ecozone and sleep in another; they may also evade observers. Plants can be immediately and directly observed and counted. However a rapid survey of animal communities has to rely partly on past experience, using vegetation as an indicator of which animals may be likely to live in or visit an area, and also on local knowledge.
People living in a locality will generally know most about the animals they hunt and/or that impede their farming activities—the 'pests'. These tend to be the vertebrates, and especially the mammals, because they are closest to humans.
Vertebrates And Mammals: when people use the term 'animal', they are often thinking only of the vertebrates rather than the whole animal kingdom. Vertebrates are animals with backbones, such as humans, elephants, grass-cutter rats, grey parrots, crocodiles, shiny-nose fish, snakes and frogs. They are most visible to us, may be most attractive or compelling to our sensibilities, and of course they are also the group to which we humans belong.
Humans are part of the class of vertebrates called mammals. Young mammals develop fully within their mother; they are born 'live' and fed with milk from her mammary glands. Elephant, grass-cutters and duikers are mammals, while grey parrots belong to the class of birds, crocodiles and snakes to the reptiles, shinynoses to the fish, and frogs to the amphibians.
However, it is important to remember that all the vertebrates together make up less than 5% of the animal species. In terms of overall bioactivity the other 95% are far more important, in particular the Arthropods which include the class of animals with the most species of all—the insects.
Arthropods And Insects: all Arthropods have jointed limbs but external, shell-like skeletons from which the internal organs hang. Insects are one group of arthropods; they have one pair of antennae, three pairs of legs and three body sections, and often also have wings. Other classes of arthropods include the Crustaceans (such as crayfish), the Arachnids (mostly spiders) and the Myriapods (such as centipedes).
The larger vertebrates, such as pangolins or parrots, may appear to be most significant because they appeal to sentiment or aesthetics. However the extinction of an as-yet unnamed insect may be of greater impact; every animal plays a role in its ecosystem, and any species loss will have an effect.
However, while the large animals should not monopolise our attention, their condition is an indicator of the overall health of an ecosystem. Their reduction may be the first obvious warning that something is wrong. Hunting pressure may often be the reason for a crash in numbers, but the prime reason is habitat degradation or loss; this is why effective and sustainable conservation efforts cannot be targeted at single species in isolation.
4.8 THE NATURAL ECOSYSTEM
In answering this Chapter's question 'What is the Niger Delta?', we are defining the natural ecosystem of the Niger Delta as a series of ecozones and sub-ecozones, within the Biome that is the West and Central African Tropical Rainforest.
