The Three-Minute Outdoorsman: Wild Science from Magnetic Deer to Mumbling Carp

61. The Dating Game, Antelope Style

A N I M A L I N T E L L I G E N C E 231 to terrestrial, even if some of the new immigrants do some cool things. But it doesn’t hurt to learn a thing or two from these unwelcome newcomers. 61 the dating game, antelope style People have known for quite some time that children born from marriages between close relatives often have serious defects. We term this inbreeding. A prime example of the negative effects of inbreeding in people was revealed in a recent study of the Habsburgs, who ruled in Spain from 1516 to 1700. There were a series of Habsburgs kings, and to keep the position in the family , many marriages were arranged between uncles and nieces and between first cousins. For example, Charles’s father, Philip IV, was the uncle of his mother, Mariana of Austria; his great-grandfather, Philip II, was also the uncle of his great-grandmother, Anna of Austria; and his grandmother, Maria Anna of Austria, was simultaneously his aunt. Family get-togethers must have been, um, interesting if not complicated. One of the Habsburgs’ hallmark physical abnormalities was a condition known as mandibular prognathism, or the Habsburg lip, resulting from the lower jaw growing faster than the upper jaw. Chewing was almost impossible. The Spanish dynasty ended with the death of King Charles II in 1700, who was physically and mentally disabled and childless despite two marriages. The “extinction” of the Habsburgs was almost certainly a result of being highly inbred. We now understand that each of us carries some genetic variants that are bad (or “deleterious” in genetics terms). However, humans have two copies of every gene (except those on the Y chromosome), and for many bad genes to be visibly expressed, you have to have two copies. That is, if you have one bad gene, it can be masked (or it is recessive) by having a t h e t h r e e - m i n u t e o u t d o o r s m a n 232 “good” copy on your other chromosome. You’re then a “carrier.” Close relatives, like siblings or first cousins, often share the same bad genes, and therefore marriage between them greatly increases the chances that a child will inherit two copies of the same bad gene. Hence, we have taboos against such marriages for very good reasons. What about the rest of the animals? A scientific study by Stacey Dunn and colleagues from the University of Idaho published in the Journal of Zoology revealed that pronghorn antelope “know” about the negative consequences of inbreeding and “try” to avoid it. Their study was a cool blend of observation of pronghorns at the National Bison Range in Montana and genetics work in the lab. And it took a lot of time and effort to figure out! First, some background. Once very abundant, pronghorns are now less common owing to habitat loss and fragmentation. So that in itself could be a potential problem. If a local population has few individuals and they don’t recognize their relatives, an individual might mistakenly mate with another antelope that’s too closely related for their offspring’s good. In fact, in an earlier study following a population crash, inbreeding was observed in these pronghorns, and the effects included decreased fawn survival to weaning, low birth mass, short foot length, and poor body condition. If you’ve hunted antelope, you know they are social and that there are “herd bucks” who have harems. However, what is probably not apparent to most of us is that females actively switch harems during the mating period, and so they can rate different males before choosing which one will sire their offspring. Yup, mate shopping and swapping. Females leave harems of males who lose fights with other males. Ouch. And as moose do, some females manage to get an external male to challenge the main guy to make sure he’s still boss. Our pronghorn doe wants to make sure she’s getting the best male, and she’s not above calling the question! Actually, there’s even more to it. Does almost always have twins, but about 10 percent of the time, each fawn has a dif- A N I M A L I N T E L L I G E N C E 233 ferent father. Apparently some...