This double pair of upper teeth are only found in rabbits and hares, and they cause a distinctive degree angle cut on browsed vegetation. Male rabbits are known as 'bucks', female rabbits are called 'does' and young rabbits are 'kittens'. A rabbit's fur colour is typically grey-brown with a pale belly. Black or ginger rabbits do occur in the wild, though they represent less than 2 per cent of the rabbit population and white rabbits are rarely seen.
Adult rabbits usually weigh between 0. Juvenile rabbits moult at 3 months of age and frequently have a white star on their forehead, which they lose when they moult. Rabbits are mostly active from dusk until dawn. Rabbits often stay above ground during the night unless they are disturbed.
Rabbits are wary of new food items and changes to their environment. When threatened, they will crouch down and freeze or try to sneak away. If this fails, they will sprint for the warren or cover, with the white underside of the tail showing as a visual warning to other rabbits.
When close to cover, rabbits will respond to threats by thumping the ground with their back legs and vocalising to warn other rabbits. Rabbits form social groups with complicated social structures. Dominant males will typically defend a territory to gain mating rights to females, while dominant females will defend access to nesting sites. At large warrens or where populations are dense, different social groups may share a common warren or feeding area.
Rabbits require a high-quality diet to maintain condition and for reproduction. As such, they are highly selective grazers, with a preference for plants or parts of plants with the highest nutritional content. Rabbits generally obtain water from green vegetation but will travel to drink if they can't obtain enough water from their diet.
Like hares, caecotrophy the re-ingestion of faecal material from the caecum is a behaviour that is used by rabbits to gain the maximum amount of nutrients from their food. Soils have a strong influence on rabbit density with deep, well-drained soils sands and light loams being most productive. Rabbit warrens are also typically larger and more complex in deeper soils. Rabbits form extensive burrows or warrens for shelter. The warren is the key to the success of rabbits in Australia.
It not only provides protection from predators but also protection from environmental extremes. Without protection from the elements, rabbits are not able to breed successfully, as newborns are very susceptible to temperature extremes.
Rabbits can exist above ground where surface harbour is present. Fallen timber and logs, rocks, dense thickets of native scrub and woody weeds along with heaps of debris are ideal shelter. Rabbits may also become a problem around houses, farm buildings and other structures such as water tanks as human activity does not deter them. Important external parasites on rabbits in Australia include the introduced European and Spanish rabbit fleas, which are important vectors in the spread of myxomatosis.
There are also two types of diseases in Australia that are deadly to rabbits, including Myxoma virus MV and rabbit haemorrhagic disease virus RHDV formerly known as calicivirus.
Variable virulence and increased genetic resistance has lessened their effectiveness on rabbits over time. Therefore, efforts are being made to identify more virulent strains of RHDV and other viruses. Rabbits have extremely high reproductive rate. A single pair of rabbits can increase to individuals within 18 months. That said, rabbits do require protein-rich, fresh growth to successfully reproduce. Therefore, they can breed year-round in good conditions, although most breeding in Victoria commences at the autumn break and continues until vegetation dries off by early summer.
Rabbits become sexually mature at 3 to 4 months. Their gestation period is 28 to 30 days and they have litters between 4 and 6 kittens. Kittens are born blind, deaf and almost naked in either short nesting burrows or above-ground nests. Mating can recur immediately after giving birth. Rabbits have high rates of dispersal that are generally broken into two dispersal events. Most rabbits disperse short distances to join adjacent social groups.
However, movements of up to 20 km have been recorded. During dispersal, rabbits are vulnerable to many hazards such as predation and environmental extremes. Despite common opinion, rabbits do not readily dig new warrens and instead prefer to find an unused warren to excavate. In , this virus escaped a quarantine facility and made its way to the wild. After its official release to control the population in , RHDV lowered rabbit numbers in Australia by up to 90 percent in especially dry areas.
Because flies serve as the viral vector , the disease does not affect European rabbits that live in Australian regions that are cooler and receive high amounts of rainfall. As with the myxoma virus, these rabbits have begun to develop resistance to RHDV. Viruses were not the only population-control measure used on European rabbits; poison proved to be another popular method. One of the main chemicals used to poison rabbits is sodium fluoroacetate, which has a very high mortality rate—more than 90 percent.
Carbon monoxide and phosphine are also used to fumigate burrows and kill any rabbits living inside. Currently, researchers are studying more deadly strains of RHDV that may be even more effective at preventing the rabbits from overwhelming the Australian environment. Since the European rabbits are an invasive species , and are extremely disruptive to the local environment, finding a solution to rein in and control their populations is imperative. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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You cannot download interactives. A limiting factor is anything that constrains a population's size and slows or stops it from growing. Some examples of limiting factors are biotic, like food, mates, and competition with other organisms for resources.
Others are abiotic, like space, temperature, altitude, and amount of sunlight available in an environment. Limiting factors are usually expressed as a lack of a particular resource. For example, if there are not enough prey animals in a forest to feed a large population of predators, then food becomes a limiting factor.
Likewise, if there is not enough space in a pond for a large number of fish, then space becomes a limiting factor. They cause considerable damage to the natural environment and to primary production. Rabbits were introduced to Australia in the s by European settlers. Free from diseases and facing relatively few predators in a modified environment, the wild populations grew rapidly.
They soon became a problem for colonists trying to establish vegetable gardens and, after the s, quickly spread across two thirds of Australia with devastating impact. Plagues of rabbits had a huge impact on the land and industries grew from rabbit shooting.
They were introduced for food and wild rabbits were later brought in for hunting. A colony of feral rabbits was reported in Tasmania in and wild European rabbits were released in Victoria in , and in South Australia shortly after. By they were found throughout that Victoria and New South Wales — even extending to the Northern Territory by the s.
By feral rabbits were found throughout most of their current range. By it is thought there were 10 billion rabbits in Australia.
The population is currently estimated to be million. Molecular analysis of current populations reveals a patchwork of varying genetics in rabbits with six main regional groupings across the country, further supporting a history of multiple introductions, followed by regional dispersal Iannella et. European rabbits are native to southwest Europe and northwest Africa — and have been introduced to every continent on earth except for Antarctica and sub-Saharan Africa. They often cause environmental harm in their new homelands, and their impact has been very pronounced in Australia where seasons permit year-round breeding and there are fewer natural predators.
For more information on invasive rabbits, their impacts in Australia, and research to control them, refer to ' Those Wild Rabbits ' by Bruce Munday.
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