Carnivore

From Palaeos.org

A carnivore (meaning 'meat eater' (Latin carne meaning 'flesh' and vorare meaning 'to devour'), is an animal that eats a diet consisting mainly of meat, whether it comes from live animals or dead ones (scavenging).

Carnivores include both vertebrates and invertebrates. Among the latter are predatory Arthropoda such as spiders or mantids that may rarely consume small vertebrate prey).

The word also refers to the mammals of the Order Carnivora, many (but not all) of which fit the first definition. Bears are an example of members of Carnivora that are not true carnivores. Carnivores that eat insects primarily or exclusively are called insectivores, while those that eat fish primarily or exclusively are called piscivores.

There are also several species of carnivorous plants, which are for the most part insectivores that capture mostly insects in order to supply nitrogen, as carnivorous plants all live in nitrogen-poor environments (ie, bogs).

Evolutionary history

It is likely that for most of the Archean and Proterozoic, heterotrophs were decomposers and, with the rise of the Eukarya (Protista), bacteriovores and suspension feeders. Carnivory requires the emergence of specialised unicellular Eukarya (e.g. Didinium which feeds on other ciliates like Paramecium) and eventually, multicelluar organisms. The rise of the Metazoa during the Vendian certainly meant the appearance of large (relative to what had gone before) carnivores, since even the most primitive Cnidaria are predatores and microcarnivores.

During the Cambrian, along with more modest sized predators there appeared the first superpredators, the Anomalocarids, which reached 60 cm to as much as two meters on length.

An important Carnivorous clade, the Cephalopoda, appear during the late Cambrian and become important during the Ordovician.

Marginal marine environments of the late Silurian and early Devonian were inhabited by Eurypterida - the "sea scorpions" which reached one to two meters in length and were the largest arthropods ever to live.

Meanwhile Vertebrates like the arthrodire placoderms and the Chondrichthyes (sharks) were important carnivores during the middle and late Devonian.

In freshwater and on land during Carboniferous times, there was a rich diversity of carnivorous sarcopterygians and tetrapods, with large insects (Protodonata), scorpions, spiders, and amphibious eurpteryids filling the msall to medium-sized carnivore role. In fact, until the middle or late Permian, all terrestrial ecosystems were predominated by detritivores or carnivores; herbivores were relatively unimportant until the emergence of Palaeodictyoidea in the Carboniferous, and anomodonts in the Permian.

From the Mesozoic, carnivores had similar ecological roles to today. Terrestrial ecosystems were represented first by a variety of early archosaurs (of the thecodont grade) by mostly carnivores (including obligate carnivores) theropod dinosaurs, which preyed upon the sauropod and ornithischian herbivorous dinosaurs.

In the seas large marine reptiles such as ichthyosaurs, pliosaurs, and later mososaurs, were at the top of the food chain. Among invertebrates, carnivorous Caenogastropoda triggered a Mesozoic arms race.

The Cenozoic saw various types of early carnivorous mammals (originally grouped under the paraphyletic Creodonta) and giant birds on land, and early toothed whales in the sea. By the Neogene, ecosystems were similar to those of today, with most large mammalian carnivores represented by the order Carnivora.

Characteristics of carnivores

Characteristics commonly 'associated' with carnivores include organs for capturing and disarticulating prey (teeth and claws serve these functions in many vertebrates) and status as a hunter. In truth, these assumptions are misleading, as many carnivores do not hunt and are scavengers. Thus they do not have the characteristics associated with hunting carnivores.

Types of carnivores

Carnivores can be classified according to what sort of prey they prefer. These include:

• Traditional carnivore - feed on other tetrapods (e.g. lion)
• Piscivore - feeds on fish (e.g. gavial)
• Insectivore - eats insects or other terrestrial arthropods (e.g. shrew, gecko, sparrow etc()
• Molluscivore - feeds on mollusks (e.g. walrus)

And so on.

Animals that subsist on a diet consisting only of meat are referred to as obligate carnivores or hypercarnivores.

Obligate carnivores

An obligate or true carnivore is an animal that subsists on a diet consisting only of meat. True carnivores lack the physiology required for the efficient digestion of vegetable matter and, in fact, some carnivorous mammals eat vegetation specifically as an emetic (for example, when the family cat eats grass when its stomach is upset).

Credits

This page MAK061101; Evolutionary history MAK061102