Validation of adipose lipid content as a body condition index for polar bears

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1 Vlidtion of dipose lipid ontent s ody ondition index for polr ers Meliss A. MKinney 1,2, Todd Atwood 3, Rune Dietz 4, Christin Sonne 4, Sr J. Iverson 1 & Elizeth Peok 3 1 Deprtment of Biology, Dlhousie University, Hlifx, Nov Soti B3H 4R2, Cnd 2 Gret Lkes Institute for Environmentl Reserh, University of Windsor, Windsor, Ontrio N9B 3P4, Cnd 3 US Geologil Survey, Alsk Siene Center, Anhorge, Alsk Deprtment of Biologil Sienes, Arti Reserh Centre, Arhus University, Roskilde, DK-, Denmrk Keywords Adipose tissue, iologil vlidtion, ondition index, mrine mmml, monitoring, qulity ontrol. Correspondene Meliss A. MKinney, Gret Lkes Institute for Environmentl Reserh, University of Windsor, 1 Sunset Ave., Windsor, ON N9B 3P4, Cnd. Tel: x4919; Fx: ; E-mil: melissmkinney@gmil.om Funding Informtion This work is prt of the US Geologil Survey s (USGS) Chnging Arti Eosystem Inititive, with dditionl funding from the Wildlife Progrm of the USGS Eosystem Mission Are, the USGS Climte nd Lnd Use Chnge Mission Are, nd the Bureu of Oen Energy Mngement. Reeived: July 13; Revised: Otoer 13; Aepted: 4 Novemer 13 Eology nd Evolution 14; 4(4): Astrt Body ondition is key inditor of individul nd popultion helth. Yet, there is little onsensus s to the most pproprite ondition index (CI), nd most of the urrently used CIs hve not een thoroughly vlidted nd re logistilly hllenging. Adipose smples from lrge dtsets of pture iopsied, remote iopsied, nd hrvested polr ers were used to vlidte dipose lipid ontent s CI vi tests of ury, preision, sensitivity, iopsy depth, nd storge onditions nd omprisons to estlished CIs, to mesures of helth nd to demogrphi nd eologil prmeters. The lipid ontent nlyses of even very smll iopsy smples were highly urte nd preise, ut results were influened y tissue depth t whih the smple ws tken. Lipid ontent of pture iopsies nd smples from hrvested dult femles ws orrelted with estlished CIs nd/or onformed to expeted iologil vrition nd eologil hnges. However, lipid ontent of remote iopsies ws lower thn pture iopsies nd hrvested smples, possily due to lipid loss during drt retrievl. Lipid ontent CI is iologilly relevnt, reltively inexpensive nd rpidly ssessed CI nd n e determined routinely for individuls nd popultions in order to infer lrge-sle sptil nd long-term temporl trends. As it is possile to ollet smples during routine hrvesting or remotely using iopsy drts, monitoring nd ssessment of ody ondition n e omplished without pture nd hndling proedures or noninvsively, whih re methods tht re preferred y lol ommunities. However, further work is needed to pply the method to remote iopsies. doi: 1.12/ee3.956 Introdution Body ondition is n importnt inditor of individul nd popultion fitness, reprodutive suess, nd overll helth (Atkinson nd Rmsy 1995; Roins et l. 12). It is mesure of individul energy reserves, often expressed s perent ody ft (Cttet et l. 2; Stevenson nd Woods 6). Vrious nonlethl ody ondition indies (CIs) hve een used in wildlife reserh, sed on morphometri, iohemil, nd physiologil prmeters. However, little onsensus exists s to the most pproprite CI (Peig nd Green 1). Indeed, mny CIs hve not een thoroughly tested for ury, preision, sensitivity, iologil signifine, or the rnge of irumstnes under whih they my e vlid (Cook et l. 1). In lrge mmmls, ody ondition hs minly een reported using morphometri-sed CIs inluding ody mss, length, skull size, girth, nd omined mesures inluding ody mss index (BMI), ody ondition index (BCI), nd storge energy (Cttet et l. 2; Stevenson nd Woods 6; Molnr et l. 9). Sujetive ftness indies (FI) from physil nd/or visul exmintion hve lso een used (Stirling et l. 1989). Some of these CIs 516 ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd. This is n open ess rtile under the terms of the Cretive Commons Attriution Liense, whih permits use, distriution, nd reprodution in ny medium, provided the originl work is properly ited.

2 M. A. MKinney et l. Adipose Lipid Content s Body Condition Index indite iologil signifine, supported y orreltive ssoitions with mesures of overll helth, suh s litter mss (Rode et l. 1). Diret ody omposition estimtes from isotope dilution or ioeletril impedne nlysis (BIA) hve lso een vlidted ginst totl ody ft nd mesures of iologil signifine in vrious speies (Frley nd Roins 1994; Jos et l. 12; Roins et l. 12). However, some of these CIs exhiit high vriility nd/or sujetivity, preventing ojetive ssessment of preise lrge-sle sptil or long-term temporl trends in ody ondition of free-rnging wildlife. Although mny nlyses (e.g., tooth-sed ging; Clvert nd Rmsy 1998) still require niml hndling, more suitle CI would e minimlly or noninvsive (e.g., remote iopsy drting during geneti smpling for mrk-repture popultion estimtes) or from regulrly hrvested popultions (e.g., susistene hunting), ompre fvorly with other CIs, show iologil signifine, nd e reltively inexpensive nd simple so tht it ould e determined routinely from suffiient numers of individuls nd popultions to infer trends. An idel pproh would e n in vitro iohemil metri tht ould e mesured on tissues lredy eing olleted y wildlife iologists or during regulr hrvesting, inluding hir, skin, dipose nd/or lood. Speifilly, dipose lipid ontent hs een proposed sed on studies linking it with totl ftness in severl mmmlin speies (e.g., Shier nd Shemmel 1975; Bek et l. 1993; Gomez- Cmpos et l. 11) nd preliminry studies in polr ers Ursus mritimus (Thiemnn et l. 6; Stirling et l. 8). These studies hve demonstrted lipid ontent vrition with FI nd, s expeted, with seson. Lipid ontent nlysis is inexpensive, preise, nd strightforwrd nd thus pplile on rod sle. However, roustness of the lortory method nd vlidtion of lipid ontent reltive to multiple epted CIs nd other inditors of helth hve not een fully evluted. Polr ers from the Southern Beufort Se (SB) nd elsewhere hve exhiited ody ondition delines ssoited with rpid limte wrming, deresing se ie hitts, nd redued ess to their min prey, sels (Stirling et l. 1999; Ord et l. 6; Rode et l. 1, 12). These ondition hnges preeded hnges in supopultion helth, inluding redued litter mss, litter size, survivl, nd overll supopultion size (Deroher nd Stirling 1994, 1996; Stirling et l. 1999; Regehr et l. 7; Rode et l. 1). Extensive dtsets from wellstudied supopultions re useful to lirte potentil helth indies for use in other supopultions with poor reserh ess (Vongrven et l. 12). Here, we exmine sustntive SB polr er dipose pture iopsy rhive, for whih detiled iologil nd pture informtion hs een reorded, inluding estlished CIs nd helth prmeters. This dtset provides n opportunity to thoroughly evlute dipose lipid ontent s CI. In response to some ommunity, mngement, nd sientist onerns (with regrd to, e.g., pture, hndling, ollring, hemil immoiliztion,), noninvsive smpling methods hve een proposed (Peok et l. 11; Vongrven et l. 12) nd developed for polr ers nd other wildlife (e.g., Fedign 1; Herremn nd Peok 13; Pgno et l. 14). Here, we lso test the ppliility of lipid ontent to reently olleted SB polr er remote iopsies for whih no estlished CIs esides FI ould e otined. Applition of the lipid ontent CI to remotely tken iopsies would minimize smpling invsiveness, inrese smple sizes nd potentilly inrese the geogrphi sope of smpling in more remote res with poor reserh ess. More generlly, vlidted lipid ontent CI ould e used to expnd lrge-sle (irumpolr) nd long-term (retrospetive) ssessment pilities. Development of lirted index of polr er helth sed on rpid nd relile ssessment method will help stisfy the need for inresed monitoring (Vongrven et l. 12) due to rpidly hnging ie onditions for polr ers (Overlnd nd Wng 13), nd would e pplile to other wildlife, whih store lipid in suutneous dipose/luer depots suh s mrine mmmls. Here, we ssess the vlidity of dipose lipid ontent s quntittive CI, uilding on previous preliminry work (Thiemnn et l. 6; Stirling et l. 8). We fous on remote iopsy, pture iopsy, nd hrvest smples to ssess the lipid ontent CI in terms of ury, preision, sensitivity, influene of iopsy depth, nd storge ondition, nd ompre lipid ontent to estlished CIs nd demogrphi nd eologil prmeters. Mterils nd Methods Smple olletion We olleted suutneous dipose tissue smples with 6 mm iopsy punh from the rump region of 55 nesthetized polr ers ptured etween W on the se ie off of northern Alsk (i.e., the southern Beufort Se) etween We smpled ers in the spring (n = 474) from Mrh to mid-my. In 8 1, we smpled dditionl SB ers in the lte summer erly fll (herein referred to s fll ) (n = 76) from August to Otoer. We reorded position (lt/long) of pture, sex, girth, totl length, FI, mss, BMI, BIA (resistne, ohms), skull width nd length, numer nd ge lss of ompnying us, u sex, weight, skull width nd/or length (Rode et l. 1). We determined ges for first-time ptured ers y ounting the growth lyer groups in ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd. 517

3 Adipose Lipid Content s Body Condition Index M. A. MKinney et l. the ementum of vestigil premolr tooth (Clvert nd Rmsy 1998) nd lssified ers y ge/sex lss: usof-the-yer (C), yerlings (C1), 2-yer-old dependent us (C2), sudult (independent 2-, 3- nd 4-yer-old) femles nd mles (SF, SM) nd dult (5-yer nd older) femles nd mles (AF, AM) (Stirling et l. 1975). We otined dipose iopsies from 96 SB ers smpled y remote iopsy drt in fll 11 (n = 45) nd spring (n = 24) nd fll 12 (n = 27) (Pgno et l. 14). As these ers were not trnquilized nd hndled, we only reorded position, sex, numer, nd ge lss of ompnying us, estimted ge lss nd remotely sertined FI. In fll 11 nd spring 12, we olleted smples from vrious ody regions, ut lrgely ner the shoulder re. To otin iopsies more omprle to those from ptured ers, fll 12 drting trgeted the rump region. For long-term storge, we kept ll SB iopsies frozen ( 8 C). We sent skin nd hir, removed prior to lipid nlysis, to Wildlife Genetis Interntionl In. (Nelson, BC, Cnd) to genetilly identify ll ptured nd remotely drted ers (Pgno et l. 14). We used dditionl dipose smples quired for other projets from polr ers hrvested in the Bffin By (BB) nd Est Greenlnd (EG) supopultions in the lortory vlidtion portion of this study. For these hrvested tissues, whih were stored t C, we susmpled from the innermost tissue setion for lipid nlysis. Adipose lipid ontent nlysis We extrted lipid from iopsies nd hrvest smples nd reported it s the rtio of extrted lipid reltive to initil wet weight of dipose tissue, in perentge. Briefly, iopsies were mesured y ruler to the nerest millimeter, trnsferred into tred glss vils, nd weighed to the nerest lg (Mettler-Toledo XP26 mirolne with ergo lip dptor; Columus, OH, USA). Chloroform ws dded ontining.1% utylted hydroxytoluene (BHT) s n ntioxidnt. Smples were flushed with nitrogen, pped, nd stored t C until lipid extrtion. Lipid ws extrted s desried previously (Budge et l. 6) with modifitions. Smples were quntittively trnsferred to glss tue, spiked with 5--holestne s internl stndrd (1 ll of mg/ml), nd homogenized y Teflon pestle tthed to n eletri stirrer. Lipids were extrted twie using 8:4:3 hloroform/methnol/wter ontining BHT, t volume/weight rtio of :1 solvent/smple. Isolted lipids were ompletely evported of solvent, then weighed y mirolne. Extrted ftty ids (FAs) were derivtized to FA methyl esters (FAMEs) nd nlyzed y gs hromtogrphy with flme ioniztion detetion (GC-FID) to quntify internl stndrd reoveries. Lortory method vlidtion We investigted ury nd preision using the Ntionl Institute of Stndrds nd Tehnology (NIST) stndrd referene mteril SRM 1945 (whle luer homogente) for whih onsensus vlue of perent lipid ( totl extrtle orgnis ) from interlortory omprison exerises hs een pulished (Kuklik et l. 1). A ~.5 g susmple of SRM 1945 (similr to pture nd remote iopsy weights of ~.1.3 g) ws nlyzed with eh smple th or 64 times in totl. We tested lipid reoveries for individul smples using the internl stndrd. We exmined the influene of iopsy depth y nlyzing equl length inner (ner musle) nd outer (ner skin) setions of suset (n = 21) of the spring 1 pture iopsies, s oth pture nd remote iopsies were generlly not tken t full depth. With lrger dipose smple from hrvested BB polr er nd with SRM1945, we exmined the sensitivity of the extrtion to smple size, tht is, whether the smll sizes of the pture nd remote iopsies were suffiient for grvimetri lipid nlysis. We mesured lipid ontent from EG dtset nd 4 11 SB pture iopsy dtset. As we only reently (11 12) nlyzed oth dtsets, internnul vrition in lipid ontent my suggest hnges in CI over time or potentil impts of long-term storge on lipid ontent. For exmple, storge effets n only result in lower lipid ontent in older smples nd not the reverse pttern. However, CI effets n led to vrition in either diretion. Thus, if we identify lower lipid ontent in the newer smples, the min driver must e CI hnges. If we identify higher lipid ontent in newer smples or no temporl trend in either diretion, then storge nd/or CI effets ould e ourring. Clultion of estlished CIs nd reltionships to dipose lipid ontent We lulted BMI (ody mss (kg)/(length (m)) 2 ), BCI (stndrd residuls from regression of ody mss (kg) on length (m), rnging from 3. to +3.), nd storge energy (x 1 (ody mss (kg)) x 2 (length (m)) 3, where the oeffiients x 1 nd x 2 re sex/ge lss-speifi) from pulished methods (Cttet et l. 2; Stevenson nd Woods 6; Molnr et l. 9). Some negtive storge energy vlues tht ourred, likely euse the oeffiients were generted for different polr er supopultion (i.e., Western Hudson By; WH) (Molnr et l. 9), were disrded. Although FI vlues (from 1 to 5, where 1 is lenest nd 5 most oese) were sometimes reported s hlf-integers (i.e. 1.5, 2.5, 3.5, 4.5), we down-ssigned these vlues to whole integers (1, 2, 3, 4, respetively) for 518 ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd.

4 M. A. MKinney et l. Adipose Lipid Content s Body Condition Index onsisteny with previous studies (Stirling et l. 8). We lso inluded skull width s CI sine skulls my hve vrile ft lyer refleting ody ondition, nd s previous studies showed skull width delines over time (Rode et l. 1, 12). We performed nonprmetri tests for lipid ontent nd other CIs, sine mesures frequently did not meet the ssumption of homogeneity of vrines even fter dt trnsformtion. We tested inner nd outer susetions for differenes y Wiloxon mthed pirs test. We tested smple size nd storge time (olletion yer) influenes on lipid ontent using Spermn s orreltion nlysis. We onsidered the potentilly onfounding vriles of sex/ge lss. First, we tested lipid ontent for sex/ge lss differenes, then grouped ordingly, nd ompred CIs. We ompred FI to other CIs using Kruskl Wllis ANOVA nd post-ho Mnn Whitney U-tests. We ompred ll other CIs using Spermn s orreltion nlysis. We used simple liner regression with AFs nd SFs to determine whether BIA (resistne) ws orrelted with trnsformed lipid ontent nd onduted n nillry nlysis using Kruskl Wllis ANOVA to determine whether gut fill (i.e., full, prtil, empty) from reent mels inflted BIA vlues (Hilderrnd et l. ). We nlyzed gut fill using smples from 12, the only yer with gut fill dt. We reported ll dt s men SE. Eologil ptterns in reltion to lipid ontent We ssessed whether lipid ontent vried with iologil nd eologil prmeters, inluding sex/ge lss, reprodutive sttus, seson, nd yer (Thiemnn et l. 6; Stirling et l. 8). We tested sex/ge lss nd sesonl differenes using Kruskl Wllis ANOVA nd post-ho Mnn Whitney U-tests. We lso ssessed more fine-sle sesonl vrition y exmining men lipid ontent vrition with ordinl dte of smpling. We exmined temporl trends for SB nd EG using orreltion nlysis, nd for SB, we ssessed internnul lipid ontent vrition etween 4 11 using Kruskl Wllis ANOVA nd Mnn Whitney U-tests. We used generlized liner models to investigte the reltionship etween lipid ontent nd se ie vilility for SB AMs nd AFs. We used two mesures of se ie vilility: durtion of the summer melt seson (Melt) for the entire SB nd the finer-sle mesure of ie-free dys (IFD) over the ontinentl shelf (Appendix S1). We lso inluded yer, ge (Age), ordinl dte (Odte) of smpling, nd numer of dependent us (Cu; for AFs) s ontinuous ovrites to ontrol for other vriles tht my influene polr er ody ondition (e.g., Rode et l. 12). We developed iologilly plusile ndidte models nd used Akike s Informtion Criterion for smll smple sizes (AIC ) to determine top models for eh sex lss (Appendix S1). We did not inlude yer nd ie vilility metris in the sme model euse they my reflet different temporl sles (Rode et l. 12). Results Lipid ontent of pture iopsies Adipose lipid ontent of the 4 11 SB pture iopsies verged % (Tle 1) nd differed mong ge/sex lsses (v 2 6 ¼ 75:3, P <.1). AMs hd the lowest lipid ontent ( %, P <.1). AFs hd lower lipid ontent ( %) thn Cs nd SFs (P.3), nd lipid ontent did not signifintly differ mong Cs, C1s, C2s, SFs, nd SMs ( %). Therefore, lipid ontent results re susequently reported seprtely for AFs, AMs, nd immture ers (omprising Cs, C1s, C2s, SFs, nd SMs). Lipid ontent of remote iopsies Lipid ontent of the SB remote iopsies verged.9 1.3% (Tle 1) nd did not signifintly differ mong AMs, AFs, nd immture (sudults only s us were not smpled) ers (P =.26). Sine lipid ontent ws lower for remote versus pture iopsies, nd vried with iopsy depth (see Vlidtion of the lortory method), we heked whether iopsy lengths differed etween the two iopsy types. Cpture nd remote iopsies were not signifintly different in length (2.3.1 m nd m, respetively; P =.7). Fll 12 remote iopsy olletions trgeted the rump region nd verged higher length of m, ut still hd lower lipid ontent ( %) thn pture iopsies. Vlidtion of the lortory method The lipid extrtion method ws determined to hve high ury nd preision, with little sensitivity to smple size (Appendix S1, Figure S1). Cpture iopsies were higher in lipid ontent for inner versus outer dipose tissue (z = 4., P <.1; Figure S2). Men SB dipose lipid ontent exhiited no signifint trend from 4 11 (P >.26) for ll ge/sex lsses, ut did differ mong yers (v 2 > 14.1, P.5; Fig. 1). For hrvested AF EG ers, lipid ontent signifintly inresed from (r 2 =.22, P =.5; Fig. 1). The pttern ws similr ut not signifint for AMs ( ) nd immture ( ) EG ers (P.9). ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd. 519

5 Adipose Lipid Content s Body Condition Index M. A. MKinney et l. Tle 1. Adipose lipid ontent SE of pture nd remote iopsies from polr ers from the Southern Beufort (SB) Se supopultion smpled from Adipose lipid ontent (%) All ers Adult femles Adult mles Immture ers Cpture iopsies All yers (4 11) (n = 55) (n = 199) (n = 197) (n = 154) All yers- spring (4 11) (n = 474) (n = 161) (n = 191) (n = 122) All yers- fll (8 1) (n = 76) (n = 38) (n = 6) (n = 32) 4-spring spring spring spring spring spring spring spring fll fll fll Remote iopsies All yers (11 12) (n = 96) (n = 45) (n = 37) (n = 14) All yers-spring (12) (n = 24) (n = 11) (n = 9) (n = 4) All yers-fll (11 12) (n = 72) (n = 34) (n = 28) (n = 1) 11-fll fll Different letters denote signifint differenes in lipid ontent mong ge/sex lsses. Comprison with other metris For AF, AM, nd immture ers, pture iopsy lipid ontent differed y FI sores (v 2 2 7:4, P.2; Fig. 2). Signifintly higher lipid ontent ws found in AFs ssigned to FI 4 ( %) versus 3 ( %), nd FI 3 versus 2 ( %; P <.3). Lipid ontent did not differ for AMs ssigned to FI 4 versus 3 ( % nd %, respetively), ut ws higher for FI 3 thn FI 2 ( %; P =.7). Similrly, lipid ontent did not differ for immture ers of FI 4 versus 3 ( % nd %, respetively), ut ws higher for FI 3 thn FI 2 ( %; P =.1). Although smple sizes were too smll to sttistilly ompre polr ers ssigned to FI 1 or 5 (n 2), the pttern ws onsistent, tht is, lower lipid ontent with lower FI sores. Differenes in estlished CIs ross FI sores were lso signifint for AFs, AMs, nd immture polr ers (v 2 2 3:9, P.5; Fig. 2), exept for skull width in immture ers. Like lipid ontent, BMI, BCI, storge energy, nd skull width were higher in AFs ssigned to FI 4 versus 3, nd ll ut skull width were higher in AFs ssigned to FI 3 versus 2 (P <.1). Agin, lthough smple sizes were too low to sttistilly ompre AFs ssigned to FI 5, these ers were higher in BMI, BCI, nd storge energy (ut not skull width) thn FI 4 ers. No BMI, BCI, or storge energy dt were ville for AFs ssigned to FI 1. Skull width ws not higher in AFs ssigned to FI 2 versus 1. Similr to lipid ontent, the estlished CIs were higher in AMs, nd in immture ers exept for skull width, ssigned to FI of 3 versus 2 (P.5). For AMs only, these CIs were lso signifintly higher for FIs of 4 versus 3 (P <.1). Adipose lipid ontent of AFs ws signifint preditor of BMI (Spermn r 2 =.21, P <.1), BCI (r 2 =.22, P <.1) nd storge energy (r 2 =.13, P <.1), ut not skull width (Fig. 3). In immture ers, it ws lso signifint preditor of BMI (r 2 =.13, P <.1), BCI (r 2 =., P <.1) nd storge energy (r 2 =.11, P =.1), ut not skull width. However, in AMs, lipid ontent ws not signifintly orrelted with BMI, BCI, storge energy or skull width (P.7). Men BIA vlues for AFs nd SFs were not predited y lipid ontent (r 2 =.1, P =.67), nd the extent of gut fill did not signifintly inflte BIA vlues (v 2 2 5:4, P =.7). The BMI, BCI, nd storge energy indies were signifintly nd strongly orrelted with one nother for AFs (r 2.95, P <.1) nd AMs (r 2.9, P <.1). Storge energy nd BMI were strongly orrelted (r 2 =.9, P <.1) in immture ers; however, the reltionship ws not s strong for storge energy nd BCI 5 ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd.

6 M. A. MKinney et l. Adipose Lipid Content s Body Condition Index Lipid ontent (%) Lipid ontent (%) Lipid ontent (%) SB dult femles SB dult mles d d d d SB immture ers EG dult femles EG dult mles EG immture ers Lipid ontent (%) Body mss index (kg/m 2 ) Body ondition index Storge energy (MJ) 1 3 Skull width (m) Adult femles Adult mles Ftness index Immture ers Figure 2. Adipose lipid ontent, ody mss index, ody ondition index, storge energy, nd skull width (SE) y ftness index for polr ers from the Southern Beufort Se supopultion smpled during pture in Signifint differenes indited y different letters. Missing dt points or those without letters were not sttistilly ompred due to 2 smples for eh sex/ge lss. Yer Yer Figure 1. Adipose lipid ontent (SE) of dult femle, dult mle nd immture polr ers smpled in the Southern Beufort Se (SB; 4 11) nd Est Greenlnd (EG; ) supopultions. Different letters indite signifint differenes in SB lipid ontent. Trendlines indite signifint liner trends. (r 2 =.38, P <.1) nd for BCI nd BMI (r 2 =.38, P <.1). Skull width ws signifintly, ut not strongly orrelted with BMI, BCI, nd storge energy for AFs (r 2.4, P <.4) nd AMs (r 2., P <.1). Skull width ws signifintly orrelted with BMI nd storge energy (r 2., P <.1), ut not BCI, in immture ers. For remote iopsies, lipid ontent omprisons were ssessed with remotely sored FI. However, due to limited smple sizes, only polr ers of FI 3 nd 4 ould e ompred nd only for AFs nd AMs. Lipid ontent ws not signifintly different in AFs of FI 4 ( %) versus 3 ( %; P =.97), nor in AMs with FI 4 ( %) versus 3 ( %; P =.11). ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd. 521

7 Adipose Lipid Content s Body Condition Index M. A. MKinney et l. BMI (kg/m 2 ) BCI Storge energy (MJ) 1 3 Storge energy Storge energy Skull width (m) BCI (MJ) 1 3 (MJ) 1 3 Skull width (m) Skull width (m) Skull width (m) Adult femles Adult mles Immture ers Lipid ontent (%) BMI (kg/m 2 ) BCI Storge energy (MJ) 1 3 Figure 3. Reltionships etween dipose lipid ontent, ody mss index (BMI), ody ondition index (BCI), storge energy, nd skull width for polr ers from the Southern Beufort Se supopultion smpled in Trendlines denote signifint regression lines. Eologil nd demogrphi ptterns Although there ws pttern of deresing lipid ontent in the fll from solitry AFs to AFs with us to AMs, there were no sttistilly signifint differenes (P =.51; Fig. 4). However, the sensitivity of the dtset to detet differenes in lipid ontent in the fll my hve een low s result of low fll smples sizes reltive to spring olletions (Tle 1). In the spring, lipid ontent ws higher in immture ers thn in AMs nd AFs (P =.8) nd in solitry AFs thn in AMs (P =.2). Fll versus spring lipid ontent ws signifintly higher for solitry AFs (16% higher), AFs with us (13%) nd immture ers (1%; P <.1). When exmined y pture dte, lipid ontent ppered to deline from Mrh to My (~55 35%), inrese in My (to >6%), nd deline slightly from Septemer to Novemer (Fig. 5). As previously desried, dipose lipid ontent of AF, AM, nd immture SB polr ers exhiited no time trends from 4 11, wheres for AF EG polr ers, lipid ontent inresed from No time trends were found for skull width of SB AFs nd AMs etween 4 11 (P >.1). However, skull width delined y. m yr 1 in immture ers. For SB dults, spring lipid ontent ws inversely orrelted with durtion of the redued se ie extent period Lipid ontent (%) * Adult femlesolitry 1* Adult femlewith us 1 Adult mle Fll Spring 1* Immture ers Figure 4. Adipose lipid ontent (SE) y ge/sex lss of polr ers from the Southern Beufort Se supopultion ptured from 4 to 11. Different numers indite signifint differenes in fll lipid ontent mong demogrphi groups, different letters indite signifint differenes in spring lipid ontent mong groups, nd sterisks indite higher lipid ontent in fll thn spring ers within group. 522 ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd.

8 M. A. MKinney et l. Adipose Lipid Content s Body Condition Index Lipid ontent (%) 8 6 during the previous open-wter seson (summer/fll). Melt ws the primry driver of lipid ontent differenes over time for AFs: five models were inluded in the top model set (Tle 2), eh retining Melt s vrile with normlized Akike weight of.31. For AMs, four models omprised the top model set (Tle 2); IFD nd Odte were retined in ll four models with normlized Akike weights of.34 nd.32, respetively. Melt ws retined in two of the top models for AMs. Smll smple sizes for immture ers preluded similr nlysis. Disussion Mr Apr My Jun We onlude tht dipose lipid ontent is potentilly effetive iohemil-sed CI for polr ers. When Jul Aug Cpture dte Figure 5. Adipose lipid ontent (SE) y pture dte for polr ers from the Southern Beufort Se supopultion smpled from 4 to 11. Tle 2. Top models (Akike s Informtion Criterion vlues [AIC ], Akike weights [w i ], nd P-vlues) of vrition in lipid ontent for dult polr ers in the southern Beufort Se supopultion, 4 11, where melt is durtion of summer melt seson, IFD is ie-free dys, ge is er ge, Odte is ordinl smpling dte, nd u is numer of dependent us. Sep Ot Model DAIC w i (model) P (model) Adult femles Melt Melt, IFD Odte, Melt Melt, Cu Age, Melt Adult mles IFD, Melt, Odte..29 <.1 Odte, IFD.69. <.1 Age, Odte, IFD Age, Odte, Melt, IFD oupled with demogrphi nd eologil dt, lipid ontent my hold promise for effiiently ssessing nd monitoring ondition of AF polr ers in rpidly hnging Arti. Monitoring the ondition of AFs is ritil s it is pregnnt nd ltting AFs nd their us tht re of gretest onern with respet to limte hnge impts (Roins et l. 12). Moreover, euse remotely olleted smples n e otined using iopsy drts (Pgno et l. 14), ody ondition ssessments n e omplished reltively noninvsively, whih my e preferentil in more remote res nd for other onerns (Peok et l. 11; Vongrven et l. 12). Though our findings re enourging, we hve lso identified limittions of the lipid ontent CI tht wrrnt further reserh. The lipid ontent CI for pture iopsies is supported y signifint reltionships to estlished CIs. Lipid ontent of AFs vried ross FI sores, s did estlished CIs exept for skull width. Lipid ontent of AFs ws lso orrelted with the pulished CIs, exept skull width, lthough not s strongly s these CIs were orrelted with one nother. BMI, BCI, nd storge energy, however, re lulted from one or more of the sme vriles (ody mss nd/or length). Thus, it is not surprising tht they showed stronger orreltions with eh other thn with lipid ontent. BIA vlues otined from SB ers in 12 were not preditive of lipid ontent. BIA resistne mesures re used s inditors of totl ody wter (TBW) ontent, whih often vries inversely with totl ft (TF) ontent (Gles et l. 1994). However, our finding of no orreltion should e interpreted utiously s (i) the smple size ws smll, (ii) the reltionship etween TBW nd TF n vry interspeifilly (e.g., Reilly nd Fedk 199), nd (iii) BIA hs yet to e lirted in the field for use with polr ers. Lipid ontent differenes with FI sores were not s strong for AMs nd immture ers; however, for immture ers, this ws lso the se for ll mesured CIs. Additionlly, the estlished CIs were not strongly or not signifintly orrelted with one nother for immture ers. These findings my e relted to differentil use of ft s stored energy depot etween ge/ sex lsses. Speifilly, AFs tend to lose/gin more ody mss s ft during fsting/hyperphgi thn other lsses; previous work demonstrted tht fsting AFs lost 43% ody mss, of whih 93% ws ody ft (Atkinson nd Rmsy 1995). In ontrst, fsting dult nd juvenile mles lost 19% ody mss, of whih only 5% ws ody ft (Atkinson et l. 1996). Thus, lipid ontent my e more suitle CI for AFs thn for AMs nd immture ers. If dipose lipid ontent is refletive of ody ondition, it should lso exhiit ertin iologil nd eologil differenes. One predition, onfirmed previously in WH polr ers, is tht AFs hve higher fll lipid ontent thn ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd. 523

9 Adipose Lipid Content s Body Condition Index M. A. MKinney et l. AMs due to the timing nd higher reprodutive osts for AFs (Thiemnn et l. 6). Here, we found similr lthough not signifint pttern, likely due to low fll smple sizes. Another predition ws tht AF lipid ontent is lower in spring thn fll due to reprodutive fsting. This ws onfirmed previously in WH ers (Thiemnn et l. 6) nd now lso in SB ers. Similrly, we found the gretest deline in lipid from fll to spring for solitry, presumly pregnnt, fll AFs (~16%) ompred to AFs with us, AMs, nd immture ers (1 15%), whih is onsistent with different fsting lengths mong these groups (Stirling et l. 1999). Lipid ontent of SB pture iopsies tended to e lower thn reported previously for SB nd WH polr er pture iopsies (Thiemnn et l. 6). The previous study used full-depth pture iopsies (down to the musle), wheres the urrent study did not. Both studies found higher lipid ontent in inner versus outer iopsy setions. Thus, the exlusion of smll portion of inner tissue my hve slightly ised our lipid ontent to e lower. Our results my lso e relted to longer-term storge, nd potentilly greter desition. However, lipid ontent differenes etween studies re more likely due to different smpling dtes. Previous SB olletions were from erly April erly My, wheres our dt spnned erly Mrh erly My. We hve shown tht the lipid ontent delines drmtilly (~%) from erly Mrh to My nd then susequently rises gin. Thus, smll vrition in smpling dtes my hve lrge impts on lipid ontent. Lipid ontent of SB remote iopsies ws lower thn for pture iopsies, possily euse lipid ontent vried with remote drt type nd ody position where the drt struk (Pgno et l. 14). Lower lipid ontent in these potentilly more superfiilly smpled remote iopsies my lso e due to not smpling muh of the inner lyer of the dipose. Adipose loser to the skin my hve more onnetive tissue resulting in lower lipid ontent (Ylitlo et l. 1). However, this is not likely good explntion for our findings s remote nd pture iopsy lengths were similr. Killer whle Orinus or nd elug whle Delphinpterus leus smples otined from neropsy (lrge full-depth tissue smple) showed higher lipid ontent versus those otined from iopsy drts of the sme individuls t similr depths nd ody positions (Krhn et l. 4). The uthors onluded tht lower iopsy drt redings were from lipid seeping from the luer during drt removl. Here, s the drts fell into the wter or onto lnd, some lipid my hve lso een wshed wy, or the smple my hve olleted smll peles/dirt, resulting in low-ised lipid redings. We ttempted to remove the peles/dirt in the l, ut this my not hve een suffiient. Beuse of lower lipid ontent redings, remote iopsy results nnot diretly e ompred to those from pture iopsies or hrvested smples. The remote iopsy method requires refinement efore it my e informtive in determining lipid ontent. This onlusion is supported y the ft tht remote iopsy lipid redings did not signifintly vry with FI sores. Nonetheless, remotely ssigned FIs my not e s roust s FIs otined from hndled ers. Both the lk of time trends in SB polr er lipid ontent from 4 11 nd inresing trends in AF EG lipid ontent from ould e due to some omintion of hnges in CI nd/or effets of storge ondition. Controlled studies re-nlyzing the sme smples fter different storge times re required to fully understnd the potentil influene of storge time. However, the omposition of ftty ids (FAs), the min lipid omponents in polr er dipose nd mrine mmml luer tissues, were reported to e stle in sel luer re-smpled fter up to 6 yers t 25 C (Lind et l. 12), supporting the stility of lipid omponents in dipose tissues. In greement, sujetive oxidtion lss did not explin signifint mount of the vrition in ftty id ptterns in the EG dtset (MKinney et l. 13) Thus, it is unlikely tht the lk of SB trends (storge for up to 8 yers t 8 C) nd the inresing trend in EG femles (storge for C for up to 27 yers) were driven y sustntil onfounding effets of longterm storge. We therefore suggest tht it is more likely tht the trends reflet true hnges in CI. Our results suggest tht oth pture iopsies nd hrvest smples n e used for studies using lipid ontent s CI, whih rodens the utility of hrvest smples olleted in remote supopultions with poor/expensive reserh ess. Hrvest smples n lso onstitute vlule long-term rhives provided storge ondition impts hve een fully ruled out, nd therefore my e useful in monitoring CI hnges over time. Chnges in ody ondition of polr ers, nd ultimtely reprodutive suess nd overll survivl, re eing driven y redued ess to, or undne of, food resoures (Rode et l. 12). High Arti Greenlnd nd Cndin Arhipelgo polr er hitts re predited to temporrily improve s multiyer ie-overed res, with lower primry prodution, re repled y nnul ie (Stirling nd Deroher 1993); onomitntly, hnge in ie hitt my lter the prey se. Inresing lipid ontent in AF EG polr ers etween 1984 nd 1 supports this hypothesis, lthough the influene of storge ondition must still e fully evluted. We reently demonstrted tht EG diets shifted over this period from predomintely Arti sels (ringed sels Pus hispid) to su-arti sels (hooded sels Cystophor ristt nd hrp sels Pgophilus groenlndius) (MKinney et l. 13), supporting link etween inresing ody ondi- 524 ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd.

10 M. A. MKinney et l. Adipose Lipid Content s Body Condition Index tion nd dditionl food resoure vilility. Similrly, Dvis Strit polr ers hve shown higher survivl rtes nd supopultion size due to n inresing undne of hrp sels (Peok et l. 13), lthough this region t the southern end of the speies rnge hs historilly een hrterized y only nnul ie. Delines in SB ody size, u reruitment, nd u, nd AF survivl hve ourred onomitnt with se ie delines in the region from (Regehr et l. 1; Rode et l. 1). Vrition in summer/ fll se ie vilility, here, ws linked to internnul (4 11) vrition in SB polr er lipid ontent. The lk of temporl deline in SB polr er lipid ontent my e due to vrine osuring the trend within this short time series, or to hnging reltionship etween se ie nd ody ondition. Similrly, we found no deline in skull width, exept for in immture ers, unlike previous delines reported for immture nd AF SB ers from 1982 to 6 (Rode et l. 1). We re urrently investigting the reltionship of ody ondition (lipid ontent) to diet (ftty id profiles), hitt use (stellite trking dt) nd ontinued hnges in limte nd se ie onditions in the SB supopultion. Reommendtions To enle ross-popultion nd temporl omprisons, reserhers should ensure onsisteny in iopsy olletions to redue lipid ontent vrition, inluding onsidertions suh s nlyzing ft iopsy smples mesured to stndrd length from the skin t, smpling fully perpendiulr to the ody surfe, nd onsistent nnul olletion dtes. Controlled studies on tissue portions from the sme individul re neessry to ompletely rule out n influene of storge onditions (time, temperture, ontiner type). Regrding FI, virtully no ers were ssigned vlues of 1 or 5, potentilly limiting the ility to eluidte ptterns from this index. Reserhers nd hunters who use the 5-point FI sle should void using noninteger vlues (e.g., 1.5) nd insted use ll points, if possile. Over the lst dede, the view of dipose tissue hs hnged drmtilly from n inert energy reservoir to eing reognized s n endorine orgn tht produes numerous proteins (dipokines) with rod iologil tivities. Severl ftors hve now een disovered, prtiulrly leptin, whih is relted to ody ft mss s well s other ftors (Hiss et l. 1998; Spdy et l. 9). We therefore reommend tht the lipid ontent CI ould e exmined for reltionships to suh iomrkers. Aknowledgments This work is prt of the US Geologil Survey s Chnging Arti Eosystem Inititive, with funding from the Wildlife Progrm of the USGS Eosystem Mission Are. Additionl support ws provided y the USGS Climte nd Lnd Use Chnge Mission Are nd the Bureu of Oen Energy Mngement. We thnk USGS stff (Kryn Rode, George Durner, Anthony Pgno, Kristin Sim, Chd Jy, Jeff Bromghin, Kren Okley) for field logistis, smple olletion, input into study design, nd interprettion of results. We thnk Mizuho Nm, Lurie Strr (Dlhousie University) for ssistne with lipid ontent nlyses nd Ree Pugh nd John Kuklik (NIST) for providing the SRM. For EG smpling, we thnk hunters, J. Brønlund nd M. Kierkegrd, nd S. Joensen nd L. Bruun, for ssistne with EG polr er ging. Funding for EG work me from the Greenlnd Institute of Nturl Resoures (Nuuk), Age V. Jensen s Foundtion, DANCEA (Dnish Coopertion for Environment in the Arti) progrmme inluding the CORE progrmme nd IPY progrmme Ber- Helth, lso supported y KVUG (The Commission for Sientifi Reserh in Greenlnd) nd The Prine Alert II Foundtion. The Nturl Sienes nd Engineering Reserh Counil (NSERC) of Cnd provided dditionl postdotorl funding (M. MKinney) nd lortory support from Disovery Grnt (S. Iverson). S. Stpleton provided helpful omments on n erlier version of the mnusript. Any use of trde nmes is for desriptive purposes only nd does not reflet endorsement y the U.S. government. Dt Aessiility The lipid ontent dt is rhived with the Polr Dt Ctlogue ( Conflit of Interests None delred. Referenes Atkinson, S. N. nd M. A. Rmsy The effets of prolonged fsting of the ody omposition nd reprodutive suess of femle polr ers (Ursus Mritimus). Funt. Eol. 9: Atkinson, S. N., R. A. Nelson, nd M. A. Rmsy Chnges in ody omposition of fsting polr ers (Ursus mritimus): the effet of reltive ftness on protein onservtion. Physiol. Zool. 69: Bek, G. G., T. G. Smith, nd M. O. Hmmill Evlution of ody ondition in the Northwest Atlnti hrp sel (Pho groenlndi). Cn. J. Fish. Aqut. Si. 5: Budge, S. M., S. J. Iverson, nd H. N. Koopmn. 6. Studying trophi eology in mrine eosystems using ftty ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd. 525

11 Adipose Lipid Content s Body Condition Index M. A. MKinney et l. ids: primer on nlysis nd interprettion. Mr. Mmm. Si. 22: Clvert, W. nd M. A. Rmsy Evlution of ge determintion of polr ers y ounts of ementum growth lyer groups. Ursus 1: Cttet, M. R. L., N. A. Culkett, M. E. Ord, nd G. B. Stenhouse. 2. A ody ondition index for ursids. Cn. J. Zool. 8: Cook, R. C., J. G. Cook, D. L. Murry, P. Zger, B. K. Johnson, nd M. W. Grtson. 1. Nutritionl ondition models for elk: Whih re the most sensitive, urte, nd preise? J. Wildl. Mnge. 65: Deroher, A. E. nd I. Stirling Age-speifi reprodutive performne of femle polr ers (Ursus mritimus). J. Zool. Lond. 234: Deroher, A. E. nd I. Stirling Aspets of survivl in juvenile polr ers. Cn. J. Zool. 74: Frley, S. D. nd C. T. Roins Development of two methods to estimte ody omposition of ers. Cn. J. Zool. 72: Fedign, L. M. 1. Ethil issues fed y field primtologists: Asking the relevnt questions. Am. J. Primtol. 72: Gles, R., D. Renouf, nd E. Noseworthy Body omposition of hrp sels. Cn. J. Zool. 72: Gomez-Cmpos, E., A. Borrell, nd A. Aguilr. 11. Assessment of nutritionl ondition indies ross reprodutive sttes in the striped dolphin (Stenell oeruleol). J. Exp. Mr. Biol. Eol. 5: Herremn, J.K. nd E. Peok. 13. Polr er use of persistent food susidy: insights from non-invsive geneti smpling in Alsk. Ursus 24: Hilderrnd, G. V., C. C. Shwrtz, C. T. Roins, nd T. A. Hnley.. Effet of hierntion nd reprodutive sttus on ody mss nd ondition of ostl rown ers. J. Wildl. Mnge. 64: Hiss, R., E. Hohtol, T. Tuoml-Srmki, T. Line, nd H. Kllio Sesonl hnges in ftty ids nd leptin ontents in the plsm of the Europen rown er (Ursus rtos rtos). Ann. Zool. Fenn. 35: Jos, S. R., K. Elliott, M. F. Guigueno, A. J. Gston, P. Redmn, J. R. Spekmn, et l. 12. Determining seird ody ondition using nonlethl mesures. Physiol. Biohem. Zool. 85: Krhn, M. M., D. P. Hermn, G. M. Ylitlo, C. A. Slon, D. G. Burrows, R. C. Hos, et l. 4. Strtifition of lipids, ftty ids nd orgnohlorine ontminnts in luer of white whles nd killer whles. J. Ceten Res. Mng. 6: Kuklik, J. R., M. M. Shntz, R. S. Pugh, B. J. Porter, D. L. Poster, P. R. Beker, et l. 1. Mrine mmml luer referene nd ontrol mterils for use in the determintion of hlogented orgni ompounds nd ftty ids. Anl. Bionl. Chem. 397: Lind, Y., B. M. B klin, K. Lundstr om, S. M. Budge, M. Wlton, nd O. Krlsson. 12. Stility of ftty id omposition in sel luer during long-term storge. Mr. Eol. Prog. Ser. 461: MKinney, M. A., S. J. Iverson, A. T. Fisk, C. Sonne, F. F. Riget, R. J. Lether, et l. 13. Glol hnge effets on the long-term feeding eology nd ontminnt exposures of Est Greenlnd polr ers. Glo. Chnge Biol. 19: Molnr, P. K., T. Klnjsek, A. E. Deroher, M. E. Ord, nd M. A. Lewis. 9. A ody omposition model to estimte mmmlin energy stores nd metoli rtes from ody mss nd ody length, with pplition to polr ers. J. Exp. Biol. 212: Ord, M. E., M. R. L. Cttet, T. Moody, L. R. Wlton, D. Potter, J. Inglis, et l. 6 Temporl trends in the ody ondition of southern Hudson By polr ers. 1-8, Ontrio Ministry of Nturl Resoures. Applied Reserh nd Development Brnh. Ontrio Ministry of Nturl Resoures Projet Report. (GENERIC) Overlnd, J. E. nd M. Wng. 13. When will the summer Arti e nerly se ie free? Geophys. Res. Lett. : Pgno, A. M., E. Peok, nd M. A. MKinney. 14. Remote iopsy drting nd mrking of polr ers. Mr. Mmm. Si. : Peok, E., A. E. Deroher, G. W. Thiemnn, nd I. Stirling. 11. Conservtion nd mngement of Cnd s polr ers (Ursus mritimus) in hnging Arti. Cn. J. Zool. 89: Peok, E., M. K. Tylor, J. Lke, nd I. Stirling. 13. Popultion eology of polr ers in Dvis Strit, Cnd nd Greenlnd. J. Wildl. Mnge. 77: Peig, J. nd A. J. Green. 1. The prdigm of ody ondition: ritil repprisl of urrent methods sed on mss nd length. Funt. Eol. 24: Regehr, E. V., N. J. Lunn, S. C. Amstrup, nd I. Stirling. 7. Effets of erlier se ie rekup on survivl nd popultion size of polr ers in western Hudson By. J. Wildl. Mnge. 71: Regehr, E. V., C. M. Hunter, H. Cswell, S. C. Amstrup, nd I. Stirling. 1. Survivl nd reeding of polr ers in the southern Beufort Se in reltion to se ie. J. Anim. Eol. 79: Reilly, J. J. nd M. A. Fedk Mesurement of the ody omposition of living gry sels y hydrogen isotope dilution. J. Appl. Physiol. 69: Roins, C. T., M. Ben Dvid, J. K. Fortin, nd O. L. Nelson. 12. Mternl ondition determines irth dte nd growth of neworn er us. J. Mmml. 93: Roins, C. T., C. Lopez-Alfro, K. D. Rode, O. Toien, nd O. L. Nelson. 12. Hierntion nd sesonl fsting in ers: the energeti osts nd onsequenes for polr ers. J. Mmml. 93: ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd.

12 M. A. MKinney et l. Adipose Lipid Content s Body Condition Index Rode, K. D., S. C. Amstrup, nd E. V. Regehr. 1. Redued ody size nd u reruitment in polr ers ssoited with se ie deline. Eol. Appl. : Rode, K. D., E. Peok, M. Tylor, I. Stirling, E. W. Born, K. L. Lidre, et l. 12. A tle of two polr er popultions: ie hitt, hrvest, nd ody ondition. Popul. Eol. 54:3 18. Shier, P. D. nd R. Shemmel Effets of diet, ge, strin nd ntomil site on ft depot triglyeride nd ftty id ontent in rts. Pro. So. Exp. Biol. Med. 149: Spdy, T. J., H. J. Hrlow, G. Butterstein, nd B. Durrnt. 9. Leptin s surrogte inditor of ody ft in the Amerin lk er. Ursus :1 1. Stevenson, R. D. nd W. A. Woods. 6. Condition indies for onservtion: new uses for evolving tools. Integr. Comp. Biol. 46: Stirling, I. nd A. E. Deroher Possile impts of limti wrming on polr ers. Arti 46: Stirling, I., D. Andrishek, P. Ltour, nd W. Clvert Distriution nd undne of polr ers in the estern Beufort Se. 59 pp., Cn. Dept. Environ. Beufort Se Proj., Beufort Se Teh. Rep. 2. (GENERIC). Stirling, I., C. Spener, nd D. Andrishek Immoiliztion of polr ers (Ursus mritimus) with telzol in the Cndin Arti. J. Wildl. Dis. 25: Stirling, I., N. J. Lunn, nd J. Iozz Long-term trends in the popultion eology of polr ers in western Hudson By in reltion to limte hnge. Arti 52: Stirling, I., G. W. Thiemnn, nd E. Rihrdson. 8. Quntittive support for sujetive ftness index for immoilized polr ers. J. Wildl. Mnge. 72: Thiemnn, G. W., S. J. Iverson, nd I. Stirling. 6. Sesonl, sexul nd ntomil vriility in the dipose tissue of polr ers (Ursus mritimus). J. Zool. 269: Vongrven, D., J. Ars, S. Amstrup, S. N. Atkinson, S. Belikov, E. W. Born, et l. 12. A irumpolr monitoring frmework for polr ers. Ursus 23:1 66. Ylitlo, G. M., C. O. Mtkin, J. Buzitis, M. M. Krhn, L. L. Jones, T. K. Rowles, et l. 1. Influene of life-history prmeters on orgnohlorine onentrtions in free-rnging killer whles (Orinus or) from Prine Willim Sound, AK. Si. Totl Environ. 281: Supporting Informtion Additionl Supporting Informtion my e found in the online version of this rtile: Appendix S1. Supplementry methods, results, nd disussion, Figures S1 nd S2 Figure S1. Lipid ontent extrted from polr er dipose (top pnel) nd Ntionl Institute of Stndrds nd Tehnology stndrd referene mteril (SRM) 1945 (pilot whle luer homogente) (ottom pnel) y initil smple mss. Figure S2. Adipose lipid ontent (SE) extrted from equl length inner (ner musle) nd outer (ner skin) dipose susetions of pture iopsies from polr ers from the Southern Beufort (SB) Se supopultion from spring 1. Signifint differenes in lipid ontent re indited y different letters. ª 14 The Authors. Eology nd Evolution pulished y John Wiley & Sons Ltd. 527