When dogs become the biggest predators of livestock

Dog Photo Kesang Chunit

Dogs were responsible for 64% of livestock deaths in the Trans-Himalayan region, much more than snow leopards. – Photo: Kesang Chunit

Dogs might be man’s best friends but they also turn out to be livestock’s biggest predators, at least in the Trans Himalayas. In the Upper Spiti landscape of the Trans-Himalayan region of India, of the 340 animals killed by predators in 2013 across 25 villages, free-ranging dogs (which move about freely in the landscape) were responsible for nearly 64% of livestock deaths, much more than snow leopards (that killed about 29%).

Even the livestock deaths attributed to wolves might indeed be attributed to dogs as there are very few wolves in the area.

While dogs predominantly killed small-bodied livestock (sheep and goats) and a few medium-sized animals such as donkeys, snow leopards killed larger animals such as horses and yaks. Even from the financial point of view, dogs caused more economic loss per year to people than snow leopards.

Sheep and goats did not display the same kind of anti-predator response towards dogs as they would do to wild predatory animals.The results of a study based on an interview survey were published in the journal Ambio. The study was jointly carried out by Ashoka Trust for Research in Ecology and the Environment (ATREE), Bengaluru, and Nature Conservation Foundation.

Livestock size

Chandrima Home from ATREE and the first author of the paper wanted to test if livestock depredation was due to abundance of dogs in a place or if it was livestock population that determined predation. “We found dogs responded strongly to livestock abundance and support the prey abundance hypothesis,” says Ms. Home.

The main reason why dogs turned out to be bigger predators than snow leopard could partly be explained by the naivety exhibited by livestock and familiarity of the predators (dogs). As a result, the sheep and goats did not display the same kind of anti-predator response towards dogs as they would do to wild predatory animals. That explains why sheep and goats accounted for 80% of the kills by dogs.

“The small-bodied livestock numbers are reducing and the large-bodied livestock is showing an increasing trend,” she says. With continued predation of livestock, there has also been a decline in the population of sheep and goat during the last five years. One village has stopped keeping small-bodied livestock since 2013 due to increased frequency of depredation by dogs. There have also been instances when dogs have killed calves of larger-bodies animals. Such attacks may increase in future as the number of sheep and goats keep reducing.

According to the paper, compensation is paid only for livestock killed by wild animals and not by dogs.

Of the 25 villages studied, two villages generated a huge volume of daily organic waste leading to an increase in the number of dogs. Totally, the researchers identified about 570 dogs in the 25 villages. “But only a subset of dogs predate on livestock and these dogs move from one village to another,” Ms. Home clarifies.

According to a 2017 paper in the journal Biological Conservation, domestic dogs have contributed to 11 vertebrate extinctions and are a known or potential threat to at least 188 threatened species worldwide.

Published in The Hindu on May 13, 2017

Role of starch food digestion in dog domestication

Published in The Hindu on January 24, 2013

The adaptation which played a crucial role in transforming wolves into domestic dogs has been finally found. Genetic changes that facilitated the digestion of a starch-rich diet and not the morphological or behavioural helped this transformation.

According to a paper published in Nature today (Jan 24), selection at just three genes with key roles in starch digestion was sufficient to bring about this adaptation.

It is not clear why and how the domestication was achieved. Even the identification of genetic changes that helped dogs digest starch better cannot explain the “driving force” behind this process. What is clear is that permanent settlement of humans and development of agriculture “catalysed” the process of domestication.

A change in the ecological niche was responsible for carnivorous wolves to turn into starch-eating dogs. The authors of the paper imagine that “scavenging in waste dumps” near human settlements would have started this process.

With increased dependence on agriculture produce for food requirements, both humans and dogs had to undergo adaptive responses to be able to digest starch-rich diet. According to Nature , the breakdown of starch takes place through three important stages, and domesticated dogs show all these genetic changes compared with wolves.

The stages are: 1) conversion of starch into maltose and other oligosaccharides by the action of a particular enzyme (alpha-amylase) found in the intestine. In the case of humans, it protein is found in the saliva and that is the reason why digestion of starch starts in the mouth itself. But in the case of dogs, the protein is expressed only in the intestine 2) production of glucose from oligosaccharides, sucrose and isomaltase, and finally 3) transportation of glucose across the biological barrier called cell membrane that separates the inside of the cell from the outside.

The scientists from the Science for Life Laboratory, Uppsala University and MIT, among other institutions, studied the whole-genome of 12 wolves and 60 dogs from 14 diverse breeds for identifying the genetic differences. Thirty-six candidate domesticated regions containing 122 genes were identified for scrutiny.

They studied changes in all the three stages of starch digestion in both dogs and wolves before arriving at a conclusion. In the case of amylase enzyme, they found the copy number was much higher in the case of dogs. While wolves had just two copy numbers, domesticated dogs had an average 7.4-fold increase in copy number.

Increase in copy number refers to a particular gene or chromosomal region (containing many genes) getting duplicated. The more the copy number, the more will be the expression level and, in turn, greater will be the activity caused by that gene(s). When a gene is expressed, it refers to the production of an appropriate protein. So the more the expression level, the more will be the production of the protein. The expression level will be more when the copy number is more. When the expression level is more, the activity of the protein gets enhanced.

In the case of amylase, the expression level was 28-fold higher in dogs than wolves. And the activity was 4.7-fold higher in dogs.

In the second stage which involves the production of glucose, the scientists found a nearly two-fold increase in glucose production in dogs when compared with wolves.

Once the starch is digested to glucose, it has to be transported through the plasma membrane where the glucose can be utilised to produce energy. “To benefit from an increased capacity to digest starch, dogs would therefore be expected to show a parallel increase in glucose uptake,” they write. They did find evidence in favour of such an enhanced uptake of glucose produced.