ANIMAL ECOLOGY

Since animals are generally free to move about, their association with definite habitats is not at first sight so obvious as in the case of plants. Nevertheless, while studying various plant associations, contact with animal life will inevitably occur. Associated, for example, with a coppice or small wood are the various birds which build their nests in its shelter, blackbirds, thrushes, robins, wrens and hedge sparrows, while the vegetation provides food and shelter for innumerable insect larvae, snails and slugs on which the birds feed. Various small mammals, e.g. field mice, weasels, stoats and even rabbits, may be found burrowing into the relatively dry soil among the tree roots, while hedgehogs hibernate beneath the piles of dead leaves which accumulate beneath the bushes. Wolf spiders and spinners are also generally abundant, the former hunting among the dead leaves for their prey and the latter spreading their webs among the branches of the bushes.

Animals are linked to the plants which provide their food, and in any one habitat food chains occur. For example, in a birch-oak wood association will be found various insect larva? feeding on the foliage of the trees, e.g. tortrix moth caterpillars ; on these in turn feed the small insectivorous birds, e.g. warblers and tits ; while on these feed the carnivorous birds, the hawks and the owls. Some insect larva? are found feeding on certain particular food plants, e.g. cinnabar moth caterpillars on the ragwort, and hence occur only where these plants are found.

Two closed associations of animals, I.e. limited habitats sharply marked off and not forming part of more general societies, are found in a fresh-water pond and in a rock pool on the seashore. Both of these repay study by the number of interesting types of animals found inhabiting these small ’worlds. ’

The Fauna of a Fresh-water Pond

The following typical examples occur :—

Protozoa

Amoeba species in the mud ; Vorticella and a similar colonial form known as Carchesium, both found clinging to water weeds and the hanging roots of duck-weed; various other free-swimming ciliates such as Paramecium and similar species, e.g. Stylonychia.

Cceletiterates

Hydra, both green and brown, clinging to the stems of water weeds.

Annelids

Leeches.

Arthropods

Minute water ’fleas, ’ e.g. Daphnia and Cyclops, on which Hydra and fish feed. Many aquatic insects and their larvae, e.g. water scorpion, water boatman, water beetles, dragon-fly, gnat, mosquito and caddis fly larva?, water skaters and whirligig beetles.

Molluscs

Pond snails of various forms, e.g. ram ’s horn and ‘winkle ’types. Occasionally fresh-water mussels.

Fish

Minnows, sticklebacks and, in large ponds, eels, roach, pike, carp and char.

Amphibia

Newts and their larva? and, in spring and summer, frog tadpoles and adult frogs.

Aves

Moorhens and sedge warblers.

Mammals

Voles with their burrows in the banks.

The Fauna of a Rock Pool

Typical examples are :—

Ceel enter ates

Sea anemones, e.g. the beadlet anemone and colonial forms allied to Hydra, e.g. Sertularia found on the surface of seaweeds such as Fucus.

Polyzoa

Seamats, common on surface of Fucus.

Annelids

Paddle worms, tube worms, comb worms and lug worms.

Arthropods

Crabs, hermit crabs, shrimps and prawns.

Molluscs

Mussels, whelks, periwinkles and limpets.

Echinoderms

Starfish and sea urchins.

Fish

Small fish such as sucker fish and gobies.

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