Huge numbers of species have been disappearing from some or all of their original range in the wild. While there are other reasons for animals to disappear from areas, humans are usually the biggest. This is certainly the case on a micro scale. The majority of impacts of climate change has shifted the entire range for a species in one direction or another. Many mountainous species have shifted their range up hill as the planet has warmed. The problem with this shifting is that often it leaves species stuck in small areas of suitable habitat at the top of hills or mountains.
One example is in Tanzania where small pockets of forest exist high on hills and mountain chains, due to the higher rainfall, but these patches of rainforest do not stretch to the foot of the elevated area, so become islands in the sky. Islands have generally been hit the hardest by humans as there was not a large area for the animals to exist in, in the first place. An example of this is in Britain. In France, as the human population has fallen, and the deer population has risen, wolves have been given the space to return. An Economist article estimates the population at around 360 animals. The wolves first crossed over from Italy in the 1990s and have been growing fast ever since. Indeed the wolves are doing so well that the population growth rate has been above 10% for much of the time since they appeared.
However, for many species there is not a remaining population to recover from. One example is the UK. While if humans disappeared tomorrow, the ecosystem would settle down over time in Europe, because of the channel, it is a different matter in the UK. It of course may be possible for a wolf or a bear to cross the channel unaided, but given that the area near the channel on both sides is well populated this is highly unlikely to happen in the numbers required. In the UK we killed all of the mammals that were capable of killing deer a long time ago. However, over the last 50 years as people have started to live in cities in greater numbers, the deer population has exploded. Humans no longer hunt them for food and without any natural predators the population has grown at a terrifying rate. Added to this is the unfortunate habit of humans to introduce non native species into new places. If the ecosystem is complete, often this will not have a detrimental effect, but if predators are missing then the new animal can survive and thrive. A few years ago, travelling in Spain, we visited the Somiado national park. About 10 years ago someone had decided that the wished to introduce Fallow deer into that part of the country after all they existed quite happily in similar areas elsewhere in Europe, as such about 200 were moved. During the first winter, every single one was killed by the local wolf population.
Deer
Can you spot the deer?
In the UK many species of deer have been introduced over time. Fallow deer were brought from France by the Romans, though it is thought that this population did not survive and were reintroduced around the 11 century from Eastern Mediterranean. Up until the 15 century these deer lived in well maintained deer parks around large homes, but around this time many of these went into disrepair and the deer escaped to found the wild population we have today. Population estimates from 1995 were 100,000 in Britain with 95% of that number residing within England.
Red deer arrived naturally around 11,000 years ago from Europe. It is estimated that there are currently around 350,000 red deer in Scotland, with 50,000 to 70,000 deer culled each year. There are additional small populations spread throughout the rest of Britain.
Roe deer has been present since the neolithic period, though due to overhunting in 1700 it was extinct from the south of and centre of Wngland and all of Wales. There were intentional reintroductions over time as well as natural recolonisation, and they now occur across most of the UK.
Deer species that were not found naturally in the UK but released by humans are:
Sika deer – invaders
Sika deer originate in Asia, but most in the UK originate in Japan. There was an intentional introduction into Ireland in 1860 and most introductions since have come from descendants of this original population. Indeed it is thought that most if not all wild ranging Sika deer in UK are descended from one stag and three hinds introduced into a deer park at Enniskerry, in Ireland 1860. There are a few hybrids as red deer can breed with Sika deer.
Reeves muntjac – introduced
These animals are highly destructive damaging woodland and rare plants as well as blue bells and other woodland flowers. Being small they would likely fall quickly to predators. Human hunting has failed to slow their advance, partly as they breed year round.
Reeves Muntjac also originate in China, and were bought to Woburn park in the early 1900s. Between intentional releases and escapes, feral populations were established across Northamptonshire and Warwickshire.
Chinese Water deer – Introduced
Chinese Water deer originate in China and Korea, these were also introduced into Woburn Abbey and Whipsnade in the late 19th century. They have mostly stayed near that area as the habitat seems to suit them. Chinese Water deer were first kept at London zoo in 1873, but escaped from Whipsnade Zoo in 1929. The UK population of Chinese water deer is now thought to account for around 10% of the wild population. An estimate from 2005 put the UK population at over 2,100 animals.
Analysis on Likely predatory effect
Fallow deer and Sika deer both originate from countries which also had wolves, so the introduction of wolves is likely to have a positive effect on behaviour. It also suggests that wolves should be an effective way to manage population. Water deer are also likely to be effectively hunted by they however this species is unlikely to become a series problem anyway as its range and therefore number is restricted by habitat that suits its semi aquatic lifestyle.
Reeves muntjac are likely to be rather different. They originate from areas with very different predators and given their size are likley to be relatively easy prey for wolves. It is unlikely that they will have any significant defence of wolves (larger deer have large antlers and can run fast) and so are likley to be significantly depleted if not exterminated shortly after wolves enter the area.