MISSOULA - Spring’s warmer temperatures and longer days are nice for people, but for wildlife, this shift can be essential.
Spring in the Northern Hemisphere begins when the sun arrives directly over the equator as the Earth moves through its orbit.
With spring comes the change in weather.
One way wildlife copes with the changes in climate and environment is adapting to when their babies are born.
Timing is everything. This maximizes reproductive success as it increases the chances of survival for their babies and enhances future reproduction for the mom and babies.
Spring offers everything newborn wildlife will need.
From warmer weather, good vegetation coverage to hide from predators, and better availability of food.
It also means longer days allowing for more time to feed.
Many seasonal carnivores have gestation periods that are short relative to their body size so that the embryo grows quickly enough between the mating period in fall and the birth date in spring.
While others have extended gestation periods so that they give birth at the right time of year.
A neat adaptation to extend the time between mating and birth is called embryonic diapause which is the suspended state of pregnancy where the embryo doesn’t attach itself to the uterine wall for several months.
Diapause -- or delayed implantation -- allows for the mother to wait out unfavorable conditions like lack of food, not enough fat stores or having juveniles that still haven’t been weaned.
Bears, for instance, breed in the late spring or early summer. The mother then hunts for food until she has enough body fat so that she can begin her pregnancy.
The embryos will then implant as she goes into her den for the winter. So the cubs would be born in late winter and then emerge with mom in the spring
Starvation or other stresses somehow provoke the pregnancy process to be put on hold. This response is an effort to protect their survival.
Read more here: https://www.sciencedaily.com/releases/2018/05/180507111834.htm