The Web of Life (121-3-5) Education


Another facet of parenting is teaching young to survive. Though many animals tutor offspring in various skills, the most common imperative for training is in carnivores teaching their young to hunt. Spotted hyena pups are weaned at a year, but it is months later before they are adept hunters. Cubs of cheetah, tigers, and polar bears are taught hunting skills for 2 years before fending for themselves.


Prolactin is a hormonal protein best known for its role in promoting mammal lactation. Prolactin has a long evolutionary employment, having been conserved in genomes for up to 800 million years. Prolactin helps fish, the oldest vertebrates, with water and salt balance.

Prolactin is an important immune system regulator as well playing a vital role in the cell cycle. Prolactin affects migratory behavior in fish and birds.

In fish, prolactin plays a role in attaining sexual maturity and in reproductive cycling. In mammals, prolactin provides sexual gratification: dampening dopamine, which causes sexual arousal.

After mammalian childbirth, previous inhibitions on prolactin – by estrogen and progesterone during pregnancy – are released. Prolactin stimulates milk production.

While prolactin plays a critical role in maternal care, it also stimulates paternal care in fish, amphibians, and birds. Male parental care in cichlids, the North American bluegill, and threespine stickleback, owes in part to pronounced prolactin levels.

In birds, prolactin levels rise during egg-laying, and peak during incubation. Levels decline when eggs hatch. Other stimuli – vocal and visual – prompt feeding hatchlings.

Prolactin is an avian paternity hormone: increasing in male birds during incubation. Nonbreeding birds that assist at the nest are primed by high levels of prolactin. Scrub jays are exemplary.

Chickens and several water birds are precocial, including ducks, geese, rails, and waders (shorebirds). Prolactin makes mom mind her ducklings, but for only a few weeks. As prolactin level drops, a hen’s bond with her brood lessens. By week 6, indifference is good behavior. A hen might even be antagonistic toward her ducklings without the influence of prolactin.