Breeding like rabbits - the true story
Although there a number of animal species that share the common name rabbit, the species under discussion here is the European rabbit and the word rabbit is referring only to the European rabbit. Its scientific name is a bit of a mouthful - Oryctolagus cuniculus.
The Misplaced
European rabbits are terrestrial herbivorous mammals.They originated in the Spain/Portugal area.
Appearance
Mass: 1.5 to 2.5 kg
Length: 38 to 50 cm
Fur colour: The coat is generally grayish/ brown with some reddish colouration , paler underneath. (Domesticated rabbits exhibit many variations in coat colour)
Special adaptations:
- long erect ears for hearing potential threats
- robust jaw and incisors for dealing with grass diet
- front legs modified for digging
- hind legs adapted for running, jumping and kicking
Breeding
Breeding rate: Under ideal conditions, breeding may occur approximately monthly, so that they can produce 18-30 young per female adult per year. This is dependent on food availability.
Breeding season: These animals breed throughout the year in some locations. In others, factors like temperature may impose restrictions.
Average number of offspring per litter: 6.
Average gestation period: 30 days.
Average weaning age: 28 days. Young are born without hair and with their eyes closed.
Average time to independence: 4 weeks.
Average age at sexual or reproductive maturity (female): 8 months.
Average age at sexual or reproductive maturity (male): 8 months
Baby rabbits are referred to as kits, or sometimes kittens.
Ecology
Habitat
Features of the ideal rabbit habitat
- an annual rainfall of <1000mm; in wetter areas, rabbits favour dunelands, dry stony riverbeds, limestone hills with outcropping rocks, and sunny coastal slopes
- light soils
- adequate cover close to feeding grounds
Rabbits dig burrows for protection from predators and particularly as a safe space to raise their kits. These burrows are often grouped into warrens as rabbits are social animals who form groups.
Diet
Rabbits eat grass and other herbaceous vegetation. They need a diet of less than 40% fibre, 10-20% protein for maintenance, and another 14% protein for reproduction. They will eat tree bark if other food is not available.
The European rabbit produces soft, mucus-covered poop pellets, which are eaten directly from its own anus. These pellets are filled with protein-rich bacteria. The rabbit swallows them whole, without breaking up the enveloping membrane. This enables the rabbit to extract maximum value from its diet.
Predators
Oryctolagus cuniculus is eaten by
- foxes
- badgers
- wolves
- lynxes
- bobcats
- wolverines
- stoats, ferrets, polecats and weasels
- rats
- feral cats and dogs
- birds of prey such as eagles and owls
- snakes
Some predators may hunt adult specimens and some burrow into rabbit warrens to eat the defenceless kits.
The Displaced
- Rabbits disrupt ecosystems that they invade by competition for food resources and space. Their ability to breed in high numbers means they must increase their range, thus multiplying their impact.
- They also change landscapes through digging warrens which often leads to erosion.
- They also impact on native plants by ringbarking, grazing and browsing, and preventing regeneration of seedlings.
- They also carry heavy pest/parasite loads which can damage native animals.
The Consequences
Where is the invasion?
Rabbits are recorded as having been introduced in 80 countries/islands.
Case study - Australia
In Australia, European rabbits are a major environmental pest species, impacting more than 300 threatened species (260 plant and 44 animal species) listed on the Environment Protection and Biodiversity Conservation Act (Commonwealth of Australia, 2016).
https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.14525
Thomas Austin introduced wild rabbits to his property in Geelong, Victoria, for hunting in 1859. By 1886, rabbits had spread north to New South Wales and Queensland. They were in Western Australia and the Northern Territory by 1900. The construction of a 1700 km rabbit-proof fence in Western Australia failed to stop the spread of rabbits and they are now found across the continent, and on several offshore islands.
Map source: https://pestsmart.org.au/toolkit-resource/rabbit-biology-ecology-and-distribution
This video made by the Australian Broadcasting Commission explains the history of the rabbit invasion in Australia.
Eradication strategies
Chemical control -Poisoning by baiting/fumigation
1080 is the common name give to a chemical used to poison rabbits and other pest species. It was chosen because it was thought to be less harmful to native animals than other poisons used in the past e.g. strychnine. Animal welfare groups maintain it s a cruel method of killing; it is now restricted in use in Australia and training must be undertaken before baiting with 1080. Pindone is another chemical used for poisoning rabbits in Australia.
Another method of control is trapping rabbits in their warrens, sealing the entrances so they cannot escape, then placing pellets into the burrows which release the poisonous gas phosphine. Once again training and licencing are mandatory for use of this substance.
Physical control - Ripping, Trapping and Snaring
Ripping out warren using machinery is another technique to eradicate rabbits.
Another is placing nets over all burrow exits and then releasing ferrets into the warren to chase the rabbits to the surface, where they are captured and killed.
Rabbit control occasionally involves individual trapping as well, although this is only effective in a few situations.
Biocontrol
The myxoma virus causes myxomatosis which is a generalised viral disease that kills European rabbits. Spread by biting insects, myxomatosis ultimately compromises the rabbit’s immune system leading to respiratory infections that often lead to death. The myxoma virus was trialled as a rabbit biocontrol option by the CSIRO in the late 1930s and 1940s, and was released into the feral rabbit population in the 1950s. Within months of its release, myxoma virus had knocked over 90 per cent of some rabbit populations in Australia. However, as with most viruses, it became less effective over time due to rabbits developing genetic resistance. Today myxoma virus affects an estimated 40 to 50 per cent of the rabbit population and it is no-longer being released to manage wild rabbits.
A newer biological control effort in the 1990s was based on the viral disease RHD which stands for Rabbit Haemorrhagic Disease. Several waves of different versions of the virus have occurred; as with the myxoma virus, initial kill rate was promising but over time, rabbits have developed resistance to the virus.
Rabbit numbers are on the rise again in the 2020s and efforts at rabbit control/eradication continue. In May, 2024, the Centre for Invasive Species Solutions announced:
Given that rabbits and viral biocontrol agents are in an ‘arms race’, a pipeline of biocontrol agents needs to be developed and ideally released every 10 to 15 years, to keep rabbit impacts in check,” said Andreas Glanznig, the Centre’s Chief Executive.
“Without this strategic national R&D approach to deliver new biocontrol agents, Australia runs the risk of being exposed to growing rabbit impacts, which already cost Australian agriculture over $200m a year and impacts 322 nationally listed threatened species.
The European rabbit is the only member of the rabbit family to have been totally domesticated and there are now over 300 varieties bred as pets and for meat.