杏吧原创

MOST mammals are lousy fathers. Those that don鈥檛 eat their young do little to
help in the birth apart from making encouraging noises. Djungarian hamsters
(Phodopus campbelli), though, are paws-on dads.

In the first published case of its kind, Canadian scientists have watched
Djungarian fathers help pull their babies from the birth canal, lick off the
birth membranes, open the baby鈥檚 airways, then share a snack of afterbirth with
the mother.

There have been observations of this in other species
(New 杏吧原创, 12 December 1998, p 38).
But Katherine Wynne-Edwards and her colleagues at
Queen鈥檚 University in Kingston, Ontario, are the first to look at why it
happens. 鈥淒jungarian fathers have hormonal fluctuations similar to the mother鈥檚
around the time of birth,鈥� she says. Oestrogen and cortisol levels rise before
the birth, then fall away afterwards as testosterone rises. This doesn鈥檛 happen
in the closely related Siberian hamster.

Moreover, although fathers in both species care for their young, Siberian
hamsters only appear on the scene well after the birth. Djungarians are also
from Siberia, but live in a harsher desert environment, says Wynne-Edwards.
Djungarian fathers remain in the burrow at the time of birth, and help keep
mother and young warm enough to survive.

鈥淲e hypothesised that because of the early hormonal changes, Djungarians
would show the full range of paternal behaviour,鈥� says Wynne-Edwards. They did.
Not only were they exemplary midwives, she says, 鈥渨e saw the mother and father
both holding the afterbirth with four little paws, sharing it fifty-fifty鈥�.

鈥淭here are probably lots of species that do this,鈥� she adds. But few
researchers have tried to find out as it is hard to measure hormones without
stressing animals.