Seasonal breeder

Seasonal breeders are

Seasonal breeders are distinct from opportunistic breeders, that mate whenever the conditions of their environment become favorable, and continuous breeders 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, however, 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]

Physiology

The

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

References