Inbreeding avoidance behaviors may spell doom for the African wild dog

African wild dogs (Lycaon pictus or Canis pictus)  are in a lot of trouble.

They once ranged over much of Sub-Saharan Africa, where they were part of an extensive guild of large Carnivorans that targeted the large herds of ungulates that once ranged over this part of the continent.

With European colonization, these animals were deemed pests. They were thought to be livestock killers of the worst sort, and it was also thought that they regularly preyed upon people– a claim for which there is very little evidence.

It was also assumed that these creatures were nothing more than feral domestic dogs.  The old name for this animal was Cape hunting dog, a name that sort of implies that these dogs were nothing more than feral hunting dogs that had run off from native settlements.

But even after colonization ended, Africa’s human development challenges mean that these animals can now only exist in fewer and fewer places.  The current populations of this species are also highly fragmented, which means the historic gene flow that once occurred over a broad swathe of territory no longer happens.

This gene flow occurs rather unusually in this species. African wild dog males almost never leave their natal packs.

However, bitches do leave within between the first and third year of life. There is a lot more competition for mates with bitches in this species than with dogs. With so much competition for mates, the younger females usually just leave to find their own mates in other packs. Like wolves, only a single female normally breeds, and if a second female breeds, it’s not unusual for the main breeding female to steal her pups and raise them in her den.  So if a bitch wants to raise her own litter, she’s got to leave.

Bitch dispersal prevents inbreeding in African wild dogs, but because they no longer can disperse over larger distances, the populations within an area are becoming more related over time.

Like many wild canids, African wild dogs exhibit inbreeding avoidance behavior.  Dogs from the same pack very rarely will mate with close kin from the same natal pack.

A recent study that was published PLoS ONE found that African wild dogs also won’t mate with aunts, uncles, nieces, nephews, or grandparents from the same natal pack, even if they encounter each other several years later. In the South African study stample, 0nly a single breeding pair was confirmed to have been between two third order or closer relatives.

With this amount of inbreeding avoidance, the authors looked at computer models to see how long it would take such a population to become extinct solely upon the basis of its inbreeding avoidance behavior. Populations that avoided incestuous breedings between a parent and siblings and between siblings were estimated to become extinct in 63 years. Those that avoided  mating with second order relatives were estimated to become extinct within 37 years, and those that avoided third order relatives were estimated to go extinct within 19 years.

With African wild dog existing in such fragmented populations, their extreme inbreeding avoidance behavior may very well spell doom for them.

Inbreeding avoidance has been a very useful for wild dogs as they have evolved. With the exception of the island foxes and domestic dogs, inbreeding is not a frequent occurrence among members of Canidae, and it has contributed to greater genetic diversity in many wild dog populations than might otherwise be assumed.

But there is also a paradox to this inbreeding avoidance.

If animals have such a resistance to doing so, they are unlikely to do so should their numbers drop significantly and the only available mates be close relatives.

And this can kill them off far more rapidly than the effects of an inbreeding depression.

Further, we know that lots of wild Carnivons have survived extreme genetic bottlenecks.

Cheetahs are the textbook example. Their population experienced a massive crash about 10,000 years ago, losing over 90 percent of their genetic variability.  Cheetahs were able to survive this bottleneck and were thriving until about a 150 years ago.

Northern elephant seals are another example  of a Carnivoran surviving an extreme genetic bottleneck.  Whalers would stop by the seals’ breeding beaches to augment their cargo, and by the end of the nineteenth century, there may have been as few as 20 northern elephant seals left.  There are now 100,000 of them, and there is no evidence of any deleterious effects of inbreeding on the population, though they may be more susceptible to disease, pollution, and climate change issues.  Of course, northern elephant seals harem breed, and only a few males of the species wind up siring the pups at any given time– a kind of natural popular sire effect. It’s very likely that elephant seals within the same populations were always in some way related, and because the animals had evolved this type of breeding system, they may have evolved a certain amount of inbreeding tolerance that hasn’t been observed in any species of dog, which almost universally reproduce within a bonded pair.

Inbreeding avoidance behaviors do keep populations genetically diverse.

But it can be an Achilles’ heel.

If a population is so adverse to inbreeding, it won’t be able to continue on if the only possible mated pairs are relatives.

Inbreeding avoidance behavior can be a boon to the long-term survival of a species.

But it can also be a great hindrance.

Read Full Post »

It’s tough being a “painted wolf”

Source.

I prefer to call these wild canids “painted wolves,” rather than calling them African wild dogs or Cape hunting dogs. These names come from a misidentification that these are nothing more than a feral domestic dog that is endemic to much of Africa. They are not as closely related to dogs or wolves as their pack behavior might suggest. They are closely related to the genus Canis, but they are in their own genus, Lycaon. I’ve even heard of this species referred to as a “hyena dog,” because they superficially resemble hyenas. They are canids, not hyenas, and they really have a tough time living in territory that is also filled with lions, hyenas, or both.

These animals have really tough lives. The niche that wolves filled in Eurasia and North America is already filled on the African savanna, so a large, pack-hunting dog really does have a tough time making a living. These dogs have very short life expectancy, generally less than 5 years in the wild. Because they have such short lives, they have to produce as many offspring as possible to carry on the next generation. These dogs have massive litters, as big as any seen in domestic dogs. (Arctic foxes and the painted wolf produce the largest litters of any wild dogs. Both have very tough lives in the wild, and they have to have large litters to carry on the next generation.)

The term “painted wolf” comes from the scientific name for this species, which is Lycaon pictus. “Lycaon” means wolf in Greek, and “pictus ” is the Latin word for painted. (You may know another word derived from the Greek word for wolf. The “medical term” for werewolfism is “lycanthropy,” derived from combining the words for wolf and man in Greek.)

Europeans considered the dogs vermin, not just because they did occasionally kill livestock, but because the animals were mistaken for a feral race of domestic dog, early conservationists often killed them in the name of wildlife preservation.  This misconception still exists in some quarters, so I highly recommend that we stop calling them African wild dogs or Cape hunting dogs. This is a unique African pack-hunting canid.

It could very easily become extinct in our lifetimes. Because it is so intensely social, disease is very easily transmitted among the remaining populations of this species, and because African conservation lands are becoming more and more isolated, these dogs have to share their habitat with high densities of spotted hyenas and lions, animals that compete with them for prey and often kill them on sight.

Read Full Post »