Evaluation of Culling Intensity and Criteria for Antler Traits in White -Tailed Deer
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Evaluation of Culling Intensity and Criteria for Antler Traits in White -Tailed Deer

Masahiro . (. Masa) Ohnishi. Ph.D. Student. Caesar Kleberg Wildlife Research Institute. Texas A&M University – Kingsville. Committee Members. Randy DeYoung. Charles DeYoung. David Hewitt. Strickland Bronson.

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Evaluation of Culling Intensity and Criteria for Antler Traits in White -Tailed Deer




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Presentation on theme: "Evaluation of Culling Intensity and Criteria for Antler Traits in White -Tailed Deer"— Presentation transcript:

Slide1

Evaluation of Culling Intensity and Criteria for Antler Traits in White -Tailed DeerMasahiro (Masa) Ohnishi Ph.D. StudentCaesar Kleberg Wildlife Research InstituteTexas A&M University – KingsvilleCommittee MembersRandy DeYoungCharles DeYoungDavid HewittStrickland BronsonSteven LukefahrDonnie Draeger

Slide2

Which buck is a better sire for antler development?GBC 159 = “Keep”GBC 123 = “Cull”6 years old

Slide3

Harvest is Artificial Selection

Harvesting ungulates is widely common Harvest is a form of artificial selection

Slide4

Improving Antler Traits Through SelectionDirectional Selection

Ideally, average breeding values and antler size increase over time

Slide5

Undesirable Effects of HarvestHigh Grading = Harvesting the best quality of animalsPotential for “negative” effects of trophy hunting

Slide6

How much variation in antler size due to genetics?■ Heritability (genetics)■ Permanent Environment■ Year of Growth

??%

??%

??%

Difficulty in determining how genes and environment affect antler size in wild populations

Slide7

Objectives: Comanche Culling StudyOverall goal: Is it possible to improve population antler traits through culling in wild deer? 1: Do offspring “resemble” their father?2: How “intense” was the culling?3: How long before “response” is apparent?

Slide8

Methods: Study AreaComanche Ranch, Maverick County, TXTexas-Tamaulipan Thornscrub Ecoregion 120,000 ac High fences at each treatment

Slide9

Moderate Culling Treatment18,000 acCulling: only ages 3.5+

Moderate

Age

Antler

Points

B&C

score

1.5

Not culled

2.5

Not culled

3.5 - 4.5

<

9

5.5

<

145

Slide10

Intensive Culling Treatment3,500 acCulling: All age classes

Intensive

Moderate

Age

Antler

Points

B&C

Score

Antler

Points

B&C

Score

1.5

<

6

Not culled

2.5

<

8

Not culled

3.5 - 4.5

<

9 pts

5.5

<

145 B&C

Slide11

Control Area: No Culling5,000 ac

Slide12

Data Collection: Falls of 2006 – 2016 MARK & helicopter survey Helicopter net-gun method before the rut Tissue biopsy for DNAAge and antler size (Gross Boone & Crockett)Sacrificed bucks that did not meet culling criteriaPit-tag if bucks were releasedStopped culling after 2012 capture

Slide13

Resemblance: Heritability and Breeding ValuesDo offspring resemble sire? If yes, then the antler trait is heritableHeritability = how phenotypes are determined by genes transmitted from parents Sire’s Breeding Value = The average antler size of offspringLargeAntlers!!

SireOffspring

??

??

Average

Antler Size

=

?

Slide14

Resemblance: Heritability and Breeding ValuesCervus 3.0Distribution of mating success Pedigree informationMTDFREMLHeritabilities antler points & GBCSire’s breeding values

3 age classes (1.5, 2.5, 3.5+)

??%

??%

??%

Slide15

Resemblance: Multi-State (Category) Analysis

Yearlings

Categorized “

Keep

bucks

2.5 years old

Categorized “

Cull

bucks

“Keep

again

Keep

Cull

“Cull”

again

*Young deer were released at moderate

and control treatments

Next Year

Slide16

Culling Intensity: Selection Differential (S)

Total Population MeanCulling Criteria

Selected Bucks Mean

S

S = Selected Bucks Mean – Total Population Mean

Antler Size

Frequency

Slide17

Response: Generation TimeGeneration Time = Average years between consecutive generations2006 2010 2014 2018 2022

Sire

Offspring

Grandson

Great-

grandson

?

a

verage

years

Slide18

Response to Selection (R) R = Predicted gain of antler size per generation “Breeder’s equation”:R = h² * SModified for selection on 1 sex:R = ½ (h² * S)Selection differential (S)Heritability of antler traits (h²)

Slide19

Results: Data Collection (2006-2016)Captured 5,447 bucks (including recaptures) Individuals: 2,937 Recaptured: 2,510 Culled: 1,333 (7 years)Total offspring assigned to sire(s): 1,718

Slide20

Resemblance: Heritabilities of Antler PointsYearlings2.5 years old

3.5+ years old■

Heritability (h²)

Unknown effects (e²)

Permanent environmental effects (p²)

h² (SD) = 0.17 (0.14)

* Not Significant

e² (SD) = 0.83 (0.14)

* Significant

h² (SD) = 0.15 (0.15)

* Not Significant

e² (SD) = 0.85 (0.15)

* Significant

h² (SD) = 0.25 (0.09)

* Significant

e² (SD) = 0.50 (0.02)

* Significant

p² (SD) = 0.25 (0.09)

* Significant

Slide21

Resemblance: Heritabilities of GBC Yearlings2.5 years old3.5+ years old

Heritability (h²)

Unknown

effects (

e²)

Permanent environmental effects (p²)

h² (SD) = 0.30 (0.28)

* Not Significant

e² (SD) = 0.70 (0.28)

* Significant

h² (SD) = 0.27 (0.14)

* Not Significant

e² (SD) = 0.73 (0.14)

* Significant

h² (SD) = 0.45 (0.09)

* Significant

e² (SD) = 0.13 (0.09)

* Significant

p² (SD)

=

0.45 (0.02)

*

Significant

Slide22

Resemblance: Multi-State Analysis “Cull” to “Keep”Categorized “Keep

”Bucks Categorized “Cull”Bucks

48%

36%

26%

18%

12%

8%

5%

3%

Keep

Keep

Keep

Keep

Keep

Keep

Keep

Slide23

Resemblance: Multi-State Analysis “Keep” to “Cull”

Cull

Cull

Cull

Cull

Cull

Cull

Cull

C

ategorized

“Keep”

Bucks

C

ategorized “

Cull

Bucks

32%

32%

33%

32%

31%

31%

30%

30%

Slide24

Genetic (Breeding Values) Improvements??Average breeding values and antler size increase over time

Slide25

Resemblance: Breeding Values: ModerateY = - 0.0031x + 0.0285R² = 0.214(+/- 1 SE)

Slide26

Resemblance: Breeding Values: Intensive

Mean Breeding Value

Y= 0.032x – 0.023

R² = 0.0272

(+/- 1 SE)

Slide27

Resemblance: Breeding Values: Control

Slide28

Culling Intensity: ModerateYearCulling Intensity: CONSISTENT!!

Slide29

Culling Intensity: Intensive Year

Slide30

Culling Intensity: Who is sire??Adult Bucks SiredMost Offspring!!!

Slide31

Culling Intensity: Average Male Offspring per Sire■ Moderate■ Intensive■ ControlMean (SD) = 1.1 (0.07)Mean (SD) = 1.3 (0.24)Mean (SD) = 0.9 (0.09)

Not Significantly Change!!

Slide32

Culling Intensity: Selection Differential “Antler Points”

Yearling = 3 Antler Points

2.5

= 1 AP

3.5+

=

2

AP

Antler Points

Frequency

AVERAGE 1 2 3

Culling Criteria is EFFECTIVE for Yearling!

Slide33

Culling Intensity: Selection Differential “GBC”

Yearling

= 18 GBC

3.5+

= 33 GBC

Gross Boone & Crockett

Frequency

Population Mean 10 20 30

2.5

= 11 GBC

Culling Criteria is EFFECTIVE for Adult Bucks!

Slide34

Response: Generation Time

 

 

 

 

2006

2010

2015

Mod Ctrl

Int

Average years between consecutive generations

Offspring

Grandson

Great-grandson

Great-great-grandson

SLOWER!!

Slide35

Predicted Response to Selection (gain per generation) Antler Points GBC Yearling

2.53.5++0.26+0.10+0.23+2.64+1.42+7.46

Sire

Offspring

Grandson

R =

½ (h²

*

S)

Slide36

Objective 1: Do sons resemble their father?Heritability of yearling antler points was ONLY 17%*Maternal, environmental, and other factors contributed 83% Breeding values did not change across years48% of yearlings: “Cull”

 “Keep”30% of all age classes: “Keep”  “Cull”

48%

36%

26%

18%

12%

8%

5%

3%

Keep

Keep

Keep

Keep

Keep

Keep

Keep

Slide37

Objective 2: How intense was the culling?Selection differential large for young, mature bucksIntense enough to:

Mature bucks sired most offspring Reduced competitors for mating

No change:

Proportion of bucks culled in each

treatment

Harvesting young deer was not sustainable

Slide38

Objective 3: How long before the response is apparent?Long generation time (7 to 9 yrs) Young bucks did not breed

Young bucks culled (Intensive TRT)Heritability was low* for young buck traits

Environment overwhelmed genetic potential

Predicted response was low:

<

0.5 antler point/generation (yearlings)

 

 

 

 

2006

2010

2015

+0.26 AP

Predicted Response to Selection

Slide39

ConclusionsMost intensive manipulative study of culling ever done More intense than recreational harvest! Juvenile antler traits not a good indicator of genetic potentialEnvironment affected young deer antler growth (phenotype vs. genotype)Intensive culling of young males (S) not based on genetic potentialSuccessful males sired <2 male offspring per year

Generation time became slower by removing young males

Slide40

ConclusionsCulling criteria was based on antler size but NOT breeding valuesThus, no sign of the GENETIC RESPONSE to culling in this studyCulling is Designed to GENETICALLY change antler size…BUT

Mean Breeding Value

Intensive

Slide41

AcknowledgementsMajor funding by: Comanche RanchAdditional funding by:Caesar Kleberg Wildlife Research InstituteTexas Parks and Wildlife DepartmentAdditional thanks to:Houston Safari

ClubMr. Kenneth LeonardMr. Bill Rauch and Mr. Ronnie HowardMr. Rene Barrientos Caesar Kleberg FoundationAll graduate studentsFamily and friends

Slide42

Which buck is a better sire?Importance of breeding values…GBC 159 = “Keep”GBC 123 = “Cull”

Lowest 10% of breeding valuesHighestbreeding values