Lop rabbit

A lop rabbit or lop-eared rabbit is any rabbit with ears that droop, as opposed to being carried erect. A number of rabbit breeds (listed below) are characterized by such lop ears. Abnormalities in the skull of a half-lop rabbit were studied by Charles Darwin in 1868.

The defining feature of the lop rabbit is its ear carriage. Unlike the erect ear of the majority of domestic rabbit breeds, lop breeds have ears loosely drooping, with the opening of the ear facing the skull. Due to the slightly-raised cartilaginous ear base, the head of many lop rabbits (with the exception of English Lops) has a small bulge, referred to as the crown. The head of a typical lop rabbit is said to resemble that of a male sheep in profile, thus the German term for a lop rabbit (Widder, meaning Aries [the ram]), the French term (bélier, meaning ram) and the Italian term (ariete, from Latin aries).

A rabbit's ear, with its blood vessels close to the surface, is an essential thermoregulator.^[1] The additional weight of a longer or thicker ear is not always fully supported by the rest of the ear structure, resulting in ears that droop. The ears of some young lop rabbits may not achieve their full adult droop until the ear growth is finished. The ears of a lop rabbit prevent them hearing predators and maintaining a healthy body temperature. Both of these disadvantages keep them from surviving outdoor conditions.

Rabbits are known to carry their ears in one of five ways:^[2]

• Erect ears (the most common): Both ears are carried upright. Such ears may at times rest atop the rabbit's back, or be temporarily smoothed down by the rabbit when it bathes or grooms itself.
• Full lop ears (less common): Both ears hang fully down, brushing the rabbit's cheeks and shoulders. Such ears may gently undulate as the rabbit hops.
• Half lop ears (uncommon): One ear is carried in a full (or nearly-full) droop, while the other ear is carried erect. Similar in appearance, a now-extinct one-eared rabbit—said to resemble a unicorn—was breeding true around the end of the 18th century, and in 1958 two such healthy specimens were photographed.^[2]
• Orejas de remo (poco comunes): Ambas orejas se llevan aproximadamente horizontales al suelo y se extienden sobre los hombros del conejo. El término proviene de su parecido con los remos de un bote en reposo. En la actualidad, a veces se las denomina orejas de helicóptero . ^{[ 3 ]}
• Orejas caídas con cuernos (raras): Ambas orejas se mantienen casi horizontales al suelo y sobresalen por encima del hocico del conejo. El término proviene de su parecido con los cuernos que apuntan hacia adelante de algunas vacas.

• 
  Orejas erguidas. Ilustración de [E. Whimper?], ca. 1862.
• 
  Orejas caídas completas. Artista desconocido, 1875.
• 
  Orejas caídas parciales. Ilustración de E. Whimper, ca. 1862.
• 
  Orejas caídas de remo. Ilustración de E. Whimper, ca. 1862.
• 
  Orejas de cuerno caído. Ilustración de E. Whimper, ca. 1862.

Las orejas más largas (o más gruesas) tienen más probabilidades de caerse. Algunos conejos de orejas caídas han sido criados deliberadamente para tener orejas de longitud exagerada. ^{[ 4 ]} Dado que esto puede considerarse perjudicial para la salud del conejo, en Alemania se prohíben los conejos con orejas de más de 65 cm (25,5 pulgadas) , y en los Países Bajos, 70 cm (27,5 pulgadas) es la longitud máxima permitida [en exposiciones] antes de la descalificación. ^{[ 2 ]} El premio Guinness World Records a las "orejas más largas en un conejo" se otorgó en 2003 a un conejo English Lop en Estados Unidos con orejas que medían 79,058 cm (31,125 pulgadas) . ^{[ 5 ]}      

Aunque la mayoría de las razas de conejos tienen orejas erguidas, las razas de orejas caídas representan aproximadamente el 15 % de todas las razas reconocidas actualmente por la Asociación Americana de Criadores de Conejos (ARBA) ^{[ 6 ]} o el Consejo Británico de Conejos (BRC). ^{[ 7 ]} Dichas razas de orejas caídas incluyen:

• Lista de razas de conejos