Cultural transmission of tool use in bottlenose dolphins by pptfiles

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									Cultural transmission of tool
use in bottlenose dolphins
Krutzen et al.




                                    Anthony Jensen
                                       Joseph Byers
                                Katherine Mahoney
Culture in the animal world

   •Source of ongoing debate
   •Consensus towards continuity
   •A behavioral trait is considered to vary culturally if
      •Acquired through social learning
      •Transmitted within/between generations
Culture in the animal world

   •Evidence for the existence of culture
      •Primate communities
          •Chimpanzees, orangutans
          •Geographic variation associated with
          behavioral variation (tool use, foraging…)
          •Evidence for observational learning
Sponging Behavior in the Bottlenose Dolphin
Sponging Behavior in the Bottlenose Dolphin

  •Longitudinal study since 1984
     •Shark Bay, Western Australia
  •Numerous and diverse foraging tactics within pop.
  •Sponging – single instance of tool use
     •Female-biased behavior
     •15 of 141 known mothers (1 male!)
     •7+ offspring (early development – time w/ mom)
  •Learned behavior?
Sponging Behavior in the Bottlenose Dolphin

  •Learned behavior?
  •Difficulties in studying transmission of behavior
     •Approach  Dismiss alternative explanations
        •Eocological?
           •Spongers & nonspongers forage together
         •Genetic?
             •Evidence for genetic transimission (ncc)
     •If not  matrilineal social transmission likely
Sponging Behavior in the Bottlenose Dolphin

  •Random mating in Shark Bay
  •Coancestry coefficient of non-inbred individuals of
  same matriline approaches ZERO rapidly
  •If the haplotypes derived from ancient coancestry,
  relatedness of spongers should NOT be above average
  •If RECENT coancestry  HIGH relatedness
         •Genetically inherited?
                OR
         •Culturally transmitted between relatives?
            Materials & Methods

•Behavioral Observations (1988-2002)
   •9,029 boat surveys
   •14,447 independent sightings
   •Identified spongers/non-spongers
•Genetic Data from 185 dolphins
   •13 adult spongers
•Statistical Analyses
   •Dolphins from sponger area and close neighbors
           Materials & Methods

•Exclusion of genetic explanations?
   •Several possible modes of genetic inheritance
   •Tested against data on family level, pop. Level
   •Examine possibility of assortative (nonrandom)
   mating as explanation


   •If data does not support modes 
                             Cultural Transmission!?...
                    Results

•Haplotype: set of closely linked genetic markers present
on one chromosome which tend to be inherited together,
it is half the genotype.

•Significant association between haplotype and sponging
                     Results

•8 different haplotypes in Shark Bay, 6 of which occur in
the study area
                     Results

•Significant non-random association between haplotype
and sponging
•Indicates sponging is mainly passed on within a single
matriline
                    Results

•10 different modes of genetic inheritance
                    Results
•10 different modes of genetic inheritance
                     Results

•Between 2001-2004 45 of the 65 adult males who
overlapped with the sponging area consorted with 11 of
the 12 female sponge carriers
•At least 88.2% of offspring sired by non-sponge carrying
males
•No observed heterozygote deficit among all 13
spongers
                     Discussion
• Study qualifies as material culture in marine mammal
  species

• Reasons: (1) not genetically passed
           (2) not assortative mating pass



• Comes to the conclusion that it is culturally transmitted
                    Not Genetic

• Tool use is highly unlikely to be a direct behavior of a
  single locus of inheritance.
• Not even multi loci inheritance.

• Note: 10 different modes of genetic inheritance
  mentioned earlier (Table 3)
                  Assortative Mating
• Extremely unlikely! Why?
• (1) Adult males almost never sponge
• (2) Sponging females have been shown to conceive from
  nonsponging males
• (3) Data show that almost all offspring of spongers are
  sired by nonsponging males
• (4) They did not observe the predicted heterozygosity
  deficit in the sample(13).

•   *Note: small sample size of 13 is not statistically powerful but offers support
    against assortative mating.
      Why Cultural Transmission?
•   Bottlenose dolphins have shown to have high
•    cognitive skills
•   imitation skills
•   vocal learning.

• Most importantly: Dolphins are highly capable of Social
  Learning in the wild and captivity

• It is most likely a very new tool use behavior that is being
  passed down a matrilineal line.
        Strengths vs. Weaknesses
• Strengths
   – High amount of observations over a long period of time
   – Clean genetic analysis
   – Good rejection of Assortative Mating Theory
   – A relatively new behavior that poses future research

    • Weaknesses
      - small concentrated sample
      - If it is culturally transmitted why do males rarely exhibit this
         behavior?
      - Possible combo of genes & culture

								
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