April 26, 2006

Alpha hyena mothers help cubs become top dog

LONDON (Reuters) - Dominant female spotted hyenas give
their young a head start in life by passing on hormones that
make their cubs more aggressive and likely to survive,
researchers said on Wednesday.

They have shown that alpha hyena mothers have higher than
normal levels of the male hormone androgen late in pregnancy
which they pass on to their cubs, enabling them to become top

Androgen is linked to male characteristics such as muscle
development, aggression and sexual behavior.

"What this means is that there are gifts a mom can give to
her baby," said Kay Holekamp of Michigan State University.

"She can manipulate her offspring's behavior and help her
kids to survive and reproduce successfully by transferring
status-related traits via prenatal hormone exposure," she added
in a statement.

Holekamp and her colleagues discovered the animals' secrets
while studying wild spotted hyenas in Kenya over two decades.
Their findings are reported in the journal Nature.

Spotted hyenas live in a female-dominated society. Females
are bigger than males and more dominant. Their reproductive
organs are similar which makes it difficult to determine their
sex and awkward for the animals to mate.

"You don't find many mammals where the female is boss,"
said Holekamp.

Although females have masculine traits and unusual
reproductive organs, they still some maintain female
characteristics. The hormones from the top-ranking mother
enables her female cubs to attain the same status and be
superior hunters.

Male offspring born to high status mothers are also more
aggressive, according to the researchers.