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 changes in the predation behaviors of other species.[1] Related sexual interest and behaviors are expressed and accepted only during this period. Female seasonal breeders will have one or more estrus cycles only when she is "in season" or fertile and receptive to mating. At other times of the year, they will be anestrus, or have a dearth of their sexual cycle. Unlike reproductive cyclicity, seasonality is described in both males and females. Male seasonal breeders may exhibit changes in testosterone levels, testes weight, and fertility depending on the time of year.[2]

Seasonal breeders are distinct from opportunistic breeders, that mate whenever the conditions of their environment become favorable, and continuous breeders, like humans, that mate year-round.

Timing of seasonal breeding

The breeding season is when seasonal breeders reproduce. Various variables can affect when it occurs.[3] A primary influence on the timing of reproduction is food availability. Organisms generally time especially stressing events of reproduction to occur in sync with increases in food availability. This is not always true although, both because of the importance of other factors and the invalidation of this generalization. For example, in species reproducing at high latitudes, food availability before breeding is more important than availability during reproduction itself. Other factors can also be responsible. For example, species that are preyed upon frequently may time reproduction to occur out of sync with the peak in density of predators.[4]


The hypothalamus is considered to be the central control for reproduction due to its role in hormone regulation.[5] Hence, factors that determine when a seasonal breeder will be ready for mating affect this tissue. This is achieved specifically through changes in the production of the hormone GnRH. GnRH in turn transits to the pituitary where it promotes the secretion of the gonadotropins LH and FSH, both pituitary hormones critical for reproductive function and behavior, into the bloodstream. Changes in gonadotropin secretion initiate the end of anestrus in females.

Day length

Seasonal breeding readiness is strongly regulated by length of day (photoperiod) and thus season. Photoperiod likely affects the seasonal breeder through changes in melatonin secretion by the pineal gland that ultimately alter GnRH release by the hypothalamus.[3]

Hence, seasonal breeders can be divided into groups based on fertility period. "Long day" breeders cycle when days get longer (spring) and are in anestrus in fall and winter. Some animals that are long day breeders include; ring-tailed lemurs, horses, hamsters, groundhogs, and mink. "Short day" breeders cycle when the length of daylight shortens (fall) and are in anestrus in spring and summer. The decreased light during the fall decreases the firing of the retinal nerves, in turn decreasing the excitation of the superior cervical ganglion, which then decreases the inhibition of the pineal gland, finally resulting in an increase in melatonin. This increase in melatonin results in an increase in GnRH and subsequently an increase in the hormones LH and FSH, which stimulate cyclicity.[6]

See also

  • Rut, the mating season of various ungulate species


  1. ^ Prendergast BJ (2005). "Internalization of seasonal time". Horm. Behav. 48 (5): 503–11. doi:10.1016/j.yhbeh.2005.05.013. PMID 16026787.
  2. ^ Johnson, A.D. (1970). Development, Anatomy, and Physiology. Academic Press. ISBN 0-12-386601-4.
  3. ^ a b M. N. Lehman; R. L. Goodman; F. J. Karsch; G. L. Jackson; S. J. Berriman; H. T. Jansen (1997). "The GnRH System of Seasonal Breeders: Anatomy and Plasticity". Brain Res. Bull. 44 (4): 445–57. doi:10.1016/S0361-9230(97)00225-6. PMID 9370210.
  4. ^ Williams, Cory T.; Klaassen, Marcel; Barnes, Brian M.; Buck, C. Loren; Arnold, Walter; Giroud, Sylvain; Vetter, Sebastian G.; Ruf, Thomas (2017). "Seasonal reproductive tactics: annual timing and the capital-to-income breeder continuum". Philosophical Transactions of the Royal Society B: Biological Sciences. 372 (1734): 20160250. doi:10.1098/rstb.2016.0250. ISSN 0962-8436.
  5. ^ "An Overview of the Hypothalamus". EndocrineWeb. Retrieved 2017-01-26.
  6. ^ L. Senger, Phillip (2005). Pathways to Pregnancy and Parturition (2nd Revised ed.). p. 154.
Bengal slow loris

The Bengal slow loris (Nycticebus bengalensis) or northern slow loris is a strepsirrhine primate and a species of slow loris native to the Indian subcontinent and Indochina. Its geographic range is larger than that of any other slow loris species. Considered a subspecies of the Sunda slow loris (N. coucang) until 2001, phylogenetic analysis suggests that the Bengal slow loris is most closely related to the Sunda slow loris. However, some individuals in both species have mitochondrial DNA sequences that resemble those of the other species, due to introgressive hybridization. It is the largest species of slow loris, measuring 26 to 38 cm (10 to 15 in) from head to tail and weighing between 1 and 2.1 kg (2.2 and 4.6 lb). Like other slow lorises, it has a wet nose (rhinarium), a round head, flat face, large eyes, small ears, a vestigial tail, and dense, woolly fur. The toxin it secretes from its brachial gland (a scent gland in its arm) differs chemically from that of other slow loris species and may be used to communicate information about sex, age, health, and social status.

The Bengal slow loris is nocturnal and arboreal, occurring in both evergreen and deciduous forests. It prefers rainforests with dense canopies, and its presence in its native habitat indicates a healthy ecosystem. It is a seed disperser and pollinator, as well as a prey item for carnivores. Its diet primarily consists of fruit, but also includes insects, tree gum, snails, and small vertebrates. In winter, it relies on plant exudates, such as sap and tree gum. The species lives in small family groups, marks its territory with urine, and sleeps during the day by curling up in dense vegetation or in tree holes. It is a seasonal breeder, reproducing once every 12–18 months and usually giving birth to a single offspring. For the first three months, mothers carry their offspring, which reach sexual maturity at around 20 months. The Bengal slow loris can live up to 20 years.

The species is listed as "Vulnerable" on the IUCN Red List, and is threatened with extinction due to a growing demand in the exotic pet trade and traditional medicine. It is one of the most common animals sold in local animal markets. In traditional medicine, it is primarily used by wealthy to middle-class, urban women following childbirth, but also to treat stomach problems, broken bones, and sexually transmitted diseases. It is also hunted for food and suffers from habitat loss. Wild populations have declined severely, and it is locally extinct in several regions. It is found within many protected areas throughout its range, but this does not protect them from rampant poaching and illegal logging. Critical conservation issues for this species include enhancing protection measures, stricter enforcement of wildlife protection laws, and increased connectivity between fragmented protected areas.


The blesbok or blesbuck (Damaliscus pygargus phillipsi) is an antelope endemic to South Africa. It has a distinctive white face and forehead which inspired the name, because bles is the Afrikaans word for a blaze such as one might see on the forehead of a horse.

Blue-headed pitta

The blue-headed pitta (Hydrornis baudii) is a species of bird in the pitta family Pittidae. It is endemic to Borneo.

Chilean swallow

The Chilean swallow (Tachycineta leucopyga) is a species of bird in the family Hirundinidae. It breeds in Chile and Patagonia, migrating north as far as Bolivia, Paraguay, and Rio Grande do Sul.


The crescentchests are a genus, Melanopareia, of birds from South America. The genus has long been placed with the tapaculos in the Rhinocryptidae family. Their placement there has been questioned and in 2007 the genus was placed in its own family, Melanopareiidae, by the South American Classification Committee. Subsequently, the family was accepted by the International Ornithological Congress Bird List and the Clements Checklist. The family Melanopareiidae was formally erected in 2009.The crescentchests range in length from 14 to 16 cm (5.5–6.3 in), in weight from 16 to 23 g (0.56–0.81 oz) and have relatively long tails compared to the tapaculos. The plumage is striking with a distinctive band across the chest that gives the group their name.The crescentchests are birds of arid scrub. They generally forage on the ground, but their diet has not yet been recorded. Two species, the collared crescentchest and olive-crowned crescentchest, are widely distributed across central and southern Brazil, Bolivia, Paraguay and northern Argentina. The double-collared crescentchest, which was recently split from the collared crescentchest, is found in eastern Bolivia, whilst the other two species, the elegant crescentchest and Marañón crescentchest, have a more restricted distribution in Peru and Ecuador.Little is known about the behaviour of the crescentchests. The only species about which anything is known about the breeding behaviour is the olive-crowned crescentchest. That species is a seasonal breeder. The nest of that species is a 15 cm high cup made of vegetable fibres and palm fronds, hidden in grasses or low shrubs close to the ground. The clutch size is two to three eggs, the eggs are white with blotches or black spots.No species of crescentchest is considered by the IUCN to be threatened by human activities, but the Marañón crescentchest is listed as near threatened. Although the species is apparently tolerant of some disturbance it has a tiny global range and is uncommon even within that range.


Esacus is a genus of bird in the stone-curlew family Burhinidae. The genus is distributed from Pakistan and India to Australia. It contains two species, the great stone-curlew and the beach stone-curlew.

Giant conebill

The giant conebill (Oreomanes fraseri) is a small passerine bird, one of the tanager family. The only member of the genus Oreomanes it is closely related to the regular conebills Conirostrum though it differs in its larger size and nuthatch-like foraging habits.

The giant conebill is 15 centimetres (5.9 in) in length and weighs 22–27 grams (0.78–0.95 oz). It is grey above, deep chestnut below, and with a white patch on the cheeks. It is found in the Andes from Colombia to Ecuador, and Peru to Bolivia. It lives in Polylepis trees of the family Rosaceae.

The giant conebill lives individually or in groups of 5 or less. It peels bark off Polylepis trees to find insects. It also eats aphids and sugary solutions secreted by Gynoxys. The species is a seasonal breeder, nesting at the start of the rainy season (September to December in Bolivia where it has been studied). The nest is an open cup set on the branches of Polylepis, and the average clutch size is 1.8 eggs. Both parents incubate the eggs, feed the chicks and remove the faecal sacs.Its decline is attributed to the destruction and fragmentation of Polylepis woodland.

The binomial commemorates the British zoologist Louis Fraser.

Grey fantail

The grey fantail (Rhipidura albiscapa) is a small insectivorous bird. It is a common fantail found in Australia (except western desert areas), the Solomon Islands, Vanuatu and New Caledonia. The species is considered by many to be conspecific with the New Zealand fantail (Rhipidura fuliginosa); however, differences in its calls lead some authorities to treat it as a separate species.

Kalahari scrub robin

The Kalahari scrub robin (Cercotricha paena) is a species of bird in the family Muscicapidae. It is sometimes known as the sandy scrub robin.

Mato Grosso dog-faced bat

The Mato Grosso dog-faced bat (Neoplatymops mattogrossensis), is a bat species from South America. It is found in Brazil, Colombia, Guyana and Venezuela.


Nasikabatrachus is a genus of frogs. It has been treated as the only genus in the family Nasikabatrachidae, or included in the family Sooglossidae. Two species are recognized, Nasikabatrachus bhupathi and Nasikabatrachus sahyadrensis, both endemic to southern India. With its closest relatives in the Seychelles, Nasikabatrachus is thought to have evolved separately for millions of years. Its discovery added to the evidence that Madagascar and the Seychelles separated from the Indian landmass sometime well after the breakup of Gondwana had started. Reproduction the purple frog is a explosive seasonal breeder specie, which completes its developmental in ephemeral streams. And, it’s breeding activities typically take place during the months of April and May, whose Breeding activities take place during the months of April–May, which is during the pre-monsoon shower.

New Zealand fantail

The New Zealand fantail (Rhipidura fuliginosa) is a small insectivorous bird, the only species of fantail in New Zealand. It has four subspecies: R. f. fuliginosa in the South Island, R. f. placabilis in the North Island, R. f. penita in the Chatham Islands, and the now-extinct R. f. cervina formerly on Lord Howe Island. It is also known by its Maori names, Pīwakawaka, Tīwakawaka or Piwaiwaka; the common pied morph is also known as pied fantail (not to be confused with the Malaysian or Philippine pied fantails), and the uncommon dark morph is also known as black fantail (not to be confused with the black fantail of New Guinea). The species has been considered by many to be conspecific (the same) as the grey fantail of Australia and New Caledonia; however, due to significant differences in its calls, many authorities now treat it as a separate species.

Opportunistic breeder

Flexible or opportunistic breeders mate whenever the conditions of their environment become favorable. Their ability and motivation to mate are primarily independent of day-length (photoperiod) 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.Thus, they are distinct from seasonal breeders that rely on changes in day length to induce entry into estrus and to cue mating, and continuous breeders 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 anurans 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.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 (Dendrolagus) previously categorized as a seasonal breeder is now suspected to be an opportunistic breeder.Additionally, opportunists can have qualities of seasonal breeders. The red crossbill 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.


The oribi (; Ourebia ourebi) is a small antelope found in eastern, southern and western Africa. The sole member of its genus, the oribi was first described by the German zoologist Eberhard August Wilhelm von Zimmermann in 1782. Eight subspecies are identified. The oribi reaches nearly 50–67 centimetres (20–26 in) at the shoulder and weighs 12–22 kilograms (26–49 lb). This antelope features a slightly raised back, and long neck and limbs. The glossy, yellowish to rufous brown coat contrasts with the white chin, throat, underparts and rump. Only males possess horns; the thin, straight horns, 8–18 centimetres (3.1–7.1 in) long, are smooth at the tips and ringed at the base.

Typically diurnal, the oribi is active mainly during the day. Small herds of up to four members are common; males defend their group's territory, 25–100 hectares (62–247 acres) large. The oribi is primarily a grazer, and prefers fresh grasses and browses occasionally. A seasonal breeder, the time when mating occurs varies geographically. Unlike all other small antelopes, oribi can exhibit three types of mating systems, depending on the habitat – polyandry, polygyny and polygynandry. Gestation lasts for six to seven months, following which a single calf is born; births peak from November to December in southern Africa. Weaning takes place at four to five months.

The oribi occurs in a variety of habitats – from savannahs, floodplains and tropical grasslands with 10–100 centimetres (3.9–39.4 in) tall grasses to montane grasslands at low altitudes, up to 2,000 metres (6,600 ft) above the sea level. This antelope is highly sporadic in distribution, ranging from Senegal in the west to Ethiopia and Eritrea in the east and southward to Angola and the Eastern Cape (South Africa). The oribi has been classified as Least Concern by the IUCN; numbers have declined due to agricultural expansion and competition from livestock.

Red-capped plover

The red-capped plover (Charadrius ruficapillus), also known as the red-capped dotterel, is a small plover.

It breeds in Australia. The species is closely related to (and sometimes considered conspecific with) the Kentish plover, Javan plover and white-fronted plover.

Sickle-billed vanga

The sickle-billed vanga (Falculea palliata) is a species of bird in the vanga family Vangidae. It is monotypic within the genus Falculea. It is endemic to Madagascar. Its natural habitats are tropical dry forests and tropical dry shrubland.

Silky sifaka

The silky sifaka (Propithecus candidus) is a large lemur characterized by long, silky, white fur. It has a very restricted range in northeastern Madagascar, where it is known locally as the simpona. It is one of the rarest mammals on Earth, and is listed by the International Union for Conservation of Nature as one of the world's 25 most critically endangered primates. The silky sifaka is one of nine sifaka species (genus Propithecus), and one of four former subspecies of diademed sifaka (P. diadema). Studies in 2004 and 2007 compared external proportions, genetics, and craniodental anatomy supporting full species status, which has generally been accepted.

The silky sifaka has a variable social structure, and lives in groups of two to nine individuals. It spends most of its day feeding and resting, though it also devotes a considerable amount of time to social behaviors, such as playing and grooming, as well as travelling. Females occasionally take priority over males during feeding. Like other eastern sifakas, it consumes mainly leaves and seeds, but also fruit, flowers, and even soil on occasion. It is a seasonal breeder and only mates one day a year during the start of the rainy season. As with other sifaka species, nonmaternal infant care is common. Group members of all ages and both sexes often groom, play with, occasionally carry, and even nurse infants that are not their own. The silky sifaka vocalizes frequently despite its moderately sized vocal repertoire consisting of seven adult calls. Like all other lemurs, it relies strongly on scent for communication. Males frequently scent-mark on top of scent marks made by other group members, particularly females. Males also gouge trees with their toothcomb (a special arrangement of the bottom, front teeth) prior to chest scent-marking. This chest marking results in males having brown-stained chests, the only visible trait that can be used to distinguish between adult males and adult females.

The species is only found within a few protected areas in the rainforests of northeastern Madagascar, with the majority of the remaining population in Marojejy National Park and Anjanaharibe-Sud Special Reserve. A few groups have also been found in the Makira Forest Protected Area, the Betaolana Corridor, and some unprotected forest fragments. The silky sifaka is hunted throughout its range as no local fady (taboo) exists against eating this species. Habitat disturbance, such as slash-and-burn agriculture (tavy), illegal logging of precious woods (particularly rosewood) and fuel-wood, also occurs within the protected areas where it is found.

Silver-eared mesia

The silver-eared mesia (Leiothrix argentauris) is a species of bird from South East Asia.

White-starred robin

The white-starred robin (Pogonocichla stellata) is a species of bird in the Old World flycatcher and chat family Muscicapidae. It is also sometimes more simply called the starred robin. It is monotypic within the genus Pogonocichla. There are around twelve subspecies. The species is found in East and southern Africa. It is a forest species, occurring in montane forest in the north of its range but closer to sea level further south. This is a brightly coloured robin with a bright yellow breast and belly, a slate coloured head with spots on the eyes and throat and blueish wings.

The white-starred robin gives a range of calls that vary geographically. The diet is dominated by insects, although some fruit is taken as well. It is a territorial and seasonal breeder that lays up to three eggs in a domed nest. The generic name Pogoncichla is derived from the Greek pogon for beard, a reference to the white spots on the throat and face, and kikhle for thrush. Similarly the specific name stellata and the species' common name are also derived from the facial spots.

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