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Social Spacing:
The social spacing of the European rabbit is a reflection of their ability to reproduce rapidly (NA, 2003). Rabbits tend to live in a warren with two to ten other rabbits staying in smaller groups to ensure greater breeding success (Daly, 1981). Territoriality and aggression are seen as major contributing factors to the maturation process of the European rabbit. These two processes are innate within a rabbit and help ensure survival of the population (Dudzinski, 1977).
Territories:
During maturation, males and females become better at fighting off predators and protecting their territory (Dudzinski, 1977). Females are more territorial than males, but the area most frequented by a female is never defended (Vastrade, 1987). The size of a rabbits’ gland, which is their territory marking mechanism, changes with age, social status, gender, season and sexual activity of the animal (Sneddon, 1991).
The European rabbit marks their territory with dung hills or patrols the area during the breeding season (Mykytowycz and Dudzinski, 1972). The European rabbits' prime mode of intra-specific communication is olfactory since they are nocturnal and live underground. Having said this, the European rabbit marks his or her territory through the odor from their submandibular (chin) gland, urine and anal gland. The European rabbit marks their territory by expelling soft, mucus-covered pellets which are reingested and larger pellets that are covered with secretion from the anal gland (Sneddon, 1991). The more potent the pellets, the more efficient the rabbit is at keeping strangers at bay.
The European rabbit visits these latrine sites they create as a defense mechanism. Males, either dominant or subordinate, visit the latrine sites more frequently than females. Females spend more time grooming and resting than males which is the reason that they do not visit the latrine sites as often. Since a male’s main duty is to guard the territory, they visit the latrine sites more often (Sneddon, 1991).
Marking the territory is extremely crucial for the rabbit because if the breeding territory is not clearly marked, out breeding can occur. Group territories do not usually overlap or become separated, but will occur during breeding season with a failure to mark a territory (Daly, 1981). However, European rabbits can have overlapping home ranges with size differences between males and females. Males have overlapping home ranges that tend to be about .54 acres, while the females’ average home range is.39 acres (Vastrade, 1987). Identification of a dominant female’s home range is easier to locate in an enclosed environment due to proximity versus a more spread out area like in rabbit populations in the sandhills. Daly did a study with the sandhill population of European rabbits which found that older females were seen outside the warren more frequently than the male population (Daly, 1981). Hence, this might be the reason that females have smaller home ranges.
During breeding, heightened defense of the territory is seen. The warren members isolate a separate part of the warren for the care of the young. Usually, the entrance of the nest is guarded by the female through urine or faecal droppings intended to detract others from invading her breeding site within the warren (Mykytowycz and Dudzinski, 1972). Once the young are born, they remain in the isolated region for 14-18 days during the time they learn their mother’s smell and secretion markings. Once they are old enough to leave the guarded area, they stay in the core area of the territory for better defense from other rabbits. If the warren is extremely populated, different results may ensue. Mykytowycz and Dudzinski have found that offspring born into highly stressful populations are not only behaviorally, but physiologically different from those not born in dense populations (Mykytowycz and Dudzinski, 1972).
The dispersal of a young rabbit from their area of birth has an effect on the European rabbit's territory, aggression and reproductive success of a female (Kunkele, 1996). Natal disperal is defined as the movement of the young from his or her place of birth. There are many factors that affect whether or not a European rabbit will leave his or her place of birth such as inter-specific competition, inbreeding or other environmental factors. Males will compete with other males for the competition of a female to mate with them. The female mainly cares about the resources her young will have and does not try to attract males. The natal dispersal plays a role in how competitive a rabbit is because those that are too young or subdominant will be forced to find a new territory where they will be able to reproduce. Inbreeding is one of the main reasons that a mammal will depart from the natal group since this tends to decrease the fitness of the individual. In the studies done by Kunkele and Von Holst, however, they found that females will look for males with a low degree of relatedness because they want a high ranking male with good quality genes and inbredding does not inhance the reproductive success (Kunkele, 1996).
Positive and negative aspects of natal dispersal exist within the European rabbit. On the one hand, they have the opportunity to find and new territory that has the potential to possess higher quality resouces and mates. Also, if the rabbit is in a low density area, a female may choose to disperse for a chance of gaining a higher rank in the new territory. A male may choose to disperse if the female decides she wants to limit inbreeding. This decreases the males ability to mate with different rabbit and he may opt to disperse and find a new territory in hopes of reproducing more (Kunkele, 1996).
Nevertheless, the choice to leave to natal unit could prove extremely costly if there are factors such as high predation, starvation and no availability to mates. Thus, rabbits do not leave their natal units due to aggression and are not kicked out of the unit, but simply choose to leave. The largest role that will determine this is age, sex, fitness ability, amount of predation, and environmental conditions (Kunkele, 1996).
Kundele and Von Holst observed that when the young leave the burrow, they either move into pre-existing territories, established territories that are unoccupied or they become non-territorial roaming animals. Overall, they found that 88% (born in 1988) and 65% (born in 1989) of the offspring that lived through their first reproductive season left their natal group. There is a difference between male and female dispersal with males moving farther away from where they were born and females moving into a neighboring territory. Female dispersal rates were lower than males. In this study, Kunkele and Von Holst also found that there were not any dispersal differences for females due to body mass and an increase in mortality was not seen in the winter or in high density areas. Interestingly enough, those females that remain in their natal territory produced more offspring than those that left during their first reproductive season. One reason this might be seen is because females invest more time and energy into building a place for their young. They have special breeding burrows, gather nest material and defend the area. Since they invest more into the breeding burrow, they are less likely to abandon this territory to search for a new area. The natal site is usually the ideal location for a rabbit to have the most resources for their offspring. Therefore, Kunkele and Von Holst suggest that female rabbits should always stay in their natal area unless they can acheive higher social rank at another territory. During dispersal of males and females, aggression is not likely to be seen among the rabbits. The researchers noted that all those rabbits that did disperse did between the first and fifth month of life before they were fully mature. This happened around 8 months for males and 5-8 months for females. Sometimes rabbits disperse earlier than this time, around 1-5 months, but that is not seen as frequently (Kunkele, 1996).
Hierarchy:
There is not an obvious female dominant hierarchy for the European rabbit. It is usually only seen during competitive situations. The social hierarchy for males is determined by how large his patrol area is, the number of females that visit the area, resting time near females, the number of shelters he visits, and the distance traveled daily. If a rabbit is not the top-ranking buck, then the subordinates have restrictions placed on their independence. The dominant buck keeps control of his territory through constant monitoring for potential invaders and using aggressive behavior. Nevertheless, those animals that live close to one another and avoid aggressive behavior create more stress for the rabbit which may lead to lower productivity and reproductive success (Vastrade, 1987).
Aggression:
The social groups of the European rabbit have linear rank order within male and females. Social rank of the European rabbit is based on the amount of group aggression observed (Rodel, 2004). The top ranking buck has a greater range of mobility and higher aggression than a dominant female. The higher aggression is seen in the males because they try and ward off other rabbits that might try to get to the female (Vastrade, 1987).
A unique type of aggressive behavior adult European rabbit’s display towards their offspring has been witnessed. Dudzinski et al. investigated the aggressive behavior displayed within the European rabbit. They looked at rabbits of different ages to determine the level of aggression seen. This type of behavior contributes to the dynamics of the social system within the European rabbit. Dudzinski found males to show a greater affection towards their young in comparison to females. Newborn kittens are treated aggressively by their mother. The reason males might treat kitten affectionately may be in order to enhance their social status by being surrounded by friendly individuals (Dudzinski, 1977).
Sometimes the aggression towards the European rabbits young results in death. Death of the young is related to the stress level of the population. The higher the stress in a rabbit population, possibly due to an overcapacity, the more likely the parents will show hostility towards their young. Interestingly enough, Mykytowycz reported that females do not show care towards offspring. Females tend to show aggression towards their young at the same time that males will display protective behavior toward the young. Males will lick and show more caring behavior towards the defenseless young. Kittens are accepted into a group when they are able to recognize the odors of the males through licking, chinning and urination (Mykytowycz and Dudzinski, 1972).
One reason that females display an aggression mechanism might be to enhance their young's survival. Both the males and females become agitated after having a young due to their shift in grazing pattern as a result of the young. Even though studies have noted observances of female rabbits protecting their young from birds of prey, they do not usually take care of young due to high stress immediately after the litter is born. Within high density populations and new young entering into the burrow, the rate of aggression is extremely high in the burrow (Mykytowycz and Dudzinski, 1972).
Issues in the Literature:
Conflicts found in the literature debate about the social status and survival rates of the European rabbit. Henderson claims that the social status and survival rates are not correlated for the European rabbit ( Henderson, 1979). He notes the main factor in survival for the rabbit is the availability of resources. However, previous research done by Rodel et al., Kunkele and Von Holst note that females who did not have as high of a rank within the dominance hierarchy did not have as many offspring. Henderson’s research conflicts with newer research that has been conducted since 1979.