Comparing Cats: A Discussion of Similarities & Differences

[Acinonyx sp.]

From Khan 2004, Ecology and Conservation of the Bengal Tiger in the Sundarbans Mangrove Forest, Bangladesh

About 65 million years ago, there was a dramatic change in mammalian evolution following the extinction of the dinosaurs, which opened up a world of opportunities for the shrew-like early mammals. In dank tropical forests and swamps, the mammals diversified and filled the niches left vacant, some becoming large herbivores, others ‘omnivores’, others predators (Macdonald 1992). The early carnivores, known as miacids, lived at the time between 60 and 55 million years ago. All modern members of the Order Carnivora (about 236 species) are the descendants of the miacids. About 55 million years ago these early arboreal carnivores split into two branches, the cats (Feloidea) and the dogs (Canoidea). The cat-branch dominated in the Old World and the dog-branch in the New World. The first true cat was Pseudaelurus, which evolved by 20 million years ago. They were medium-sized ambushers of small vertebrates. Among all the families of the carnivores only the members of the family Felidae (i.e. true cats) are specialised hunters and they are purely carnivorous. They are characterised by having high-domed skulls and short snouts, which provide anchorage for muscles that power a lethal bite. The cats have the sharpest carnassial teeth among all the carnivores (Macdonald 1992). They also have acute hearing, specialised paws and camouflaged coat colour to make their hunt successful. The larger cats, like the sabre-toothed cats, were originated from the medium-sized ancestors and they were common at the end of the Miocene, between five and six million years ago, when the world’s climate changed in ways that revolutionised the lives of most carnivore families. During that climatic change, a new lineage of swifter and more agile cats rose, which are known as pantherines. All today’s larger members of the cat family, including the tiger, are their descendants (Macdonald 1992). Evidence for the evolution of the tiger comes from the fossil remains, as well as from the modern molecular phylogenies. The genus Panthera probably evolved within the last five million years or so (Hemmer 1976, Collier and O’Brien 1985, Wayne et al. 1989, Kitchener 1999). Molecular phylogenies confirm the close relationship among the members of the genus Panthera and show that the tiger diverged more than two million years ago and before the divergence of the lion, leopard and jaguar (Collier and O’Brien 1985, Wayne et al. 1989, Wentzel et al. 1999). It is almost certain that the tiger originated in eastern Asia (Hemmer 1981, 1987; Herrington 1987; Mazak 1981, 1996; Kitchener 1999). The oldest fossil remains of the tiger have been discovered from northern China and Java (Hemmer 1971, 1976, 1987). Originally described as Felis palaeosinensis (Zdansky 1924), the fossil of a small tiger from Henan, northern China, is thought to date from the end of the Pliocene and the beginning of the Pleistocene and so may be up to two million years old (Hemmer 1967, 1987). Perhaps this was the ancestor of two or more Panthera cats of today, including the modern tiger (Kitchener 1999). Abundant tiger fossils have been discovered from China, Sumatra and Java, which are dated from the middle to late Pleistocene, but tiger fossils only appeared in the Indian sub-continent, the Altai, northern Russia and elsewhere in the late Pleistocene (Brandt 1871, Lydekker 1886, Tscherski 1892, Dubois 1908, Zdansky 1924, Brongersma 1935, Loukashkin 1937, Hooijer 1947; Hemmer 1971, 1976, 1987). According to Hemmer (1987) and Mazak (1996), the tiger originated in east Asia, from where two major dispersals took place about two million years ago. To the northwest, tigers migrated through woodlands and along the river systems into south-west Asia. To the south and south-west, tigers moved through continental south-east Asia, some crossing to the Indonesian islands, and others finally reaching India (Nowell and Jackson 1996). The South China tiger may be regarded as the relict population of the ‘stem’ tiger, living in the probable area of origin. Its skull morphology is the most primitive among all the living tiger sub-species (Herrington 1987). The radiation of tigers was driven by two primary factors: changes in climate and vegetation, which in turn led to the radiation of large ungulate prey species across Asia (Karanth 2001). The late arrival of the tiger in the Indian sub-continent is apparently supported by its absence in Sri Lanka, which was cut off by rising sea levels at the beginning of the Holocene (Kitchener 1999). Tigers had colonised this area either coming through north-east Asia via central Asia (Hemmer 1987, Mazak 1981), or through north-west India (Heptner and Sludskii 1992). Reply