The wolves of Ethiopia

Ethiopian wolf (c) Michael Gunther

When most people hear the word “wolf,” they think of the burly gray wolves of the Great White North. But wolves are present all over the world, even in Africa. The Ethiopian wolf, Canis simensis is incredibly endangered. As its name implies, it lives in Ethiopia, but it lives only in seven highland mountain ranges, above the tree line, from 3,000 – 4,500 meters. It is distributed north and south of the Rift Valley. (It is also the only wolf in all of Africa.) These wolves live in social packs, but the animals hunt individually for the most part. They are rodent specialists, but occasionally also hunt antelope and lambs together. {1} Their territory averages about 6 square kiolmeters, and their packs number about 3 to 13, averaging around 6 members with one breeding female. This video is taken from the BBC’s “Life of Mammals” and features an Ethiopian wolf hunting:

(You gotta love David Attenborough!)

To hear them howling, visit this page. Superficially, this wolf looks similar to a fox which led some naturalists to think it was more closely related to foxes of the genus Vulpes than it was to canids of the genus Canis. It’s also been thought to be a type of jackal. But today, most systematicists and taxonomists think it is more closely aligned with wolves. In fact, mitochondrial DNA analyses show that it is more closely related to gray wolves and coyotes than it is to any other canid originating in Africa. These anayses suggest a wolf-like ancestor crossing from Eurasia to northern Africa about 100,000 years ago. {1} This supports the idea of gray wolves (and closely related canids) evolving in Asia and then dispersing to Europe, Africa and North America.  Males are up to 20 percent larger than females, and males do not typically disperse from their natal packs. Rather, females disperse at about two years of age and join packs that need a breeding female. Today, there are thought to be seven isolated populations with about 500 total individuals. {1}

About half the population of Ethiopian wolves is thought to live in the Bale Mountains, and so a recent study on the genetic structure of these wolves focused on this region. {2}  The researchers used three sub-populations and tested them for 17 microsatellite markers to better understand the influence of past demographic events upon the wolves’ modern genetic structure. In the past, a previous study (Gottelli et al. 2004) showed that climate change at the end of the Pleistocene caused a contraction in the range of habitat used by these wolves, effectively shrinking their habitat 10,000 – 15,000 years ago to a series of small sky islands. This range contraction coincided with a population bottleneck of a few thousand individuals.  Today, this contracted range is experiencing further pressure as agriculture and livestock activities continue to press in on the wolves and take more land away from them, leading the population to dwindle to only a few hundred animals. The study authors were interested in finding out how social structure, dispersal, and disease outbreaks affected genetic diversity and structure. Recent outbreaks of canine distemper and rabies among Ethiopian wolves in the past two decades may have further affected their diversity.

On the one hand, genetic drift may have led to the build up of some genetic differences over time between the sub-populations given their distribution in a sky-island habitat range. On the other hand, social structures and dispersals, combined with mortality rates of diseases, could have led to uneven differences too. The three populations the authors studied were: Web Valley, WV; Morebawa, MB, and Sanetti, SN. “Overall, we carried out analyses using genotypes from 140 wolves present in three subpopulations (43 wolves in WV, 44 wolves in MB, and 53 wolves in SN) and 16 individuals in WV2,” they wrote. (The difference between WV and WV2 wolves is basically a before-and-after snapshot of a rabies outbreak.)

They found a loss of four alleles (from a group of six) unique to the Web Valley population after a rabies outbreak in their sampled individuals, but surprisingly they did not find much loss of genetic diversity after the disease outbreaks. They did find statistically significant genetic  differentiation between subpopulations however, and they concluded:

Our results reveal strong genetic structure in a population that has been in decline for thousands of years (Gottelli et al. 2004) as well as having suffered more recent bottlenecks due to disease outbreaks. Not surprisingly then, the Ethiopian wolf population in the Bale Mountains is not in equilibrium.

The authors write that the management implication for this is that each sub-population is genetically distinct enough that it can be managed as a conservation unit. Because only the dominant, breeding female reproduces, each pack within a sub-population is important. In my mind, the worry here is that continued bottlenecks due to disease outbreaks at the sub-population level could lead to differentiation sufficient to lose rare alleles and therefore reduce diversity at the meta-population level. The authors also call for “dispersal corridors” to help Ethiopian wolves that are dispersing to travel between habitat fragments housing sub-populations. This is a great idea, but it is compounded by human activities in this area and, apparently, a growing density of domestic dogs. While I haven’t heard about domestic dogs hybridizing with Ethiopian wolves, they are a reservoir for the disease agents hounding this rare canid: rabies and distemper. This was my first read about Ethiopian wolves, and it surely won’t be my last. If anyone has reading suggestions for better understanding the human/dog interactions with Ethiopian wolves, please let me know in the comments.

NOTES:

{1} From chapter 6, “Sub-Saharan Africa: Ethiopian” of Canids: Foxes, Wolves, Jackals and Dogs – 2004 Status Survey and Conservation Action Plan edited by the IUCN’s Species Survival Commission, Canid Specialist Group.

{2} Randall, D., Pollinger, J., Argaw, K., Macdonald, D., & Wayne, R. (2009). Fine-scale genetic structure in Ethiopian wolves imposed by sociality, migration, and population bottlenecks Conservation Genetics, 11 (1), 89-101 DOI: 10.1007/s10592-009-0005-z