![]() ![]() ^ Hugh Tyndale-Biscoe (22 April 2005)."Diet salinity and vasopressin as reproduction modulators in the desert-dwelling golden spiny mouse (Acomys russatus)". "Integration of photoperiodic and food cues to time changes in reproductive physiology by an opportunistic breeder, the red crossbill, Loxia curvirostra (Aves: Carduelinae)". "The influence of daylength on reproductive timing in the red crossbill". Straham, ed., Mammals of Australia, Washington, DC: Smithsonian Institution Press, 1995, pp. In: Conn PM, Freeman ME, ed., Neuroendocrinology in physiology and medicine. The Neuroendocrine Control of Seasonal Rhythms. The Johns Hopkins University Press, 1994, p. Partial list of opportunistic breeders Mammals While reproduction is generally independent of photoperiod, animals can still experience reduced fertility with changes in day-length. Increased levels of salinity in drying vegetation cause females to experience a reproductive hiatus. An example is the golden spiny mouse where changes in dietary salt in its desert habitat due to rainfall appear to cue reproductive function. Opportunistic breeders are typically capable of breeding at any time or becoming fertile within a short period of time. Conversely, food availability by itself incompletely promotes reproductive development. 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. Īdditionally, opportunists can have qualities of seasonal breeders. Thus, the tree kangaroo (Dendrolagus) previously categorized as a seasonal breeder is now suspected to be an opportunistic breeder. In equatorial climes, the change in seasons is not always perceptible and thus, changes in day length not remarkable. Since changes in season can coincide with favorable changes in environment, the distinction between seasonal breeder and opportunistic can be muddled. ![]() Those that are mammals tend to be small rodents. Many opportunistic breeders are non-mammals. These include sporadic wet and sporadic dry, describing animals that breed sporadically not always under favorable conditions of rain or lack thereof. 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. 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. Another factor is the presence of suitable breeding sites, which may only form with heavy rain or other environmental changes. 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. Flexible or opportunistic breeders mate whenever the conditions of their environment become favorable. ![]()
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