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What's Wrong with Animal Incest?

I don't know about where you're from, but in Minnesota, dolphins are a pretty big deal. It might have something to do with how far we need to travel in order to see dolphins in the wild. Or it might just be that dolphins are really cool. Either way, you can imagine that when the Minnesota Zoo announced on Monday that our dolphins will be leaving for good, it was kind of a big deal.

The fuss was amplified by the fact that the Minnesota state government recently allocated $4 million to the zoo in order to refurbish the dolphin tank. In response to the uproar, the zoo's CEO, Lee Ehmke, later released a statement providing further explanation as to why the current dolphins have to leave and why there are no dolphins available to replace them.

dolphinsPhoto by my dolphin-loving friend Jenna

Knowing I wasn't the only one still disappointed about the change, I decided to delve further into why our dolphin friends got the boot. After corresponding with Kevin Willis, the MN Zoo's Director of Bioprograms, I found out that the issue is a lot more complicated than I realized.

Willis said that the MN Zoo, belongs to a "Dolphin Consortium," which includes 25% of all U.S. facilities that house dolphins. Members of the Consortium work together to maintain a collective population of dolphins. Part of the Consortium's concern is to maintain genetic variance in the population.

"In brief, the Consortium is working to maintain genetic variation by

preferentially breeding wild caught ("founder") animals to capture as

much of their genetic (allelic) variation as possible," Willis told me. "We are also

preventing the breeding of relatives using contraception and


As Willis explained, the Consortium's strategy involves loaning dolphins between zoos. That way

every dolphin can be fit to a good social situation and can be bred to a

genetically compatible mate. In fact, the two dolphins currently living at the Minnesota Zoo, Semo and Allie, aren't actually owned by that zoo.

While considerations of genetic variation didn't

directly impact the MN Zoo's decision to send Semo and Allie away,

genetic variation has impacted the zoo's past decisions.

A few

years ago, the MN Zoo relocated the only dolphin they actually own, a

female named Spree, to keep her from mating with her own dad. "She was on contraceptives so that she and Semo

(her sire) would not produce an offspring, but of course we did want

her to produce offspring. We moved her to a facility so that she could

live with other females and not be with her sire," said Willis.

I think we all realize there are many reasons why incest is not a good habit for humans, but what exactly would be wrong with Spree getting together with Semo?

Willis explained that it comes down to heterozygosity, which is genetic variation at the individual level. "Inbreeding,

the mating of related animals, results in a decrease in the

heterozygosity of the offspring relative to the parents. That decrease

in heterozygosity can lead to an increased incidence of congenital

anomalies and poor health."

Heterozygosity often influences a zoo's decisions when breeding captive animals of all kinds. Unfortunately, some zoos intentionally breed relatives in order to produce offspring with rare features. White tigers, for instance, are so rare that they can only be produced through incest. As a result, many of these would-be majestic cats are born with less-than-regal deformities such crossed vision and facial deformities. Thankfully, in June 2011, the Association of Zoos and Aquariums published an official statement cracking down on this twisted practice.

Incest can even be a problem in wild animal populations, especially when meddling humans are involved. In Australia, Tasmanian devil populations have taken a dive due to a facial tumor disease. By hunting devils and killing them as pests, humans effectively exterminated a large chunk of the devils' genetic diversity.

The remaining devils were forced to inbreed, which gave them very similar immunological genes, leaving them open to the facial tumor disease. The disease is passed between devils through biting and is almost always fatal.

Moral of the story: no one, including animals, should breed with their relatives.  

512px-Tasmanian_Devil_Facial_Tumour_Disease.png"I look just like my mama/sister!"

Photo by Menna Jones via Wikimedia Commons

Katherine Dickinson
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