Computer-aided photographic pelage pattern analysis of Giraffa camelopardalis (Artiodactyla:Girrafidae)

Author(s)Nora Hausen
Year Published2017
JournalMaster of Science Degree Thesis
Page Numbers1-34
Size4.17 MB
Abstract:

The giraffe (Giraffa camelopardalis) is one of the most recognisable animal species on earth. Yet hunting and habitat loss and fragmentation have led to severe, but until recently largely unnoticed, declines of giraffe populations all over Africa. The IUCN recognised one single species with nine subspecies and changed the status from ‘Least Concern’ to ‘Vulnerable’ in 2016. However, the number of giraffe species and its subspecies has been a topic of ongoing discussion for more than a century. To date, a comprehensive and objective assessment of the giraffe taxonomy is lacking, resulting in an ambiguous status of the species and its subspecies. While the understanding of genetic analyses has increased substantially over the last decade, morphological studies remain the exception. This study assessed the variations between giraffe subspecies by means of a quantitative pelage pattern analysis (PPA). The spatial pattern analysis programme FRAGSTATS was used to systematically assess and compare how giraffe populations differ based on their pelage. Images of giraffe flanks were converted into black-and-white raster images, processed in FRAGSTATS and tested by means of a Principal Component Analysis (PCA). The principal components with proportions of explained variance >10% were tested for significance (p<0.05) by means of a one-way ANOVA. In total, 145 images from eight of the nine subspecies were compared. Results indicated that G. c. reticulata, G. c. tippelskirchi, G. c. thornicrofti and G. c. giraffa were more distinguishable, while G. c. angolensis, G. c. antiquorum, G. c. peralta and G. c. rothschildi showed less significant pairwise comparisons. No clear separation of all subspecies emerged from the PCA, though some unique characteristics for some subspecies as well as clusters of comparable subspecies could be identified. A number of influential metrics for the separation of subspecies were identified. The findings were partially congruent with previous studies using qualitative analysis on smaller sample sizes. The indication of trends of population separations demonstrates the potential of quantitative PPAs with many facets to expand on. This analysis offers a novel discipline to complement taxonomic assessments in general and a taxonomic review of the giraffe in particular. In the ongoing debate around giraffe taxonomy, this study marks an important step in the endeavour to unravel the variation of giraffe coat patterns in support of the species taxonomy.

Keywords: Morphology, Subspecies, Identification, Taxonomy, Picture analysis

Authors: Nora Hausen

Journal: Master of Science Degree Thesis


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