Monitoring of effective population size in a hunted population of - - PowerPoint PPT Presentation

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Monitoring of effective population size in a hunted population of - - PowerPoint PPT Presentation

Oct 23, 2022 202 likes •464 views

23rd International Conference on Bear Research and Management, Thessalonki, Greece, 2014 Monitoring of effective population size in a hunted population of brown bears (Ursus arctos) shows effects of different management approaches in neighboring

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Monitoring of effective population size in a hunted population

  • f brown bears (Ursus arctos) shows effects of

different management approaches in neighboring countries

Tomaž Skrbinšek, Maja Jelenčič, Klemen Jerina, Djuro Huber*, Slaven Reljić*, Peter Trontelj Biotechnical Faculty, University of Ljubljana, Slovenia **Veterinary Faculty, University of Zagreb, Croatia

23rd International Conference on Bear Research and Management, Thessalonki, Greece, 2014 LIFE DINALP BEAR LIFE13 NAT/SI/000550

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Possibly one of the most important parameters for evolutionary and conservation biology.

Effective population size (Ne)

Index describing the rate of random genetic change - direct indicator of both evolu

  • lutionary

ry pot

  • ten

enti tial and sen ensit itivit ity to gen enetic stoc

  • chasticit

ity. Directly effects the via viabili lity of

  • f a

a pop

  • pulation.
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Population stratification -> Ne

  • Unequal reproductive success
  • Age structure (generation overlap)
  • Unequal sex ratio
  • Spatial structure
  • Age of first reproduction
  • ….

Effect of unequal sex ratio on Ne

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Discontinuous habitat – population break? Study area

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Monitoring Effective Population Size

Bears have diffe ifferent prote tection st statu

  • tus. All are hunte

ted.

NW Dinaric Mts.

Croatia ia: Protected, culled. ~ 1000 bears. Big (trophy) males killed. Slo lovenia: Protected, cull to regulate population size. ~500 bears. Young animals killed. Bos

  • snia

ia: Game species. Poor data. ~ 550 bears(?)

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Skrbinšek et al. (2012) „Mon

  • nitoring

g the he eff effec ective e po popu pulation siz size e of

  • f a

a bro brown n bea bear (Ursu sus arc arctos) ) po popu pulation n us using ing ne new sin singl gle-sa sample ap appro proache hes“.Molecular Ecology 21:862-875

Ne of Dinaric bears estimated ~ 183-350 (276) (SLO samples)

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Ne Ne^1 Ne Ne^2

Panmixia –> Ne^1 = Ne^2!

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Slo+Hr Slo

Adding Croatia in the mix

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Slo+ Hr Slo

As time moves on…

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1414 individuals, age determined 20 microsatellites. Linkage-Disequilibrium (LD LDNe) estimates. Yearly samples= bears age e 0 – 8 8 yea ears (~GI) alive in ea each ch yea ear from 2001 – 2012.

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Linkage-Disequilibrium (LDN LDNe) estimates. Ne* - index of effective pop. size Each sample = bears ag age 0 0 – 8 8 year ears (~generation interval) alive in a si single year ear.

*low sample size

Ne* ~ harmonic mean

  • f Ne* in T to T - 8yrs.
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Steady growth at the population level, stabilizing after 2007. Estimates w/ Croatian samples similar to estimates w/ all samples. Slower growth (and lower estimates) detected using

  • nly Slovenian samples, decine after 2008.

Why the difference?

*low sample size

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?? - approximate Detected bear mortality 2008 2009

Time lag + smoothing Ne* ~ harmonic mean

  • f Ne* in T to T - 8yrs.

Effective Pop. Size (Index)

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?? - approximate Effective Pop. Size (Index) Detected bear mortality

Time lag + smoothing Ne* ~ harmonic mean

  • f Ne* in T to T - 8yrs.
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Effective Pop. Size (Index) Sex-specific Mortality Slovenia Croatia

Higher mortality of males Skewed sex ratio - Ne

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Effective Pop. Size (Index) Age Structure Culled Bears

Considerably higher age of killed bears in Croatia, mostly males.

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Effective Pop. Size (Index) Age Structure Culled Bears

High hunting of young bears in Slovenia, low recruitment = decrease Ne Includes high hunting of older males in Croatia, high recruitment = increase Ne

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Management – caused drivers of Ne dynamics in NW Dinaric Mts.

Sl Slovenia ia: mortality young mean age reproductive males recruitment variance in lifetime reprod. success relatedness Ne Ne (de detectable in loc

  • cal es

esti timates) Cr Croa

  • atia (Bos

Bosnia ia?): mortality adult males mean age reproductive males recruitment variance in lifetime reprod. success relatedness Ne Ne

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Effective Pop. Size (Index) Age structure of Mortality Slovenia vs. Croatia Brown bear mortality

Growing population… Different management – different outcomes!

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So… which bears should we shoot?

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Pro:

  • Remove „troublemakers“
  • Preserve „reproductive core“

Con Con:

  • Decreasing Ne
  • Low value of bears for hunters

Pro:

  • Increasing Ne
  • Better hunter acceptance
  • Removal of scarry old bears –

less conflict bears?? Con Con:

  • Infanticide!
  • Removal of the least

conflict animals (?)

  • Evolution?!

Shooting young bears Shooting old bears

VS

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Systematic monitoring of effective population size?

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The research was funded by the

En Environmental Agency of

  • f the Republic of
  • f Sl

Slovenia, Min inis istry ry of

  • f En

Environment of

  • f the Republi

lic of

  • f Cr

Croa

  • atia,

FP7 FP7 pr project „Hunting for

  • r Sus

Sustainabilit ity“ and the project Li Life Din DinAlpBe Bear.

We would like to thank Slo lovenia Forest t Ser ervice for continous help and support.

Photo: Miha Krofel