Biodiversity

Sunday, April 01, 2007

A LOSS OF GENETIC INTEGRITY- Hybridization in the most endangered canid, Canis simensis

By Dane E. McDonald


Image 1 Canis simensis with characteristic fur markings

Canis simensis, also called the Ethiopian wolf or Simien jackal, is a canid that occurs in the geographical isolation of a compact group of Ethiopian mountains or highlands (Gottelli et al, 2004). This animal’s geographic isolation can be explained by the last glaciation (70 000-10 000 years BP), which allowed its cold-adapted European ancestors (gray wolves and coyotes) to immigrate into Africa (Gottelli et al 2004; Gottelli et al 1994).

C. simensis is endemic to the Ethiopian highlands and occur above the tree line at altitudes above 3000 meters (IUCN data). This area is generally termed alpine tundra (Miller, 2004) or more specifically Afro-alpine habitat (Gottelli et al, 1994). According to Sillero-Zubiri and Macdonald (1998) the Afro-alpine zone is characterized by short, sparse vegetation, dominated by Alchemilla sp. pasture and a short herb community including Helichrysum sp. and Artemisia sp. shrubs. Marino et al (2006) suggests that the optimal habitat would be one with open and flat landscapes with meadows and grasslands, which sustain an exceptionally high biomass of rodents.

The giant mole rat, Tachyoryctes macrocephalus, is one of the most common and important prey species that occur in this zone. C. simensis has developed an extreme feeding specialization on such rodents (Gottelli et al, 2004). It follows that its distribution is also limited by the availability of these rodents.

The Conservation Problem

Ethiopian wolves are diurnal, medium-sized canids with body mass ranging between thirteen and twenty kilograms (Randall et al, 2006; Haydon et al, 2002). According to Gottelli et al (1994) these animals are very distinctive, having a reddish coat, with white underparts, throat, chest, and tail markings (Image 1). They also display a skull morphology that indicates adaptations for catching rodents. Dalton et al (unpublished data) identifies features such as a very elongated skull with long jaws in which teeth (especially the premolars) are widely spaced. According to Gottelli et al (1994) they are territorial, social animals that live in multi-male packs, which have been observed to be as large as thirteen adults. A general trend shows that only dominant females breed. This is due to dominance hierarchies within packs (Sillero-Zubiri et al, 1996).


Image 2 A map of C. simensis habitat in the Ethiopian highlands showing the large historic extent (yellow) and the limited present extent (red)

Ethiopian wolves are currently the most endangered canids in the world, with approximately 600 individuals remaining (Randall et al, 2006). They are limited to seven isolated Afro-alpine ranges across the Ethiopian highlands (Image 2). In a study done by Gottelli et al (1994) hybridization with domestic dogs was identified as one of the main threats to the genetic integrity of the canids in this area. Andersone et al (2002) suggest that hybridization has the potential to produce morphological, physiological and behavioural changes in wild canids. This deserves serious attention due to its ecological and management consequences.

Gottelli et al (1994) explains that the Ethiopian highlands are among the most densely populated agricultural areas, where Afro-alpine grasslands are increasingly being used for grazing. As a result, Ethiopian wolves cannot easily avoid contact with humans and their domestic dogs. This is exemplified in the Bale Mountain area (Image 2) where 8500 surrounding village households have more than 12500 domestic dogs (Randall et al, 2006).

Recommendations

By using mt DNA restriction fragments and microsatellite alleles, Gottelli et al (1994) provided convincing evidence that male domestic dogs were hybridizing with female (Web valley) Ethiopian wolves. It was recommended that feral domestic dogs be controlled to eliminate this threat. Furthermore captive breeding with genetically pure founders was suggested with immediate effect.


Image 3..


References

Andersone BZ, Lucchini V, Ozolins J (2002) Hybridisation between wolves and dogs in Latvia as documented using mitochondrial and microsatellite DNA markers. Mammalian Biology 67: 79-90

Gottelli D, Marino J, Sillero-Zubiri C, Funk SM (2004) The effect of the last glacial age on speciation and population genetic structure of the endangered Ethiopian wolf (Canis simensis). Molecular ecology 13: 2275-2286

Gottelli D, Sillero-Zubiri C, Applebaum GD, Roy MS, Girman DJ, Garcia-Moreno J, Ostrander EA, Wayne RK (1994) Molecular genetics of the most endangered canid: the Ethiopian wolf Canis simensis. Molecular ecology 3: 301-312

IUCN data (web reference)- http://www.iucnredlist.org/search/details.php/3748/doc

Marino J, Sillero-Zubiri C, Macdonald DW (2006) Trends, dynamics, and resilience of an Ethiopian wolf population. Animal conservation 9: 49-58

Miller, GT (2004) Living in the environment-13th Ed. McGraw/Hill, Canada.

Randall DA, Marino J, Haydon DT, Sillero-Zubiri C, Knobel DL, Tallents LA, Macdonald DW, Laurenson MK (2006) An integrated disease management strategy for the control of rabies in Ethiopian wolves Biological conservation 131: 151-162

Sillero-Zubiri C, Gottelli D, Macdonald DW (1996) Male philopatry, extra-pack copulations and inbreeding avoidance in Ethiopian wolves (Canis simensis). Behavioural Ecology and Sociobiology 38:331-340 In: Randall DA, Marino J, Haydon DT, Sillero-Zubiri C, Knobel DL, Tallents LA, Macdonald DW, Laurenson MK (2006) An integrated disease management strategy for the control of rabies in Ethiopian wolves Biological conservation 131: 151-162

Sillero-Zubiri C, Macdonald DW (1998) Scent marking and territorial behaviour of Ethiopian wolves Canis simensis. J. Zool, Lond. 245: 351-361

Image credits: National Geographic magazine, March 2006.
photographs by: Anup Shah
Available from:
http://www7.nationalgeographic.com/ngm/0603/feature6/index.html

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