Humans tend to know that incest is taboo. Nature even hints that there is more to this than just cultural restrictions. Most mammals avoid the practice too, as young males instinctively travel far away from their immediate families in search of a prospective mate. However, one population of banded mongooses seems to have missed the memo, and researchers are now investigating why.
According to a study recently published in the journal Biology Letters, several large groups of wild banded mongooses in Queen Elizabeth National Park, Uganda, seem to be making incest commonplace, ignoring what has long been seen as an unspoken rule of nature against inbreeding.
Inbreeding, of course, still happens. In shrinking or isolated habitats, and among disappearing species, naturalists have observed dominant males turning to incest and patricide to ensure that reproduction goes on. A powerful example of this can be seen among the Santa Monica mountain lions. However, this has always been seen as a last-ditch effort to keep the species alive, where all other concerns (such as genetic diversity) are abandoned.
However, for the banded mongoose, its territory isn't shrinking, and its populations remain strong and numerous. So what's with the incest?
The researchers studied 14 groups living in the park over a period of 16 years, using tracking devices and markings to help identify various family members. They quickly noticed that these groups stayed very tight knit - maintaining about 18 adults at one time. Much like wolf packs, these groups also boasted a limited number of dominant males and females who did most of the breeding.
However, unlike wolves, young males and females were never seen splintering away from their family to join another or start a new one. Instead, the naturally short lives of female mongooses seemed to encourage dominant males to mate with their daughters and sisters, ensuring the groups' numbers were always peaked.
The researchers suspect that this may be a consequence of the naturally over-aggressive nature of the mongoose, in which groups will often violently turn away males and females that have split from another group. It also may have a lot to do with the idea of "safety in numbers," meaning waiting for fresh blood to breed with is far riskier than simply and constantly breeding among one another.
Still, the consequences of incest are well known, resulting in averse genetic mutation, birth complications, and even depression. How these mongoose populations compensate for that, remains to be seen.
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