Unclean animal

The Torah does not classify animals under modern scientific categories of mammals, fish, reptiles and birds. Rather, the religious categories are land-dwelling animals (land mammals, flightless birds, and land reptiles, etc.), flying animals (birds, insects, flying mammals such as bats), and given that each of these religious categories of animals includes species of at least two or more of each scientific categories of animals, there is no general kashrut rules relating per se to mammals, birds, reptiles, or fish. However, rules for each of these classes of animals can be extrapolated from the biblical requirements.

Mouse

Townsend's big-eared bat

According to the Torah, land-dwelling animals that both chew the cud (ruminate) and have cloven hooves, are kosher.[9] By these requirements, any land-dwelling animal that is kosher can only possibly be a mammal, but even then, permitted are only those mammals that are placentals and strictly herbivorous (not omnivores nor carnivores) that both ruminate and also have cloven hooves, such as bovines (cattle/cows, bison, buffalos, yak, etc.), sheep, goats, deer, antelope, and technically, also giraffes.

Although the giraffe falls under the kosher category by its characteristics, it does not have a masorah (tradition) for its consumption by any Jewish community. Though it is commonly believed that it is not known where on a giraffes neck shechita (ritual slaughter) can be performed, this is incorrect as the shechita can be performed anywhere on the neck.

All other mammals, land-dwelling or otherwise, are forbidden by the Torah, including "crawling creatures" such as mammalian mice,[10] and flying mammals such as the various species of bats.[11] Water-bound mammals, such as whales, dolphins, dugongs, etc., are also not kosher as they do not have the characteristics required of kosher water-bound creatures which must have both fins and scales.

Those land-dwelling mammals that have only one of the two characteristics of kosher land-dwellers (only ruminant or only cloven hooved) are impure and cannot be consumed. By default, therefore, not only are most land-dwelling mammals not kosher, but all land-dwelling non-mammals are also not kosher, including reptiles, amphibians, molluscs (including snails), etc.

Among mammals that Leviticus cites explicitly as an example of unclean is the camel, because it ruminates but does not have a cloven hoof;[12] the hyrax and the hare are also explicitly given as an example of being excluded as kosher on the same grounds. Quintessentially, the Torah explicitly declares the pig unclean, because it has cloven hooves but does not ruminate.

It is of interest to note that Australia is the only continent that has no kosher native mammals, nor kosher native birds. Thus, prior to European settlement, there were no kosher land-dwelling or flying animals in Australia. Though the kangaroo chews its cud, for instance, it does not have hooves, and is therefore not kosher. No mammals that are marsupial or monotreme are kosher.

Blue crab for sale in Piraeus.

According to Leviticus 11:9–10, anything that comes from the water ("in the seas, and in the rivers") that has both fins and scales may be eaten. By those requirements, kosher water creatures can only possibly be fish, but even then, permitted are only those fish that have both fins and scales.

All other non-fish water creatures are, by default, also not kosher, including amphibians, crustaceans, molluscs, water-bound mammals, water-bound reptiles, etc.

While there is nothing specifically mentioned in Jewish halakha requiring kosher fish having an endoskeleton ("inner skeleton") and gills (as opposed to lungs), every true fish that has both scales and fins by default also possesses an endoskeleton and gills. Any sea creature that lacks gills and can only breathe oxygen from air through lungs, or has an exoskeleton instead of and endoskeleton,[13]^:343 is by default not kosher.

The definition of scales does not include the shells of prawns and shrimp, which are in fact the exoskeleton ("outer skeleton") of these animals, in the same manner as the shells of lobsters or crabs. Even if these shells were to be misidentified as scales, these creatures would still not be kosher as they lack fins.

While not every fish that has fins will have scales, every true fish that has true fish scales by default also has fins.[14]

The Torah names only a few birds that may not be eaten; those not in the list are presumed to be kosher. However, the precise identity of the unclean birds is a matter of contention in traditional Jewish texts. It is therefore common to eat only birds with a clear masorah (tradition) of being kosher in at least one Jewish community, such as domestic fowl.

Leviticus 11 lists, among other things, the specifically unkosher birds.[15] The Hebrew names listed have been translated as follows:

• Eagle
• Vulture and Black Vulture
• Red and Black Kite
• Raven
• Owl (Horned, Screech, Little, Great, White, and Desert)
• Gull
• Hawk
• Cormorant
• Osprey
• Stork
• Heron
• Hoopoe

Bats are also mentioned (though biologically, these are mammals rather than birds).

Desert locust

The Torah allows eating certain kinds of "winged swarming things" (i.e. insects) while prohibiting others.[16] However, due to uncertainty about the Hebrew insect names, rabbis today recommend that all insects be considered unclean.[17] An exception is made for certain locusts (Schistocerca gregaria), which are traditionally considered kosher by some Yemenite Jewish communities. Leviticus 11:20–23 details which insects are not to be eaten, and due to the wording all insects are considered impure to avoid mistaken consumption.

Bees' honey is considered kosher[18][19] because the honey is not a product made of bees.

The following animals are considered to be impure according to Leviticus 11 and Deuteronomy 14, based on Rashi's identification:

Camel

Some scholars have conjectured that the Jewish concept of "unclean animals" arose out of public health concerns by community leaders, since, in the conditions of the times, some of those animals are indeed more likely to cause food poisoning or transmit diseases to people who consume them.[21]

British anthropologist Mary Douglas proposed that the "unclean" label had philosophical grounds, namely it was cast on foods that did not seem to fall neatly into any symbolic category. The pig, for example, was seen as an "ambiguous" creature, because it had cloven hoof like cattle, but did not chew cud.[22]

In the Roman Catholic Church, it was forbidden to eat meat (defined as the flesh of any warm-blooded animal) on Friday, but as a penance to commemorate Christ's death rather than for meats being regarded as "unclean". In the 1983 Code of Canon Law, the current code of canon law for the Roman Catholic Church, the Friday abstinence from meat is prescribed for "those who have completed their fourteenth year of age". Once a person has begun his or her sixtieth year, the abstinence is no longer obligatory. Canon 1253 allows each particular conference of bishops to "determine more precisely the observance of fast and abstinence as well as substitute other forms of penance, especially works of charity and exercises of piety, in whole or in part, for abstinence and fast".[32] The current disciplinary norms from a document produced by the United States Conference of Catholic Bishops, titled "Pastoral Statement On Penance And Abstinence", remove the penalty of sin for Roman Catholics in the United States who choose not to abstain from meat, while the document "give[s] first place to abstinence from flesh meat". Roman Catholics in the United States are, therefore, free to substitute some form of penance on Fridays of the whole year, while the Lenten abstinence remain obligatory.[33]

Adventists are known for presenting a "health message" that advocates vegetarianism and expects adherence to the kosher laws,[34] particularly the consumption of kosher foods described in Leviticus 11, meaning abstinence from pork, shellfish, and other animals proscribed as "unclean".

Saluki dog

According to the majority of Sunni scholars, dogs can be owned by farmers, hunters, and shepherds for the purpose of hunting and guarding and the Qur'an states that it is permissible to eat what trained dogs catch.[37] Among the Bedouin, the saluki dogs are cherished as companions and allowed in the tents.

Nevertheless, many Islamic teachers state dogs should be considered unclean and that Muslims licked by them must perform ritual purification. According to a Sunni Islam Hadith, a plate that a dog has used for feeding must be washed seven times, including once with clean sand mixed with the water, before a person may eat from it.