Genetic Welfare Problems of Companion Animals

An information resource for prospective pet owners

English Lop

Overlong Ears

Outline: The abnormal ear length of lop rabbits compromises their agility and mobility. Because of their size and because they cannot be held erect, the ears are at risk of trauma, soiling (through contact with the ground), infection and frostbite and the resulting discomfort and pain, which may be severe and chronic.

Summary of Information

(for more information click on the links below)

1. Brief description

All domesticated breeds of rabbit originate from the European wild rabbit Oryctolagus cuniculus. In the wild, rabbits are the prey of many animals. They have evolved physically and behaviourally to this, being “constantly vigilant, lightweight and fast moving” and adopted a burrow lifestyle, spending their little time above ground feeding (Meredith 2000). Possession of an acute sense of hearing is another adaptation and the ears of wild rabbits are accordingly relatively large and have many blood vessels; having a role also in the control of body temperature (Meredith 2000).

During the domestication of the rabbit, selection for breeds of rabbits showing longer than usual ears has occurred. The English lop is one such breed, whose origins date back to England in the 19th century when pet rabbits first became popular (Espinoza 2010) (NB: Lop is the term used for any breed of rabbit whose ears hang down).

Indeed, English lops can be recognised by their extremely large lop ears (larger than those of any other breed). Generally, ear size varies in proportion to body size and leg length in rabbits, but this is not the case in English lops which have a much larger ear relative to their body size (Castle & Reed 1936). The ears may measure up to 70 cm from tip to tip (http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/).

This selective breeding for exaggerated ear size has led to a number of specific problems, including increased risk of trauma to the ears and problems with regulation of their temperature, resulting in a tendency to frostbite in cold conditions. The size of the ears also profoundly affects the rabbit’s mobility and so increases the risk of obesity associated with the imposed sedentary lifestyle. Lop-eared rabbits are also predisposed to bacterial infections of the external ear canal (otitis externa) because of the narrowed, flattened and obstructed shape of the canal that results from the bending of the ears into the lop position (Saunders and Shrubsole-Cockwill 2010).

2. Intensity of welfare impact

English lops have the most extreme ear size of any rabbit breed. This affects the quality of their life by profoundly limiting normal movement. Because of their size and because they cannot be held erect, their ears are at risk of trauma, soiling (through contact with the ground), infection and frostbite and the resulting discomfort and pain, which may be severe and chronic.

3. Duration of welfare impact

The mobility of English lops is compromised throughout their life. They may suffer episodes of injury, infection or frostbite and these may cause pain for long periods of time and recur.

4. Number of animals affected

Mobility is compromised in all animals of this breed. We are unaware of any data on the frequency and duration of ear injuries and infections but understand that these can occur quite commonly.

5. Diagnosis

Ear trauma and obesity are usually apparent on visual inspection and examination. Diagnosis of infection of the ear canal requires veterinary examination.

6. Genetics

English lops breed true (ie all offspring have the exaggerated, lop, ears). Castle & Reed (1936) suggested the lop-eared condition has a polygenetic basis i.e. it is controlled by multiple genes. However, as far as we know, this has yet to be confirmed.

7. How do you know if an animal is a carrier or likely to become affected?

As the English lop is defined by its ear size and shape, all English lops are affected by the inherited features which cause the welfare concerns discussed above.

8. Methods and prospects for elimination of the problem

It is the English lop’s ear size that is the primary anatomical abnormality that presents the risk to welfare. Selecting for normal ears would involve out-crossing to other breeds.

Opinions differ as to whether it is ethically acceptable to breed animals whose welfare is likely to be compromised.

For further details about this condition, please click on the following:
(these link to items down this page)

1. Clinical and pathological effects

All domesticated breeds of rabbit originated from the European wild rabbit Oryctolagus cuniculus (Meredith 2000). They were probably introduced to Britain and northern Europe by the Romans and then later to elsewhere in the world with human travel. The English lop is a relatively old breed, dating back to England in the 19th Century when pet rabbits first became popular (Espinoza 2010). Lop is the term used for any breed of rabbit where the ears hang down, and this occurs because affected individuals have a deficiency of the cartilage that makes it is less rigid than usual (Castle & Reed 1936).

In the wild, rabbits are the prey of many animals. They have evolved physically and behaviourally to suit this niche, being “constantly vigilant, lightweight and fast moving” and, adopted a burrowing lifestyle, spending little time above ground – just long enough to forage for food (Meredith 2000). As part of their adaptations to avoid attracting the attention of predators, rabbits naturally avoid overt visual communications, show few outward signs when ill, diseased or distressed and do not show obvious signs of pain (McBride et al 2006). (Rabbits are still considered to feel pain, however, just like any other mammal).

Possession of an acute sense of hearing is another adaptation and the ears of wild rabbits are accordingly relatively large (Mitchell & Tully 2009). In addition, the ears have a role in thermoregulation (temperature control) of the body, and are highly vascularised, ie they have lots of blood vessels (Meredith 2000).

Rabbits originated from Mediterranean countries, where at times they would need to be able to lose heat efficiently. Because of their size, ears form a significant proportion of the surface area of all rabbits. By allowing more blood to be shunted through the ear vessels, near to the surface of the body, heat can quickly be lost to the surrounding air.

English lops can be recognised by their exaggerated lop ears (larger than any other breed). Generally, rabbit ear size varies in proportion to the body size and leg length, however, this is not the case in English lops, which have a much larger ear relative to their body size (Castle & Reed 1936) - the ears can be up to 70 cms from tip to tip (http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/) with the record being 79cms (http://www.omlet.co.uk/breeds/breeds.php?breed_type=Rabbits&breed=English+Lop). Males have larger ears than females (http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/).

This breed is generally considered docile and inactive (http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/; http://www.petplanet.co.uk/small_breed_profile.asp?sbid=11), whether this is purely due to their inherited temperament or partially due to the physical impediment of their ears is unknown.

English lops are recognised by the British Rabbit Council (BRC) in the UK and the American Rabbit Breeders Association (ARBA) in the USA. The ARBA standards, which are more extreme than those of the BRC, include the following details for the ears:

Ears: Ears are to be carried low on the head, with no noticeable crown. Ears should hang loose and close to the body. Length is to be at least 21 inches from tip to tip. The width of the ears should be approximately 1/4 of the total length of the ear. Ideal ear length is to be as long as possible, with width to be in proportion.

Substance and Shape of Ears: Ears are to be uniformly thick enough not to be easily blemished or torn, yet thin enough to maintain the longitudinal crease in the ear. Ears are to be well rounded and wide at the tips.

Texture and Condition of Ears: Ears are to be very soft, smooth and pliable. They are to be free from tears, pimples, and blemishes” (http://www.furrycritter.com/resources/rabbits/English_Lop.htm)

Both governing councils suggest that ear shape and size is important to success in shows. The breed seems to be kept mainly for showing and less as a family pet.

The selective breeding for exaggerated ear size has lead to a number of specific problems for the rabbits:

Trauma to the ears: Because of their excessive length and drooping nature, the ears are at an increased risk of trauma from the animal standing on them or from contact with objects in their environment. This leads to regular advice to owners to house affected individuals in large enclosures and for the rabbits to have their nails trimmed regularly to minimise possible damage inflicted by scratching (http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/).

Lack of normal mobility: Standing on the ears stops free forward motion and rabbits may trip over. They can find it awkward to climb or jump (http://www.petplanet.co.uk/small_breed_profile.asp?sbid=11). The ears are also a substantial weight to carry around and the rabbits have limited control of their positioning.

Poor temperature regulation: Due to their abnormally high surface area, the ears lose heat more readily than normal and the thermoregulatory function of the ears is affected (http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/). During cold weather, this can lead to the extremities (toes, tail and, in this case, particularly the ears) getting so cold that they become frostbitten (ie they freeze). This results in tissue damage and necrosis (tissue death) of the affected body part (http://www.helium.com/items/1764740-what-are-english-lop-breed-facts; http://www.rabbit-cages-and-hutches.com/english-lop-rabbits.html).

Bacterial otitis externa (infections of the outer ear canal caused by bacteria): This is a common problem and all lop breeds are predisposed because of their narrowed ear canals – the ear canal is obstructed where the ear flexes over into the lop position (Mitchell & Tully 2009, Saunders & Shrubsole-Cockwill 2010). Signs include scratching at the ear, holding the head in a tilted position, a foul smell or discharge coming from the ear, resistance to any handling of the area around the ear and, if severe, anorexia (not eating) and depression. The pain associated with this condition has been described as “exquisite” (Saunders & Shrubsole-Cockwill 2010).

Obesity:As a result of the sedentary lifestyle enforced by the size of the ears. ( http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/; http://www.petplanet.co.uk/small_breed_profile.asp?sbid=11).

To help minimise these problems, specific husbandry is recommended for the breed. These include having lots of space to exercise, a large hutch to allow affected individuals to move freely without damaging the ears, a water bottle rather than ground water bowl, regular nail trimming, enhanced protection from cold through better draft proofing and insulation of housing and careful diet control to avoid obesity (http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/; http://www.petplanet.co.uk/small_breed_profile.asp?sbid=11; http://www.omlet.co.uk/breeds/breeds.php?breed_type=Rabbits&breed=English+Lop).

The Lop Rabbit Club of America suggests “The English lop is a challenge to all who raise them” (http://www.lrca.us/AbouttheLRCA.htm).

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2. Intensity of welfare impact

English lops have the most extreme ear size of any rabbit breed. This affects the quality of their life by profoundly limiting normal movement and affects their ability to show natural behaviours - one of the five basic requirements of the UK’s Animal Welfare Act 2006. Because of their size and because they cannot be held erect, their ears are at risk of trauma, soiling (through contact with the ground), recurrent infection and frostbite and the resulting discomfort and pain, which may be severe and chronic.

It is possible they may suffer from mental distress due to their relative immobility and therefore inability to escape from perceived dangers; whether this is the case is unknown.

As rabbits do not show signs of pain that are readily apparent, their suffering may easily be underestimated and problems may not be detected until they are severe (RSPCA 2011).

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3. Duration of welfare impact

The mobility of English lops is compromised throughout their life. They may suffer episodes of injury, infection or frostbite and these may cause pain for long periods and recur.

The problems created by long ears are life-long but may be greater for young animals, as they have relatively even larger ears compared to body size than the adult. It is suggested that the ears grow rapidly during early development and by four weeks of age the ears are longer than the kit (young rabbit), and by four months the ears have grown to their full size whereas the rest of the animal’s body keeps growing for up to 12 months of age (Castle & Reed 1936; http://www.rabbit-cages-and-hutches.com/english-lop-rabbits.html; http://www.gopetsamerica.com/small-animals/rabbit/english-lop.aspx).

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4. Number of animals affected

Mobility is compromised in all animals of this breed. We are unaware of any data on the frequency and duration of ear injuries and infections but understand that these can occur quite commonly. The numbers of English lops currently owned as show and pet animals are not known.

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5. Diagnosis

Ear trauma and obesity are usually apparent on visual inspection and examination. Diagnosis of infection of the ear canal requires veterinary examination.

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6. Genetics

English lops breed true (ie all offspring have the exaggerated, lop, ears). Castle & Reed (1936) suggested the lop-eared condition has a polygenetic basis ie it is controlled by multiple genes. However, as far as we know, this has yet to be confirmed.

Return to top

7. How do you know if an animal is a carrier or likely to become affected?

As the English lop is defined by its ear size and shape, all English lops are affected by the inherited features which cause the welfare concerns discussed above.

Return to top

8. Methods and prospects for elimination of the problem

The English lop’s ear size is the primary anatomical abnormality that causes welfare concerns for this breed. Eliminating the condition would involve radical changes to the breed including out-crossing to other breeds.

Currently, breed standards encourage breeders to select for very long ears, such as the ARBA’s breed standard in the USA which insists on ears of at least 21 inches in length, and larger ear size influencing success rates on the show benches. If the onus when breeding continues to be for ear length then it seems likely that ear length will further increase. This in turn is likely to adversely affect rabbit welfare.

Opinions differ as to whether it is ethically acceptable to breed animals whose welfare is likely to be compromised.

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9. Acknowledgements

UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section and to Nina Taylor for her contribution to it.

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10. References

Castle WE and Reed SC (1936) Studies of inheritance in lop-eared rabbits. Genetics 21: 297-309

Espinoza T (2010) Rabbit Breed Facts: English Lop. On-line. http://www.helium.com/items/1764740-what-are-english-lop-breed-facts. Accessed 21.3.11

McBride EA, Hearne G and Magnus E (2006) Thumper, fiver, wee-er, biter - The natural behaviour of rabbits and its influence on behaviour problems. In: Companion Animal Behaviour Therapy Study Group: Natural Behaviour and its Influence on Behavioural Problems Birmingham, UK 19 Apr 2006. 3: 15-17

Meredith A (2000) General Biology and Husbandry. In: Flecknell P (ed) Manual of Rabbit Medicine and Surgery pp 13-25. BSAVA: Cheltenham, UK

Mitchell M and Tully T (2009) Manual of exotic pet practice. Saunders: St Louis, USA pp 393

RSPCA (2011) Rabbits/ Health and Welfare. On-line http://www.rspca.org.uk/allaboutanimals/pets/rabbits/health. Accessed 21.3.11

Saunders R and Shrubsole-Cockwill A (2010) Vetstream Lapis: otitis externa. On-line http://www.vetstream.com/lapis/content/Freeform/fre00371.asp. Accessed 21.3.11

http://www.clickpets.co.uk/rabbit_breed_guides/english_lop/

http://www.furrycritter.com/resources/rabbits/English_Lop.htm. Accessed 21.3.11

http://www.gopetsamerica.com/small-animals/rabbit/english-lop.aspx

http://www.lrca.us/AbouttheLRCA.htm

http://www.omlet.co.uk/breeds/breeds.php?breed_type=Rabbits&breed=English+Lop

http://www.petplanet.co.uk/small_breed_profile.asp?sbid=11

http://www.rabbit-cages-and-hutches.com/english-lop-rabbits.html

Credit for main photo above:

By Oldhaus (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Common