‘Habitat and Population’ examines the relationship between living organisms and their environment. Using the design of suitable habitats at Chester Zoo as a starting point we consider the important physical factors which need to be controlled if animals or plants are to thrive. The design of a new jaguar house must include suitable water, land and vegetation in an area big enough to meet the needs of these impressive animals.

Keeping animals in captivity is a controversial issue. We find out how a zoo can protect breeding populations of endangered animals. Animals are bred for release into the wild.

In some cases populations can grow out of control. Japanese knotweed has invaded the UK after being brought back to this country by a plant collector. We find out how moths, insects and fungi keep the population under control in Japan. Without these natural predators in the UK the plant has become a pest.

Too many predators can also be a problem. American mink have escaped from farms into the countryside. The mink have dramatically reduced the number of other species such as the water vole. Voles are also threatened by the dredging of rivers and the use of riverbanks for farming. We find out how the Environment Agency is keeping an eye on the voles by inserting microchips under their skin.

The plight of the red squirrel is well known. The American grey squirrel is bigger, more aggressive and can eat a wider range of food. The red squirrel is also susceptible to a disease called parapox, which is carried by the grey squirrel. Because of this, the number of red squirrels in most of the country has declined. We see how scientists working with the Forestry Commission monitor the populations of red and grey squirrels in Thetford, East Anglia. Perhaps the only hope for the red squirrel is a parapox vaccine.

Time-coded programme outline
00.00-03.25 How can a jaguar’s habitat be recreated?
At Chester Zoo, designers are creating a new enclosure for jaguars. The temperature will be a warm 30^oC and there will be a 2m deep swimming pool. The fence has to be 5m high and it goes 1m under the ground to stop the jaguars digging their way out. At the recently completed Komodo dragon enclosure the temperature is similar. These giant lizards need large sunny rocks to bask on in the morning. A lot of research has to be done to design a suitable habitat for these animals.

03.25-06.26 How can a zoo save a population of bats?
In the Twilight Zone at Chester Zoo, fruit bats from Mauritius enjoy a carefully constructed environment. These bats are an endangered species and the aim of keeping them at Chester is to build up a breeding colony that could provide bats for release into the wild. The atmosphere in the enclosure is very humid to prevent the skin of the bats from drying out. The lighting is controlled to provide 12 hours of daylight and 12 hours of night. Bats won’t eat and sleep in the same tree so special perching and feeding areas have been created.

06.26-09.53 What happens when a plant has no predators?
In a churchyard in Swansea an alien invader is taking over! Japanese knotweed was introduced in Victorian times. The plant has a perfect appearance because British pests won’t eat it. For the same reason it has become an environmental nuisance, taking over empty land and even invading houses. In Japan, it is eaten by people and a range of pests. In the absence of these pests it grows very quickly.

09.53-14.34 Can the water vole be saved?
Some creatures are less fortunate than Japanese knotweed. A small group of water voles has been captured on the banks of the River Don. They will be kept at Blackpool Zoo whilst flood defence work is completed. The number of water voles has fallen dramatically because of predation by American mink. It has become more difficult for voles to find nest sites because of dredging of rivers, and grazing and cultivation right up to the river’s edge. Ecologists from the Environment Agency check the animals’ health and insert a microchip under their skin. They will be able to keep an eye on the voles’ welfare once they are released into the environment.
We see the water voles released into a riverside cage where they will be left to get used to their surroundings. The cage will keep them safe from predators but allow them to burrow into the bank and establish nests.

14.34-18.32 Why are there more grey squirrels than red?
The red squirrel has declined in numbers by 75% over the past thirty years. In the Thetford Forest, the Forestry Commission are monitoring their numbers. Janie Steele explains how the grey squirrel competes with the red squirrel for food supplies and how it has brought with it the deadly parapox virus. Janie uses a number of techniques to monitor the squirrel population. Bait encourages squirrels to enter through a pipe where sticky tape picks up hairs, which indicate the species. A more sophisticated technique is to trap squirrels and attach a radio collar. Janie can then track these animals using an antenna.

8.32-End What about the future?
Across the world, 11,000 species of plants and animals are facing a high risk of extinction. The most common reason for this is the destruction of habitats. How can we prevent more species from becoming extinct in future?