Cranio-morphometric Study of Asiatic Big Cats for Forensic Identification

Dinesh Kumar Jha^*, Raju Panday, Nirajan Thapa Kshetry, Anshu Upadhayay and Nanda Kumar Aryal
^*Correspondence: Dinesh Kumar Jha, Department of Biology Division, National Forensic Science Laboratory, Kathmandu 44600, Nepal, Email:

Keywords

Wildlife forensics • Asian big cat skull • Cranio-morphometry • Species identification • Illegal trade • felids • Wildlife conservation

Introduction

Asia holds wilder cat species than any other continent. Asian Big Cats (ABC) parts have become items of illegal trade in Asia [1,2]. Live along with ABC parts are used for various purposes i.e. pets, entertainment, human consumption, decoration, jewelry, traditional Asian medicine, customary culture, modern fashion and beliefs [3-6]. All Asian big cats i.e. tiger (Panthera tigris tigris), Indian indigenous Asiatic lion (Panthera leo leo), common leopard (Panthera pardus), snow leopard, (Uncia uncia) and clouded leopard (Neofelis nebulosa) are classified under CITES Appendix I (CITES 2019). All big cats are found in Nepal excluding lion. Nepal is signatory to the CITES and thus prohibits commercial trans-border trade of big cats listed in CITES Appendix. Except common leopard, all other indigenous big cats are highly protected by national law in Nepal (National Parks and Wildlife Conservation ACT 1973). Currently, Bengal tiger is classified as endangered and Asiatic lion, common leopard, snow leopard and clouded leopard as vulnerable under the IUCN Red List. Since these species are given different levels of protection under national and international laws, an effective prosecution requires specieslevel identification but it is a challenging task for the forensic biologists [7-8]. It demands practical methods that identify species with near certainty when the species identity is in question [9]. Trustworthy identification depends on nature, type of samples and available methods. DNA is proven as decisive and widely accepted tool but it has its own limitations and cannot be applied in all cases [10]. Due to simple and easily accessibility, morphometric technique is always choice for scientific community and concerned field-based authorities. Samples are often commingled with heterogeneous species. Therefore, morphometric techniques help either to identify or segregate for direct genetic analysis [7].

Felid skulls often appear as evidence in wildlife forensic casework [7,11-13]. Our laboratory record shows feline skeletons and skulls cover almost 12% (70/600) of total wildlife cases. Skull is often the sample of choice for identification of species. Morphometric measurements help in understanding the skull morphology of different animal species contributes to the phylogenetic structure of the head, animal’s taxonomic affiliations as well as gender determination [14-18]. Closely related species (especially felids) often lack single diagnostic characters that pinpoint a particular species [19]. A combination of characters must be used in comparative analysis [20]. Appropriately, functional anatomy and evolutionary studies of skulls include metric approaches [20,21]. In the meantime, morphological analysis using qualitative characters seen with the naked eye is easier because wildlife law enforcement agents and other field investigators might lack the logistics to perform a sophisticated metric analysis [7].

Allowing these facts, an effective and reliable identification system based on comparative metric and morphology is formulated. The main objective of the present study is to develop morphometry-based species level identification technique from skull of Asiatic big cats which could be implemented in wildlife forensic cases. Also, from the study, similarly sized skulls of common leopard and clouded leopard were compared using various metric parameters for greater stringent discrimination. This study might become beneficial for law enforcement authorities too.

Methodology

Materials

In the present study, a total of 25 skulls of felids i.e. Bengal tiger, Panthera tigris tigris (n=16), common leopard, Panthera pardus (n=6), Asiatic lion, Panthera leo leo (n=1), snow leopard, Uncia uncia (n=1) and clouded leopard, Neofelis nebulosa (n=1) were examined. Source of sample are Office of the Chitwan National Park, Chitwan, Armed Forest Protection Training Centre, Tikauli, Natural History Museum, Kathmandu and Central Zoo, Kathmandu, Nepal. Clouded leopard and snow leopard skull associated with skin layer were received as a case in the laboratory. Limitation of the study is small sample size of clouded leopard, snow leopard and Asiatic lion.

Metric data

A total of 29 craniometric parameters were recorded with the help of measuring scale and digital Vernier caliper (Mitutoyo, 500-197-20 CD-8 CSX, Japan) and entered into Excel sheets for subsequent analysis according to the literature [22]. These measurements along with their abbreviations are illustrated in Figure 1.

Morphological features

Metric parameters have limitations to express all essential morphological characteristics. Comparative morphological features like overall skull profile, nasal profile, nature of sagittal crest etc. were examined as well.

Data analysis

After the entry of all data measured, analysis was carried out in Microsoft Excel 2010. Mean, minimum, maximum and standard deviations (SD) were calculated. Similarly, meaningful ratios from some parameters were established. One skull each of common leopard and clouded leopard having similar Condylobasal length were compared and metric wise ratio was calculated. Relevant data was also analyzed with Tukey’s b One-way ANOVA.

Results and Discussion

Studied parameters and ratios results are presented in Table 1 and 2 respectively. Some cranio-metric values and their ratios are highly informative i.e. either separated into group or pinpointing the species.

Table 1. Different craniometric parameters results (min-max) of the five ABC species studied.

Table 2. Different craniometric parameters ratio (min-max) of the five ABC species studied.

Skull size and features

Feline show different predatory habits, prey size range, ecological preferences and have several morpho-metric variations in skull, some of them related to the size differences [15,23,24]. Among studied big cats, tiger is the largest followed by Asiatic lion, common leopard, snow leopard and clouded leopard and accordingly differences found in skull size which was also observed in the present study (Table 1) [21,25,26]. However, ratios of different parameters are not related with species size (Table 2).

Comparatively, higher GSL, CBL, BZB as well as HS value were observed in tiger and lion skulls (Table 1) in contrast to others. The tiger and lion skull bear very wide zygomatic arches [27-28]. Collective CBL value observed in common leopard, snow leopard and clouded leopard (CBL 16.0-21 cm) is significantly lesser than tiger and lion (CBL 25.5 – 33 cm) which indicates that CBL is one of the principal cranial character discriminating the leopard groups [29]. Based on these facts (Table 1), Asiatic big cats can be differentiated into Group I (tiger and lion) and Group II (common leopard, snow leopard and clouded leopard) [21]. Alternatively, clouded leopard as ‘small’, common leopard and snow leopard as ‘medium’ and lion and tiger as ‘Large’ cats’ or genus Panthera as ‘massive headed cats’, snow leopard as ‘stout headed cat’ and clouded leopard as ‘tapering headed cat’ [7,24]. Highest Skull index (SI) (BZB*100/GSL) result was observed in tiger (Table 2). A significant difference between the Groups I and II was confirmed for GSL (P<0.05), CBL (P <0.05), BZB (P <0.05), HS (P <0.05) and SI (P <0.004) parameters.

Observed GSL, CBL and BZB values (Table 1) in the present study was accordance to other studies i.e. tiger (Skull length >25.5 cm, usually 28.5 – 36.0 cm), lion (Skull length: 38.50 – 41 cm), common leopard (GSL: av. 19.3 cm, range 16.6-21.3 cm, CBL: av. 17.7 cm, range 15.1-19.4 cm, BZB: av. 12.1 cm, range 10.5-13.2 cm), snow leopard (GSL: 16.5 – 20.0 cm, CBL: 15.5-18.2 cm, BZB: 11.4 – 13.9 cm), clouded leopard (CBL: 16.0 – 17.05 cm) [30-34].

Frontal features

Among studied frontal features, comparatively RL, nasal cavity and nasal bone related characteristics were found to be highly significant.

RL and FL is one of the striking features to differentiate clouded leopard and lion from others. The facial part of the skull of lion is relatively large [28]. Similar finding was observed in the present study (Table 1). Highest RL/FL ratio result was found in tiger (Table 2). In clouded leopard, lowest RL/FL and RL/ GSL result was observed (Table 2). Though clouded leopards have one of the widest gaps during biting; they have a relatively short rostrum when compared with the other panthers [20,21]. Widest and narrowest RB was found in tiger (10.14 cm) and clouded leopard (4.37 cm) respectively.

Morphometric features of nasal bone are another imperative parameter to differentiate species. Tiger has proportionally longer nasal bones than lion [22]. Similar result was observed in the current study (Table 1). Maximum GLN/CBL ratio was found in tiger (0.38, range 0.34-0.39) followed by common leopard (0.33, range 0.31-0.36) and lion (0.33). In other studies, similar GLN/CBL for tiger (0.37, range: 0.35-0.40; 0.37; range: 0.34–0.41) and lion (0.318, range: 0.27-0.35; 0.32; range: 0.27–0.35) was observed [22].

In the context of great similarities of skull between tiger and lion [22,34- 36], an important difference observed is the disparity proportion of posterior projections of nasal-frontal suture (NFS) and maxilla-frontal suture (MFS) (Figure 2 and Table 2). The NFS tip is always exceeding (by av. 1.47 cm, range 0.95 – 1.93 cm) the MFS tip in tiger. NFS is always posterior to the MFS in tiger as well as its projection degree is variable and subspecies-specific [12,22,37]. In lion, MFS tip is exceeding NFS tip mildly (by 0.14 cm). However, in common leopard all three possibilities existed i.e. both tips terminate at same point; exceed the MFS tip (0.33cm) or NFS tip (0.2-0.4 cm) with sample frequency of 33.33%, 16.66% and 50% respectively. In clouded leopard both tips are equally terminated but in snow leopard MFS tip exceeded NFS tip (by 0.67 cm).

Common leopard and tiger have convex nasal profiles whereas snow leopard has concave nasal profile [30]. Similar results were observed in the present study. Clouded leopard also has convex nasal profile. However, horizontal slope form of nasal profile is observed in lion (Figure 3). Besides this, individual nasal bone of tiger showed ‘inverted U shaped’ contour at dorsal surface from anterior to posterior end. On the other hand, across elevation between two nasal bones was noticed in others (Figure 4).

As depicted in the Table 1 and 2, highest NW, IB, LIB, LBS, SH, RL and GOH was observed in Group I but majority of its higher ratio in Group II Asiatic big cat with interspecies variations. Higher LBS/GSL and LBS/BZB in snow leopard and lowest in clouded leopard (Table 2) re-support the fact of snow leopard has short, stout skull, clouded leopard with elongated, narrower skull and others in between them [24]. The highest NW/ GLN ratio was found in snow leopard (0.63). Snow leopard has short and broad and highly vaulted skull that supports an enlarged nasal cavity which is an adaption to cold climates [7,33,38].

Forehead profile

Among the studied big cat skulls, FHB/BZB ratio indicates that snow leopard (0.6) has a broadest forehead over others (Table 2). Broadened forehead of snow leopard is an adaptive feature for colder climate [33,38]. Marked central longitudinal depression on the frontal bone, a unique feature for snow leopard and lion was also observed in the present study [28,29]. The highest and lowest FHB was observed in lion (11.87 cm) and clouded leopard (5.4 cm) respectively.

Posterior profile features and sagittal crest

One of the notable features of tiger observed in the present study that separates it from others is that the former has convex posterior lateral profile; however common leopard, snow leopard and clouded leopard have concave profile; while lion has more or less horizontal slant type profile (Figure 3).

Large cats have evolved a flange of bone on top of the skull called sagittal crest which provide space for muscle attachments [40]. In the present study, morphometry of sagittal crest is co-related with skull length and species (Figure 5) i.e. larger the cat, the larger is the crest [40].

sH ranged from 0.14 cm (tiger and common leopard) to 1.17 cm (lion) and its thickness (sT) ranged from 0.12cm (common leopard) to 0.87 cm (tiger). As illustrated in the table 2, highest and lowest sT/sH ratio was observed in tiger and clouded leopard respectively (Table 2). These findings can be concluded as well-developed sagittal crest in lion; low or inconspicuous sagittal crest in tiger in comparison to thinner but prominent sagittal crest in others [28,41]. Inconspicuous sagittal crest in tiger may be due to its increased thickness in comparison to height (Figure 5). Sagittal crest reaches about 0.3 - 0.4 cm in the middle region in tiger [41]. Similar result (av.0. 44 cm) was observed in the present study.

As observed in other study, comparatively higher POC/CBL ratio (0.32) recorded in snow leopard [21]. In other studies, similar POC/CBL ratio value for snow leopard (0.33) and clouded leopard (0.31, 0.31 in present study) was observed [26,34]. The postorbital process of snow leopard is elevated due to the inflated or broader nasal cavity and flat nasal bones [36,37].

NcW increased with increasing skull size but in the meantime its proportional ratio value with BZB decreased. Hence these parameters and ratio results separated ABC skull in two groups but in different manner. Higher NcW was observed in Group I species (8.33-11.22 cm) in comparison to Group II (5.76 – 7.88 cm) species (Table 1). However, higher NcW / BZB ratio was observed in Group II than Group I members (Table 2). Similarly, observed CL distinctly separated ABC into Group I and Group II (Table 1).

Ventral region skull parameters

There is distinct line of separation in UCL, c-Pm-4 and distance between PC-MM value between Group I and Group II but not significantly varies among species (Table 1). PL and C-C are useful parameters to separate species in some extent (Table 1). The ratio of C-C/GSL did not vary markedly (Table 2). PC-PM/GSL (Table 2) results differentiate common leopard, tiger and snow leopard from lion and clouded leopard.

The highest PFDO value was observed in tiger and lowest in lion and common leopard (Table1). Similarly, highest and lowest PFDO/GSL ratio was observed in tiger and lion respectively (Table 2). The GBP was found to be highest in lion and tiger (range 10.7-14.12 cm) in comparison to common leopard, snow leopard and clouded leopard (range 6.5 - 8.58 cm). However, ratio of GBP/BZB was found to be highest in common leopard and lowest in tiger (Table 2). Similarly, the LPB was found to be higher in Group I (6.96–9.0 cm) than Group II (4.4-5.44 cm). Ratio of LPB/BZB did not vary among studied species (Table 2). The highest DAB was observed in lion (Table 1).

Overall, PFDO, PFDO/GSL and GBP/BZB results suggested these are not related with skull size absolutely. Similarly, GBP and LBP are group discriminating parameters. Lowest PFDO/GSL in lion is one of the diagnostic features of the species.

Parallel common leopard and clouded leopard skull comparison

Among studied big cat species, comparatively more morphological similarities were observed between common leopard and clouded leopard skull. However significant variations were found in different metric parameters and their ratio between these two species. The apparent distinguishable parameters observed among these two species are FL, FHB, POC, RL, LBS and PC-MM. The recorded FL, FHB, POC, RL, LBS, PC-MM of common leopard (and clouded leopard) are 10.29 cm (7.66 cm), 6.76 cm (5.4 cm), 6.7 cm (5.0 cm), 6.24 cm (4.5 cm), 5.57 cm (2.66 cm) and 1.8 cm (1.0 cm). Leopard-human conflict is common in Nepal [43]. Therefore, some of the skulls received for the identification are broken which might be due to attack from the humans in the skull with blunt or sharp object. Thus, variable parameter ratios were calculated using BZB for possible discrimination between these two species where CBL ratio becomes ineffective. Entire discriminating parameters and their BZB ratios (Figure 6) were found to be higher in common leopard. These results clearly suggest that though alike in skull length and width (CBL16.5 cm, BZB 12.23 cm for common leopard; CBL 16 cm, BZB 11.34 cm for clouded leopard) but these two species can be well distinguished (Figures 7).

Conclusion

From the present study, it is concluded that some morphometric variables and ratios could be used to characterize a suspected ABC skull with greater accuracy. In condition of intersect of some skull metric, sufficient other parameters, their ratio and important morphological features are available for reliable identification. For example, convex lateral posterior profile is the vital feature of tiger skull. Among studied morphometric features, GSL, SI, FHB and central depression, NFS and MFS ratio, posterior skull profile, sagittal crest nature, nasal profile are key parameters for differentiating ABC into groups or pinpointing the species. Similarly, based on ‘exclusionary means inclusion’ approach, a flowchart showing identification landmark is proposed (figure 8). The proposed identification strategy is simple. It becomes highly useful to the scientific community and wildlife enforcement agencies where there is lack of advanced techniques. This study equally helps in forensic identification of partial skull (figure 7).

The data was taken from skulls obtained from Office of the Chitwan National Park, Chitwan, Armed Forest Protection Training Centre, Tikauli, Natural History Museum, Kathmandu and Central Zoo, Kathmandu, Nepal.

Acknowledgements

The authors are deeply indebted to the Ministry of Education, Science and Technology, Ministry of Forest and Soil Conservation, Department of National Parks and Wildlife Conservation, Department of Forests for all the necessary permissions to carry out this work. We also are grateful to Office of the Chitwan National park, Chitwan, Armed Forest Protection Training Centre, Tikauli, Natural History Museum, Kathmandu and Central Zoo, Kathmandu for providing the samples. In this moment, we memorize our colleague (late) Basanta Raj Pokharel for his appreciative participation in the data collection.

References

1. Sharma, Vipin, Vinita Sharma, Chandra Prakash Kumar and Surendra Prakash Goyal." Pioneer identification of fake tiger claws using morphometrics and DNA- based analysis in wildlife forensics in India." Forensic Sci Lnt 266 (2016): 226-233.

Google Scholar, Crossref

2. Jha, Dinesh Kumar, Nirajan Thapa Kshetry, Basanta Raj Pokharel and Sudhir K. Lal, et al. "Identification and differentiation of the asian elephant ivory by using schreger lines." J lnst of Sci and Tech 22 (2017): 99-103.

Google Scholar, Crossref

3. Nijman, Vincent, Thais Morcatty, Jaima H. Smith and Sadek Atoussi, et al. "Illegal wildlife trade–surveying open animal markets and online platforms to understand the poaching of wild cats." Biodiversity 1 (2019): 58-61.

Google Scholar, Crossref

4. Mills, Judy A and Peter Jackson. Killed for a cure: A review of the worldwide trade in tiger bone. Cambridge: Traffic International, 1994.

Google Scholar

5. Driscoll, Carlos A, David W. Macdonald, and Stephen J, O'Brien. "From wild animals to domestic pets, an evolutionary view of domestication." Proc Natl Acad Sci 106 (2009): 9971-9978.

Google Scholar

6. Fitzherbert, Emily, Tim Caro, Paul J. Johnson and David W. Macdonald, et al. "From avengers to hunters: Leveraging collective action for the conservation of endangered lions." Biol Conserv 174 (2014): 84-92.

Google Scholar, Crossref

7. Sims, Margaret E. "Cranial morphology of five felids: Acinonyx jubatus, Panthera onca, Panthera pardus, Puma concolor, Uncia uncia." Russ J Theriol 2 (2012): 157-170.

Google Scholar

8. Wilson-Wilde, Linzi. "Combating wildlife crime." Forensic Sci Med Pathol 3 (2010): 149-150.

Google Scholar, Crossref

9. Williams, Vivienne L, Andrew J, Loveridge, David J Newton, and David W, Macdonald. "‘Skullduggery’: Lions align and their mandibles rock!." PloS one 11 (2015):0135144.

Google Scholar, Crossref

10. Panday, Raju, Dinesh K Jha, Nirajan Thapa and Basant R Pokharel, et al. "Forensic wildlife parts and their product identification and individualization using DNA barcoding." J Forensic Sci 1 (2014).

Google Scholar, Crossref

11. Maheshwari, Aishwarya, Shekhar Kumar Niraj. "Monitoring illegal trade in snow leopards." Glob Ecol Conserv 14 (2018):00387.

Google Scholar, Crossref

12. Williams, Vivienne L, Andrew J, Loveridge, David J, Newton, and David W, Macdonald. "A roaring trade? The legal trade in Panthera leo bones from Africa to East-Southeast Asia." PLoS One 10 (2017):0185996.

Google Scholar, Crossref

13. Haken, Jeremy. "Transnational crime in the developing world." Global financial integrity 2 (2011): 11-30.

Google Scholar

14. Onar, Vedat and Hali̇l Güneş. "On the variability of skull shape in German shepherd (Alsatian) puppies." The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology: An Official Publication of the American Association of Anatomists 1 (2003): 460-466.

Google Scholar, Crossref

15. knzel,W.,S. Breit and M.Oppel. “Morphometric investigations of breed specific features in feline skulls and considerations on their functional implication." Anatomia, Histologia, Embroyological 32 (20030: 218- 223.

Google Scholar, Crossref

16. Brünner, Harald, Nicolas Lugon-Moulin, François Balloux, Luca Fumagalli, and Jacques Hausser. "A taxonomical re-evaluation of the Valais chromosome race of the common shrewSorex araneus (Insectivora: Soricidae)." Acta Theriologica 3 (2002): 245-275.

Google Scholar, Crossref

17. Yahaya A., J.O, Olopade, H.D, Kwari. "Morphological analysis and osteometry of the foramen magnum of the one‐humped camel (Camelus dromedarius)." Anatomia, Histologia, Embryologia 2 (2013):155-159.

Google Scholar, Crossref

18. Mazak J.H "On the sexual dimorphism in the skull of the tiger (Panthern tigris)." Mamm Biol 6 (2004): 392-400.

Google Scholar, Crossref

19. García-Perea, Rosa. "The Pampas cat group (genus Lynchailurus Severtzov, 1858)(Carnivora, Felidae): A systematic and biogeographic review. Am Mus Novit (1994).

Google Scholar

20. Christainsen P and S Adolfssen. "Bite Foreces, canine strength and skull allometry in carnivores (Mammalia, carnivore)." J Zool 266 (2005):133-151.

Google Scholar, Crossref

21. Sicuro, Fernando Lencastre, and Luiz Flamarion B. Oliveira. "Evolutionary trends on extant cat skull morphology (Carnivora: Felidae): a three-dimensional geometrical approach." Zoological J Linn Soc 2 (2011): 414-462.

Google Scholar, Crossref

22. Christiansen, Per. "Distinguishing skulls of lions (Panthera leo) and tigers (Panthera tigris)." Mamm Biol 6 (2008): 451-456.

Google Scholar, Crossref

23. Mattern, Michelle Y. and Deborah A. McLennan. "Phylogeny and speciation of felids." Cladistics 2 (2000): 232-253.

Google Scholar, Crossref

24. Sicuro, Fernando Lencastre. "Evolutionary trends on extant cat skull morphology (Carnivora: Felidae): a three-dimensional geometrical approach." Biol J Linn Soc 1(2011):176-190.

Google Scholar, Crossref

25. Menon V. "Indian mammals: A field guide. Hachette India." (2014): 528.

Google Scholar

26. Austin, S.C., M.E.Tewes, L.I. Grassman and N.J Silvy. “Ecology and conservation of the leopard cat P rionailurus bengalensis and clouded leopard Neofelis nebulosa in Khao Yai National Park, Thailand" Acta Zoologyca Sinica 53 (2010):1-14.

Google Scholar

27. Mazak, V."Panthera tigris." The American society of mammologists 152 (1981): 1-8
28. Mohamed, Reda. "Anatomical and radiographic study on the skull and mandible of the African Lion (Panthera leo)." J Morphol Sci 3 (2019):174- 181.

Google Scholar, Crossref

29. Khorozyan IG, Baryshnikov AV Abramov. “Taxonomic status of the leopard, Panthera pardus (Carnivora, Felidae) in the Caucasus and adjacent areas.” Russ J Theriol (2006).

Google Scholar

30. Mazák J. ‘’Craniometric variation in the tiger (Panthera tigris).’’implications for patterns of diversity, taxonomy and conservation (2008).

Google Scholar, Crossref

31. Saber, Ashraf Sobhy Mohamad and B. Gummow. "Skull morphometry of the lion (Panthera leo), dog (Canis lupus familiaris) and cat (Felis catus)." J Vet Anat 1 (2015):13-30.

Google Scholar, Crossref

32. Kitchener, Andrew C, Carlos A. Driscoll, and Nobuyuki Yamaguchi. "What is a snow leopard? Taxonomy, morphology, and phylogeny."In Snow leopards. Academic Press (2016): 3-11.

Google Scholar, Crossref

33. Hemmer,H. Mammalian Species: Uncia uncia." American Society of Mammal 20 (1972): 1-5.

Google Scholar

34. Christiansen, Per, and Andrew C. Kitchener. "A neotype of the clouded leopard (Neofelis nebulosa Griffith 1821)." Mamm Biol 3 (2011): 325-331.

Google Scholar, Crossref

35. Hemmer,H." The phylogeny of the tiger (Panthera tigris)." In: Tilson, RI, Seal US (Eds.), Tigers of the world. The Biology, Biopolitics, Management, and Conservation of an Endangered Species. Noyes Publications, New Jersey" (1987) 28- 35.

Google Scholar

36. Marcella, J Kelly. "Sunquist, M, F Sunquist. Wild Cats of the World". University of Chicago Press, Chicago and London. (2004):365-366.

Google Scholar

37. Pocock R.I. "Tiger" Journal of Bombay Natural History Society 33(3) (1929):505-541.
38. Haltenorth, Theodor. Die verwandtschaftliche Stellung der Großkatzen zueinander. Berger, 1937.
39. Salles, Leandro O. Felid phylogenetics: Extant taxa and skull morphology (Felidae, Aeluroidea). Am Mus Novit. (1992).3047.

Google Scholar

40. Hunter, Luke. “Cats of Africa: Behavior, ecology, and conservation.” JHU Press, 2006.

Google Scholar

41. Mazák, Ji H and Colin P. Groves. "A taxonomic revision of the tigers (Panthera tigris) of Southeast Asia’’ .Mamm Biol 5(2006):268-287.

Google Scholar, Crossref

42. Pocock R.I. "XXXVI.—On the tooth-change, cranial characters, and classification of the snow-leopard or ounce (Felis uncia)." J Nat Hist 105 (1916): 306-316.

Google Scholar, Crossref

43. Koirala, Raj Kumar, Achyut Aryal A. and Parajuli A. David. "Humancommon leopard (Panthera pardus) conflict in lower belt of Annapurna Conservation Area, Nepal." J Res Conserv Biol 1 (2012): 5-12.

Google Scholar