A litter is the live birth of multiple

offspring In biology, offspring are the young creation of living organisms, produced either by sexual reproduction, sexual or asexual reproduction. Collective offspring may be known as a brood or progeny. This can refer to a set of simultaneous offspring ...

at one time in

animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...

s from the same mother and usually from one set of

parent A parent is either the progenitor of a child or, in humans, it can refer to a caregiver or legal guardian, generally called an adoptive parent or step-parent. Parents who are progenitors are First-degree relative, first-degree relatives and have ...

s, particularly from three to eight offspring. The word is most often used for the offspring of

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s, but can be used for any animal that gives birth to multiple young. In comparison, a group of eggs and the offspring that hatch from them are frequently called a

clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

, while young birds are often called a brood. Animals from the same litter are referred to as littermates.

Litter size (typical count)

In most female mammals the average litter size is about half the number of mammae. Presumably this enables females to successfully nurse litters even if some mammae fail to produce milk. Naked mole-rats break this "one-half rule" – field caught and lab born litters averaged 11 to 12 pups, and numbers of mammae on wild and captive females were similarly 11 to 12. Maximum litter sizes were 28 in the field and 27 in captivity, whereas the maximum number of mammae was 15. Breeding female naked mole-rats can bear and successfully rear litters that are far more numerous than their mammae because young take turns nursing from the same mammary and breeding females and pups are fed and protected by colony mates, enabling queens to concentrate their reproductive efforts on gestation and lactation. Animals frequently display grouping behavior in

herd A herd is a social group of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with this is called '' herding''. These animals are known as gregarious animals. The term ''herd'' ...

s, swarms, flocks, or

colonies A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...

, and these multiple births derive similar advantages. A litter offers some protection from

predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

, not particularly to the individual young but to the parents' investment in breeding. With multiple young, predators could eat several and others could still survive to reach maturity, but with only one offspring, its loss could mean a wasted breeding season. The other significant advantage is the chance for the healthiest young animals to be favored from a group. Rather than it being a conscious decision on the part of the parents, the fittest and strongest baby competes most successfully for food and space, leaving the weakest young, or

runt In a group of animals (usually a litter of animals born in multiple births), a runt is a member which is significantly smaller or weaker than the others.. Owing to its small size, a runt in a litter faces disadvantage, including difficulties in c ...

s, to die through lack of care. In the wild, only a small percentage, if any, of the litter may survive to maturity, whereas for domesticated animals and those in captivity with human care the whole litter almost always survives.

Kittens A kitten is a juvenile cat. After being born, kittens display primary altriciality and are fully dependent on their mothers for survival. They normally do not open their eyes for seven to ten days. After about two weeks, kittens develop quick ...

and

puppies A puppy is a juvenile dog, generally one less than 12-18 months old. Puppies are markedly underdeveloped and dependent on their mothers at birth (displaying '' altriciality''), but healthy puppies grow quickly and begin walking thereaft ...

are in this group.

Carnivorans Carnivora ( ) is an Order (biology), order of Placentalia, placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s, and

pig The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus '' Sus''. Some authorities cons ...

s usually have litters, while primates and larger herbivores usually have singletons.

References

{{reflist Zoology Reproduction Multiple births Animals by adaptation