The Battle to be Born: Sand Tiger Shark edition

It’s a dog-eat-dog world and inside a sand tiger shark’s womb, it’s a shark-eat-shark world. While inside the womb, baby sand tiger sharks duke it out with their fellow unborn baby tiger shark siblings to be the lone victor (and only child) in this real life Hunger Games battle to the death.

In a report by National Geographic, Ed Yong discusses new information about sand tiger sharks gathered from a new study.

“The first embryo to emerge in each uterus—the ‘hatchling’—always cannibalises its younger siblings. It’s so voracious that at least one scientist has been bitten by a sand tiger pup while unwisely sticking a finger in a pregnant female’s uterus.”

From their diet of nutrients from its mother and the bodies of their siblings, these cannibalistic sharks emerge from the womb at a size that is big enough so that they can protect themselves from predators. Makes you re-think your own sibling rivalry a bit.

Check out more on sharks and animal family life from PUP!

1. A Natural History of Families by Scott Forbes

Why do baby sharks, hyenas, and pelicans kill their siblings? Why do beetles and mice commit infanticide? Why are twins and birth defects more common in older human mothers? A Natural History of Families concisely examines what behavioral ecologists have discovered about family dynamics and what these insights might tell us about human biology and behavior. Scott Forbes’s engaging account describes an uneasy union among family members in which rivalry for resources often has dramatic and even fatal consequences.

In nature, parents invest resources and control the allocation of resources among their offspring to perpetuate their genetic lineage. Those families sometimes function as cooperative units, the nepotistic and loving havens we choose to identify with. In the natural world, however, dysfunctional familial behavior is disarmingly commonplace.

While explaining why infanticide, fratricide, and other seemingly antisocial behaviors are necessary, Forbes also uncovers several surprising applications to humans. Here the conflict begins in the moments following conception as embryos struggle to wrest control of pregnancy from the mother, and to wring more nourishment from her than she can spare, thus triggering morning sickness, diabetes, and high blood pressure. Mothers, in return, often spontaneously abort embryos with severe genetic defects, allowing for prenatal quality control of offspring.

Using a broad sweep of entertaining examples culled from the world of animals and humans, A Natural History of Families is a lively introduction to the behavioral ecology of the family.

2. Sharks of the World by Leonard Compagno, Marc Dando, & Sarah Fowler

Everyone’s heard of the Great Whites. But most people know little of the hundreds of other types of sharks that inhabit the world’s oceans. Written by two of the world’s leading authorities and superbly illustrated by wildlife artist Marc Dando, this is the first comprehensive field guide to all 440-plus shark species. Color plates illustrate all species, and detailed accounts include diagnostic line drawings and a distribution map for each species. Introductory chapters treat physiology, behavior, reproduction, ecology, diet, and sharks’ interrelationships with humans.