Artemis
Lupine
Fern
Coyote
15
19
M
16
29
F
11
18
13
M
Allie
Timothy
ColumbiaBasin
Male
Female
ldaho
30
M
1 À
M
F
M
F
F
M
F
F
M
Age
5
D
D
D
D
D
D
D
D
D
D
D
D
D
D
Origin
CB
ID
CB
CB
CB
CB
CB
CB
ID
ID
ID
CB
ID
ID
ID
051
051
0.50
0.47
0.13
10.81
0.86
60
2.41
013
0.10
10.75
8.25
8.41
0.89
0.89
0.74
50
62
z¿a
8.41
8.88
8.88
6.06
0.74
0.87
67
67
36
0.86
0.48
36
48
004
003
003
0.02
3.50
19
20
20
19
001
0.00
0.00
063
0.50
052
0.51
0.30
026
0.13
012
0.75
o44
080
395.00
22500
0.30
6 12 5
36.34
24.91
0.25
20 75
050
0 . r0
0.10
0.11
0.11
0.07
20
z.oJ
2.63
1.56
0.31
0.31
0.87
0 6'l
5
5
5
170.00
124.00
1.83
1.73
1.72
1.M
1.42
0.26
-0 97
-1.15
- 11 6
-1.83
-2 44
-2.75
-2.76
2001(Founders)
2002
2003
FrcuRE1. The first threepopulationsof ColumbiaBasinpygmy rabbit captivebreeding
program. Except for the Founderspopulation and parentswith extant offspring, only tht-rse
individualsalive at the beginningof the year that designatesthe populationareincludedin the
by filled squares(males)or circles(females). Males are
figure. Dead offspring arerepresented
with eachof the Foundersarethe
Datesassociated
red
boxes.
females
within
boxes,
within blue
capturedates.
2l
2004
B e h l e m( l D )
Figure 2. The 2004 Columbia Basin pygmy rabbit populationin captivity at WSU andOZ. This population representsthe first populaticn
with intercrossanimals. Alder and Behlem labeledas (ID) arepure IDINEEL individuals. SeeFizure 1.
22
10000
p
o
o
o
g
looo
J
o
(9
E
Y 9
ïq¡ õ+,
( J O
I rìn
õ-?
.9,
o
o
=
o
to
r
n
-o
o td a h o
I Go l u mbia
Basin
Ø
I
z
1
1
100
10
1000
10000
E-W Absolute Distance from Group Gentroid
(meters)
FlcuR¡ 3. The absolutedistancebetweenan individual sampleand
the centroidfor all sampleswithin a singlelocality for the
Washington(SagebrushFlat), and Idaho (IDWILD; Lemhi County)
localities. Distanceswere calculatedusing UTM coordinatesfor
eachsample,where available(Idaho),or from initial x-y telemetry
coordinates(Washington;seeGahr, 1993).
23
4.0
C B - P u re
CB - Mixed
3.5
o
Ø
o
e
e
3 .0
o
E
.9
o
2.5
=
2.0
0 .5 5
0.50
.Ë
Ø
¡-
o
0.45
.l
o
o
o
o
0.40
0.35
0 .3 0
0 .2 5
1949 1992 2001 2002 2003 2004 2005 2006
Population
FIcUR¡ 4. Allelic Richnessand GeneDiversity statisticsfor the eight ColumbiaBasin
populationsdescribedin the text and listed in Table 2. Thesegraphsareintendedto show two
points: (1) the declinein geneticdiversity of pure ColumbiaBasinrabbits;and (2) the dramatic
increasein geneticdiversity when intercross,or mixed animalsareincludedin the population.
SeeTable2.
24