Thursday, December 8, 2016

Bandicoots Are Naïve to Dogs

Historical coexistence with dingoes may explain bandicoot avoidance 
of domestic dogs.Photo credit: Narawan Williams; CCAL.
Domestic dogs and cats were introduced to Tasmania two centuries ago, but bandicoots still fail to recognize these introduced predators as threats, according a study published September 7, 2016 in the open-access journal PLOS ONE by Anke Frank from University of Tasmania, Australia, and colleagues.

Worldwide, introduced predators have caused declines and extinctions of native wildlife, presumably in part because native species do not see novel predators as threats and thus fail to flee or defend themselves. But this naiveté is not necessarily forever: bandicoots in Sydney avoid backyards with domestic dogs. Interestingly, however, Sydney bandicoots do not avoid domestic cats even though they, like domestic dogs, were introduced about 200 years ago. This varying behavior to introduced predators has been attributed to the fact that dingoes arrived in mainland Australia 4000 years ago, predisposing Sydney bandicoots to avoid domestic dogs.

To test this hypothesis, Frank and colleagues assessed bandicoot behavior in Tasmania, where domestic dogs have been present for 200 years but where dingoes have never been present. The researchers surveyed 548 people in Hobart, Tasmania -- 37% of whom owned at least one dog and 20% of whom owned at least one cat -- about bandicoot sightings and scats in their backyards.

More than a quarter of participants reported that their pets had killed bandicoots, showing that predation from these introduced predators was a real threat. Even so, the survey showed that Tasmanian bandicoot sightings and scats were equally likely in backyards with or without domestic dogs or cats. These findings support the hypothesis that bandicoots on mainland Australia may recognize dogs as predators due to thousands of years of exposure to dingoes, and suggests that naiveté to introduced predators can ultimately be overcome.

"By using a citizen science approach, my collaborators and I found that -- unlike Australian mainland bandicoots -- bandicoots from the island state of Tasmania are naïve to domestic dogs," said Anke Frank. "This study supports our hypothesis that naiveté towards unfamiliar predators may eventually be overcome, but that in Tasmania 200 years of exposure have been an insufficient time for bandicoots to recognize cats as well as dogs as a threat."

Anke S. K. Frank, Alexandra J. R. Carthey, Peter B. Banks. 2016. Does Historical Coexistence with Dingoes Explain Current Avoidance of Domestic Dogs? Island Bandicoots Are Naïve to Dogs, unlike Their Mainland Counterparts. PLOS ONE, 2016; 11 (9): e0161447 DOI: 10.1371/journal.pone.0161447

The Sardinian Fonni's Dog and human migration

The Fonni’s Dog (Cane Fonnese or Sardinian Sheepdog) is
endemic to Sardinia and is known for its fiercely protective
guarding behaviors. Photo Credit: Stefano Marell
A genomic analysis of 28 dog breeds has traced the genetic history of the remarkable Fonni's Dog, a herd guardian endemic to the Mediterranean island of Sardinia. The results, published in the journal GENETICS, reveal that the regional variety has developed into a true breed through unregulated selection for its distinctive behavior, and that its ancestors came from the very same geographic areas as Sardinia's human migrants. Just as Sardinian people have long provided a wealth of genetic insights to scientists, the canine natives are an example of an isolated population that could prove a powerful resource for finding genes that influence health and behavior.

Fonni's Dogs (Cane Fonnese in Italian) are large, rugged dogs known for their wariness towards strangers and their intense facial expression. Although there are descriptions of these shephard's companions dating to at least the mid-nineteenth century, it is not officially recognized as a breed by most international registries, including the largest federation of kennel clubs, the Federation Cynologique Internationale.

"If you were to look at ten Fonni's Dogs, you would see there's a lot of variation in coat color and fur length. But they are all good protectors of their flocks. That's because nobody cares what they look like; they've been bred to do a job and to do it right," says study leader Elaine Ostrander of the National Human Genome Research Institute (NHGRI).

That job is guarding the possessions of their owner, to whom they are fiercely loyal. "Fonni's are also outstanding thieves," says Ostrander. "They can be trained to sneak over to the neighbors' and bring items home." While this particular duty isn't required by today's Fonni Dogs, written records from the mid-1800's indicate that thievery was part of their historical repertoire.

The island home of the Fonni's Dog has long held the interest of geneticists. Because Sardinia is geographically isolated, its human inhabitants share a unique ancestry and relatively low genetic diversity. Those characteristics make it easier to study genetic influences on disease and aging in Sardinians than in other human groups. Ostrander and other canine geneticists argue that each of the hundreds of different dog breeds also represents an isolated population that could be harnessed for genetic studies.

"Dogs get all the same diseases as humans, and there are lots of dog breeds with genetic predispositions, for example to particular types of cancer," Ostrander says. "Once we understand the genetic history of a breed we can search for disease genes in a much more powerful way than is possible in humans, enabling us to hone in on medically-relevant genes."

To better understand how the Fonni's Dog developed, scientists from the NHGRI, the University of Milan, and G. d'Annunzio University analyzed blood samples from Fonni's Dogs living in different parts of Sardinia and sequenced the whole genome of one of these dogs. To trace the Fonni's relationship to dogs from around the Mediterranean, the team compared the data to DNA from 27 other European, Middle Eastern, and North African breeds.

The data revealed that the Fonni's dog shows all the genetic hallmarks of being a breed, even though it developed in the absence of a regulated pedigree program and only arose through the tendency of Sardinian shepherds to choose their best guard dogs for breeding. The researchers compared individual dogs from within the same breed and across different breeds, quantifying many aspects of genome variation and genetic distinctiveness. All these measures confirmed that the Fonni's Dog, in genetic terms, is a breed.

The study also revealed the ancestors of the Fonni's Dog were related to the Saluki, a swift and graceful "sight" hound from the Near and Middle East, and a large mastiff like the Komondor, a powerfully-built sheep guardian from Hungary that looks a bit like a mop.

Strikingly, the origins of the Fonni's Dog mirror human migration to Sardinia. Studies of the island's human inhabitants have shown they share greatest genetic similarity with people from Hungary, Egypt, Israel, and Jordan. "The map we can draw of the dog's origins is the same as the map of human migration to Sardinia," says Ostrander. "Clearly ancient people traveled with their dogs, just as they do now."

The close parallels between the history of the dog and human inhabitants of the island has a practical implication, says Ostrander. "Our study shows how closely dog migration parallels human migration. It could be that if you have missing pieces in a study of a human population's history, samples collected from dogs in the right place could fill in those gaps."

The team plans next to study in greater detail eleven regions of the genome that likely make the Fonni's Dog distinct -- these may be responsible for their characteristically loyal and protective behavior.

Ostrander points out the study was a collaborative effort with scientists from Italy, including Sardinia, and says she is gratified to find so many researchers across the world interested in similar questions. Her group is hoping to work with colleagues in a range of countries to explore other so-called "niche" dog populations, regional varieties that often have a history of being bred for a particular job. Their goals are to better understand how dogs have evolved and to demonstrate yet another important job for these faithful human companions: tracking down disease genes.

Citation
D. L. Dreger, B. W. Davis, R. Cocco, S. Sechi, A. Di Cerbo, H. G. Parker, M. Polli, S. P. Marelli, P. Crepaldi, E. A. Ostrander. 2016. Commonalities in Development of Pure Breeds and Population Isolates Revealed in the Genome of the Sardinian Fonni's Dog. Genetics, 204 (2): 737 DOI: 10.1534/genetics.116.192427