Flexible or opportunistic breeders mate whenever the conditions of their environment become favorable. Their ability and motivation to

mate Mate may refer to: Science * Mate, one of a pair of animals involved in: ** Mate choice, intersexual selection ** Mating * Multi-antimicrobial extrusion protein, or MATE, an efflux transporter family of proteins Person or title * Friendship ...

are primarily independent of day-length (

photoperiod Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light a ...

) and instead rely on cues from short-term changes in local conditions like rainfall, food abundance and temperature. Another factor is the presence of suitable breeding sites, which may only form with heavy rain or other environmental changes.WE Duellman, L Trueb. ''Biology of amphibians.'' The Johns Hopkins University Press, 1994, p. 20 Thus, they are distinct from

seasonal breeder Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and cha ...

s that rely on changes in day length to induce entry into

estrus The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestrous p ...

and to cue mating, and

continuous breeder Continuous breeders are animal species that can breed or mate throughout the year. This includes humans and apes ( bonobos, chimpanzees, gorillas, orangutans, and gibbons), who can have a child at any time of year. In continuous breeders, female ...

s like humans that can mate year-round. Other categories of breeders that perhaps can be subdivided under the heading "opportunistic" have been used to describe many species, such as many that are

anuran A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

s like frogs. These include sporadic wet and sporadic dry, describing animals that breed sporadically not always under favorable conditions of rain or lack thereof. Many opportunistic breeders are non-mammals. Those that are mammals tend to be small

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

. Since changes in season can coincide with favorable changes in environment, the distinction between seasonal breeder and opportunistic can be muddled. In equatorial climes, the change in seasons is not always perceptible and thus, changes in day length not remarkable. Thus, the

tree kangaroo Tree-kangaroos are marsupials of the genus ''Dendrolagus'', adapted for arboreal locomotion. They inhabit the tropical rainforests of New Guinea and far northeastern Queensland, along with some of the islands in the region. All tree-kangaroos ...

(Dendrolagus) previously categorized as a seasonal breeder is now suspected to be an opportunistic breeder.Martin R, Johnson P. ''Bennett's Tree-kangaroo.'' In: R. Straham, ed., Mammals of Australia, Washington, DC: Smithsonian Institution Press, 1995, pp. 307-8, Additionally, opportunists can have qualities of seasonal breeders. The

red crossbill The red crossbill or common crossbill (''Loxia curvirostra'') is a small passerine bird in the finch family Fringillidae. Crossbills have distinctive mandibles, crossed at the tips, which enable them to extract seeds from conifer cones and other ...

exhibits a preference (not a requirement) for long-day seasonality, but requires other factors, especially food abundance and social interactions, in order to breed. Conversely, food availability by itself incompletely promotes reproductive development.

Physiology

Opportunistic breeders are typically capable of

breeding Breeding is sexual reproduction that produces offspring, usually animals or plants. It can only occur between a male and a female animal or plant. Breeding may refer to: * Animal husbandry, through selected specimens such as dogs, horses, and ra ...

at any time or becoming fertile within a short period of time. An example is the

golden spiny mouse The golden spiny mouse (''Acomys russatus'') gets its name from the reddish-orange spiny fur that covers its body from head to tail. This coarse, inflexible fur is thought to protect it from predation.

where changes in dietary salt in its desert habitat due to rainfall appear to cue reproductive function. Increased levels of salinity in drying vegetation cause females to experience a reproductive hiatus. While reproduction is generally independent of photoperiod, animals can still experience reduced fertility with changes in day-length.

Partial list of opportunistic breeders

Mammals

Golden spiny mouse The golden spiny mouse (''Acomys russatus'') gets its name from the reddish-orange spiny fur that covers its body from head to tail. This coarse, inflexible fur is thought to protect it from predation.

Red kangaroo The red kangaroo (''Osphranter rufus'') is the largest of all kangaroos, the largest terrestrial mammal native to Australia, and the largest extant marsupial. It is found across mainland Australia, except for the more fertile areas, such as sou ...

Tree kangaroo Tree-kangaroos are marsupials of the genus ''Dendrolagus'', adapted for arboreal locomotion. They inhabit the tropical rainforests of New Guinea and far northeastern Queensland, along with some of the islands in the region. All tree-kangaroos ...

Musk shrew The white-toothed shrews or Crocidurinae are one of three subfamilies of the shrew family Soricidae. The outer layer of these shrews' teeth is white, unlike that of the red-toothed shrews. These species are typically found in Africa and souther ...

Cape spiny mouse The Cape spiny mouse (''Acomys subspinosus'') is a murid rodent found in the Western Cape Province of South Africa. They have a dorsal covering of spiny hairs with dark grey-brown coloration, and a white underbelly. The Cape Spiny Mouse has large ...

Fleming, P. A., and S. W. Nicolson.
Opportunistic breeding in the Cape spiny mouse (Acomys subspinosus)
" African Zoology 37.1 (2002): 101-105.

Birds

Zebra finch The zebra finches are two species of estrildid finch in the genus ''Taeniopygia'' found in Australia and Indonesia. They are seed-eaters that travel in large flocks. The species are: Previously, both species were classified as a single specie ...

Crossbill The crossbill is a genus, ''Loxia'', of birds in the finch family (Fringillidae), with six species. These birds are characterised by the mandibles with crossed tips, which gives the group its English name. Adult males tend to be red or orange in ...

Budgerigar The budgerigar ( ; ''Melopsittacus undulatus''), also known as the common parakeet or shell parakeet, is a small, long-tailed, seed-eating parrot usually nicknamed the budgie ( ), or in American English, the parakeet. Budgies are the only spe ...

Princess parrot The colourful princess parrot (''Polytelis alexandrae'') is an Australian bird of the parrot family. Its name was given in honour of Princess Alexandra of Denmark, who in 1863 married the Prince of Wales Edward VII and eventually became Queen of ...

Blue-footed booby The blue-footed booby (''Sula nebouxii'') is a marine bird native to subtropical and tropical regions of the eastern Pacific Ocean. It is one of six species of the genus '' Sula'' – known as boobies. It is easily recognizable by its distinct ...

Amphibians

Frogs and toads including: *

Long-thumbed frog The long-thumbed frog, Fletcher's frog or barking marsh frog (''Limnodynastes fletcheri'') is a species of non-burrowing ground frog native to south-eastern Australia. The species belongs to the genus Limnodynastes. The twelve species in the gen ...

*Southern spadefoot toad (

Scaphiopus ''Scaphiopus'' is a genus of North American amphibian commonly referred to as the North American spadefoots, southern spadefoots, or eastern spadefoot toads. They differ greatly from true toads (those of the family Bufonidae) by having eyes w ...

) *

African clawed frog The African clawed frog (''Xenopus laevis'', also known as the xenopus, African clawed toad, African claw-toed frog or the ''platanna'') is a species of African aquatic frog of the family Pipidae. Its name is derived from the three short claws o ...

Fowler's toad Fowler's toad (''Anaxyrus fowleri'') is a species of toad in the family Bufonidae. The species is native to North America, where it occurs in much of the eastern United States and parts of adjacent Canada. It was previously considered a subsp ...

References

{{reflist Animal breeding Reproduction Fertility