Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 September 2022 | 14(9): 21805–21810
ISSN
0974-7907 (Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.7727.14.9.21805-21810
#7727 | Received 26 October 2021 |
Final received 10 March 2022 | Finally accepted 14 August 2022
Age estimation of Tiger Panthera tigris
(Linnaeus, 1758) and Lion Panthera leo
(Linnaeus, 1758) (Mammalia: Carnivora: Felidae): applicability of cementum
annuli analysis method
1 vipinsharma_24@yahoo.com, 2 cpsharma@wii.gov.in,
3 vinita302003@gmail.com, 4 goyalsp@wii.gov.in,
5 customerservice@deerage.com, 6 skg@wii.gov.in
(corresponding author)
Abstract: We describe the applicability of the cementum
annuli analysis technique for estimating the age of Tiger Panthera tigris and Asiatic Lion Panthera leo
using incisor teeth. We used I2 and I3 incisor teeth from
the right mandible of Tiger and I2 and I3 from the left
premaxilla of the Lion. The longitudinal sections of the teeth were prepared
using an economical hand grinding technique with the help of sandpaper,
followed by decalcification and staining with hematoxylin.
Two cementum layers were observed under the microscope in each of the I2
and I3 incisor teeth of the Tiger and six cementum layers were
observed in each of the I2 and I3 incisor teeth of the
Lion. The permanent incisors in Tiger and Lion erupt between 12 and 14 months
of age; hence, we added one year to the counted number of cementum layers to
estimate the final age of Tiger and Lion incisors. The age of Tiger and Lion
incisors were estimated to be of three years and seven years, respectively.
This method may be suitable for estimating other carnivores’ age and applicable
in wildlife forensic studies.
Keywords: Big cats, carnivore, epoxy,
grinding, incisor, premolar, teeth, wildlife forensics.
Editor: Angie Appel, Wild Cat Network, Bad Marienberg,
Germany. Date of publication: 26 September 2022 (online &
print)
Citation: Vipin, C.P. Sharma, V. Sharma, S.P.
Goyal, H. Stevens & S.K. Gupta (2022). Age estimation of Tiger Panthera tigris (Linnaeus, 1758) and Lion Panthera leo (Linnaeus, 1758) (Mammalia: Carnivora: Felidae):
applicability of cementum annuli analysis method. Journal of Threatened Taxa 14(9): 21805–21810.
https://doi.org/10.11609/jott.7727.14.9.21805-21810
Copyright: © Vipin et al. 2022.
Creative Commons Attribution 4.0 International License. JoTT allows
unrestricted use, reproduction, and distribution of this article in any medium
by providing adequate credit to the author(s) and the source of publication.
Funding: The study was funded by the Wildlife Institute of India, Dehradun
Competing interests: The authors declare no competing
interests.
Author
details: Vipin is working as a Director of Research at DeerAge,
Missoula, Montana, USA. His areas of research interest are wildlife
conservation, age estimation, wildlife forensics and disease diagnosis. Chandra Prakash Sharma is working as a
Senior Technical Officer, Wildlife Forensic and Conservation Genetics Cell,
Wildlife Institute of India, Dehradun. He is dealing with wildlife offence
cases with morphological and other relevant techniques. Along with the primary
task of developing new protocols for the identification of species from
wildlife parts, he is involved in teaching and training wildlife enforcement
officials in curbing illegal wildlife trade and morphological identification of
wildlife articles. Vinita Sharma is an Assistant Professor
in the Department of Zoology, Central University of Jammu, Jammu and Kashmir.
Her area of research is related to animal taxonomy, systematics and behavior,
wildlife and conservation biology, human-wildlife conflict, wildlife forensics,
comparative anatomy and geometric morphometrics. Surendra Prakash Goyal was Scientist G and now working as a
subject matter specialist at the Wildlife Institute of India, Dehradun. His
research areas include wildlife ecology, field research methods,
wildlife-habitat relationships of ungulates and carnivores, estimation of food
habits, habitat fragmentation and corridors, use of lab methods, especially in
nutritional ecology, molecular ecology, landscape genetics. Heather Stevens is heading Nationwide
Histology Inc providing the highest quality service for research clients and
the DeerAge, Wildlife Analytical Laboratories,
dedicated to quality age estimation of game animals across the United States of
America. Sandeep Kumar Gupta is
Scientist E, Head, Department of Animal Ecology and Conservation Biology and
Nodal Officer, Wildlife Forensic and Conservation Genetics Cell, Wildlife
Institute of India, Dehradun. His areas of research interest are conservation
genetics, wildlife forensics, evolutionary genetics of rare and endangered
species. He is also undertaking teaching and training courses on illegal
wildlife trade.
Author
contributions: V, CPS, SPG &
SKG conceived the study. V, CPS & VS carried out the laboratory work. V
& HS did the data analysis. V, VS & SKG wrote the article. CPS, SKG,
SPG & HS reviewed the article.
Acknowledgements:
We gratefully
acknowledge the support of the director and dean, Wildlife Institute of India,
Dehradun.
Introduction
The age of carnivores needs to be
estimated in studies about the demography of species and for understanding
population dynamics (Skalski et al. 2005; Foresman
2012), age class (Angerbjorn et al. 2004; Creel et
al. 2004), population monitoring trends (Barthold et
al. 2016), human-wildlife interactions (Conover 2002; Frank et al. 2005), and
illegal wildlife trade (Williams et al. 2015). The widely used methods for age
estimation of carnivores are assessments of tooth eruption (Slaughter et al.
1974), wearing of a tooth crown (Harris 1978; Stander 1997; Gipson et al.
2000), closure of pulp chamber (Marks & Erickson 1966; Zapata et al. 1997;
Binder & Van Valkenburgh 2010), and cementum
analysis (Klevezal & Kleinenberg
1967; Matson 1981; White & Belant 2016).
The method to estimate the age of the
Tiger Panthera tigris has mostly been limited
to assessing tooth eruption, wearing (Mazak 1979, 1981; Miles & Grigson
2003), and gum line recession (Fŕbregas & Garcés-Narro 2014). The methods described to assess the age
of the Lion Panthera leo refer to sizes of
body and mane, pigmentation on the nose, tooth wear (Schaller 1972; Smuts et
al. 1978; Whitman et al. 2004; Whitman & Packer 2007; Ferreira & Funston
2010), closure of the pulp chamber (White & Belant
2016), the ratio of tooth areas (White et al. 2016), tooth eruption (Schneider
1959) and cementum analysis (Spinage 1976; Smuts et
al. 1978; White & Belant 2016).
Amongst the various age determination
methods available, the cementum analysis method has been recommended for its
accuracy (Mundy & Fuller 1964; Marks & Erickson 1966; Klevezal & Kleinenberg 1967;
Craighead et al. 1970; Willey 1974, Grue & Jensen
1979; Johnston et al. 1987; Matson et al. 1993; Mbizah
et al. 2016; Vipin et al. 2018). The described technique does not need a costly
microtome for tooth sectioning, so most of the items required are generally
available in a standard lab (Vipin et al. 2018).
To date, studies on age estimation of
South Asian mammals through cementum layer analysis are limited to Chital Axis
axis (Vipin et al. 2018). Here we present the
applicability of this method for estimating the age of Tiger and Asiatic Lion.
Material and Methods
We used Tiger mandible and Lion skull
from Wildlife Forensic and Conservation Genetics Cell’s repository. We tested
the applicability of the developed method to estimate the age of an incisor (I3)
from the mandible of a Tiger seized in the illegal wildlife trade, which was
sent to Wildlife Institute of India, Dehradun, for species confirmation.
Sample collection and preparation of
longitudinal section of teeth
Canines of Tigers and Lions are in high
demand compared to other species’ teeth in the illegal wildlife trade. Hence,
in comparison to other types, the chances of their availability for determining
age are limited. In both species, the permanent incisors number is six times
more than premolar (PM2), which is a plus point if some tooth gets
damaged during processing for cementum analysis. Therefore, we selected
incisors in the current study and based on the availability of their types, the
incisors were extracted.
Two permanent incisor teeth (I2,
I3) out of three were used from the right mandible of a Tiger (Image
1A, B, C) and two incisors (I2, I3) from the left
premaxilla of a Lion. The teeth from the Tiger mandible were extracted by
boiling it in water for ten minutes, after which they detached easily from the
mandible. From the Lion premaxilla, the teeth were removed with the help of
pliers with utmost care so that the periodontal membrane remained intact. We
used the protocol described by Vipin et al. (2018) for preparing the
longitudinal sections of the incisor teeth with a thickness of around 57 µm
with steps, as shown in Image 2. We then used a Leica DMR microscope to examine
the tooth sections.
Calculation of age from cementum annuli
In felids, all permanent incisors
except I3 erupt before other teeth (Miles & Grigson 2003). In
Tiger, the permanent tooth eruption starts between 8.8–9.5 months and completes
at the age of 12–14 months (Mazák 1979, 1981). In
Lion, permanent I1, I1, I2, I2
fully erupts between 9–11 months and I3 and I3 start
erupting by the end of this period (Smuts et al. 1978). I3 and I3
completely replace their deciduous counterparts at the age of 12 to 14 months,
while P2 starts erupting between this period in Lions (Smuts et al.
1978). Though no published data related to age estimation of Tiger using
cementum analysis is available; many researchers have used permanent incisors,
canine, and second premolar teeth to develop age estimation methods in Lions
utilizing this technique (Smuts et al. 1978; Cheater 2006; White & Belant 2016). The time taken by different tooth types for
their permanent eruption has been reported unequal in other species of
carnivores and ungulates (Zapata et al. 1995; Azorit
et al. 2004). In P2 of African Lions, it is established that the
first rest is formed in the second year of age, so we had to add one to the
counted number of cementum lines to estimate the final age (White & Belant 2016). We counted the acellular cementum layer in
the root portion of the teeth, which is formed annually and stains dark with
hematoxylin (Matson et al. 1993). Therefore, we added a minimum of one year in
both species’ final age estimation. The presence of one cementum layer in a
permanent incisor tooth of Tiger and Lion indicates that the animal has lived
one year at least. The age of sectioned teeth in years was calculated according
to the formula
Age in year = Number of cementum layers
+ 1 year
The cementum layers in the incisor
teeth were photographed wherever these were seen distinctly and clearly.
Results
The teeth sections of the Tiger showed
two cementum layers for I2 (Image 3 A, B, C) and I3
(Image 4 A, B); thus, the Tiger’s age was estimated to be three years. The Lion
had six cementum layers in I2 (Image 5A, B) and I3 (Image
6); therefore, Lion’s age was estimated to be seven years
We found two dark cementum layers on
the Tiger’s incisor seized in the illegal wildlife trade; hence its age was
estimated as three years (Image 7). Therefore, the developed method may also be
applied to estimate the age of tigers in the illegal wildlife trade.
Discussion
White & Belant (2016) used
paired PM2 teeth for estimating the age of free-ranging African
Lions of unknown age through cementum line count and showed that cementum layer
count in PM2 is unsuitable for ageing Lions. Their analysis revealed
that in 19 out of 31 PM2 pairs, the cementum line count differed by
1–2 lines and even increased to seven lines for other pairs. According to Smut
et al. (1978), cementum lines in canine teeth of Lions complied significantly
with their known ages. So to compare the results of
White & Balent (2016) about Asiatic Lions, a
large sample size of the PM2 teeth is needed, or more incisors or a
different tooth type needs to be analysed for
cementum layer count. In ungulates, the accuracy of age estimation through
cementum analysis decreases with the age of the specimens (Hamlin et al. 2000).
More research is necessary to assess whether this is also true for carnivores.
We recommend validating the current procedure while
estimating age based on cementum layer count. Matson et al. (1993)
suggested two main tests for validating the cementum analysis for estimating
age, namely the “blind” duplicate test when two or more teeth are available and
using a tooth of known age but without having the prior knowledge of its age.
Teeth of known age were not available for both species; however, all incisor
teeth showed clear and distinct cementum layers. The periodontal membrane in
all studied teeth confirms that all cementum layers were present in the
longitudinal sections. Hence, the current method can show all cementum layers
clearly and distinctly in incisor teeth.
The same protocol may be applied to develop age estimation
protocols for other mammal species.
For images—click
here for full PDF.
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