Animal Fertility: "Mothers in Waiting" Survival Strategies in Mammal Fertilization, Gestation and Birth

Spring is underway and mammals are emerging. Juveniles will soon be spotted.  Mammals have several unique strategies that ensure that a fertilized egg becomes a fully realized juvenile. Some of the unique reproductive adaptations like delayed implantation or embryonic diapause are fascinating physiological mechanisms that allow some mammals to give birth to healthy young at the right time of year thus aiding survival. In this diary entry of Voices of the Valley Floor-a and Fauna, the physiology and theories around these various types of delayed implantation are brought to light.

Photo: Winter white ermine and most likely a Long-tailed Weasel (Mustela frenata), pictured here in Telluride.  The tail length to body ratio is difficult to judge with certainty because of the angle of the photo. The length of the tail is a way to discern Long-tailed Weasels (3 to 6 1/2 inch tails) from Short-tailed Weasels (1 1/2 to 3 1/2 inch tails). This ermine has a black-tipped tail as well. The long-tailed weasel delays implantation for months. This radio show discusses different reasons for this strategies.

Photo Credit: Randy Stephens 2017.