Use of handheld X-ray fluorescence as a non-invasive method to distinguish between Asian and African elephant tusks
Identifieur interne : 000079 ( Pmc/Curation ); précédent : 000078; suivant : 000080Use of handheld X-ray fluorescence as a non-invasive method to distinguish between Asian and African elephant tusks
Auteurs : Kittisak Buddhachat [Thaïlande] ; Chatchote Thitaram [Thaïlande] ; Janine L. Brown [États-Unis] ; Sarisa Klinhom [Thaïlande] ; Pakkanut Bansiddhi [Thaïlande] ; Kitichaya Penchart [Thaïlande] ; Kanita Ouitavon [Thaïlande] ; Khanittha Sriaksorn [Thaïlande] ; Chalermpol Pa-In [Thaïlande] ; Budsabong Kanchanasaka [Thaïlande] ; Chaleamchat Somgird [Thaïlande] ; Korakot Nganvongpanit [Thaïlande]Source :
- Scientific Reports [ 2045-2322 ] ; 2016.
Abstract
We describe the use of handheld X-ray fluorescence, for elephant tusk species identification. Asian (n = 72) and African (n = 85) elephant tusks were scanned and we utilized the species differences in elemental composition to develop a functional model differentiating between species with high precision. Spatially, the majority of measured elements (n = 26) exhibited a homogeneous distribution in cross-section, but a more heterologous pattern in the longitudinal direction. Twenty-one of twenty four elements differed between Asian and African samples. Data were subjected to hierarchical cluster analysis followed by a stepwise discriminant analysis, which identified elements for the functional equation. The best equation consisted of ratios of Si, S, Cl, Ti, Mn, Ag, Sb and W, with Zr as the denominator. Next, Bayesian binary regression model analysis was conducted to predict the probability that a tusk would be of African origin. A cut-off value was established to improve discrimination. This Bayesian hybrid classification model was then validated by scanning an additional 30 Asian and 41 African tusks, which showed high accuracy (94%) and precision (95%) rates. We conclude that handheld XRF is an accurate, non-invasive method to discriminate origin of elephant tusks provides rapid results applicable to use in the field.
Url:
DOI: 10.1038/srep24845
PubMed: 27097717
PubMed Central: 4838944
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<author><name sortKey="Sriaksorn, Khanittha" sort="Sriaksorn, Khanittha" uniqKey="Sriaksorn K" first="Khanittha" last="Sriaksorn">Khanittha Sriaksorn</name>
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, Chiang Mai 50100,<country>Thailand</country>
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<front><div type="abstract" xml:lang="en"><p>We describe the use of handheld X-ray fluorescence, for elephant tusk species identification. Asian (n = 72) and African (n = 85) elephant tusks were scanned and we utilized the species differences in elemental composition to develop a functional model differentiating between species with high precision. Spatially, the majority of measured elements (n = 26) exhibited a homogeneous distribution in cross-section, but a more heterologous pattern in the longitudinal direction. Twenty-one of twenty four elements differed between Asian and African samples. Data were subjected to hierarchical cluster analysis followed by a stepwise discriminant analysis, which identified elements for the functional equation. The best equation consisted of ratios of Si, S, Cl, Ti, Mn, Ag, Sb and W, with Zr as the denominator. Next, Bayesian binary regression model analysis was conducted to predict the probability that a tusk would be of African origin. A cut-off value was established to improve discrimination. This Bayesian hybrid classification model was then validated by scanning an additional 30 Asian and 41 African tusks, which showed high accuracy (94%) and precision (95%) rates. We conclude that handheld XRF is an accurate, non-invasive method to discriminate origin of elephant tusks provides rapid results applicable to use in the field.</p>
</div>
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<pmc article-type="research-article"><pmc-dir>properties open_access</pmc-dir>
<front><journal-meta><journal-id journal-id-type="nlm-ta">Sci Rep</journal-id>
<journal-id journal-id-type="iso-abbrev">Sci Rep</journal-id>
<journal-title-group><journal-title>Scientific Reports</journal-title>
</journal-title-group>
<issn pub-type="epub">2045-2322</issn>
<publisher><publisher-name>Nature Publishing Group</publisher-name>
</publisher>
</journal-meta>
<article-meta><article-id pub-id-type="pmid">27097717</article-id>
<article-id pub-id-type="pmc">4838944</article-id>
<article-id pub-id-type="pii">srep24845</article-id>
<article-id pub-id-type="doi">10.1038/srep24845</article-id>
<article-categories><subj-group subj-group-type="heading"><subject>Article</subject>
</subj-group>
</article-categories>
<title-group><article-title>Use of handheld X-ray fluorescence as a non-invasive method to distinguish between Asian and African elephant tusks</article-title>
</title-group>
<contrib-group><contrib contrib-type="author"><name><surname>Buddhachat</surname>
<given-names>Kittisak</given-names>
</name>
<xref ref-type="aff" rid="a1">1</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Thitaram</surname>
<given-names>Chatchote</given-names>
</name>
<xref ref-type="aff" rid="a2">2</xref>
<xref ref-type="aff" rid="a3">3</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Brown</surname>
<given-names>Janine L.</given-names>
</name>
<xref ref-type="aff" rid="a4">4</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Klinhom</surname>
<given-names>Sarisa</given-names>
</name>
<xref ref-type="aff" rid="a2">2</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Bansiddhi</surname>
<given-names>Pakkanut</given-names>
</name>
<xref ref-type="aff" rid="a2">2</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Penchart</surname>
<given-names>Kitichaya</given-names>
</name>
<xref ref-type="aff" rid="a5">5</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Ouitavon</surname>
<given-names>Kanita</given-names>
</name>
<xref ref-type="aff" rid="a5">5</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Sriaksorn</surname>
<given-names>Khanittha</given-names>
</name>
<xref ref-type="aff" rid="a5">5</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Pa-in</surname>
<given-names>Chalermpol</given-names>
</name>
<xref ref-type="aff" rid="a6">6</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Kanchanasaka</surname>
<given-names>Budsabong</given-names>
</name>
<xref ref-type="aff" rid="a6">6</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Somgird</surname>
<given-names>Chaleamchat</given-names>
</name>
<xref ref-type="aff" rid="a2">2</xref>
</contrib>
<contrib contrib-type="author"><name><surname>Nganvongpanit</surname>
<given-names>Korakot</given-names>
</name>
<xref ref-type="corresp" rid="c1">a</xref>
<xref ref-type="aff" rid="a1">1</xref>
<xref ref-type="aff" rid="a2">2</xref>
</contrib>
<aff id="a1"><label>1</label>
<institution>Animal Bone and Joint Research Laboratory, Department of Veterinary Biosciences and Public Health, Faculty of Veterinary Medicine, Chiang Mai University</institution>
, Chiang Mai 50100,<country>Thailand</country>
</aff>
<aff id="a2"><label>2</label>
<institution>Center of Excellence in Elephant Research and Education, Faculty of Veterinary Medicine, Chiang Mai University</institution>
, Chiang Mai 50100,<country>Thailand</country>
</aff>
<aff id="a3"><label>3</label>
<institution>Maesa Elephant camp</institution>
, 119/9, Tapae Road, Muang, Chiang Mai 50100,<country>Thailand</country>
</aff>
<aff id="a4"><label>4</label>
<institution>Smithsonian Conservation Biology Institute, Center for Species Survival</institution>
, 1500 Remount Road, Front Royal, VA 22630,<country>USA</country>
</aff>
<aff id="a5"><label>5</label>
<institution>DNP Wildlife Forensic Science Unit (DNP-WIFOS), Wildlife Research Division, Wildlife Conservation Office, Department of National Parks</institution>
, Wildlife and Plant Conservation. 61 Phaholyothin Rd., Chatuchak Bangkok 10900<country>Thailand</country>
</aff>
<aff id="a6"><label>6</label>
<institution>Wildlife Research Division, Wildlife Conservation Office, Department of National Parks</institution>
, Wildlife and Plant Conservation. 61 Phaholyothin Rd., Chatuchak Bangkok 10900<country>Thailand</country>
</aff>
</contrib-group>
<author-notes><corresp id="c1"><label>a</label>
<email>korakot.n@cmu.ac.th</email>
</corresp>
</author-notes>
<pub-date pub-type="epub"><day>21</day>
<month>04</month>
<year>2016</year>
</pub-date>
<pub-date pub-type="collection"><year>2016</year>
</pub-date>
<volume>6</volume>
<elocation-id>24845</elocation-id>
<history><date date-type="received"><day>21</day>
<month>10</month>
<year>2015</year>
</date>
<date date-type="accepted"><day>06</day>
<month>04</month>
<year>2016</year>
</date>
</history>
<permissions><copyright-statement>Copyright © 2016, Macmillan Publishers Limited</copyright-statement>
<copyright-year>2016</copyright-year>
<copyright-holder>Macmillan Publishers Limited</copyright-holder>
<license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by/4.0/"><pmc-comment>author-paid</pmc-comment>
<license-p>This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit <ext-link ext-link-type="uri" xlink:href="http://creativecommons.org/licenses/by/4.0/">http://creativecommons.org/licenses/by/4.0/</ext-link>
</license-p>
</license>
</permissions>
<abstract><p>We describe the use of handheld X-ray fluorescence, for elephant tusk species identification. Asian (n = 72) and African (n = 85) elephant tusks were scanned and we utilized the species differences in elemental composition to develop a functional model differentiating between species with high precision. Spatially, the majority of measured elements (n = 26) exhibited a homogeneous distribution in cross-section, but a more heterologous pattern in the longitudinal direction. Twenty-one of twenty four elements differed between Asian and African samples. Data were subjected to hierarchical cluster analysis followed by a stepwise discriminant analysis, which identified elements for the functional equation. The best equation consisted of ratios of Si, S, Cl, Ti, Mn, Ag, Sb and W, with Zr as the denominator. Next, Bayesian binary regression model analysis was conducted to predict the probability that a tusk would be of African origin. A cut-off value was established to improve discrimination. This Bayesian hybrid classification model was then validated by scanning an additional 30 Asian and 41 African tusks, which showed high accuracy (94%) and precision (95%) rates. We conclude that handheld XRF is an accurate, non-invasive method to discriminate origin of elephant tusks provides rapid results applicable to use in the field.</p>
</abstract>
</article-meta>
</front>
<floats-group><fig id="f1"><label>Figure 1</label>
<caption><p>Schematics illustrate longitudinal (<bold>A</bold>
) and transversal (<bold>B</bold>
) XRF scanning sites of the enamel layer on elephant tusks for Asian and African elephants combined. Comparison of elemental levels (ppm) among longitudinal and transversal sites, and coefficients of variation (CV) are shown in (<bold>C</bold>
). Significant <italic>p</italic>
values (<0.05) are highlighted in blue, with concentration differences highlighted by the level of red intensity. (Mg = magnesium, Al = aluminum, Si = silicon, P = phosphorous, S = sulfur, Cl = chlorine, K = potassium, Ca = calcium, Ti = titanium, V = vanadium, Cr = chromium, Mn = manganese, Fe = iron, Co = cobalt, Ni = nickel, Cu = copper, Zn = zinc, As = arsenic, Zr = zirconium, Ag = silver, Cd = cadmium, Sn = tin, Sb = antimony, W = tungsten, Pb = lead, LE = light element).</p>
</caption>
<graphic xlink:href="srep24845-f1"></graphic>
</fig>
<fig id="f2"><label>Figure 2</label>
<caption><p>Differences in elemental composition between genders (Asian only, <bold>A</bold>
), cross-sectional layers (<bold>B</bold>
) and species (<bold>C</bold>
). Coefficients of variation (CV), with darker red boxes indicating higher CVs. Elements in the blue boxes are those used as a denominator in creating the discriminant equation (<bold>D</bold>
). (Mg = magnesium, Al = aluminum, Si = silicon, P = phosphorous, S = sulfur, Cl = chlorine, K = potassium, Ca = calcium, Ti = titanium, V = vanadium, Cr = chromium, Mn = manganese, Fe = iron, Ni = nickel, Cu = copper, Zn = zinc, Zr = zirconium, Ag = silver, Cd = cadmium, Sn = tin, Sb = antimony, W = tungsten, Pb = lead, LE = light element).</p>
</caption>
<graphic xlink:href="srep24845-f2"></graphic>
</fig>
<fig id="f3"><label>Figure 3</label>
<caption><title>Pearson’s correlation coefficients between each element for Asian and African elephant tusks combined, as determined by XRF analysis.</title>
<p>Colored boxes indicate direction and strength of each correlation. (Mg = magnesium, Al = aluminum, Si = silicon, P = phosphorous, S = sulfur, Cl = chlorine, K = potassium, Ca = calcium, Ti = titanium, V = vanadium, Cr = chromium, Mn = manganese, Fe = iron, Co = cobalt, Ni = nickel, Cu = copper, Zn = zinc, Zr = zirconium, Mo = molybdenum, Ag = silver, Cd = cadmium, Sn = tin, Sb = antimony, W = tungsten, Pb = lead).</p>
</caption>
<graphic xlink:href="srep24845-f3"></graphic>
</fig>
<fig id="f4"><label>Figure 4</label>
<caption><title>Hierarchical cluster analysis of individual elemental compositions obtained from XRF scanning of Asian and African tusks.</title>
</caption>
<graphic xlink:href="srep24845-f4"></graphic>
</fig>
<fig id="f5"><label>Figure 5</label>
<caption><title>Effectiveness of the elemental composition data for estimating origin of elephant tusks.</title>
<p>(<bold>A</bold>
) Scatter plot and density of values using discriminant analysis with Zr as the denominator based on scans of 72 Asian and 85 African tusks. (<bold>B</bold>
) Predicting Asian or African tusk origins (Asian = 0, African = 1) as a function of the discriminant values (DV) subjected to Bayesian logit regression, referred as to a Bayesian hybrid classification model. Data of DV are indicated by the dots according to tusk species. (<bold>C</bold>
) The set of cut-off values for predicting Asian or African tusk origin. Dashed red line shows the level of kappa at 0.8. (<bold>D</bold>
) Scatter plot testing the reliability of the model for estimating tusk origin for 30 Asian and 41 African tusks with a cut-off value of 55% (dashed red line).</p>
</caption>
<graphic xlink:href="srep24845-f5"></graphic>
</fig>
<fig id="f6"><label>Figure 6</label>
<caption><title>Phylogenetic tree based on cytochrome b sequence.</title>
</caption>
<graphic xlink:href="srep24845-f6"></graphic>
</fig>
<table-wrap position="float" id="t1"><label>Table 1</label>
<caption><title>Characterization of each discriminant function using the different elemental denominations.</title>
</caption>
<table frame="hsides" rules="groups" border="1"><colgroup><col align="left"></col>
<col align="center" char="."></col>
<col align="center" char="."></col>
<col align="center"></col>
<col align="center" char="."></col>
</colgroup>
<thead valign="bottom"><tr><th align="left" valign="top" charoff="50">Ratio of each element</th>
<th align="center" valign="top" char="." charoff="50">Valid data<xref ref-type="fn" rid="t1-fn1">1</xref>
(%)</th>
<th align="center" valign="top" char="." charoff="50">Eigen value</th>
<th align="center" valign="top" charoff="50">Number of ratios used</th>
<th align="center" valign="top" char="." charoff="50">Successive discrimination (%)</th>
</tr>
</thead>
<tbody valign="top"><tr><td align="left" valign="top" charoff="50">No ratio</td>
<td align="center" valign="top" char="." charoff="50">100.0</td>
<td align="center" valign="top" char="." charoff="50">1.297</td>
<td align="center" valign="top" charoff="50">11</td>
<td align="center" valign="top" char="." charoff="50">87.5</td>
</tr>
<tr><td align="left" valign="top" charoff="50">To Zr</td>
<td align="center" valign="top" char="." charoff="50">97.4</td>
<td align="center" valign="top" char="." charoff="50">1.045</td>
<td align="center" valign="top" charoff="50">8</td>
<td align="center" valign="top" char="." charoff="50">87.6</td>
</tr>
<tr><td align="left" valign="top" charoff="50">To P</td>
<td align="center" valign="top" char="." charoff="50">100.0</td>
<td align="center" valign="top" char="." charoff="50">0.618</td>
<td align="center" valign="top" charoff="50">12</td>
<td align="center" valign="top" char="." charoff="50">84.9</td>
</tr>
<tr><td align="left" valign="top" charoff="50">To Ag</td>
<td align="center" valign="top" char="." charoff="50">82.0</td>
<td align="center" valign="top" char="." charoff="50">0.914</td>
<td align="center" valign="top" charoff="50">12</td>
<td align="center" valign="top" char="." charoff="50">85.9</td>
</tr>
<tr><td align="left" valign="top" charoff="50">To Cd</td>
<td align="center" valign="top" char="." charoff="50">93.7</td>
<td align="center" valign="top" char="." charoff="50">0.809</td>
<td align="center" valign="top" charoff="50">13</td>
<td align="center" valign="top" char="." charoff="50">85.5</td>
</tr>
<tr><td align="left" valign="top" charoff="50">To Sn</td>
<td align="center" valign="top" char="." charoff="50">87.8</td>
<td align="center" valign="top" char="." charoff="50">0.725</td>
<td align="center" valign="top" charoff="50">14</td>
<td align="center" valign="top" char="." charoff="50">84.1</td>
</tr>
<tr><td align="left" valign="top" charoff="50">To Sb</td>
<td align="center" valign="top" char="." charoff="50">87.8</td>
<td align="center" valign="top" char="." charoff="50">0.684</td>
<td align="center" valign="top" charoff="50">12</td>
<td align="center" valign="top" char="." charoff="50">83.8</td>
</tr>
<tr><td align="left" valign="top" charoff="50">Combined<xref ref-type="fn" rid="t1-fn2">2</xref>
</td>
<td align="center" valign="top" char="." charoff="50">79.4</td>
<td align="center" valign="top" char="." charoff="50">1.526</td>
<td align="center" valign="top" charoff="50">24</td>
<td align="center" valign="top" char="." charoff="50">89.8</td>
</tr>
</tbody>
</table>
<table-wrap-foot><fn id="t1-fn1"><p>(P = phosphorous, Zr = zirconium, Ag = silver, Cd = cadmium, Sn = tin, Sb = antimony).</p>
</fn>
<fn id="t1-fn2"><p><sup>1</sup>
Accepted data for entering into discriminant analysis.</p>
</fn>
<fn id="t1-fn3"><p><sup>2</sup>
Ratios of Zr, P, Ag, Cd, Sn and Sb were pooled before analyzing through discriminant analysis.</p>
</fn>
</table-wrap-foot>
</table-wrap>
<table-wrap position="float" id="t2"><label>Table 2</label>
<caption><title>The classification results of assigning tusk origin through the hybrid classification model with cut off at 55% for samples used to create the discriminate equation and a separate set of independent samples used to validate the technique.</title>
</caption>
<table frame="hsides" rules="groups" border="1"><colgroup><col align="left"></col>
<col align="center"></col>
<col align="center"></col>
<col align="center"></col>
<col align="center"></col>
<col align="center"></col>
</colgroup>
<thead valign="bottom"><tr><th rowspan="2" align="center" valign="top" charoff="50"> </th>
<th rowspan="2" align="center" valign="bottom" charoff="50">Average probability (SD)</th>
<th colspan="2" align="center" valign="top" charoff="50">Prediction<hr></hr>
</th>
<th rowspan="2" align="center" valign="bottom" charoff="50">Accuracy</th>
<th rowspan="2" align="center" valign="bottom" charoff="50">Precision</th>
</tr>
<tr><th align="center" valign="top" charoff="50">Asian</th>
<th align="center" valign="top" charoff="50">African</th>
</tr>
</thead>
<tbody valign="top"><tr><td colspan="6" align="left" valign="top" charoff="50">Dependent study</td>
</tr>
<tr><td align="left" valign="top" charoff="50"> Asian (n = 72)</td>
<td align="center" valign="top" charoff="50">0.24 (0.23)</td>
<td align="center" valign="top" charoff="50">64 (89%)</td>
<td align="center" valign="top" charoff="50">8 (11%)</td>
<td align="center" valign="top" charoff="50"> </td>
<td align="center" valign="top" charoff="50"> </td>
</tr>
<tr><td align="left" valign="top" charoff="50"> African (n = 85)</td>
<td align="center" valign="top" charoff="50">0.75 (0.14)</td>
<td align="center" valign="top" charoff="50">6 (7%)</td>
<td align="center" valign="top" charoff="50">79 (93%)</td>
<td align="center" valign="top" charoff="50">91.08</td>
<td align="center" valign="top" charoff="50">91.12</td>
</tr>
<tr><td colspan="6" align="left" valign="top" charoff="50">Independent study</td>
</tr>
<tr><td align="left" valign="top" charoff="50"> Asian (n = 30)</td>
<td align="center" valign="top" charoff="50">0.16 (0.17)</td>
<td align="center" valign="top" charoff="50">29 (97%)</td>
<td align="center" valign="top" charoff="50">1 (3%)</td>
<td align="center" valign="top" charoff="50"> </td>
<td align="center" valign="top" charoff="50"> </td>
</tr>
<tr><td align="left" valign="top" charoff="50"> African (n = 41)</td>
<td align="center" valign="top" charoff="50">0.74 (0.13)</td>
<td align="center" valign="top" charoff="50">3 (7%)</td>
<td align="center" valign="top" charoff="50">38 (93%)</td>
<td align="center" valign="top" charoff="50">94.37</td>
<td align="center" valign="top" charoff="50">95.49</td>
</tr>
</tbody>
</table>
<table-wrap-foot><fn id="t2-fn1"><p>SD = standard deviation.</p>
</fn>
</table-wrap-foot>
</table-wrap>
</floats-group>
</pmc>
</record>
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