Who’s the daddy? Badger reproduction not black and white

Monogamy works fine for swans, beavers and humans, but don't include badgers in this group. Irish research has shown that badgers can carry a collection of babies fathered by different males at different times.

Females are also highly likely to go on sorties into neighbouring badger territories to mate with multiple males from different groups.

It was not known for sure that badgers had the capability of carrying multiple fertilised eggs and holding them for a time before allowing implantation and full pregnancy, said Prof Nicola Marples of Trinity College Dublin.

"It was a complete surprise," said Prof Marples, associate professor of zoology who co-authored the research, published on Thursday in the journal PLOS One.

Known as “natural superfoetation”, it is also an extremely rare ability with just four other species known to be able to do it, she said. Others include the American mink, the brown hare and less well known animals such as the shrew-like Madagascan tenrec.

There are all sorts of advantages, say the zoologists from Trinity, veterinary staff from University College Dublin and scientists from the Department of Agriculture who participated in the project.

The fertilised eggs can be held back for a long time allowing the female to implant one of her choice at a time when there is plenty of food.

And once born the dominant male in her own group will happily protect the newborn, not realising that there may uncertainty over “Who’s the daddy”.

This would have been a near impossible study were it not for the availability of deceased females due to an ongoing national cull of badgers, Prof Marples said.

“The Department of Agriculture has been culling badgers and so there was an opportunity to look at them in more detail. It was a side effect of the cull that is going on, but it allowed us to look at their physiology in great detail.”

The researchers now know that a female badger can hold at least four fertilised eggs of different ages and therefore likely from separate inseminations, she said.

The information is highly valuable for a number of reasons, but chiefly to find ways to reduce the transfer of diseases from badgers to cattle.

“The females will cross territories and it is useful to know who is travelling where,” she said. “And we are trying to set up a vaccine programme where we put down food with vaccine for them. The dominant male will come and eat it all so if you put it around several sets you want to know how many badgers have come into contact with it,” she said.

“This type of research will aid in the effective delivery of a vaccine against tuberculosis, helping badgers and cattle alike,” said Dr Lynsey Stuart of Trinity and a co-author on the paper.