Mother’s Day may have come and gone, but mothering is just beginning for much of Nevada’s Wildlife! Desert tortoises are burying their eggs, birds are building their nests, and deer are beginning to lactate (secreting milk from their mammary glands).
The variety of mothering in nature is diverse; some mothers will leave their young before they are born, but others will stay and continue to provide care for several years. Why, though, do some mothers invest more time and energy into rearing their offspring than others? Part of the answer lies in the evolution of their relationship with the embryos. For example, birds and mammals which fertilize their eggs internally tend to invest more time and energy into rearing their offspring compared to fish and frogs which fertilize their eggs externally. Does this mean that birds and mammals care more about their babies than fish and frogs do?
Whether or not mothers
stick around after the birth of their babies is not a behavior that is driven
by choice. It is driven by instinct. All animals, including humans, have
maternal instincts that influence the parental care they provide for their
offspring. Maternal instincts are innate (born with) sets of knowledge that
influence caregiving behaviors associated with motherhood. For example, the
maternal instincts of fish and frogs are to find the most ideal oviposits
(egg-laying areas) for their eggs so that predators will not eat them. This
helps to ensure that the males of their species will be able to find the eggs
and fertilize them. The maternal instincts of reptiles, like tortoises, which
fertilize their eggs internally, are to find suitable nesting grounds for
burying their broods so that they will be safe from predators and unfavorable
temperatures. There’s no need for Mama Tortoise to stick around because by the
time her babies hatch they will instinctively know to go to the water.
Photo by Vincent van Zalinge on Unsplash
For birds and mammals, though, which also fertilize internally, parental care is a little more complex. Compared to fish, frogs, and reptiles, birds and mammal babies are much more helpless and dependent at birth. Both rely on their mothers to feed them and protect them from predators. For example, a Mama Bird Killdeer will lure predators away from the nest by faking a broken wing. Mama Badger will attack anything perceived as an oncoming threat to their offspring.
As you get outside to explore this spring, keep your eyes sharp for mommas and their babies. Look up into trees to see if you can spy nests, and look down low, too. Look for signs of motherhood in streams and mud-puddles. Evidence of the reproduction cycle is all around us. If you spy a baby, enjoy their irresistible cuteness, but remember that Mama may be close by, so respect their space.