Deciduous and mixed woodland
The deciduous woodlands of the Palaearctic realm are found mostly north of the mountains at the western end of the continent, where the continent narrows and few places are far from the sea. It is a region of high rainfall and temperate climate. There are four marked seasons: dormant winter; spring in which leaves and flowers appear; summer with the most vigorous growth; and autumn, which is a time of fruiting just before the trees lose their leaves for winter. The predominant trees are oaks, ashes and beech, below which is usually an understorey of smaller trees and a thick undergrowth. A typical animal of this environment is the bricket, a small browsing hadrosaur, not dissimilar from its Cretaceous ancestors. In the Cretaceous period there were only the non-crested hadrosaurs living in this corner of the continent, but later the crested forms migrated here from further east - part of the great spread of the hadrosaurs over the northern continents. The bricket lives in small herds in the dense undergrowth and bramble thickets, usually resting during the day and feeding at dusk and at dawn. The expanded crest, found in both males and females, is both used as a display structure, particularly during the autumnal mating season, and as a deflecting device when it must move swiftly through the vegetation.
The long flat tail of the bricket is used both as a prop (a), when browsing from high branches, and as a warning flag (b) at times of danger. Stuck straight up in the air its bright colours warn the rest of the herd of approaching predators.
The brickets streamlined shape is ideal for fast movement through the tangles and thickets of the temperate woodlands. The shape of the crest (c) parts the vegetation as the animal runs, and the slim body allows it to pass between close-growing trees. The brownish colour camouflages the animal when motionless, but when it breaks cover and runs it can do so quickly, vanishing at speed into the depths of the forest.Ticks, fleas and other parasites are easily picked up by thicket-living animals. The bricket has a cleansing ritual that deals with this. A bricket suffering badly from parasites seeks out a piece of fur or a mat of hair that has been lost by another animal on the bramble thorns. Then, holding the fur in its beak (1), it walks backwards into a river (2), very slowly, until it is totally submerged, but for its snout. The parasites move up the body, the neck and the head, and are eventually all stranded in the piece of fur. The bricket then abandons the fur and its passengers to the current (3). There usually follows a period of playful high spirits in the water as several newly cleansed brickets frolic with one another. Mating usually takes place at this time. Further downstream the fur is seized by hungry zwims that feast on the parasites (4).
Deciduous and mixed woodland
In outward appearance many of the mammals have changed little since they evolved from the mammal-like reptiles in Triassic times. Throughout the Jurassic, Cretaceous and Tertiary periods they have remained small, compact creatures, not adapting into any of the wide ranges of life styles occupied by the great reptiles. However, some of them have a number of interesting specializations. The zwim is an aquatic, insect-eating mammal. It inhabits the streams and rivers of the Palaearctic realm and is particularly common in regions of deciduous forest. It has a length of about 30 centimetres (1 ft), most of which is taken up by a long flattened tail. The tail, and the long webbed hind feet, allow the animal complete freedom in the water. Its long sensitive snout is used for probing under stones and in dead vegetation for the insects and other invertebrates on which it feeds, both at the bottom of the stream and on land. It lives in burrows on the river banks and can defend itself against predatory reptiles and fish by biting with its sharp teeth. The saliva is venomous and any bite is quickly effective. The zwim is a social animal and as many as a dozen burrows can be found within a short distance from one another on heavily wooded river banks. Large numbers may congregate at the wallowing-pools of the bricket in order to feast on the parasites that are shed there.
The zwim is an active swimmer, thanks to its webbed hind feet and its flattened tail that works with a strong up and down undulation. The eye is large and it can adjust its focus to see both underwater and on land.