Notes on population estimates:Bale minimum estimate of N=210 adults was derived from intensive observations of wolf packs across the Bale Mountains. In April 2009 the population was estimated at 291 adult (>1 year old) wolves (EWCP annual report 2008–2009) and in April 2010 at 290–320 (EWCP annual report 2009-2010). Since then 23 carcasses have been retrieved, and 56 individuals have gone missing, probably as a result of a canine distemper epizootic that affected several subpopulations in Bale.
Ethiopian Wolves are restricted to seven isolated mountain enclaves in the highlands of Ethiopia. The Afroalpine range available to the species is shrinking and increasingly fragmented. The species’ extent of occurrence is estimated at 4,200 km² with an area of occupancy of 2,779 km². Population estimates across the species’ range suggest that between 360 and 440 adult (>1 year old) wolves remain, of which <250 are mature individuals. One relict population in northern Ethiopia (Mt Guna) is now functionally extinct.
The largest population occurs in the Bale Mountains in southern Ethiopia, where intensive monitoring of wolf packs indicate that population size varies widely due to the recurrence of infectious disease epizootics affecting local subpopulations. Since 2008 to date this population has declined by ~30%, from approximately 300 to an estimated 210 adults, due to consecutive epizootics of rabies and canine distemper. This equates to a 20% global decline in the population in the last three years; although narrowly below the threshold for uplisting to Critically Endangered under C1, this continued decline merits careful ongoing monitoring of population numbers (and a reassessment if necessary) and sustained conservation interventions.
Number of "Mature Individuals"
The number of mature individuals in the population (population size) was determined using the IUCN's new definition (in: Guidelines for Using the IUCN Red List Categories and Criteria) and the following formula:
Mature individuals = 0.31N1+ 0.4N1+0.57N2 +0.16 N2 then
Mature individuals = 0.71N1+ 0.73 N2 where:
N1= adult male population
N2= adult female population
Calculations of mature individuals capable of reproduction were derived from empirical data on wolf populations in the Bale Mountains, between 1988–1992 and 1997–2000. Of all adult males in a population, 31% are alpha males and thus reproductive individuals (= 0.31N1). Of all subordinate adult males (= 0.69N1), some may access reproduction either by replacing the alpha male or through extra-pack copulations. This proportion was subjectively estimated at 60% and thus the contribution of subordinate adult males potentially capable of reproduction is 0.6 x 0.69N1 = 0.41N1.
Of all adult females in a population, 57% are in alpha position and thus reproduce (= 0.57N2). Of the suppressed adult females (= 0.33N2) we estimated a 50% likelihood to access reproduction in their lifetime (0.5 x 0.33N2=0.16N2). This was derived from the rate of breeding opportunities, calculated as 0.12 for female per year from empirical data, over four years (0.12 x 4 years= 0.5).
Population estimates were derived from current availability of habitat types and extrapolations of the density of adult and subadult wolves to the area of each habitat type. Population estimates (N) are numbers of adult and subadult wolves. Given a population sex ratio of 2:1 males to females then the male population is 2/3N = 0.67N and the female population is 1/3N= 0.34N. Eighty percent of males and 70% of females are adults, therefore:
N1= adult male population= 0.8 x 0.67N = 0.53N
N2= adult female population= 0.7 x 0.33N = 0.23N
and, Mature individuals = 0.71N1 + 0.73N2, so:
Mature individuals = 0.37N + 0.17N= 0.54N
Mature individual estimates for 2010 based on IUCN/SSC Canid Specialist Group (2011):
Bale Mountains: N = 210; mature individuals = 113
Arsi Mountains: N = 54; mature individuals = 29
Simien Mountains: N = 52; mature individuals = 28
North Wollo: N = 19; mature individuals = 10
South Wollo: N = 16; mature individuals = 9
Menz : N = 15; mature individuals = 8
Mt Guna: N = 0; mature individuals = 0
Total: N = 366; mature individuals = 197
Guassa-Menz estimate of 15 adult wolves was derived from intensive observation of wolf packs in recent years which yielded an estimate of 25 adult wolves, and was corroborated by DNA fingerprinting in 2008 (which identified 23 individuals). During 2010 40% of the known wolves have died or disappeared due to canine distemper, resulting in the revised estimate.
Arsi and Simien estimates (EWCP unpublished) were derived from intensive observations of wolf packs across both ranges. Recent improvements in monitoring resulted in a larger estimate for Simien, and a smaller one for Arsi. These revised figures reflect improved field techniques and effort rather than actual population change.
For North and South Wollo, population estimates are conservative and were based on habitat availability. Using field maps, the extent of suitable habitat were estimated and populations extrapolated from known densities in Bale for habitats with similar characteristics (Marino 2003a). Here the lower value of densities observed were used (i.e., good habitat: 0.2 wolves/km²; marginal habitat 0.1 wolf/km²).
Other parameters used:
Generation time: mean 4.5 yr, range 3–8; extent of occurrence: 4,200 km² [defined as area above 3,000 m asl]; area of occupancy: 2,800 km²; number of populations: 7; number of sub-populations: 10.
Given the information above, Canis simensis meets the criteria for Endangered under criterion B based on <5,000 km² extent of occurrence (B1), as the population is severely fragmented (a), and there is a continuing decline (b) in area, extent and or quality of habitat (iii) and number of mature individuals (v). It also meets the criteria under C based on <2,500 mature individuals in the population (EN C and D), exceeding a 20% decline in the population in the past eight years (two generations), and a continuing decline in population size (EN C2) and <250 mature individuals in each subpopulation (EN C2a(i)). Finally, it also meets the threshold of <250 mature individuals for listing under D.