Succession, creating the perfect habitat for wild deer

With Neal Finch

Any experienced deer hunter will tell you that farm fringe country can be very productive areas to find wild deer in Australia. There is a good reason for this and some basic ecological principles can help explain why. All of the six species of wild deer present in Australia graze (eat grasses) and browse (eat shrubs and herbage) to varying degrees. The extent to which any of these species graze compared to browse depends on the season and what plant species available. The proportions will change throughout the year and from place to place. All wild deer in Australia would be classified as dietary generalists due to the ability to change their diet according to what is available.

As wild deer are not constrained by fences they will move to wherever the most preferable food is within their home range (so long as they feel safe or confident of their ability to avoid danger). What they are seeking is the most nutritious food available, be it grass or browse, usually a combination of both. Unlike horses or cattle, deer have relatively narrow jaws and can be very selective in the plant matter they choose. A particular plant may have unpalatable mature leaves but the new growth, flowers, fruits or seed pods could be quite palatable and nutritious. Wild deer are very good at finding this food and exploiting the very best a habitat has to offer.

Succession is a term that explains the change in species that occur through time after a new habitat has been created. An extreme example of succession would be the colonisation of living organisms on a newly formed volcanic island. Because there are no existing biological organisms present this kind of succession is known as primary. Other examples of primary succession would include plants colonising a newly formed sand dune or even the side of a building. My farm ute hasn’t been cleaned in 15 years and has developed several pockets of soil that now sprout when there is sufficient moisture about. The natural process of primary succession would eventually reclaim the ute as a habitat if it were left parked long enough!

Farms aren’t really examples of primary succession although sometimes the creation of new farm land from forest or woodland can be quite extreme. Where there are existing biological processes occurring, such as soil microbes breaking down organic matter, succession occurs and is referred to as secondary. When trees and shrubs are cleared and burnt to make way for pasture or crops then the new landform created will be radically different. However in the absence of further input from a farmer the land will slowly revert back to the original habitat. The first species to colonise the cleared ground are called pioneer species and in a relatively short time these species will create an early successional community. As they mature they change the habitat making it viable for the next stage of successional species to establish. Eventually the species present will be the same as any uncleared country nearby although the size of individual plants and overall structure may be different for a long time. The principal of succession explains the changing community of species that are found on farm fringes.

Forest clearings after logging create early successional communities and can be as desirable to wild deer as farm fringes for the same reasons. The significant changes that occur after intense wildfires can create successional communities over very large areas. For years after these events the habitat becomes ideal for wild deer that thrive on the early successional plant species. These plant communities have several characteristics that make them very productive and therefore attractive to herbivores. Features of plants in these habitats include fast growth, short life cycles and rapid seed dispersal through several means (wind, water, insects, birds and mammals). One of the features of a typical early successional plant is seeds presented in an edible fruit. Blackberries are a classic example. These plant species are also growing at a height below two metres tall. This means that all the available sunlight, water and soil nutrients being converted to new plant matter is right there at mouth height and available to a hungry deer. It is worth noting that many of the food crops grown by humans fit the description of early successional plant species.

One of the defining attributes of succession is the directional pattern of change. The habitat will be constantly changing as the succession process occurs until eventually a stable community is reached. Many older texts and websites will refer to a ‘climax community’ as the end result of succession. This suggests that succession has an end point which is not correct and few ecologists in Australia would use the term today. More appropriate is to think of a mature plant community in a stable state. A stable habitat will alter little from year to year particularly in environments with relatively uniform rainfall and temperature patterns. A characteristic of a stable habitat is resilience to change. Unlike a successional community which is always changing into something new a stable habitat is by definition not undergoing significant change. Many such habitats exist throughout Australia where the community of species we see today is essentially the same as what was present hundreds of years ago. New introduced species may have joined the community and some species may no longer be present but the overall structure and composition is pretty much the same.

Stable habitats will change eventually; this is a certainty. No existing environment has always been present and none will remain forever. Stable habitats are part of a cycle and within any plant community there will be the opportunity for succession to occur, on either a small or large scale, depending on what external forces come to bear. Wild deer will find and use successional habitats within their home range. This could be a farm fringe, recently burnt country or even an area within a forest where a large tree has fallen. What makes farm fringes such reliable hunting areas is the maintenance of early successional plant communities by the landowner. Where this doesn’t occur the country will eventually cease to be a farm fringe.

In the eastern United States today many of the farms abandoned in the early twentieth century are now becoming stable habitats, not successional plant communities. This process has been identified as detrimental to many wildlife species that the current human population consider desirable. Natural resource managers in these states are taking proactive steps to maintain early successional communities as they are deemed of worth to human interests. In Australia this process is occurring as part of land management, but not with the intent to maintain successional communities.

Wild deer really don’t care why these habitats are created but they will certainly utilise them wherever possible.