Monday, January 4, 2010
Christal Pollock DVM, Dipl. ABVP-Avian
House rabbits can make wonderful pets, and more American households report owning rabbits than any other exotic mammal. Small animal veterinarians are being called upon to care for rabbits with increasing frequency, however approach to the pet rabbit often requires a significant shift in perspective for those used to dealing solely with cats and dogs. Normal rabbit behavior may be unfamiliar and rabbits possess few muscles of facial expression making them difficult to “read” when compared to cats and dogs.
The first step in understanding rabbits is to understand the behavior of their wild predecessors. Free-ranging rabbits are communal, territorial animals that live in groups or warrens numbering anywhere from six to eight individuals up to several hundred animals. Rabbits live in burrows that make up a complex network of underground tunnels measuring up to 3 meters in depth and 45 meters in length. Rabbits spend most of the day in their burrows, coming out during early evening and morning hours.
Prey species behavior
Rabbits are prey species. Their survival in the wild depends on the ability to be alert and respond quickly, and this instinct has survived in the house rabbit. Rabbits possess acute senses of smell and hearing. Their first defense when danger is near is to be very still to avoid detection. If that doesn’t work, then rabbits will run using quick bursts of speed and rapid changes in direction.
Prey species like the rabbit tend to mask pain and discomfort, especially when frightened. Recognition and management of pain is crucial since pain in the rabbit may lead to gastrointestinal stasis, or even shock and death.
• Signs of fear in the rabbit include the body flattened in a crouched, motionless position with the feet tucked underneath and the head extended. Ears are often tucked tightly against the head, and the eyes may bulge. The clinician should respond by speaking softly, moving slowly, and approaching the rabbit at eye level.
• Signs of pain may include: anorexia, lethargy (reluctance to move, decreased interest in the environment), teeth grinding in a slow, loud crunching fashion, bulging, often unfocused, eyes, and a hunched posture with the head in an elevated, extended position. Rabbits may lick excessively or even pluck hairs over a painful area or seek hiding places. Respirations may be rapid and shallow.
Normal sounds and actions
Although comparatively silent, rabbits do make a variety of sounds.
• “Purring” is a sound of contentment made when the rabbit is getting a good petting or very tired. The teeth click softly, the head trembles, and the whiskers quiver.
• “Honking” or “oinking” sounds are made in courtship or to gain food or attention.
• Whimpering or low squealing are fretful noises made by a rabbit that does not want to be picked up.
• Finally, but most importantly for veterinarians, some rabbits “talk” by making wheezing or sniffing sounds.
These sounds may be distinguished from congestion by being heard inconsistently and only in conjunction with social interaction.
Interaction with a house rabbit tends to make one more one adept in non-verbal communication.
• A sign of possessiveness is “chinning” when the rabbit rubs its chin on items or people.
• One of the least subtle behaviors is called the “happy hop” or “binky”. The rabbit will jump into the air with the head going in one direction and the rest of the body going in the other direction. “Binkies” appear to denote pure joy. A video clip demonstrating the “happy hop” may be found at: http://www.thebunnyshed.co.uk/TheFAQ.htm.
Age and Breed
Not surprisingly, juvenile rabbits tend to be energetic and extremely inquisitive. Owners are most likely to complain of chewing and other “problem behaviors” in this age group. After one year of age, most rabbits become more sedate and predictable. Rabbits are considered geriatric after 6 to 7 years. At this age they generally sleep more and move more slowly. There are also breed differences in behavior. Large rabbits such as the New Zealand white tend to be calmer than smaller rabbits like the Netherland Dwarf.
Proper house rabbit care is based on normal rabbit behavior:
1. Most rabbits tend to urinate and defecate in the same place each time. This habit of picking a latrine spot means that most rabbits are easily litter trained.
• Place the litter pan in one area of the cage or just outside the cage door, and place many boxes around the room. Initially, limit the rabbit to a small space and limit the amount of time for the rabbit to roam outside of its cage. Placing hay or treats in the litter box may also attract the rabbit to the pan.
• A trained rabbit may urinate outside of its pan if it needs to mark territory due to a stressful event, or with urinary tract disease.
• Rabbits will also mark territory by depositing hard fecal pellets. This behavior is most intensely practiced by adult intact males, however even castrated rabbits mark new areas in this manner.
2. To feel comfortable and safe, rabbits like to go on, under, beside, or beneath objects.
• Boxes are often a favored item, however few rabbits will use a box with only one hole in it. After all, a predator can trap you if your burrow has only one opening.
• Females often have a stronger urge to burrow than males.
3. Rabbits have an instinctive urge to chew.
• “Bunny proofing” prevents property destruction and protects rabbits from harm. Avoid rooms with wall to wall carpet, low shelves, high numbers of electrical cords, and/or books or plants within 2 feet of the floor. Protect exposed cords using polyethylene tubing or armoured cable.
• Provide safe and fun chewing and digging alternatives free of chemicals or varnishes such as rice matting and willow bark. Many rabbit toys focus on the need to chew. The House Rabbit Society [link to http://www.rabbit.org/faq/sections/toys.html] has an excellent recommended toy list.
4. Rabbits are crepuscular creatures that normally rest and sleep during most of the day, and are most active at dusk and dawn.
5. Many experts on house rabbit care agree that most rabbits are not meant to live in solitude away from members of their own kind.
• The need for companionship can only be met partially by a human, although rabbits may display affection and acceptance for their owners through grooming.
• Signs of loneliness in rabbits commonly include boredom, depression, and withdrawal. Destructiveness and hyperactivity are seen in some smaller breed rabbits.
• Despite their need for companionship, introductions can prove challenging, and some aggression should be expected. Introducing two intact rabbits of any gender is likely to result in fighting, breeding behavior, or both. Introductions may be least stressful when they involve neutered adults of opposite sexes. Strive to match ages, however mixing breeds often works well such as a dwarf rabbit placed with a large breed rabbit. Introduce rabbits for short 20-minute sessions in a neutral territory.
Puberty occurs just after the maximal rate of growth, with small breeds reaching puberty between 3.5 to 5 months of age and large breeds maturing at 5 to 8 months. Does mature earlier than bucks. Signs of sexual maturity may include aggression, territoriality, circling and spraying urine, and frenzied digging. Males show constant libido, attempting to mount cage mates, while females tend to behave quite aloof. Rabbits are induced ovulators, with potentially long periods of estrus. If mating does not occur, ovarian follicles regress and new follicles mature, therefore sexual behavior does not go away in the rabbit unless the animal is neutered or bred.
Spaying and neutering improves litter box habits and reduces territorial aggression, mounting, and spraying. The average time for negative sexual activity to lessen significantly after surgery is 2 weeks, and activity may be completely gone by this time in females. It generally takes 2 months until sexual activity is completely gone in males, and cessation of sexual activity may take 4 to 8 months in larger breeds.
The approach to a prey species like the rabbit often calls for a profound paradigm shift for clinicians used to dealing only with cats and dogs. The ability to truly understand rabbits will improve the clinician’s ability to not only diagnose and treat medical conditions, but also help owners love and care for their pets.
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By C. Scott Bailey, DVM, MS, DACT
Keeping up with the discussion surrounding ovariohystorectomy can be difficult. In veterinary school, most of us were taught, as dogma, that dogs and cats should be neutered. Once in practice, however, other points of view and experiences make this decision less straightforward. We are faced with questions such as, “Should all animals be neutered? At what age should they be neutered? Are there contraindications or risk-factors associated with neutering beside the obvious surgical complications?” Often owners come with preformed opinions about these questions, and as veterinarians it is our job to give them balanced and scientifically accurate information so that their decision is based on more than blogs on the internet.
In the last 2 years, three well-written reviews of the veterinary literature have become available detailing benefits and potential complications (Root Kustritz MV - JAVMA 2007, Sanborn MS - Internet Source 2007, Reichler IM – Reprod Dom Anim 2009). Each discusses the potential population benefits in reducing the number of unwanted animals, many of which end up in shelters. In fact, the overall benefits of neutering animals for population control go largely unquestioned in all three reviews, despite a relative lack of epidemiologic studies to support the concept.
Perhaps of greater importance to the practitioner are the benefits to the individual animal and owner. Castration of male cats is often performed to avoid unwanted male sexual behaviors such as spraying and to control territorial behaviors. These behaviors can be so severe that intact males are considered undesirable by many owners. This incentive to neuter is often not present for owners of dogs or female cats; consequently the discussion can be much more heated.
In male dogs, the benefit to population control is likely the greatest, but the scientific evidence pointing to health benefits is the weakest. Intact male dogs have a low incidence of testicular neoplasms (0.9%), which rarely metastasize and have little impact on the dog’s wellbeing. Unlike men, the incidence of prostatic neoplasms is lower in intact animals (0.2-0.6%) than in castrated animals, which have roughly twice the risk of prostatic neoplasia and 2-5 x the risk of osteosarcoma and hemangiosarcoma (each 0.2% of animals, with significant breed variations). In addition, the risk of obesity is somewhat higher in neutered dogs of both gender, corresponding with a slightly increased risk of diabetes mellitus and rupture of the cranial cruciate ligament. That being said, the primary health benefit to a male dog is a dramatic decrease in the incidence of benign prostatic hyperplasia (BPH) and prostatitis, which can be seen in up to 80% of intact male dogs by 6 years of age. However, both these conditions are treatable (either medically or by castration) and BPH often is present in older intact animals without clinical signs and so only a small portion of those animals will be spared discomfort by preventive surgery.
With females, the situation is only slightly clearer. The primary benefit of neutering females lies solidly in the reduction of mammary gland tumors, which affect 2.5% (80% malignancy) of all queens and 3.4% (50% malignancy) of all bitches and which may cause significant morbidity and mortality. Furthermore, these neoplasms can be reduced by more than 90% if the animals are spayed before their first heat. In addition, the risk of pyometra is eliminated by ovariectomy or ovariohysterectomy. Pyometra affects up to 25% of dogs by the age of 10 years and may be associated with significant morbidity and mortality in some of these.
However, potential detriments of neutering include surgical complications (reported incidence of 2.6% in cats and 6.1% in dogs), obesity, and slightly increased risks of diabetes mellitus in both dogs and cats, as well as cranial cruciate rupture in dogs. With reported incidences of 5-20%, urinary incontinence is a common problem of spayed bitches. This has the potential to significantly impact the animal’s welfare, depending on the severity and the owner’s tolerance of this. In addition, spayed females are at increased risk of urinary tract infections, particularly those spayed at an early age and those animals spayed in the face of “puppy vaginitis”. These cases can result in chronic recurrent UTIs that may dramatically affect the animal’s welfare and result in large expenses to the owner.
As in males, neutered bitches also have a roughly 2-5x greater risk for osteosarcoma and hemangiosarcoma than intact animals. Overall the incidence of these neoplasms is low, affecting approximately 0.2% of all dogs. It should be noted, however, that significant breed variation is reported and that this may greatly influence the benefit-risk ratio of neutering a given animal. Dr. Root-Kustritz tabulated the relative risks for the population overall and also noted the breeds that were predisposed to a particular disease, but not the degree to which this would have an effect. Unfortunately, breeders/owners are often more aware of the diseases affecting their particular breed than their veterinarians. Consequently, they may question the traditional viewpoint presented to them. As an example, a study investigating 683 Rottweilers found an overall incidence of osteosarcoma of 12.6% (compared to 0.2% across all breeds), with the diagnosis twice as likely in neutered animals as in intact animals (Cooley DM - Cancer Epidemiology 2002). Furthermore, they demonstrated that Rottweilers neutered prior to one year of age had a significantly greater risk of osteosarcoma than other dogs, with diagnoses occurring in approximately 25% of animals. This example is one of several that highlights the need for breed- or animal-specific decision-making and owner consultation as opposed to a blanket approach to canine contraception.
A recent paper by the same group out of Purdue University further questions the policy of routine gonadectomy (Waters DJ – “accepted article”, Aging Cell 2009). An analysis of lifetime medical histories, age at death and cause of death for exceptionally long-lived Rottweiler dogs (>= 13 years, or >30% longer than the average life-expectancy) demonstrated that female dogs were more likely to achieve this age than male dogs and that gonadectomy before 4 years of age erased this advantage. “In females, a strong positive association between ovaries and longevity persisted in multivariate analysis that considered other factors, such as height, body weight and [genetics]”. This appears to fly the face of accepted tradition, which states that neutered animals live longer than their intact counterparts and may be interpreted as a reason to avoid gonadectomy by the larger community. However, the study focused only on exceptionally long-lived animals, not animals overall. In that larger population, it remains well-documented that neutered animals live longer than intact animals (Kraft W – Eur J Med Res 1998, Greer KA – Res Vet Sci 2007).
In conclusion, while many benefits of neutering the small animal patient remain important and valid, it is critical for veterinarians to remain aware of both benefits and contraindications to neutering in order to give owners a balanced, scientifically sound recommendation, individually tailored to the needs and benefits of our patients.